Abstract
Background
Tai Chi, a systematic callisthenic exercise first developed in ancient China, involves a series of slow and rhythmic circular motions. It emphasises use of 'mind' or concentration to control breathing and circular body motions to facilitate flow of internal energy (i.e. 'qi') within the body. Normal flow of 'qi' is believed to be essential to sustain body homeostasis, ultimately leading to longevity. The effect of Tai Chi on balance and muscle strength in the elderly population has been reported; however, the effect of Tai Chi on dyspnoea, exercise capacity, pulmonary function and psychosocial status among people with chronic obstructive pulmonary disease (COPD) remains unclear.
Objectives
• To explore the effectiveness of Tai Chi in reducing dyspnoea and improving exercise capacity in people with COPD.
• To determine the influence of Tai Chi on physiological and psychosocial functions among people with COPD.
Search methods
We searched the Cochrane Airways Group Specialised Register of trials (which included the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Allied and Complementary Medicine Database (AMED) and PsycINFO); handsearched respiratory journals and meeting abstracts; and searched Chinese medical databases including Wanfang Data, Chinese Medical Current Contents (CMCC), Chinese Biomedical Database (CBM), China Journal Net (CJN) and China Medical Academic Conference (CMAC), from inception to September 2015. We checked the reference lists of all primary studies and review articles for relevant additional references.
Selection criteria
We included randomised controlled trials (RCTs) comparing Tai Chi (Tai Chi alone or Tai Chi in addition to another intervention) versus control (usual care or another intervention identical to that used in the Tai Chi group) in people with COPD. Two independent review authors screened and selected studies.
Data collection and analysis
Two independent review authors extracted data from included studies and assessed risk of bias on the basis of suggested criteria listed in the Cochrane Handbook for Systematic Reviews of Interventions. We extracted post‐programme data and entered them into RevMan software (version 5.3) for data synthesis and analysis.
Main results
We included a total of 984 participants from 12 studies (23 references) in this analysis. We included only those involved in Tai Chi and the control group (i.e. 811 participants) in the final analysis. Study sample size ranged from 10 to 206, and mean age ranged from 61 to 74 years. Programmes lasted for six weeks to one year. All included studies were RCTs; three studies used allocation concealment, six reported blinded outcome assessors and three studies adopted an intention‐to‐treat approach to statistical analysis. No adverse events were reported. Quality of evidence of the outcomes ranged from very low to moderate.
Analysis was split into three comparisons: (1) Tai Chi versus usual care; (2) Tai Chi and breathing exercise versus breathing exercise alone; and (3) Tai Chi and exercise versus exercise alone.
Comparison of Tai Chi versus usual care revealed that Tai Chi demonstrated a longer six‐minute walk distance (mean difference (MD) 29.64 metres, 95% confidence interval (CI) 10.52 to 48.77 metres; participants = 318; I2 = 59%) and better pulmonary function (i.e. forced expiratory volume in one second, MD 0.11 L, 95% CI 0.02 to 0.20 L; participants = 258; I2 = 0%) in post‐programme data. However, the effects of Tai Chi in reducing dyspnoea level and improving quality of life remain inconclusive. Data are currently insufficient for evaluating the impact of Tai Chi on maximal exercise capacity, balance and muscle strength in people with COPD. Comparison of Tai Chi and other interventions (i.e. breathing exercise or exercise) versus other interventions shows no superiority and no additional effects on symptom improvement nor on physical and psychosocial outcomes with Tai Chi.
Authors' conclusions
No adverse events were reported, implying that Tai Chi is safe to practise in people with COPD. Evidence of very low to moderate quality suggests better functional capacity and pulmonary function in post‐programme data for Tai Chi versus usual care. When Tai Chi in addition to other interventions was compared with other interventions alone, Tai Chi did not show superiority and showed no additional effects on symptoms nor on physical and psychosocial function improvement in people with COPD. With the diverse style and number of forms being adopted in different studies, the most beneficial protocol of Tai Chi style and number of forms could not be commented upon. Hence, future studies are warranted to address these topics.
Plain language summary
Tai Chi for chronic obstructive pulmonary disease (COPD)
Background
People with chronic obstructive pulmonary disease (COPD) frequently experience shortness of breath (dyspnoea). Tai Chi is a systematic callisthenic exercise first developed in ancient China that involves a series of slow and rhythmic circular motions. It emphasises use of the 'mind' or concentration to control breathing and circular body motions to facilitate the flow of internal energy (i.e. 'qi') to sustain equilibrium within the body and improve life expectancy. Its effects on balance and muscle strength in the elderly population have been reported, but its effects on dyspnoea, exercise capacity, pulmonary function and psychosocial well‐being for people with COPD remain inconclusive. This review explores whether Tai Chi is beneficial for reducing dyspnoea and improving exercise capacity and physiological and psychosocial well‐being among people with COPD.
Study characteristics
We included a total of 811 participants from 12 studies in the final analysis of this review. The number of participants in each study ranged from 10 to 206, and mean age ranged from 61 to 74 years. The programme lasted for six weeks to one year. Included studies adopted different styles and numerous forms of Tai Chi. The most commonly reported form is the simplified 24‐form Yang‐style Tai Chi.
Key results
No unwanted events or side effects were reported throughout the study period. Quality of evidence of all outcomes of interest ranged from very low to moderate. After training was completed, levels of shortness of breath in Tai Chi and control (i.e. usual care) groups were similar. Participants in the Tai Chi group walked farther, by 29.64 metres in six minutes, and had better pulmonary function, than those who received usual care. However, changes in quality of life were not apparent. When the effect of Tai Chi used in addition to another intervention (i.e. breathing exercise or exercise) was examined, we did not find that Tai Chi offered additional benefit in terms of shortness of breath or functional and psychosocial well‐being. Currently, only one study has investigated the beneficial effects of Tai Chi on muscle strength and balance; investigators provided insufficient information to allow comment on the data in this review. Future studies addressing these topics are warranted.
Summary of findings
Summary of findings for the main comparison. Tai Chi versus usual care.
| Tai Chi versus usual care | |||||
| Patient or population: chronic obstructive pulmonary disease (COPD) Setting: outpatient/community Intervention: Tai Chi Comparison: usual care | |||||
| Outcomes | Anticipated absolute effects* (95% CI) | Number of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Usual care | Tai Chi | ||||
| Level of dyspnoea Assessed with Modified Borg Scale (unit) Scale from 0 to 10 | Mean level of dyspnoea was 2.1 units | Mean level of dyspnoea in the intervention group was 0.2 unit lower (95% CI ‐0.67 to 0.27 unit) |
137 (1 RCT) | ⊕⊕⊝⊝ LOWa,b | Lower score indicates improvement |
| Functional capacity Assessed with 6‐minute walk test (metre) | Mean functional capacity was 317.38 metres | Mean 6‐minute walk distance in the intervention group was 29.64 metres farther (95% CI 10.52 to 48.77 metres) |
318 (6 RCTs) | ⊕⊝⊝⊝ VERY LOWa,b,c | Increase in walking distance indicates improvement |
| Functional capacity Assessed with endurance shuttle walk test (second) | Mean functional capacity was 430 seconds | Mean endurance shuttle walk duration in the intervention group was 373 seconds longer (95% CI 135.42 to 610.58 seconds) | 38 (1 RCT) | ⊕⊕⊝⊝ LOWa,b | Increase in duration indicates improvement |
| Peak aerobic capacity Assessed with peak oxygen consumption (mL/kg/min) | Mean peak aerobic capacity was 11 mL/kg/min | Mean peak oxygen consumption in the intervention group was 2 mL/kg/min lower (95% CI ‐5.76 to 1.76 mL/kg/min) |
10 (1 RCT) | ⊕⊕⊝⊝ LOWa,b | Increase in peak oxygen consumption indicates improvement |
| Pulmonary function Assessed with forced expiratory volume in 1 second (FEV1) (litre) | Mean pulmonary function was 1.09 litres | Mean FEV1 in the intervention group was 0.11 litres greater (95% CI 0.02 to 0.2 litres) |
258 (4 RCTs) | ⊕⊕⊕⊝ MODERATEb | Increase in volume indicates improvement |
| Quality of life Assessed with St. George's Respiratory Questionnaire (SGRQ) ‐ Total score (unit) Scale from 0 to 100 | Mean quality of life was 48.93 units | Mean SGRQ total score in the intervention group was 7.85 units lower (95% CI ‐16.53 to 0.83 unit) |
233 (3 RCTs) | ⊕⊝⊝⊝ VERY LOWa,b,d | Lower score indicates improvement |
| Quality of life Assessed with Chronic Respiratory Questionnaire (CRQ) ‐ Total score (unit) Scale from 1 to 7 | Mean quality of life was 4.75 units | Mean CRQ total score in the intervention group was 0.41 unit higher (95% CI ‐0.54 to 1.35 units) |
48 (2 RCTs) | ⊕⊕⊝⊝ LOWa,b | Higher score indicates improvement |
| CI: Confidence interval | |||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of effect Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of effect but may be substantially different Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | |||||
aPerformance bias
bOptimal information size criterion is not met
cStatistical significance of moderate heterogeneity (30% to 60%)
dInadequate description of random sequence generation or allocation concealment
Summary of findings 2. Tai Chi and breathing exercise versus breathing exercise.
| Tai Chi and breathing exercise versus breathing exercise | |||||
| Patient or population: chronic obstructive pulmonary disease (COPD) Setting: outpatient/community Intervention: Tai Chi and breathing exercise Comparison: breathing exercise | |||||
| Outcomes | Anticipated absolute effects* (95% CI) | Number of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Breathing exercise | Tai Chi and breathing exercise | ||||
| Level of dyspnoea Assessed with Modified Borg Scale (unit) Scale from 0 to 10 | Mean level of dyspnoea was 4.6 units | Mean level of dyspnoea in the intervention group was 1.3 units lower (95% CI ‐2.02 to ‐0.58 unit) |
80 (1 RCT) | ⊕⊝⊝⊝ VERY LOWa,b,c | Lower score indicates improvement |
| Functional capacity Assessed with 6‐minute walk test (metre) | Mean 6‐minute walk distance was 280 metres | Mean 6‐minute walk distance in the intervention group was 22 metres farther (95% CI ‐6 to 50 metres) |
60 (1 RCT) | ⊕⊝⊝⊝ VERY LOWa,b,c | Increase in walking distance indicates improvement |
| Pulmonary function Assessed with forced expiratory volume in 1 second (FEV1) (litre) | Mean FEV1 was 1.63 litres | Mean FEV1 in the intervention group was 0 litres (95% CI ‐0.11 to 0.12 litres) |
120 (2 RCTs) | ⊕⊕⊝⊝ LOWa,c | Increase in volume indicates improvement |
| Quality of life Assessed with St. George's Respiratory Questionnaire (SGRQ) ‐ total score (unit) Scale from 0 to 100 | Mean SGRQ total score was 47.44 units | Mean SGRQ total score in the intervention group was 1.32 units lower (95% CI ‐5.92 to 3.28 units) |
120 (2 RCTs) | ⊕⊝⊝⊝ VERY LOWa,b,c | Lower score indicates improvement |
| CI: Confidence interval | |||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of effect Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of effect but may be substantially different Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | |||||
aOptimal information size criterion is not met
bInadequate description of random sequence generation or allocation concealment
cPerformance bias
Summary of findings 3. Tai Chi and exercise versus exercise.
| Tai Chi and exercise versus exercise | |||||
| Patient or population: chronic obstructive pulmonary disease (COPD) Setting: outpatient/community Intervention: Tai Chi and exercise Comparison: exercise | |||||
| Outcomes | Anticipated absolute effects* (95% CI) | Number of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Exercise | Tai Chi and exercise | ||||
| Functional capacity Assessed with 6‐minute walk test (metre) | Mean 6‐minute walk distance was 339.5 metres | Mean 6‐minute walk distance in the intervention group was 1.5 metres farther (95% CI ‐18.76 to 21.76 metres) |
192 (1 RCT) | ⊕⊕⊝⊝ LOWa,b | Increase in walking distance indicates improvement |
| Quality of life Assessed with St. George's Respiratory Questionnaire (SGRQ) ‐ total score (unit) Scale from 0 to 100 | Mean SGRQ total score was 30.16 units | Mean SGRQ total score in the intervention group was 3.76 units lower (95% CI ‐8.72 to 1.2 units) |
192 (1 RCT) | ⊕⊕⊝⊝ LOWa,b | Lower score indicates improvement |
| CI: Confidence interval | |||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of effect Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of effect but may be substantially different Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | |||||
aPerformance bias
bOptimal information size criterion is not met
Background
Description of the condition
Chronic obstructive pulmonary disease (COPD), a condition characterised by partially reversible airflow limitation (Vestbo 2013), is associated with both local (airway) and systemic inflammation (Gan 2004; Fabbri 2007). The severity of this condition is categorised according to the standardised lung function criteria set by the Global Initiative for Chronic Lung Disease (GOLD) (Vestbo 2013). The pooled prevalence of COPD at category Stage II or above was reported by the Burden of Obstructive Lung Disease Initiative (BOLD) as 10.1% (Buist 2007). COPD is also a major cause of morbidity and mortality globally (Vestbo 2013). In 2001, COPD was the fifth leading cause of death; it ranked seventh in a list of disability‐adjusted life years (DALYs) among high‐income countries (Lopez 2006).
Exertional dyspnoea is a key disabling factor and is reported as the main factor that deters people with COPD from participating in regular exercises or physical activity, subsequently leading to poor exercise tolerance. This, in turn, leads to muscle deconditioning and decline of overall fitness, and hence a poor quality of life. Co‐morbidity such as increased risk of cardiovascular disease (Sin 2003), osteopenia or osteoporosis (Biskobing 2002), metabolic disease (Marquis 2005), cachexia and skeletal muscle wasting (Wouters 2007) have been reported in people with COPD. This is explained in part by COPD‐related systemic inflammation (Sin 2003) and associated risk factors such as smoking (Biskobing 2002), physical inactivity (Fabbri 2007), abnormal changes in body composition (Wouters 2007), shifting of muscle fibre distribution (Wouters 2007) and use of medications such as glucocorticoids (Fabbri 2007; Jorgensen 2007). Investigators reported that study participants with COPD at Stage II or above had an average of 2.7 acute exacerbations per annum (Seemungal 1998), resulting from COPD itself or from its complicated co‐morbidities. Acute exacerbation of COPD (AECOPD) has been reported to be associated with accelerated decline in lung function, reduced exercise capacity, impaired quality of life and increased overall mortality (Seemungal 1998; Sethi 2005).
Description of the intervention
Tai Chi is a systematic callisthenic exercise that was first developed in ancient China (Lan 2001). It involves a series of slow and rhythmic circular motions moving from one form to another. From the perspective of Traditional Chinese Medicine (TCM), health is governed by the free flow of 'qi' or 'chi', which is internal energy, within the body. Tai Chi emphasises the use of 'mind' or concentration for control of breathing and circular body movement to facilitate the flow of 'qi' to sustain the harmony of body homeostasis, ultimately leading to longevity. To date, various styles of Tai Chi have been developed. 'Chen', 'Yang', 'Wu' and 'Sun' styles are commonly practised; the Chen style is the oldest and the Yang style the most popular (Lan 2002). Styles of Tai Chi can be differentiated by the varying 'forms' or postures, the order of the movement sequence, focus on muscle work, pace of movement and the angle of knee flexion during practice (Lan 2002; Chen 2005). For example, the classic Yang style consists of 108 forms, and the Wu style consists of 119 forms. A review reported that peak heart rate and oxygen consumption achieved during Tai Chi practice were less than 60% of the age‐predicted maximal heart rate and 55% of maximal oxygen consumption (Li 2001), providing evidence to support that Tai Chi is an exercise of moderate intensity (Li 2001; Lan 2004). Duration of practice is dependent on the complexity and number of forms performed. In the Yang style alone, each cycle may last from five minutes (for 'Simplified Yang‐style 24 forms') to about 20 to 30 minutes (for 'Classical Yang‐style 108 forms') (Lan 2001). Participants usually repeat the cycle of Tai Chi until they reach the desired training or practice duration (Leung 2011). Beneficial effects of Tai Chi, regardless of the style, have been reported both in people with normal health and in those with chronic disease (Lan 2002; Wang 2004) such as hypertension (Tsai 2003), chronic heart failure (Yeh 2004) and COPD (Chan 2010). Previous studies have showed that Tai Chi could modulate heart rate; reduce cardiovascular risk factors by lowering blood pressure and improving the lipid profile (Tsai 2003; Wang 2004; Ko 2006; Yeh 2009); promote peripheral microcirculation (Wang 2002); increase aerobic capacity (Lai 1995; Lan 1996; Taylor‐Piliae 2004); delay the age‐associated annual decrease in oxygen consumption (Lai 1995); enhance balance and proprioception (Jacobson 1997); improve muscle strength and endurance (Jacobson 1997; Lan 2000; Wang 2004); and improve psychosocial function (Wang 2004).
How the intervention might work
Tai Chi is recognised as an exercise of moderate intensity (Li 2001; Lan 2004). Each style of Tai Chi comprises different forms or postures and has its own specific order during practice. Regardless of the style, Tai Chi is performed most often in a semi squat position. Each form or posture, depending on its uniqueness, varies in terms of base of support (single‐ or double‐leg stance), shifting of body weight and types of muscle work (concentric or eccentric control of muscles), as well as in patterns of upper and lower limb movement (Lan 2002). For example, the form titled 'Waving hands in the cloud' involves waving the arms up and down alternately in circular forms while side stepping and shifting weight of the lower limbs concurrently. The form called 'Pushing the mountain' involves stepping forward, while at the same time pushing the arms forward. Regular practice of exercise, at moderate intensity, has been shown to induce cardiovascular and musculoskeletal adaptations such as enhancing cardiopulmonary fitness through optimisation of oxygen utilisation, increasing exercise capacity and improving muscle strength and endurance in older adults (Chodzko‐Zajko 2009). This may provide one explanation for the currently reported beneficial effects of Tai Chi in populations with normal health and in those with chronic disease. As aforementioned, Tai Chi emphasises the integration of diaphragmatic breathing into its slow, circular and rhythmic movements. Controlled breathing, such as pursed‐lip breathing, diaphragmatic breathing or active expiration, has been used in the management of COPD (Gosselink 2003). The clinical efficacy of different breathing strategies in alleviating dyspnoea at rest or during exercise, however, remains controversial (Gosselink 2003; Holland 2010). Thus, the potential role of controlled breathing in the COPD population during Tai Chi remains unclear.
Why it is important to do this review
Despite the recent increase in the number of research studies conducted to evaluate the effects of Tai Chi on people with COPD and in the various Tai Chi protocols adopted, effects of Tai Chi remain inconclusive. Therefore, this review was undertaken to explore the evidence from randomised controlled trials (RCTs) supporting or disputing whether Tai Chi practice is effective in ameliorating dyspnoea, facilitating exercise capacity and influencing psychosocial functions in people with COPD.
Objectives
To explore the effectiveness of Tai Chi in reducing dyspnoea and improving exercise capacity in people with COPD.
To determine the influence of Tai Chi on physiological and psychosocial functions among people with COPD.
Methods
Criteria for considering studies for this review
Types of studies
We considered RCTs comparing the effectiveness of a Tai Chi programme (Tai Chi alone or in addition to another intervention) versus control (usual care or another intervention) in the treatment of individuals with COPD.
Types of participants
We included in this review participants with a clinical diagnosis of COPD based on the definition of investigators. No exclusions were based on age, gender, disease severity or smoking history.
Types of interventions
Intervention
We considered Tai Chi programmes, regardless of styles and forms, lasting a minimum of four weeks and including regular practice (at least once a week). The intervention could be provided in the format of a Tai Chi programme alone or as a Tai Chi programme in addition to another intervention.
Control
We included participants continuing with usual care or another intervention (should be the same as in the Tai Chi group) during the study period.
Types of outcome measures
Primary outcomes
Exertional dyspnoea is one of the major disabling symptoms that limits people with COPD in performing activities of daily living, thereby reducing their exercise capacity. Exercise capacity, on the other hand, is considered one of the predictors of mortality in people with COPD (Celli 2010), as exercise capacity reflects the ability of the pulmonary and cardiovascular system to meet the increased demand of oxygen supply to the body. Hence the primary outcomes of this review included the following.
Level of dyspnoea: All measures related to dyspnoea were considered (e.g. Borg Scale, Modified Medical Research Council (MMRC) Dyspnoea Scale, Dyspnoea Visual Analogue Scale (DVAS)).
Functional capacity or aerobic capacity: Both clinical and field tests were included (e.g. distance walked in six‐minute walk test (6MWT) or incremental shuttle walk test (ISWT), or volume of oxygen (VO2) consumption measured during exercise testing).
Secondary outcomes
Pulmonary function measures the degree of airway obstruction, and validated questionnaires on quality of life measure the impact of general health or disease and its associated symptoms on physical and psychosocial functions. These outcomes have been reported to deteriorate when disease progresses or reaches an exacerbation stage. As these outcomes could reflect the current conditions of people, they may be used as a tool to predict overall mortality (Celli 2010). Impaired muscle strength and endurance in association with inactivity (Serres 1998) and systemic inflammation (Sin 2006) have been reported in people with COPD. Quadriceps strength, in particular, was suggested as a possible predictor of mortality in people with COPD (Swallow 2007). Deficits in functional balance have also been demonstrated (Butcher 2004). Furthermore, both muscle strength and balance have been used as predictors of functional capacity in people with COPD. In view of the above, we included the following secondary outcomes.
Pulmonary function: forced expiratory flow volume in one second (FEV1), forced vital capacity (FVC), the ratio FEV1/FVC.
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Quality of life status: both generic and disease‐specific health‐related quality of life measurements.
Generic health‐related quality of life: Medical Outcome Survey 36‐Item Short Form (SF‐36), Sickness Impact Profile (SIP).
Disease‐specific health‐related quality of life: Chronic Respiratory Questionnaire (CRQ), St George's Respiratory Questionnaire (SGRQ).
Quadriceps or other muscle strength.
Balance.
Search methods for identification of studies
Electronic searches
We identified trials from the Cochrane Airways Group Specialised Register of Trials (CAGR), which is derived from systematic searches of bibliographic databases including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Allied and Complementary Medicine Database (AMED) and PsycINFO; and by handsearching of respiratory journals and meeting abstracts (please see Appendix 1 for additional details). We searched all records in the CAGR using the search strategy presented in Appendix 2.
We conducted a search using the same terms adapted appropriately in ClinicalTrials.gov and Chinese medical databases including Wanfang Data, Chinese Medical Current Contents (CMCC), Chinese Biomedical Database (CBM), China Journal Net (CJN) and China Medical Academic Conference (CMAC).
We searched all databases from their inception to September 2015 and applied no restrictions on language of publication.
Searching other resources
We checked reference lists of all primary studies and review articles for relevant additional references and contacted authors of identified trials for information on other relevant published and unpublished studies. We also contacted experts in the field.
Data collection and analysis
Selection of studies
Two independent review authors (SN and WT) screened the titles and abstracts generated by electronic and manual searches. We reviewed potential articles for inclusion on the basis of pre‐specified inclusion criteria. We applied no restrictions on language during study selection and categorised studies into three types.
Include: Study met all of the pre‐set review criteria.
Exclude: Study did not meet all of the pre‐set review criteria.
Further explore: Study appeared to meet some of the pre‐set review criteria, but insufficient information was given, and further exploration of the full text was needed.
The two review authors then reviewed the full text of each study assigned to the categories of 'Include' and 'Further explore', to determine which included studies met all of the pre‐set criteria. We resolved discrepancies in judgement by discussion and consensus.
Data extraction and management
Two independent review authors (SN and WT) extracted all relevant data including demographics of participants, study methods, outcome measures (dyspnoea level, functional capacity, lung function, scores on quality of life questionnaires, quadriceps or other muscle strength and balance) and results of included studies using a pre‐defined data extraction form designed by the primary review author (SN). We contacted the original authors to obtain missing numerical outcome data, then entered extracted data into Review Manager software (RevMan 2014) for analysis.
Assessment of risk of bias in included studies
Two independent review authors (SN and WT) assessed risk of bias on the basis of suggested categories listed in theCochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We assessed the following risks of bias and graded each as high, low or unclear for each study. We resolved disagreements by discussion and consensus and contacted the original authors to verify study characteristics. We created plots demonstrating the following risks of bias using RevMan software.
Random sequence generation.
Allocation concealment.
Blinding of outcome assessments.
Incomplete outcome data.
Selective outcome reporting.
Measures of treatment effect
For continuous data, we entered post‐programme measurements for each of the outcome measures reported in the included RCTs for comparison, as suggested in the Cochrane Handbook for Systematic Reviews of Interventions (16.1.3.2) (Higgins 2011). We reported mean differences (MDs) and 95% confidence intervals (CIs) using RevMan 5.3 (RevMan 2014).
Unit of analysis issues
Not applicable.
Dealing with missing data
We contacted the original investigators to verify study characteristics and to obtain missing numerical outcome data.
We adopted the intention‐to‐treat (ITT) principle while analysing outcomes and used 'imputation methods' to impute standard deviations.
We performed sensitivity analyses to assess the effects of missing data on overall results and conclusions.
Assessment of heterogeneity
We used the I2 statistic to measure heterogeneity among the trials in each analysis. We considered an I2 value greater than 50% as providing evidence of heterogeneity. If we identified substantial heterogeneity, we planned to conduct pre‐specified subgroup analyses.
Assessment of reporting biases
We planned to use a funnel plot to assess the presence of publication bias if more than 10 studies were included in the meta‐analysis.
Data synthesis
We created a summary of findings table including the following outcomes: primary outcomes: dyspnoea score, functional capacity; secondary outcomes: lung function, scoring from quality of life questionnaires. We divided analyses into three groups according to the comparisons made: (1) Tai Chi versus usual care; (2) Tai Chi and breathing exercise versus breathing exercise; and (3) Tai Chi with exercise versus exercise. We analysed and synthesized the data using RevMan 5.3 software (RevMan 2014). For continuous data, we used the mean difference (MD) to calculate overall effect size of primary outcomes (dyspnoea score and functional capacity) and secondary outcomes (lung function and scores from quality of life questionnaires). We reported means with 95% confidence intervals (CIs). We assessed study heterogeneity by using the I2 statistic. We used the fixed‐effect model for homogeneous studies, and the random‐effects model for others.
Subgroup analysis and investigation of heterogeneity
We performed subgroup analyses, if applicable, to examine the source of any heterogeneity. We considered the following subgroups.
Duration of Tai Chi programme (i.e. programme with duration of three months or less vs programme with duration longer than three months).
Sensitivity analysis
We performed sensitivity analysis based on the quality of included studies. We analysed results again by including only studies that had low risk of bias to examine whether risk of bias might alter the synthesised results.
Results
Description of studies
Refer to Characteristics of included studies and Characteristics of excluded studies for complete details of included and excluded studies.
Results of the search
We conducted the initial search in January 2015 and updated the search in September 2015. We identified a total of 80 records from the CAGR and via handsearching of Chinese medical journals. After removing the duplicates, we extracted 49 records from the list for assessment of eligibility by title screening. Reasons for exclusion were irrelevant topics/irrelevant intervention/irrelevant population/non‐RCT/outcome measures not matched (n = 22). We further evaluated the abstracts and/or full texts of 27 records and finally included 23 records (12 in English and 11 in Chinese) in this review. Among these, some studies had generated multiple reports identified as separate records (e.g. conference proceedings, full‐text articles, dissertations). We identified five records from the study conducted by Chan 2010 (one full‐text paper reporting lung function and exercise capacity (Chan 2011), one full‐text paper reporting quality of life of the same study (Chan 2010), two follow‐up studies, which are extensions of the previously reported studies (Chan 2013a; Chan 2013b) and one dissertation abstract (Chan 2013c)); five records from the study by Du 2013 (one full‐text report of lung function and exercise capacity (Du 2013a), one full‐text report of inflammatory markers (Du 2014a), one full‐text report of blood gas analysis (Du 2014b), one full‐text report of BODE Index (body mass index (BMI), airflow obstruction, dyspnoea and exercise capacity) and quality of life (Du 2013b) and one full‐text report (Xing 2014) of methods, areas in which studies were conducted and comparisons of data reported in this study with those reported in Du 2013a. In addition, six out of seven authors of Xing 2014 were authors of Du 2013a; thus, we considered this to be the same study as Du 2013a); three records from the study by Leung 2013 (one full‐text article and two abstracts); and two records from the study by Niu 2014 (one full‐text article and one abstract). Thus, by counting each study as the unit of interest, we finally included 12 studies in this analysis (Included studies) and summarised details in a flow diagram (Figure 1) (Moher 2009).
1.
Flow diagram.
Included studies
The electronic search and screening of the articles retrieved yielded a total of 12 studies (involving 23 references) that met the inclusion criteria and were eligible for this review. A total of 984 participants from the 12 studies were included in the review. Sample size of each study ranged from 10 (Yeh 2010) to 206 (Chan 2010) participants. Only those involved in the Tai Chi group and the usual care group (i.e. 811 participants) were included in the final analysis. Details of each included study can be found in the Characteristics of included studies table.
Populations
All studies recruited participants with stable COPD with confirmed diagnosis based on study authors' definitions according to the guidelines of the American Thoracic Society, the Global Initiative of Chronic Obstructive Lung Disease (GOLD) and the Chinese Thoracic Society. The sample size of ranged from 10 to 206 participants, with reported mean age from 61 to 74 years. Disease severity ranged from mild to very severe as reported by study authors. Two studies (Zhou 2009; Du 2013) recruited participants with disease severity ranging from mild to moderate; two (Chan 2010; Zhang 2014) from mild to severe; three (Yao 2004; Li 2012; Niu 2014) from moderate to severe; and one from mild to very severe (Ng 2014). Four studies did not specify the level of severity included but provided the mean value of % predicted FEV1 and standard deviation (SD) within the range of moderate to severe COPD (Yeh 2010; Zhang 2012; Leung 2013; Wang 2014).
Settings
One of these 12 studies was conducted in Australia (Sydney) (Leung 2013), one in the USA (Boston) (Yeh 2010), two in Hong Kong (Chan 2010; Ng 2014) and the rest in different provinces in China (Yao 2004; Zhou 2009; Li 2012; Zhang 2012; Du 2013; Niu 2014; Wang 2014; Zhang 2014).
Interventions
All studies compared effects of a Tai Chi training programme (alone or in addition to another intervention) versus a control (i.e. usual care or other interventions). Eight studies compared a Tai Chi training programme against usual care (Zhou 2009; Chan 2010; Yeh 2010; Du 2013; Leung 2013; Niu 2014; Wang 2014; Zhang 2014); three compared effects of Tai Chi training against control adopting a breathing exercise (Yao 2004; Li 2012; Zhang 2012); and one compared Tai Chi training in addition to exercise (exercise component as part of a pulmonary rehabilitation programme) against exercise (the same type of exercise component as part of a pulmonary rehabilitation programme) (Ng 2014).
Regarding the practice style of Tai Chi, six studies used Simplified 24‐form Yang style (Zhou 2009; Li 2012; Zhang 2012; Du 2013; Wang 2014; Zhang 2014); one used 13‐form Tai Chi Qigong (Chan 2010); one used 5‐form Tai Chi selected from Yang style (Yeh 2010); one used Chen style (Yao 2004); another used 21‐form Sun style Tai Chi (Leung 2013); one used 5‐form Tai Chi selected from Sun style (Ng 2014) and one did not mention the style used (Niu 2014). Each Tai Chi session lasted for 15 (Ng 2014) to 60 minutes (Chan 2010; Yeh 2010; Li 2012; Du 2013; Leung 2013; Wang 2014) for five to seven days (including supervised and home sessions) per week. The duration of the whole programme ranged from six weeks to one year. The most commonly reported training duration was 12 weeks (Yao 2004; Chan 2010; Yeh 2010; Du 2013; Leung 2013); the others lasted for six weeks (Ng 2014), eight weeks (Wang 2014), 16 weeks (Zhou 2009), 24 weeks (Niu 2014), 36 weeks (Li 2012) and one year (Zhang 2012; Zhang 2014). Details of these studies are summarised in the Characteristics of included studies table.
Outcome measures
Primary outcome measures
Five studies examined changes in dyspnoea using different scales, including modified Borg Scale (scale of 0 to 10) (Yao 2004; Chan 2010), University of California At San Diego Shortness of Breath Questionnaire (UCSD SOB questionnaire) (Yeh 2010) and modified Medical Research Council (MMRC) Dyspnoea Scale (Du 2013; Wang 2014). Regarding changes in functional capacity, eight studies compared the change in six‐minute walk distance (6MWD) (Yeh 2010; Chan 2010; Zhang 2012; Du 2013; Ng 2014; Niu 2014; Wang 2014; Zhang 2014); one compared the change in incremental shuttle walk distance and endurance shuttle walk duration (Leung 2013) and one compared the change in exercise duration during a symptom‐limited ergometry test and the peak VO2 measured (Yeh 2010) at the end of the test to evaluate aerobic capacity.
Secondary outcome measures
Eleven studies had included changes in pulmonary function as one of the outcome measures (Yao 2004; Zhou 2009; Chan 2010; Yeh 2010; Li 2012; Zhang 2012; Du 2013; Ng 2014; Niu 2014; Wang 2014; Zhang 2014). Seven of these studies evaluated changes in FEV1 (L) (Zhou 2009; Chan 2010; Li 2012; Zhang 2012; Ng 2014; Niu 2014; Zhang 2014), and eight examined the percentage predicted FEV1 (Yao 2004; Zhou 2009; Zhang 2012; Du 2013; Ng 2014; Niu 2014; Wang 2014; Zhang 2014); four studies compared changes in FVC (Zhou 2009; Chan 2010; Li 2012; Ng 2014); and six compared the ratio of FEV1 and FVC (Yao 2004; Yeh 2010; Li 2012; Zhang 2012; Du 2013; Zhang 2014). For quality of life, eight studies used quality of life questionnaires to evaluate programme effectiveness, including SGRQ (Chan 2010; Li 2012; Zhang 2012; Du 2013; Ng 2014; Wang 2014) and CRQ (Yeh 2010; Leung 2013). One study evaluated changes in muscle strength (quadriceps muscles) and balance as outcome measures (Leung 2013).
Excluded studies
The most common reasons for exclusion upon screening of the record title were irrelevant intervention, irrelevant topic, irrelevant population and non‐RCT (n = 22). By retrieving abstracts and/or full‐text articles, we excluded four studies. Reasons for exclusion included non‐RCTs (n = 3) and cross‐sectional measurement (n = 1). Details of excluded studies can be found in the Characteristics of excluded studies table.
Risk of bias in included studies
An overview of risk of bias among the 12 studies is provided in Figure 2 and Figure 3 shows a summary of our judgement on potential risks of bias across studies, which are listed in the Characteristics of included studies table.
2.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
3.
Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
Allocation
All studies were reported to be RCTs. Of these, eight studies reported the method of randomisation in terms of computer‐generated randomisation (Chan 2010; Yeh 2010; Ng 2014; Niu 2014), drawing of lots (Li 2012), random number table (Du 2013; Zhang 2014) and computerised dial‐up system (Leung 2013), and we classified the remaining four studies as having unclear risk of bias because insufficient information was provided. Only three studies reported the use of concealed allocation (Leung 2013; Ng 2014; Niu 2014).
Blinding
Participant blinding was not feasible because of the nature of the intervention. Six studies reported the use of blinded assessors (Chan 2010; Yeh 2010; Du 2013; Leung 2013; Ng 2014; Niu 2014) in text, and the other articles provided insufficient information. Only one study reported that the data analyst was blinded to treatment allocation (Niu 2014).
Incomplete outcome data
Six studies reported the number of participants who had completed the whole programme, including the number of dropouts or individuals lost to follow‐up (Chan 2010; Yeh 2010; Li 2012; Leung 2013; Ng 2014; Niu 2014). Of these, four studies reported use of ITT analysis (Chan 2010; Yeh 2010; Ng 2014; Niu 2014) and the others performed per‐protocol analysis (Li 2012; Leung 2013). The number of participants who dropped out or were lost to follow‐up in these studies ranged from one (Niu 2014) to 48 (Chan 2010), contributing to dropout rates ranging from 2.5% to 28.1% (Chan 2010; Yeh 2010; Li 2012; Leung 2013; Ng 2014; Niu 2014). Of these, three studies (Chan 2010; Yeh 2010; Ng 2014) reported the use of ITT analysis, and the remaining three adopted per‐protocol analysis. However, despite the ITT analysis, we rated Chan 2010 as having high risk of attrition bias due to uneven dropout. The remaining studies did not report clearly any dropouts or losses to follow‐up but listed the numbers of participants in the data tables and therefore were judged as having unclear risk (Yao 2004; Zhou 2009; Zhang 2012; Du 2013; Wang 2014; Zhang 2014).
Selective reporting
Three studies were listed in the clinical trial registry (Yeh 2010; Leung 2013; Ng 2014) and therefore were rated as having low risk in this category. The remaining studies did not report any prior protocol registration, nor could we search for any related information in the clinical trial registry; we therefore rated these studies as having unclear risk in this category (Yao 2004; Zhou 2009; Chan 2010; Li 2012; Zhang 2012; Du 2013; Niu 2014; Wang 2014; Zhang 2014).
Other potential sources of bias
All of the included studies were RCTs with no cross‐over design. No further reporting revealed potential sources of bias.
Effects of interventions
See: Table 1; Table 2; Table 3
Data collection and analysis tables summarise results of the meta‐analysis comparing effects of Tai Chi against usual care. We included 12 studies in the meta‐analysis. We conducted subgroup analyses for duration of the Tai Chi programme but not for styles of Tai Chi because we found great variability in the Tai Chi protocol adopted. Quality of evidence ranged from very low to moderate, and details of grading are reported in Table 1, Table 2 and Table 3. Results are presented according to the three types of comparisons ‐ (1) Tai Chi versus usual care; (2) Tai Chi and breathing exercise versus breathing exercise; and (3) Tai Chi and exercise versus exercise ‐ and are followed by primary and secondary outcomes.
1. Tai Chi versus usual care
1.1 Primary outcome: level of dyspnoea
Four studies involving 243 participants reported the level of dyspnoea ‐ one using the Borg Scale ranging from 0 to 10 at rest and/or after activities (Chan 2010), one using the University of California At San Diego Shortness of Breath Questionnaire (UCSD SOB questionnaire) ranging from 0 to 120 to record the severity of dyspnoea during various activities (Yeh 2010) and two using the modified Medical Research Council (MMRC) Dyspnoea Scale ranging from 0 to 4 to evaluate the level of dyspnoea during functional activities (Du 2013; Wang 2014).
1.1.1 Borg scale
The MD reported from Chan's study (Chan 2010) was ‐0.20 unit (95% CI ‐0.67 to 0.27 unit; Analysis 1.1).
1.1. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 1 Dyspnoea (Borg).
1.1.2 UCSD SOB score
No significant difference (MD 5 units, 95% CI ‐11.62 to 21.62 units) was found in UCSD SOB scores from a sample of 10 participants in Yeh's study (Yeh 2010) (Analysis 1.2).
1.2. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 2 Dyspnoea (UCSD SOB Questionnaire).
1.1.3 MMRC score
Two studies (Du 2013; Wang 2014), involving 96 participants, compared the level of dyspnoea by using the MMRC Dyspnoea Scale. A post‐programme MD of ‐0.15 units was noted (MD ‐0.15 unit, 95% CI ‐0.56 to 0.26 unit) (Analysis 1.3).
1.3. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 3 Dyspnoea (MMRC).
1.2. Primary outcome: functional capacity or aerobic capacity
1.2.1 Walking tests
1.2.1.1 Six‐minute walk test
Six studies, involving 318 participants, examined changes in functional capacity using the six‐minute walk test (6MWT) (Chan 2010; Yeh 2010; Du 2013; Niu 2014; Wang 2014; Zhang 2014). The combined MD from six studies (n = 318) was 29.64 metres (95% CI 10.52 to 48.77 metres, P value = 0.002). Investigators detected no subgroup differences between short‐ and long‐term effects (P value = 0.7) (Analysis 1.4; Figure 4).
1.4. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 4 6‐Minute walk test (m).
4.
Forest plot of comparison: 1 Tai Chi versus usual care, outcome: 1.4 6‐Minute walk test (m).
1.2.1.2 Shuttle walk tests
One study examined changes in functional capacity using both the incremental shuttle walk test (ISWT) and the endurance shuttle walk test (ESWT) (Leung 2013) involving 38 participants (out of 42 who originally joined the study). No significant effect was evident in the Tai Chi group in ISWT (MD 2 metres, 95% CI ‐95.26 to 99.26 metres) (Analysis 1.5), but a significant effect of Tai Chi was seen by an MD of 373 seconds (95% CI 135.42 to 610.58 seconds) in ESWT (Analysis 1.6) when compared with post‐programme data from the control group.
1.5. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 5 Incremental shuttle walk test (m).
1.6. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 6 Endurance shuttle walk test (s).
1.2.2 Cardiopulmonary exercise tests ‐ exercise duration and oxygen consumption
One study (Yeh 2010), with 10 participants, examined changes in exercise capacity by ergometry testing (i.e. five participants in each of the Tai Chi and control groups). Comparison of post‐programme data revealed an insignificant MD in exercise duration in the symptom‐limited ergometry test by one minute (95% CI ‐1.1 to 3.1 minutes) (Analysis 1.7), along with an insignificant MD in oxygen consumption by ‐2 mL/kg/min (95% CI ‐5.76 to 1.76 mL/kg/min) (Analysis 1.8).
1.7. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 7 Exercise duration (symptom limited ergometry test) (min).
1.8. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 8 Peak VO2 uptake (mL/kg/min).
1.3 Secondary outcome: pulmonary function
Eleven studies examined post‐programme pulmonary function by presenting different parameters as shown below.
1.3.1 Forced expiratory flow volume in one second (FEV1)
Four studies (Zhou 2009; Chan 2010; Niu 2014; Zhang 2014) reported actual values of FEV1 in litres by comparing post‐programme data from a total of 570 participants. The combined MD from the four studies (n = 258) was 0.11 L (95% CI 0.02 to 0.20, P value = 0.01). No subgroup differences between short‐ and long‐term effects were evident (P value = 0.97; Analysis 1.9).
1.9. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 9 FEV1 (L).
1.3.2 Forced vital capacity (FVC)
Two studies (Zhou 2009; Chan 2010) reported FVC (L), with a total of 183 participants ‐ 93 and 90 participants in Tai Chi and control groups, respectively. The combined MD from the two studies was 0.26 L (95% CI ‐0.01 to 0.52 L, P value = 0.06). Significant subgroup differences between short‐ and long‐term effects were evident (P value = 0.03; Analysis 1.10).
1.10. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 10 FVC (L).
1.3.3 Ratio of FEV1/FVC
We pooled data from three studies (Yeh 2010; Du 2013; Zhang 2014) to compare the ratio between FEV1 and FVC (in %) (n = 120); the combined MD was 5.35% (95% CI ‐0.63 to 11.64%, P value = 0.08). No subgroup differences between short‐ and long‐term effects were evident (P value = 0.06; Analysis 1.11).
1.11. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 11 FEV1/FVC (%).
1.3.4 Percentage predicted FEV1 (% predicted FEV1)
Five studies evaluated differences in percentage predicted values of FEV1 (i.e. % predicted FEV1) in a sample of 549 participants. The combined MD from five studies (n = 217) (Zhou 2009; Du 2013; Niu 2014; Wang 2014; Zhang 2014) was 1.33% (95% CI ‐4.25 to 6.91%, P value = 0.64). No subgroup differences between short‐ and long‐term effects were evident (P value = 0.91; Analysis 1.12).
1.12. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 12 % predicted FEV1 (%).
1.3.5 Other pulmonary function parameters
Zhou and co‐workers (Zhou 2009) examined changes in vital capacity (VC, L) among 46 participants (i.e. 23 participants in each of the Tai Chi and control groups) and observed an MD of 0.14 L (95% CI 0.07 to 0.21 L) (Analysis 1.13). One study evaluated changes in functional residual capacity (FRC, %) in 10 participants (i.e. five participants in each of the Tai Chi and control groups) (Yeh 2010) and reported an insignificant MD of ‐19% (95% CI ‐39.44 to 1.44%) (Analysis 1.14). Two studies examined changes in maximal voluntary ventilation (MVV, %) with 120 participants (i.e. 59 and 61 participants in Tai Chi and control groups, respectively) (Zhou 2009; Du 2013) and reported an MD of 6.12% (95% CI 3.91 to 8.33%) (Analysis 1.15). One study, involving 74 participants with programme duration of three months or less, reported an MD of 5.27% (95% CI 2.74 to 7.8%) (Du 2013); the other study, involving 46 participants with a programme duration longer than three months, reported an MD of 8.89% (95% CI 4.33 to 13.45%) (Zhou 2009). No subgroup differences were evident (P value = 0.17).
1.13. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 13 VC (L).
1.14. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 14 FRC (%).
1.15. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 15 MVV (%).
1.4 Secondary outcome: quality of life
1.4.1 SGRQ
Three studies (Chan 2010; Du 2013; Wang 2014) used the SGRQ to evaluate quality of life for participants; the combined MD for SGRQ ‐ Total, Activity, Symptoms and Impact scores ‐ was ‐7.85 units (95% CI ‐16.53 to 0.83, P value = 0.08; Analysis 1.16), ‐13.97 units (95% CI ‐30.16 to 2.22, P value = 0.09; Analysis 1.17), ‐4.48 units (95% CI ‐14.35 to 5.39, P value = 0.37; Analysis 1.18) and ‐7.06 units (95% CI ‐18.80 to 4.68, P value = 0.24; Analysis 1.19), respectively.
1.16. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 16 SGRQ ‐ Total score.
1.17. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 17 SGRQ ‐ Activity.
1.18. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 18 SGRQ ‐ Symptoms.
1.19. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 19 SGRQ ‐ Impact.
1.4.2 CRQ
Two studies used CRQ to evaluate changes in quality of life (Yeh 2010; Leung 2013), with a total of 24 participants in the Tai Chi group and 24 in the control group. The MD in total score was 0.41 units (95% CI ‐0.54 to 1.35 units, P value = 0.4; Analysis 1.20). For component scores, a significant difference in mastery was observed between groups ‐ 0.89 units (95% CI 0.30 to 1.47, P value = 0.003; Analysis 1.21), along with no significant differences in other scores, namely, emotion (MD 0.7 unit, 95% CI ‐0.06 to 1.46 units, P value = 0.07; Analysis 1.22), dyspnoea (MD 0.05 unit, 95% CI ‐1.32 to 1.42 units, P value = 0.94; Analysis 1.23) and fatigue (MD 0.37 unit, 95% CI ‐1.20 to 1.93 units, P value = 0.65; Analysis 1.24).
1.20. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 20 CRQ ‐ Total.
1.21. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 21 CRQ ‐ Mastery.
1.22. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 22 CRQ ‐ Emotion.
1.23. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 23 CRQ ‐ Dyspnoea.
1.24. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 24 CRQ ‐ Fatigue.
1.5 Secondary outcome: muscle strength
One study examined quadriceps strength with the isokinetic machine set at 90 degrees/s in a sample of 38 participants (19 participants in each of the Tai Chi and control groups) (Leung 2013). An MD of ‐12 Newton (95% CI ‐42.55 to 18.55 Newton, P value = 0.44; Analysis 1.25) in left quadriceps muscle strength was reported, along with an MD of 0 Newton (95% CI ‐32.19 to 32.19 Newton, P value = 1; Analysis 1.26) in right quadriceps muscle strength.
1.25. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 25 Quadriceps muscle strength (left).
1.26. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 26 Quadriceps muscle (right).
1.6 Secondary outcome: balance
One study evaluated the balance status of participants by assessing functional reach and body sway (in the dimension of anterior‐posterior, i.e. AP, or medial‐lateral, i.e. ML) in semi tandem stand and body sway in side‐by‐side stand for a sample of 38 participants (19 participants in each of the Tai Chi and control groups) (Leung 2013). An MD in improvement in functional reach of 6 cm (95% CI 1.22 to 10.78 cm, P value = 0.01) was found in the Tai Chi group (Analysis 1.27), along with an MD of ‐6.9 mm (95% CI ‐15.01 to 1.21 mm, P value = 0.1) in AP sway (Analysis 1.28) and ‐15 mm (95% CI ‐21.25 to ‐8.75 mm, P value < 0.01) in ML sway (Analysis 1.29) in semi tandem stand. A similar effect was seen in side‐by‐side stand, with an MD of ‐4.8 mm (95% CI ‐9.58 to ‐0.02 mm, P value = 0.05) in AP sway (Analysis 1.30) and ‐8.8 mm (95% CI ‐15.05 to ‐2.55 mm, P value = 0.006) in ML sway (Analysis 1.31).
1.27. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 27 Functional reach (cm).
1.28. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 28 Semi tandem stand (AP sway).
1.29. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 29 Semi tandem stand (ML sway).
1.30. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 30 Side‐by‐side stand (AP away).
1.31. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 31 Side‐by‐side stand (ML sway).
1.7 Secondary outcome: BODE Index
Two studies (Du 2013; Wang 2014) examined the BODE Index, that is, the Body mass index (BMI), airflow Obstruction, Dyspnoea and Exercise capacity index, involving a total of 96 participants (i.e. 47 and 49 participants in Tai Chi and control groups, respectively). These studies reported a significant combined MD of ‐1.04 unit (95% CI ‐1.69 to ‐0.40 unit, P value < 0.01; Analysis 1.32). However, the two studies were highly heterogeneous, with I2 = 95%, as one favoured the intervention (Du 2013) and the other favoured the control (Wang 2014).
1.32. Analysis.
Comparison 1 Tai Chi versus usual care, Outcome 32 BODE Index.
1.8 Secondary outcome: adverse events
No included studies reported any adverse events.
2. Tai Chi and breathing exercise versus breathing exercise
2.1 Primary outcome: level of dyspnoea
Only one study (Yao 2004) examined the level of dyspnoea by using the Borg Scale score and reported an MD as ‐1.30 units (95% CI ‐2.02 to ‐0.58 units; Analysis 2.1).
2.1. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 1 Dyspnoea (Borg).
2.2. Primary outcome: functional capacity or aerobic capacity
One study examined the functional capacity of participants by using the 6MWT (Zhang 2012) and reported an MD of 22 metres, with 95% CI ‐6.0 to 50.0 metres (Analysis 2.2; Figure 5).
2.2. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 2 6‐Minute walk test (m).
5.
Forest plot of comparison: 2 Tai Chi and breathing exercise versus breathing exercise, outcome: 2.2 6‐Minute walk test (m).
2.3 Secondary outcome: pulmonary function
2.3.1 Forced expiratory flow volume in the first second (FEV1)
Two studies (Li 2012; Zhang 2012), including 120 participants, reported actual values of FEV1 in litres by comparing post‐programme data; the combined MD was 0 L with 95% CI ‐0.11 to 0.12 L (P value = 0.97; Analysis 2.3).
2.3. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 3 FEV1 (L).
2.3.2 Forced vital capacity (FVC)
One study reported FVC (L) with a total of 60 participants (Li 2012); the MD between intervention and control groups was 0.05 L, with 95% CI ‐0.33 to 0.43 L (P value = 0.8; Analysis 2.4).
2.4. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 4 FVC (L).
2.3.3 Ratio of FEV1/FVC
We pooled data from three studies, with 200 participants, to compare the ratio between FEV1 and FVC (in %) (Yao 2004; Li 2012; Zhang 2012); the pooled MD was ‐0.15 L with 95% CI ‐1.55 to 1.24 L (P value = 0.83) and no subgroup differences between short‐ and long‐term effects (P value = 0.79; Analysis 2.5).
2.5. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 5 FEV1/FVC (%).
2.3.4 Percentage predicted FEV1 (% predicted FEV1)
The combined MD from two studies (n = 140) (Yao 2004; Zhang 2012) was 0.96% (95% CI ‐2.36 to 4.27%, P value = 0.57) with no subgroup differences between short‐ and long‐term effects (P value = 0.62; Analysis 2.6).
2.6. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 6 % predicted FEV1 (%).
2.3.5 Other pulmonary function parameters
We found no studies exploring these outcomes.
2.4 Secondary outcome: quality of life
Two studies (Li 2012; Zhang 2012), involving 120 participants, evaluated quality of life using SGRQ; the MD for Total, Activity, Symptoms and Impact scores from the two studies was ‐1.32 units (95% CI ‐5.92 to 3.28, P value = 0.57; Analysis 2.7), ‐0.79 units (95% CI ‐5.25 to 3.68, P value = 0.73; Analysis 2.8), ‐2.91 units (95% CI ‐7.12 to 1.31, P value = 0.18; Analysis 2.9) and 0.46 unit (95% CI ‐7.03 to 7.94, P value = 0.9; Analysis 2.10), respectively.
2.7. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 7 SGRQ ‐ Total score.
2.8. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 8 SGRQ ‐ Activity.
2.9. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 9 SGRQ ‐ Symptoms.
2.10. Analysis.
Comparison 2 Tai Chi and breathing exercise versus breathing exercise, Outcome 10 SGRQ ‐ Impact.
No study in this type of comparison reported outcomes on muscle strength, balance, BODE Index and adverse events.
3. Tai Chi and exercise versus exercise
Only one study (Ng 2014) examined differences between Tai Chi and exercise versus exercise alone (n = 192).
3.1 Primary outcome: level of dyspnoea
We found no studies exploring this outcome.
3.2 Primary outcome: functional capacity or aerobic capacity
Ng 2014 used the 6MWT to examine the functional capacity of participants and reported an MD of 1.5 metres (95% CI ‐18.76 to 21.76 metres; Analysis 3.1; Figure 6).
3.1. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 1 6‐Minute walk test (m).
6.
Forest plot of comparison: 3 Tai Chi and exercise versus exercise, outcome: 3.1 6‐Minute walk test (m).
3.3 Secondary outcome: pulmonary function
One study (Ng 2014) examined pulmonary function by measuring FEV1, FVC and % predicted FEV1. All outcomes showed insignificant between‐group differences in pre‐programme data except for FEV1. Thus, post‐programme data for FEV1 have been removed from the final analysis in this section. Comparison of FVC and % predicted FEV1 revealed an insignificant MD of 0.13 L (95% CI ‐0.11 to 0.37 L; Analysis 3.2) and 5.33 L (95% CI ‐2.20 to 12.86 L; Analysis 3.3), respectively.
3.2. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 2 % predicted FEV1 (%).
3.3. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 3 FVC (L).
3.4 Secondary outcome: quality of life
One study (Ng 2014) evaluated quality of life using SGRQ and reported an MD for Total, Activity, Symptoms and Impact scores of ‐3.76 units (95% CI ‐8.72 to 1.20 units; Analysis 3.4), ‐5.81 units (95% CI ‐12.32 to 0.70 units; Analysis 3.5), ‐3.21 units (95% CI ‐8.69 to 2.27 units; Analysis 3.6) and ‐2.75 units (95% CI ‐7.75 to 2.25 units; Analysis 3.7), respectively.
3.4. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 4 SGRQ ‐ Total score.
3.5. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 5 SGRQ ‐ Activity.
3.6. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 6 SGRQ ‐ Symptoms.
3.7. Analysis.
Comparison 3 Tai Chi and exercise versus exercise, Outcome 7 SGRQ ‐ Impact.
No study in this type of comparison reported outcomes on muscle strength, balance, BODE Index and adverse events.
4. Sensitivity analysis
Standard deviations for the six‐minute walk were much smaller in Du 2013 than in other studies. We contacted study authors for clarification but received no replies. Therefore, we conducted a sensitivity analysis by excluding results from this study; the updated result of MD 38.49 metres with 95% CI 22.14 to 54.85 metres is larger than previous findings (29.64 meters), but the two confidence intervals do overlap.
Discussion
Summary of main results
In this review, we sought to explore evidence from randomised controlled trials (RCTs) to support or dispute whether Tai Chi practice is effective in ameliorating dyspnoea and facilitating exercise capacity, as well as to show its impact on psychosocial functions among people with chronic obstructive pulmonary disease (COPD). We included 12 studies, regardless of language, which compared the immediate effects of a Tai Chi programme (Tai Chi alone or in addition to another intervention) versus a control (i.e. usual care or other interventions identical to that adopted in the Tai Chi group, such as breathing exercise or exercise). This systematic review involves a total of 984 participants. Of these, 811 were randomly allocated to a Tai Chi group (with Tai Chi alone or added to another intervention) or a control group (i.e. usual care or other interventions identical to those adopted in the Tai Chi group) for minimum training of six weeks (Ng 2014) to maximum training of one year (Zhang 2012; Zhang 2014). The quality of evidence for the main outcomes of interest ranged from very low to moderate (Table 1; Table 2; Table 3).
When Tai Chi was compared with usual care only, post‐programme data revealed that the Tai Chi group attained better functional capacity (as reflected by the lengthened six‐minute walk test (6MWT)) and improved pulmonary function (as reflected by the level of forced expiratory volume in one second (FEV1)) when compared with the control group given usual care only. For quality of life, we observed no significant between‐group differences in total scores and domain scores for health‐related quality of life in three studies using St George's Respiratory Questionnaire (SGRQ) and in two studies using the Chronic Respiratory Questionnaire (CRQ), although we noted a better domain score for mastery of CRQ in the Tai Chi group (mean difference (MD) 0.89 unit, 95% confidence interval (CI) 0.31 to 1.47 unit; Analysis 1.21). Given the very low to moderate level of the quality of evidence, participants in the Tai Chi group, when compared with those in the usual care alone group, may have showed better functional capacity and pulmonary function.
However, comparison of Tai Chi in addition to other interventions (i.e. breathing exercise or exercise) revealed no between‐group differences in post‐programme data for level of dyspnoea and functional or psychosocial outcomes. Current data suggest that Tai Chi does not show a superior effect to other interventions and shows no additional effects when used with other interventions in terms of promoting physical and psychosocial functions.
Evidence from one study suggests that a Tai Chi programme may improve endurance capacity, with low quality of evidence noted in people with COPD. However, additional studies are needed to examine these effects. Currently, available data are insufficient for evaluation of the impact of Tai Chi on maximal exercise capacity, dynamic balance and muscle strength in people with COPD. In addition, evidence is insufficient to show whether Tai Chi style or duration of a Tai Chi programme will affect overall outcomes in COPD.
Overall completeness and applicability of evidence
The studies included in this review recruited participants with mild to very severe forms of COPD according to the Global Initiative for Chronic Lung Disease (GOLD) classification (Vestbo 2013) or that of the Chinese Thoracic Society (Chinese Thoracic Society 2013). Only one study specified recruiting people with a very severe form of COPD (Ng 2014). As disease severity may be one potential factor affecting response to treatment outcomes, we originally planned to perform a subgroup analysis to examine the impact of disease severity. However, in the light of overlapping of disease severity as reported in different studies, we found that the subgroup analysis based on disease severity was not feasible. When the results of individual studies were reviewed, differences in magnitude change for each of the outcome measures among studies with different levels of severity recruited were not apparent. Thus, additional studies are needed to evaluate the treatment effect in relation to disease severity. Lack of adverse events in any of the included studies despite various severity levels reported among people with COPD may imply that Tai Chi is safe to practise, and that it could have potential beneficial effects in this disease population.
As discussed, exertional dyspnoea is one of the major complaints among people with COPD that may prevent physical activity, thereby reducing their level of functional capacity. In this review, we observed a trend toward reduced dyspnoeic levels in modified Borg Scale scores (Yao 2004; Chan 2010) and in other dyspnoeic parameters (i.e. MMRC) (Du 2013; Wang 2014). However, pooled results suggest that evidence was insufficient to show beneficial effects of Tai Chi in reducing the level of dyspnoea.
At similar baseline levels, the Tai Chi group (when compared with the group given usual care alone) in six of the included studies showed a significantly longer 6MWT during post‐programme measurement than was reported in the control group, by 29.64 metres (95% CI 10.52 to 48.77 metres; Analysis 1.4). Such a difference falls within the range of minimal clinically important differences (MCIDs) (i.e. 25 to 35 metres) in 6MWT suggested for people with COPD (Holland 2013). In addition, one study (Leung 2013) evaluated the change in endurance shuttle walk test (ESWT) and reported an increase of 373 seconds. This change was greater than the MCID reported in ESWT by 65 seconds after use of bronchodilator (Pepin 2011), or by 165 seconds after an eight‐ to 10‐week ground walking programme (Ng 2013). These findings suggest that a Tai Chi programme may be beneficial in promoting functional capacity. However, available data were insufficient to show changes in aerobic capacity as reflected by changes in the incremental shuttle walk test (ISWT) (Leung 2013) and in peak oxygen consumption (Yeh 2010) probably associated with the nature of low and moderate intensity of Tai Chi and the small sample size used (n = 38 in Leung 2013 and n = 10 in Yeh 2010). In contrast, when comparing the additional effects of Tai Chi on top of other interventions (i.e. breathing exercise (Zhang 2012) or exercise (Ng 2014)) versus other interventions, we found no between‐group differences in 6MWT, suggesting that Tai Chi did not show a superior effect nor an additional effect when provided with other interventions to induce extra health benefits.
As Tai Chi involves a series of rhythmic movements conducted in a semi squatting position, it may promote muscle endurance after training, thereby prolonging exercise tolerance as reflected by longer distance capacity in 6MWT and longer duration in ESWT. However, only one study (Leung 2013) examined effects of Tai Chi on other physical functions and demonstrated a significant improvement in dynamic balance but an insignificant change in muscle strength. Thus, currently available evidence is insufficient to prove the effect of Tai Chi in this area among people with COPD.
Pooled values of post‐programme FEV1 in the Tai Chi group were significantly greater than those in the control group given usual care only by 0.11 L (95% CI 0.02 to 0.20 L; Analysis 1.9) in four studies (Zhou 2009; Chan 2010; Niu 2014; Zhang 2014). As Tai Chi incorporates deep breathing into a body movement, this improvement may be associated with the repetitive deep breathing training provided during the practice of Tai Chi. The commonly reported MCID of FEV1 in a clinical trial ranged from 0.045 to 0.18 L (Donohue 2005). Although the difference appears to fall within the reported range, interpretation of pulmonary function (e.g. FEV1) should be reviewed carefully, as the MCID reported could be influenced by the baseline level of FEV1, diurnal variability, decline in baseline over time, baseline reversibility and repeatability of the data (Donohue 2005). As discussed, when Tai Chi and breathing exercise was compared with breathing exercise alone (Li 2012; Zhang 2012), we observed no between‐group differences in post‐programme data (MD 0 L, 95% CI ‐0.11 to 0.12 L). Such findings could probably be explained by the similarity of breathing components involved in both Tai Chi and the corresponding control. Specifically, the Tai Chi group incorporated deep breathing into each form of body movement, and the breathing exercise group emphasised deep breathing exercise and/or pursed‐lip breathing as the routine control training (i.e. breathing exercise). Hence, similar effects on promoting pulmonary function could be induced. Additional studies are needed to support this hypothesis.
Quality of life is another important domain of disease management for people with COPD. Most studies used the health‐related quality of life (HRQoL) questionnaire, which consisted of individual component scores and total score, to evaluate disease impact on overall quality of life. In this review, six studies adopted SGRQ and two used CRQ to evaluate HRQoL. Of these, three studies compared effects of a Tai Chi programme versus usual care (Chan 2010; Du 2013; Wang 2014), and one study compared effects of Tai Chi and exercise (in pulmonary rehabilitation) versus exercise (in pulmonary rehabilitation) (Ng 2014). This demonstrated an insignificant improving trend, while minimal or even no changes were observed when Tai Chi and breathing exercise were compared against control adopting breathing exercises (Li 2012; Zhang 2012). Two studies used CRQ to evaluate the change in quality of life (Yeh 2010; Leung 2013) in people receiving Tai Chi against people receiving usual care. A significant between‐group difference was demonstrated in the component scores of mastery by 0.89 unit (95% CI 0.30 to 1.47 units), which was greater than the reported MCID of 0.5 unit in people with COPD (Schunemann 2005). Pooled data may be related to higher weighting (85.7%) in one study, which involved a greater number of participants (i.e. 19 participants per group) (Leung 2013) than the other (i.e. five participants per group) (Yeh 2010). Thus, the conclusion in CRQ is mainly related to the findings of one study, and interpretation should be carefully reviewed.
The BODE Index predicts risk of mortality in people with COPD (Celli 2004). A one‐point increase may increase the hazard ratio to 1.34 for all cause‐mortality and to 1.62 for respiratory‐related mortality (Celli 2004). In this review, two studies (Du 2013; Wang 2014) demonstrated significantly lower post‐programme data in the Tai Chi group by 1.04 points (95% CI ‐1.69 to ‐0.40 point). However, high heterogeneity (I2 = 95%) was reported because one study favoured Tai Chi (Du 2013), while the other favoured control (Wang 2014) with similar weightings. Thus, interpretation of these findings may confer potential bias.
Variation in Tai Chi training duration and protocol is another factor that may influence the results. All included studies adopted the practice of Tai Chi for 30 minutes or longer per session. The study that compared effects of Tai Chi and exercise (i.e. 40 minutes of aerobic exercise in pulmonary rehabilitation) against exercise (i.e. 40 minutes of aerobic exercise in pulmonary rehabilitation) (Ng 2014) reported that Tai Chi practice lasted for 15 minutes and emphasised repeating the practice of five of the whole 21 forms of short‐form Sun‐style Tai Chi. Hence, such a difference in practice duration and in the number of forms practiced may explain the non‐superiority or the additional effect observed. Given the limited studies retrieved, the impact of training protocol variation on outcomes could not be analysed.
Apparently, people in the Tai Chi group demonstrated significantly better functional capacity and pulmonary function, although with very low to moderate quality of evidence. When outcomes are interpreted, other factors may be found to influence the results. As discussed in the Background section, different styles and numbers of forms of Tai Chi may affect the amount of energy expended during practice (Lan 2001). Thus, different styles of Tai Chi training may yield varied outcomes (i.e. styles that involve a greater angle of squatting and a greater number of forms may involve greater energy expenditure, which may trigger a relatively larger cardiopulmonary and/or neuromuscular effect and in turn may induce a better therapeutic response). Thus, these differences may add bias to the current interpretation of results. In this review, practice styles and numbers of forms reported in the included studies were scattered and diverse; this made it not feasible to perform subgroup analyses based on styles and numbers of forms of Tai Chi. Future studies are needed to explore these topics.
Quality of the evidence
The overall risk of bias of studies included in this review ranged from very low to moderate. Four studies (Yeh 2010; Leung 2013; Ng 2014; Niu 2014) had four or more categories ranked as having low risk of bias; four studies were rated as having one or two categories of low risk (Chan 2010; Li 2012; Du 2013; Zhang 2014); and the remaining studies provided insufficient information and therefore were graded as having unclear risk (Yao 2004; Zhou 2009; Zhang 2012; Wang 2014). All studies reported the use of randomisation, but eight reported the randomisation methods used (Chan 2010; Yeh 2010; Li 2012; Du 2013; Leung 2013; Ng 2014; Niu 2014; Zhang 2014). Three of these studies were graded as having low risk of allocation concealment (Leung 2013; Ng 2014; Niu 2014), and the others had unclear risk because of insufficient data reporting. As Tai Chi is a physical exercise that consists of different forms and postures, participants could not be blinded about group allocation; therefore, blinding of participants is not practical. Lack of group blinding of participants may influence the performance of participants during post‐programme assessment, leading to performance bias. Thus, all studies were graded as having 'high risk' in this category. Half of the studies reported blinded assessors of outcome measures (Chan 2010; Yeh 2010; Du 2013; Leung 2013; Ng 2014; Niu 2014). The overall dropout rate ranged from 2.5% to 28.1%. Three studies reported use of intention‐to‐treat (ITT) analysis (Chan 2010; Yeh 2010; Ng 2014), while other studies used per‐protocol analysis or did not mention the number of participants who completed the trial. High dropout rates may also have influenced overall effects. Among the 12 included studies, three studies had pre‐registered a protocol and were then graded as having low risk in the categories of selective reporting. More than half of the included studies were written in Chinese and reported insufficient information;therefore, they were graded as having unclear or high risk of bias.
The overall quality of evidence for the main outcomes of interest ranged from very low to moderate, with details listed in Table 1 for the comparison between Tai Chi and usual care; in Table 2 for the comparison of Tai Chi and breathing exercise versus breathing exercise; and in Table 3 for the comparison of Tai Chi and exercise (in pulmonary rehabilitation) versus exercise (in pulmonary rehabilitation). We downgraded most of the outcomes because of performance bias in relation to the un‐blinding of participants and/or outcome assessors; selection bias due to inadequate information on random sequence generation or concealment allocation; and imprecision in relation to a small sample size. We downgraded few outcomes as the result of inconsistency in relation to moderate heterogeneity. Thus, interpretation of pooled findings of this review and its included studies should be considered carefully because of potential risks of bias.
Potential biases in the review process
In this review, we followed our pre‐defined protocol (Ngai 2012) with one minor alteration (see Differences between protocol and review) and included all studies regardless of language of publication. We compared Tai Chi alone or in addition to another intervention versus control (usual care or another intervention identical to Tai Chi) to examine effects of Tai Chi and the superiority of its effects when compared with other interventions, or its additional effects alongside other interventions (i.e. breathing exercise or exercise). Most studies included some of our pre‐defined outcome measures as their outcomes of interest. Thus, in the light of the limited number of studies (i.e. fewer than 10 studies for each outcome measure), we did not prepare a funnel plot analysis to explore potential publication bias. In addition, not all of the authors of included studies could be contacted because incomplete contact details were provided in some of the Chinese papers. The limited information available may have affected grading of risk of bias in this review. All studies reported no significant between‐group differences in all pre‐programme data, except Ng 2014, which reported a significant baseline pre‐programme difference in FEV1 and FVC, which may have affected the results of pooled data on FEV1 and FVC (as listed in the pulmonary function section of the secondary outcomes of this review). Thus, we removed from the final pooled analysis data on pulmonary function as reported by Ng and colleagues (Ng 2014).
Agreements and disagreements with other studies or reviews
Currently, two systematic reviews and meta‐analytical studies have examined effects of Tai Chi in people with COPD (Yan 2013; Ding 2014). The former review (Yan 2013) included eight studies(four written in English and four in Chinese) that were also included in this current review. The review by Ding 2014 included 10 studies. Of these, only three studies evaluated the effects of Tai Chi (two written in English and one in Chinese ‐ also included in this review), and remaining studies evaluated the use of Qigong. As Tai Chi and Qigong are two different types of interventions, we did not include studies that used Qigong alone. Thus, results as interpreted in this review may be different from the interpretation reported by Ding 2014, and a direct comparison of that review against the current one may not be appropriate.
In accordance with results provided in Yan 2013, this review also showed a significant difference in post‐programme 6MWT between the Tai Chi group and the control group (usual care) by 29.64 metres (vs 34.22 metres in Yan's review) and in FEV1 by 0.11 L (vs 0.07 L in Yan 2013). Although we noted a similar improvement trend in reduction of dyspnoea, our findings did not show significant changes, as were reported by Yan 2013, possibly because additional studies were included in this review, data extraction was performed using different methods and three types of data analysis were performed (i.e. Tai Chi vs usual care; Tai Chi in addition to breathing exercise and vs breathing exercise; and Tai Chi in addition to exercise and vs exercise).
In this current review, all included studies reported no significant pre‐programme differences except baseline FEV1 as reported by Ng 2014; thus, we included in the analysis the comparison between Tai Chi and control along with post‐programme data, as suggested in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), while not including data on FEV1. However, for Yan's paper, differences were evident between pre‐ and post‐programme data used in the imputation process to compare effects of Tai Chi and control. Differences in the imputation method used in this meta‐analysis (i.e. post‐programme data compared in this review and increased number of papers reviewed) may explain in part the discrepancies observed for some outcomes.
Authors' conclusions
Implications for practice.
This review presents evidence of low to moderate quality showing effects of a Tai Chi programme on improving functional capacity and pulmonary function in people with COPD when compared with usual care. Effects of a Tai Chi programme on reducing dyspnoea and quality of life remain inconclusive because only limited evidence is available. However, when Tai Chi in addition to another intervention (i.e. breathing exercise or exercise) was compared with another intervention alone (i.e. breathing exercise or exercise), Tai Chi did not show a superior effect when combined with the other intervention nor an additional effect when other interventions were provided to induce additional health benefits.
Tai Chi does not require equipment or a large space during practice. Given its nature of low‐ to moderate‐intensity exercise (Lan 2004), no adverse effects of Tai Chi were reported. Tai Chi may have beneficial effects if introduced as part of a training programme during rehabilitation, and its use may even be extended when it is included as part of a home exercise programme. Effects of programme duration and style of Tai Chi on outcome measures are not evident because only limited evidence is available.
Implications for research.
Different styles and numbers of forms of Tai Chi have been reported to use up different levels of energy (Lan 2001). As a result of the limited number of available articles and the great variety of Tai Chi styles and numbers of forms adopted in the training protocol of reviewed studies, the influence of these on outcome measures could not be compared. In addition, limited evidence shows the long‐term effects of Tai Chi. Thus, additional studies are needed to examine programme duration and long‐term carry‐over effects of the programme. Other factors such as disease severity may also influence treatment outcomes. Thus future studies are needed to explore issues involving a Tai Chi training protocol and disease severity.
Effects of Tai Chi on balance and muscle strength have been extensively reported in other populations. As discussed before, people with COPD have poor balance and impaired muscle strength, related in part to the systemic inflammation and inactivity associated with their condition. Currently, only one study is exploring the effects of Tai Chi in this aspect. Thus, in addition to focusing on measurement of functional capacity, level of dyspnoea and quality of life, future studies should investigate effects of Tai Chi on balance and muscle strength in people with COPD.
Acknowledgements
We would like to thank Dr. Emma Welsh for advice and Ms. Elizabeth Stovold for kind assistance with the literature search during the whole review process, and we extend our sincere thanks to Dr. Anne Holland, who served as Editor for this review and commented critically on review content.
The Background and Methods sections of this review are based on a standard template used by the Cochrane Airways Group.
This project was supported by the National Institute for Health Research (NIHR), via Cochrane Infrastructure funding to the Cochrane Airways Group. The views and opinions expressed therein are those of the review authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, the National Health Service (NHS) or the Department of Health.
Appendices
Appendix 1. Sources and search methods for the Cochrane Airways Group Specialised Register (CAGR)
Electronic searches: core databases
| Database | Frequency of search |
| CENTRAL | Monthly |
| MEDLINE (Ovid) | Weekly |
| EMBASE (Ovid) | Weekly |
| PsycINFO (Ovid) | Monthly |
| CINAHL (EBSCO) | Monthly |
| AMED (EBSCO) | Monthly |
Handsearches: core respiratory conference abstracts
| Conference | Years searched |
| American Academy of Allergy, Asthma and Immunology (AAAAI) | 2001 onwards |
| American Thoracic Society (ATS) | 2001 onwards |
| Asia Pacific Society of Respirology (APSR) | 2004 onwards |
| British Thoracic Society Winter Meeting (BTS) | 2000 onwards |
| Chest Meeting | 2003 onwards |
| European Respiratory Society (ERS) | 1992, 1994, 2000 onwards |
| International Primary Care Respiratory Group Congress (IPCRG) | 2002 onwards |
| Thoracic Society of Australia and New Zealand (TSANZ) | 1999 onwards |
MEDLINE search strategy used to identify trials for the CAGR
COPD search
1. Lung Diseases, Obstructive/
2. exp Pulmonary Disease, Chronic Obstructive/
3. emphysema$.mp.
4. (chronic$ adj3 bronchiti$).mp.
5. (obstruct$ adj3 (pulmonary or lung$ or airway$ or airflow$ or bronch$ or respirat$)).mp.
6. COPD.mp.
7. COAD.mp.
8. COBD.mp.
9. AECB.mp.
10. or/1‐9
Filter to identify RCTs
1. exp "clinical trial [publication type]"/
2. (randomized or randomised).ab,ti.
3. placebo.ab,ti.
4. dt.fs.
5. randomly.ab,ti.
6. trial.ab,ti.
7. groups.ab,ti.
8. or/1‐7
9. Animals/
10. Humans/
11. 9 not (9 and 10)
12. 8 not 11
The MEDLINE strategy and RCT filter are adapted to identify trials in other electronic databases
Appendix 2. Search strategy used to identify relevant trials from the CAGR
#1 MeSH DESCRIPTOR Pulmonary Disease, Chronic Obstructive Explode All
#2 MeSH DESCRIPTOR Bronchitis, Chronic
#3 (obstruct*) near3 (pulmonary or lung* or airway* or airflow* or bronch* or respirat*)
#4 COPD:MISC1
#5 (COPD OR COAD OR COBD):TI,AB,KW
#6 #1 OR #2 OR #3 OR #4 OR #5
#7 MeSH DESCRIPTOR Tai Ji
#8 "Tai Chi"
#9 "T'ai Chi"
#10 Taiji or "tai ji"
#11 taijiquan
#12 "Tai Chih"
#13 #7 or #8 or #9 or #10 or #11 OR #12
#14 #6 and #13
[Note: in search line #4, MISC1 denotes the field in which the reference has been coded for condition, in this case, COPD]
Data and analyses
Comparison 1. Tai Chi versus usual care.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 Dyspnoea (Borg) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 1.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 1.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 2 Dyspnoea (UCSD SOB Questionnaire) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 2.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 2.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 3 Dyspnoea (MMRC) | 2 | 96 | Mean Difference (IV, Random, 95% CI) | ‐0.15 [‐0.56, 0.26] |
| 3.1 Duration ≤ 3 months | 2 | 96 | Mean Difference (IV, Random, 95% CI) | ‐0.15 [‐0.56, 0.26] |
| 3.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 6‐Minute walk test (m) | 6 | 318 | Mean Difference (IV, Random, 95% CI) | 29.64 [10.52, 48.77] |
| 4.1 Duration ≤ 3 months | 4 | 243 | Mean Difference (IV, Random, 95% CI) | 27.71 [4.36, 51.07] |
| 4.2 Duration > 3 months | 2 | 75 | Mean Difference (IV, Random, 95% CI) | 35.97 [1.36, 70.59] |
| 5 Incremental shuttle walk test (m) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 5.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 5.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 6 Endurance shuttle walk test (s) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 6.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 6.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 7 Exercise duration (symptom limited ergometry test) (min) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 7.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 7.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 8 Peak VO2 uptake (mL/kg/min) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 8.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 8.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 9 FEV1 (L) | 4 | 258 | Mean Difference (IV, Fixed, 95% CI) | 0.11 [0.02, 0.20] |
| 9.1 Duration ≤ 3 months | 1 | 137 | Mean Difference (IV, Fixed, 95% CI) | 0.11 [‐0.01, 0.23] |
| 9.2 Duration > 3 months | 3 | 121 | Mean Difference (IV, Fixed, 95% CI) | 0.11 [‐0.01, 0.23] |
| 10 FVC (L) | 2 | 183 | Mean Difference (IV, Random, 95% CI) | 0.26 [‐0.01, 0.52] |
| 10.1 Duration ≤ 3 months | 1 | 137 | Mean Difference (IV, Random, 95% CI) | 0.40 [0.20, 0.60] |
| 10.2 Duration > 3 months | 1 | 46 | Mean Difference (IV, Random, 95% CI) | 0.13 [‐0.01, 0.27] |
| 11 FEV1/FVC (%) | 3 | 120 | Mean Difference (IV, Random, 95% CI) | 5.35 [‐0.93, 11.64] |
| 11.1 Duration ≤ 3 months | 2 | 84 | Mean Difference (IV, Random, 95% CI) | 7.39 [2.77, 12.01] |
| 11.2 Duration > 3 months | 1 | 36 | Mean Difference (IV, Random, 95% CI) | ‐0.61 [‐7.63, 6.41] |
| 12 % predicted FEV1 (%) | 5 | 217 | Mean Difference (IV, Random, 95% CI) | 1.33 [‐4.25, 6.91] |
| 12.1 Duration ≤ 3 months | 2 | 96 | Mean Difference (IV, Random, 95% CI) | 1.07 [‐13.18, 15.32] |
| 12.2 Duration > 3 months | 3 | 121 | Mean Difference (IV, Random, 95% CI) | 0.26 [‐3.13, 3.66] |
| 13 VC (L) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 13.1 Duration ≤ 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 13.2 Duration > 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 14 FRC (%) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 14.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 14.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 15 MVV (%) | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | 6.12 [3.91, 8.33] |
| 15.1 Duration ≤ 3 months | 1 | 74 | Mean Difference (IV, Fixed, 95% CI) | 5.27 [2.74, 7.80] |
| 15.2 Duration > 3 months | 1 | 46 | Mean Difference (IV, Fixed, 95% CI) | 8.89 [4.33, 13.45] |
| 16 SGRQ ‐ Total score | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐7.85 [‐16.53, 0.83] |
| 16.1 Duration ≤ 3 months | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐7.85 [‐16.53, 0.83] |
| 16.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 17 SGRQ ‐ Activity | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐13.97 [‐30.16, 2.22] |
| 17.1 Duration ≤ 3 months | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐13.97 [‐30.16, 2.22] |
| 17.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 18 SGRQ ‐ Symptoms | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐4.48 [‐14.35, 5.39] |
| 18.1 Duration ≤ 3 months | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐4.48 [‐14.35, 5.39] |
| 18.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 19 SGRQ ‐ Impact | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐7.06 [‐18.80, 4.68] |
| 19.1 Duration ≤ 3 months | 3 | 233 | Mean Difference (IV, Random, 95% CI) | ‐7.06 [‐18.80, 4.68] |
| 19.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 20 CRQ ‐ Total | 2 | 48 | Mean Difference (IV, Fixed, 95% CI) | 0.41 [‐0.54, 1.35] |
| 20.1 Duration ≤ 3 months | 2 | 48 | Mean Difference (IV, Fixed, 95% CI) | 0.41 [‐0.54, 1.35] |
| 20.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 21 CRQ ‐ Mastery | 2 | 48 | Mean Difference (IV, Fixed, 95% CI) | 0.89 [0.30, 1.47] |
| 21.1 Duration ≤ 3 months | 2 | 48 | Mean Difference (IV, Fixed, 95% CI) | 0.89 [0.30, 1.47] |
| 21.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 22 CRQ ‐ Emotion | 2 | 48 | Mean Difference (IV, Fixed, 95% CI) | 0.70 [‐0.06, 1.46] |
| 22.1 Duration ≤ 3 months | 2 | 48 | Mean Difference (IV, Fixed, 95% CI) | 0.70 [‐0.06, 1.46] |
| 22.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 23 CRQ ‐ Dyspnoea | 2 | 48 | Mean Difference (IV, Random, 95% CI) | 0.05 [‐1.32, 1.42] |
| 23.1 Duration ≤ 3 months | 2 | 48 | Mean Difference (IV, Random, 95% CI) | 0.05 [‐1.32, 1.42] |
| 23.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 24 CRQ ‐ Fatigue | 2 | 48 | Mean Difference (IV, Random, 95% CI) | 0.37 [‐1.20, 1.93] |
| 24.1 Duration ≤ 3 months | 2 | 48 | Mean Difference (IV, Random, 95% CI) | 0.37 [‐1.20, 1.93] |
| 24.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 25 Quadriceps muscle strength (left) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 25.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 25.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 26 Quadriceps muscle (right) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 26.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 26.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 27 Functional reach (cm) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 27.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 27.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 28 Semi tandem stand (AP sway) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 28.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 28.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 29 Semi tandem stand (ML sway) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 29.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 29.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 30 Side‐by‐side stand (AP away) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 30.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 30.2 Duraton > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 31 Side‐by‐side stand (ML sway) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 31.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 31.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 32 BODE Index | 2 | 96 | Mean Difference (IV, Random, 95% CI) | ‐0.99 [‐3.82, 1.83] |
| 32.1 Duration ≤ 3 months | 2 | 96 | Mean Difference (IV, Random, 95% CI) | ‐0.99 [‐3.82, 1.83] |
| 32.2 Duration > 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
Comparison 2. Tai Chi and breathing exercise versus breathing exercise.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 Dyspnoea (Borg) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 1.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 1.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 2 6‐Minute walk test (m) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 2.1 Duration ≤ 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 2.2 Duration > 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 3 FEV1 (L) | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | 0.00 [‐0.11, 0.12] |
| 3.1 Duration ≤ 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 3.2 Duration > 3 months | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | 0.00 [‐0.11, 0.12] |
| 4 FVC (L) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 4.1 Duration ≤ 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 4.2 Duration > 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 5 FEV1/FVC (%) | 3 | 200 | Mean Difference (IV, Fixed, 95% CI) | ‐0.15 [‐1.55, 1.24] |
| 5.1 Duration ≤ 3 months | 1 | 80 | Mean Difference (IV, Fixed, 95% CI) | ‐1.0 [‐7.44, 5.44] |
| 5.2 Duration > 3 months | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐0.11 [‐1.54, 1.32] |
| 6 % predicted FEV1 (%) | 2 | 140 | Mean Difference (IV, Fixed, 95% CI) | 0.96 [‐2.36, 4.27] |
| 6.1 Duration ≤ 3 months | 1 | 80 | Mean Difference (IV, Fixed, 95% CI) | 2.0 [‐3.33, 7.33] |
| 6.2 Duration > 3 months | 1 | 60 | Mean Difference (IV, Fixed, 95% CI) | 0.30 [‐3.93, 4.53] |
| 7 SGRQ ‐ Total score | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐1.32 [‐5.92, 3.28] |
| 7.1 Duration ≤ 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 7.2 Duration > 3 months | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐1.32 [‐5.92, 3.28] |
| 8 SGRQ ‐ Activity | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐0.79 [‐5.25, 3.68] |
| 8.1 Duration ≤ 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 8.2 Duration > 3 months | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐0.79 [‐5.25, 3.68] |
| 9 SGRQ ‐ Symptoms | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐2.91 [‐7.12, 1.31] |
| 9.1 Duration ≤ 3 months | 0 | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 9.2 Duration > 3 months | 2 | 120 | Mean Difference (IV, Fixed, 95% CI) | ‐2.91 [‐7.12, 1.31] |
| 10 SGRQ ‐ Impact | 2 | 120 | Mean Difference (IV, Random, 95% CI) | 0.46 [‐7.03, 7.94] |
| 10.1 Duration ≤ 3 months | 0 | 0 | Mean Difference (IV, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 10.2 Duration > 3 months | 2 | 120 | Mean Difference (IV, Random, 95% CI) | 0.46 [‐7.03, 7.94] |
Comparison 3. Tai Chi and exercise versus exercise.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 6‐Minute walk test (m) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 1.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 1.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 2 % predicted FEV1 (%) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 2.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 2.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 3 FVC (L) | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 3.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 3.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 4 SGRQ ‐ Total score | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 4.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 4.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 5 SGRQ ‐ Activity | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 5.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 5.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 6 SGRQ ‐ Symptoms | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 6.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 6.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 7 SGRQ ‐ Impact | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 7.1 Duration ≤ 3 months | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 7.2 Duration > 3 months | 0 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
Characteristics of studies
Characteristics of included studies [ordered by study ID]
Chan 2010.
| Methods | Randomised controlled trial; 3 parallel groups; 3‐month intervention period | |
| Participants |
|
|
| Interventions |
Other points to note about group activities
Measurement
|
|
| Outcomes |
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "Two hundred and six subjects were recruited and were randomly assigned to one of the three groups, namely Tai Chi Qigong (TCQ) group, exercise group, and control group, as decided by a computer‐generated randomizer" |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "Research assistants for data collection were blind to the study..., inter‐rater reliability test among RAs was conducted in a pilot to ensure consistency in data collection" |
| Incomplete outcome data (attrition bias) All outcomes | High risk |
Overall dropout rate: 23.3% (48 out of 206 participants) TCQ group: 10 participants dropped out (14.3%) Control group: 19 participants dropped out (28.3%) Both groups have similar discontinued reasons listed, including hospital admission, no interest, increased SOB But in TCQ group, joint pain and deceased were other reasons for loss to follow‐up "Intention‐to‐treat approach was used in analysing the data" As the result of high and unbalanced dropout, judged to be at high risk |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration Outcomes were presented in different published papers, i.e. Chan 2010 (presenting data on health‐related quality of life); Chan 2011 (presenting data on lung function and activity level); Chan 2013 (dissertation abstract); Chan 2013 (presenting follow‐up data for Chan 2010); Chan 2013 (presenting follow‐up data for Chan 2011) |
Du 2013.
| Methods | Randomised controlled trial; 3 parallel groups; 12‐week intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "Patients were randomly allocated into Tai Chi group (36 cases), exercise group (38 cases) and control group (38 cases) using random number table" |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "On every assessment day, the spirometry was measured by specific assigned person to reduce the measurement error" "Doctors distributed SGRQ to participants and told them how to complete the questionnaire" "CAT" was interviewed by doctor |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No description nor dropout rate reported |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration found (Outcomes were presented in different published papers) i.e.Du 2013 (presenting data on lung function and exercise tolerance); Du 2013 (presenting data on quality of life and BODE); Du 2014 (presenting data on serum concentration of inflammatory markers); Du 2014 (presenting data on blood gas analysis) |
Leung 2013.
| Methods | Randomised controlled trial; 2 parallel groups; 12‐week intervention period | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "Participants were randomly allocated to a Tai Chi Group (TCG) or a Control Group (CG) via a computerised phone dial‐up system" |
| Allocation concealment (selection bias) | Low risk | "A randomised controlled trial was conducted with concealed allocation" |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "An assessor, blinded to group allocation, performed the outcome measures at the beginning and end of the study" |
| Incomplete outcome data (attrition bias) All outcomes | Low risk |
Overall dropout rate: 9.5% (4 out of 42 participants) TC group: 3 participants dropped out (13.6%) because of exacerbation of COPD (n = 2) and cardiovascular event unrelated to the study (n = 1) Control group: 1 participant dropped out (5%) because of work commitments (n = 1) "Per‐protocol approach was used in analysing the data" |
| Selective reporting (reporting bias) | Low risk | "The trial was registered in Australian New Zealand Clinical Trials Registry ACTRN12608000383369" |
Li 2012.
| Methods | Randomised controlled trial; 2 parallel groups; 36‐week (6‐month) intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Participants were randomly allocated into Observation group (i.e. Tai Chi group) or control group by drawing lots |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No description |
| Incomplete outcome data (attrition bias) All outcomes | Low risk |
Overall dropout rate: 14.3% (10 out of 70 participants) TC group: 5 participants dropped out (14.3%) Control group: 5 participants dropped out (14.3%) Both groups have similar discontinued reasons including loss of follow up and changing of living location "Per‐protocol approach was used in analysing the data" |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration |
Ng 2014.
| Methods | Randomised controlled trial; 2 parallel groups; 6‐week intervention period | |
| Participants |
|
|
| Interventions |
Other points to note about the group activities
Measurement
|
|
| Outcomes |
*Only dyspnoea score taken after 6MWT was reported, no resting dyspnoea score was reported |
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "A research assistant, who was not involved in recruitment, generated 200 random number sequences using Microsoft Excel 2002 for the investigators to randomly allocate patients to two groups" |
| Allocation concealment (selection bias) | Low risk | "The same RA could conceal the allocation sequence with sequentially numbered envelopes. Each participant would receive one envelope and would be opened and allocated to assigned grouping by a different research assistant upon recruitment in baseline visit" |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comments: It is unlikely to blind participants in different intervention groups |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "Research assistants for data collection were blind to the study" |
| Incomplete outcome data (attrition bias) All outcomes | Low risk |
Overall dropout rate: 28.1% (54 out of 192 participants) TC + PRP group: 26 participants dropped out (27.7%) PRP group (control): 28 participants dropped out (28.6%) Both groups have similar discontinued reasons including health problems, hospital admission, no interest, need family members to take them to attend lessons, refuse or deceased "Intention‐to‐treat approach was used in analysing the data" |
| Selective reporting (reporting bias) | Low risk | Trial registration ID: NCT01259245 in clinical.trials.gov |
Niu 2014.
| Methods | Randomised controlled trial; 2 parallel groups; 6‐month intervention period | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "Participants were assigned randomly to two groups: the control and Tai Chi group with 1:1 allocation ratio" "A computer‐generated randomisation algorithm was adopted to generate treatment assignments. There were no restriction on the randomisation" |
| Allocation concealment (selection bias) | Low risk | "A study coordinator generated the random allocation sequence and enrolled participants. The therapists assigned the participants to different interventions" |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | "Patients were blind to the study design. The therapists were not blind to the study" Comments: Although participants did not know the study design, they still knew that they were doing Tai Chi training Therapists were not blinded to the study |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "Researcher for data analysis were blind to the intervention assignments" |
| Incomplete outcome data (attrition bias) All outcomes | Low risk |
Overall dropout rate: 2.5% (1 out of 40 participants) TC group: no participants dropped out (0%) Control group: 1 participant dropped out (2.5%) when deceased "Per‐protocol approach was used in analysing the data" |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration |
Wang 2014.
| Methods | Randomised controlled trial; 2 parallel groups; 8‐week intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | "Patients were randomly allocated into 2 groups, each group has 12 cases" Comment: method not reported |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No description |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No description nor dropout rate reported |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration |
Yao 2004.
| Methods | Randomised controlled trial; 2 parallel groups; 12‐week (3‐month) intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | "80 participants were randomly divided into control and training group" Comment: Method not reported |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No description nor dropout rate reported |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No dropout rate reported |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration |
Yeh 2010.
| Methods | Randomised controlled trial; 2 parallel groups; 12‐week intervention period | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "We used a computer‐generated randomization algorithm to generate treatment assignments" |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were unlikely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "Cardiopulmonary tests and functional assessments were performed by staff blinded to subject assignment" |
| Incomplete outcome data (attrition bias) All outcomes | Low risk |
Overall dropout rate: 10% (1 out of 10 participants) TC group: 1 participant dropped out (20%) because of poor adherence related to family medical circumstance unrelated to the study Control group: no participant dropped out (0%) "Intention‐to‐treat approach was used in analysing the data" |
| Selective reporting (reporting bias) | Low risk | Trial registry found in Clinicaltrial.gov (Trial ID: NCT01007903) |
Zhang 2012.
| Methods | Randomised controlled trial; 3 parallel groups; 12‐month intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | "Participants were randomly allocated into 3 groups of A, B and C" Comment: Method not reported |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No description |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No description nor dropout rate reported |
| Selective reporting (reporting bias) | Unclear risk | No protocol or trial registration |
Zhang 2014.
| Methods | Randomised controlled trial; 4 parallel groups; 12‐month intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "Patients were randomly allocated into Tai Chi group, Purse‐lip breathing group, combination of Tai Chi and Purse‐lip breathing group and control group by random number" |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No description |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No description nor dropout rate reported |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration |
Zhou 2009.
| Methods | Randomised controlled trial; 2 parallel groups; 16‐week intervention period (original text in Chinese) | |
| Participants |
|
|
| Interventions |
|
|
| Outcomes |
Measurement
|
|
| Notes |
Funding source:
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | "randomly allocated to equal number of patients in control and intervention group" Comment: method not reported |
| Allocation concealment (selection bias) | Unclear risk | No description |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: Participants were not likely to be blinded to the intervention assigned |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No description nor dropout rate reported |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No dropout rate reported |
| Selective reporting (reporting bias) | Unclear risk | No protocol nor trial registration |
6MWT = 6‐minute walk test; AECOPD = acute exacerbation of COPD; BMI = body mass index; BPM = beat per minute; COPD = chronic obstructive pulmonary disease; CRQ = Chronic Respiratory Disease Questionnaire ESWT = Endurance shuttle walk test; FEV1 = Forced expiratory volume in 1 second; FRC = Functional residual capacity; FVC = Forced vital capacity; HADS = Hospital Anxiety and Depression scale; MPPB = Modified Physical Performance Battery Test; MVV = Maximal Voluntary Ventilation; PaO2 = partial pressure of oxygen; PaCO2 = partial pressure of carbon dioxide; % pred FEV1 = percentage of predicted FEV1; PRP = Pulmonary Rehabilitation Program; SCL‐90 = Symptom checklist‐90; SGRQ‐HKC = St George's respiratory questionnaire Hong Kong Chinese version; SSTC = Short form Sun‐Style Tai Chi; TCQ = Tai Chi Qigong; VC = Vital capacity
Characteristics of excluded studies [ordered by year of study]
| Study | Reason for exclusion |
|---|---|
| Kaminsky 2011 | Not a randomised controlled trial (reported in abstract) |
| Shi 2012 | Not a randomised controlled trial |
| Gu 2012 | Not a randomised controlled trial |
| Guo 2013 | Abstract: not a training programme |
Differences between protocol and review
Regarding imputation of data, review authors compared final measurements as reported by included RCTs according to the imputation method suggested in Chapter 16.1.3.2 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
In our original protocol, we aimed to compare the effects of Tai Chi or Tai Chi in addition to another intervention versus a control. Given the varied nature of "other interventions", i.e. breathing exercise or aerobic exercise, we summarised the types of other interventions and split the analysis into three parts ‐ Tai Chi against control (i.e. usual care); Tai Chi and breathing exercise against control (i.e. breathing exercise); and Tai Chi and exercise against control (i.e. exercise) ‐ in the final analysis for fair comparison of the effects of Tai Chi and determination of whether Tai Chi has a superiority effect over other interventions, or whether Tai Chi and other interventions have additional effects versus other interventions alone.
The BODE Index and the number of adverse effects were added as outcomes in this full review. In the original review, we proposed to use disease severity and different styles of Tai Chi in performing the subgroup analysis. However, the range of disease severity included in the reviewed studies was diverse, and review authors agreed that this may not be an effective way to evaluate heterogeneity of study results. In addition, we did not compare the effects of different Tai Chi styles on outcome measures because a great variety of styles and numbers of forms of Tai Chi have been adopted in different studies. Instead, review authors added programme duration (≤ 3 months and > 3 months) for subgroup analysis to evaluate the potential heterogeneity of results.
Contributions of authors
All review authors (Shirley Ngai (SN), Alice Jones (AJ), Wilson Tam (WT)) contributed to the writing of this systematic review for publication. SN and WT screened studies and extracted data. SN and WT conducted the data analysis. All review authors were involved in writing, proofreading and approving the final review for publication.
Sources of support
Internal sources
The authors declare that no such funding was received for this systematic review, Other.
External sources
The authors declare that no such funding was received for this systematic review, Other.
Declarations of interest
None known.
New
References
References to studies included in this review
Chan 2010 {published data only}
- Chan AWK, Lee A, Lee DTF, Sit JWH, Chair SY. Evaluation of the sustaining effects of tai chi qigong in the sixth month in promoting psychosocial health in COPD patients: a single‐blind, randomized controlled trial. The Scientific World Journal 2013a;425082. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chan AWK, Lee A, Lee DTF, Suen LKP, Tam WWS, Chair SY, et al. The sustaining effects of Tai Chi Qigong on physiological health for COPD patients: a randomized controlled trial. Complementary Therapies in Medicine 2013b;21(6):585‐94. [DOI] [PubMed] [Google Scholar]
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