Abstract
Background
Globally, 20% to 50% older adults have been found to have thoracic hyperkyphosis. Negative effects on physical performance have been reported. However, there has been a lack of research on the prevalence and negative effects of thoracic hyperkyphosis among Chinese community-dwelling elderly.
Design
A cross-sectional study.
Setting
The communities in Wuhan, China.
Participants
Three hundred and ninety-five Chinese community-dwelling older adults with thoracic hyperkyphosis.
Measures
Chinese community-dwelling older adults aged 60 or above lived in Wuhan, China from August to December 2018 were recruited for spine and physical performance assessments. The primary outcome was the prevalence of thoracic hyperkyphosis estimated according to the angle of kyphosis which was measured by manual inclinometers. The secondary outcomes were the effects of thoracic hyperkyphosis on physical performance measured by One-leg Standing Test (OLS), Timed Up & Go Test (TUG), Chest Expansion Test (CE), Six Minutes Walking Test (6MWT), and Farsi Version of Functional Gait Assessment (FGA). The socio-demographic and health-related information were collected by a questionnaire.
Results
Among 395 participants, the mean angle of kyphosis was 49.0° ± 10.5°, 75.2% of participants had the angle of kyphosis >40° (i.e., having thoracic kyperkyphosis). Compared with older adults having no thoracic hyperkyphosis, older adults with thoracic hyperkyphosis had increased risks performing impaired in OLS (OR=4.55, 95% CI 2.18–9.53, p<0.001), TUG (OR=6.08, 95% CI 2.57–14.40, p<0.001), CE (OR=3.23, 95% CI 1.63–6.38, p=0.001), 6MWT (OR=4.64, 95% CI 1.98–10.86, p<0.001), and FGA (OR=5.18, 95% CI 2.25–11.89, p<0.001) after controlling socio-demographic and health-related factors.
Conclusion
The thoracic hyperkyphosis had high prevalence and associated with impaired performance in balance, gait, and cardiopulmonary function tests among Chinese community-dwelling older adults, which calls for the future intervention.
Key words: Thoracic hyperkyphosis, prevalence, negative effects, physical performance, Chinese old adults
Introduction
Thoracic hyperkyphosis, the exaggerated outward curvature of the thoracic spine, is referred to as the angle of kyphosis beyond 40° (1). Older people are vulnerable to thoracic hyperkyphosis because of age-related diseases, such as osteoporosis or vertebral fractures associated with hyperkyphosis (2). Moreover, other age-related degeneration, such as bone loss, degenerative disk disease, muscle strength reduction, mobility decrease, and proprioceptive deficit, were also found to be associated with increased angle of kyphosis (3).
Globally, thoracic hyperkyphosis affects approximately 20% to 50% of older adults (4., 5., 6., 7.). A study conducted in China found that 56.6% of primary osteoporosis older female patients had the angle of kyphosis >40° (8). However, there was a lack of studies reporting the prevalence of thoracic hyperkyphosis in the general Chinese community-dwelling older population.
Besides, thoracic hyperkyphosis had negative effects on the health of older people. An increased angle of kyphosis was related with diminished physical function, declined respiratory function, increased chronic upper back pain, decreased balance, and decreased quality of life (9., 10., 11., 12., 13.). Thoracic hyperkyphosis was also associated with decreased gait performance (13). Compared with other negative effects, fewer studies were investigating this association.
Studies about thoracic hyperkyphosis conducted in China mainly focused on patients with ankylosing spondylitis (14), spinal fracture (14, 15), or osteoporosis (8). Neither had a study investigated the prevalence of thoracic hyperkyphosis in general community-dwelling elderly, nor investigated the relationship between thoracic hyperkyphosis with physical performance and gait performance in Chinese older adults. Therefore, we conducted a cross-sectional study aiming at estimating the prevalence of thoracic hyperkyphosis and investigating its negative effects on Chinese community-dwelling older people.
Methods
Study population
The study population was community-dwelling adults aged 60 and above from Wuhan, Hubei province, mainland China. The inclusion criteria were as follows: Chinese; aged ≥60; no cognitive impairment or communication problems. The older adults had health problems, such as central or peripheral neuropathy, untreated severe heart and lung disease, unable to stand or walk by him or herself, the angle of scoliosis≥10° or taking drugs that affected the nervous system or affected balance and strength were excluded in the study.
The sample size was calculated based on the primary outcome proportion of thoracic hyperkyphosis. Based on previous studies, the prevalence was approximately 20% to 40% (6, 7, 17, 18). Assuming the proportion of thoracic hyperkyphosis would be 40%, to estimate a 95% confidence interval (CI) of such a proportion with a precision of 5%, a sample of 369 older adults was required (19). To account for 5% missing data, at least 390 older adults would be recruited.
Outcome measures
The primary outcome was the prevalence of thoracic hyperkyphosis, which was estimated from the angle of kyphosis. Manual inclinometer (model: Baseline 12–1149), a validated tool (20, 21), was used to accomplish the spine measurement. Participants exposed their upper body in a relaxed standing posture. The researcher identified and marked the spinous processes of C7, T1, T2, T12, and L1 with an erasable pen. Two feet of the inclinometers were placed over the spinous processes of T1–T2 and T12-L1 (22, 23). The angles were read directly from the inclinometers. This process was performed three times in succession to calculate the mean.
The secondary outcome was physical performance. The physical performance assessments included two balance tests, two cardiopulmonary function tests, and one gait assessment. The balance tests were One-leg Standing Test (OLS) and the Timed Up & Go Test (TUG). In OLS, the participants chose either leg on which to stand. The longer time indicated a better static balance. Standing longer than one minute was considered as having a normal static balance (24, 25). In the TUG test, the participant was asked to rise from a chair, walk 3 meters, turn around, walk back to the chair, and sit down while the researchers timed the whole process (26). The shorter time indicated a better dynamic balance, as participants were considered as having normal dynamic balance when completed within 10s (27, 28).
Two cardiopulmonary function tests were performed, including the Chest Expansion test (CE) and the Six Minutes Walking Test (6MWT). CE measured the bust difference in the fourth intercostal level between deep inhale and deep exhale. Less than 2.5cm difference indicated abnormal respiratory function (8). The 6MWT was completed in a 30 meter long, flat square in the community. The participant was asked to walk as far as possible within six minutes. The blood pressure and heart rate of the participant were measured before the test. Participants had contraindications, such as unstable angina during the previous month, myocardial infarction during the previous month, resting heart rate more than 120 times-minute, systolic blood pressure more than 180 mmHg, or diastolic blood pressure of more than 100 mmHg were not allowed to test (29). The result >375 meters indicated cardiopulmonary function being close to normal or normal, while <375m indicated abnormal cardiopulmonary function (8).
Gait performance was tested by the Farsi Version of Functional Gait Assessment (FGA), a 6-meter 10-task dynamic gait assessment (13, 30). Every task was scored from 0 to 3, according to the participant's performance. The total score of FGA is 30, and higher scores, considered normal when > 22, indicated better gait performance (30). All five physical performance tests were reported having satisfying validity and reliability (8, 24, 26, 30).
Social-demographic information, including age, gender, marital status, and education level, were collected. Health-related information, including spine surgery history, chronic illnesses, daily exercise intensity, and Body Mass Index (BMI), were also collected. Participants selected diagnosed chronic diseases from a list of nine common chronic diseases in the Wuhan area (31., 32., 33., 34.). Height and weight for BMI calculation were measured on-site. Daily exercise intensity and daily sitting time were measured by the International Physical Activity Questionnaire (IPAQ-SF), of which satisfactory reliability and validity had been reported in 12 countries, including China (35).
Procedures
This cross-sectional study was conducted from August to December 2018 in four communities in Wuhan by using convenience sampling. Every potential participant had a trained research assistant responsible for explaining the study details with the information sheet and re-assuring the respondents that data collected in the study were kept strictly confidential and then seeking permission for conducting assessments. The potential participants were screened according to inclusion and exclusion criteria, and written consent was sought.
The participants completed the questionnaire and spine measurement in rooms having privacy protection and a comfortable environment. Trained research assistants helped with face-to-face interviews based on the structured questionnaire described above. Then, participants were invited to take the physical performance assessments. Briefing and de-briefing sessions were arranged before every test to ensure that the participants adequately understood the procedures. Resting time was given between each test. For 6MWT, participants with contraindications, such as systolic blood pressure over 180mm Hg or diastolic blood pressure over 100mm Hg would not perform the 6MWT (29). Ethics approval was obtained from the Institutional Review Board of the University of Hong Kong-Hospital Authority Hong Kong West Cluster.
Data analysis
SPSS version 23.0 was used to analyze data, and a significance level of 0.05 was adopted. Descriptive statistics were used to explore the characteristics of the participants. The prevalence of thoracic hyperkyphosis in Chinese community-dwelling older adults was calculated based on the cut-off point of 40° (8). The results of balance, cardiopulmonary functions, and gait performance were classified by the corresponding cut-off points into impaired and normal as described above. Overweight was defined based on the Asian population BMI cut-off (i.e., BMI ≥23) (36). Sedentary behavior was defined by sitting more than seven hours per day (35).
Logistic regression was conducted to explore the relationships between thoracic hyperkyphosis with socio-demographic variables and health-related factors. Age and Gender were entered into the model while other factors were selected to the model using the backward procedure. Logistic regression was also used to analyze the relationships between thoracic hyperkyphosis and physical performance, including balance, cardiopulmonary functions, and gait performance. Both crude Odds Ratio (OR) and adjusted OR, adjusted for social demographic and health-related factors, were estimated. Missing values were not brought into the data analysis models.
Results
A total of 400 older adults were recruited. Five quit the study for not being willing to expose their upper body after reconsideration, resulting in 395 (male: 88 and female: 307) participants in the analysis. The socio-demographic and health-related characteristics of participants are summarized in Table 1 and Table 2.
Table 1.
Socio-demographic characteristic of 395 participants
| Variables | Total N=395 | No Kyphosis N= 98 | Have Kyphosis N= 297 |
|---|---|---|---|
| Age | |||
| Young-old (aged 60–74) | 307 (77.7%) | 85 (86.7%) | 222 (74.7%) |
| Old-old and oldest-old (aged ≥75) | 88 (22.3%) | 13 (13.3%) | 75 (25.3%) |
| Gender | |||
| Male | 88 (22.3%) | 30 (30.6%) | 58 (19.5%) |
| Female | 307 (77.7%) | 68 (69.4%) | 239 (80.5%) |
| Education level | |||
| Primary school or less | 155 (39.2%) | 25 (25.5%) | 130 (43.8%) |
| Middle school and high school | 222 (56.2%) | 66 (67.3%) | 156 (52.5%) |
| College and above | 18 (4.6%) | 7 (7.2%) | 11 (3.7%) |
| Job | |||
| Current working | 56 (14.2%) | 11 (11.2%) | 45 (15.2%) |
| Homemaker | 35 (8.9%) | 4 (4.1%) | 30 (10.1%) |
| Retired | 302 (76.8%) | 83 (84.7%) | 220 (74.1%) |
| Missing | 2 (0.5%) | 2 (0.6%) | |
| Marriage | |||
| Married | 306 (77.7%) | 87 (88.8%) | 219 (73.7%) |
| Widowed/devoiced/single | 88 (22.3%) | 11 (11.2%) | 77 (25.9%) |
| Missing | 1 (0.3%) | 1 (0.4%) | |
Table 2.
Health-related characteristic of 395 participants
| Variables | Total N=395 | No Kyphosis N= 98 | Have Kyphosis N= 297 |
|---|---|---|---|
| Exercise level | |||
| Low intensity (< 600 MET-minutes/week) | 30 (7.6%) | 6 (6.1%) | 24 (8.1%) |
| Moderate intensity (600 to 3000 MET-minutes/week) | 311 (78.7%) | 71 (72.5%) | 240 (80.8%) |
| High intensity (≥ 3000 MET-minutes/week) | 54 (13.7%) | 21 (21.4%) | 33 (11.1%) |
| Sitting time | |||
| Normal (< 7 hours) | 295 (74.7%) | 79 (80.6%) | 216 (72.7%) |
| Long (> 7 hours) | 95 (24.1%) | 17 (17.3%) | 78 (26.3%) |
| Missing | 5 (1.3%) | 2 (2.1%) | 3 (1.0%) |
| BMI | |||
| Underweight to normal (< 23) | 159 (40.3%) | 42 (42.9%) | 117 (39.4%) |
| Overweight (≥ 23) | 236 (59.7%) | 56 (57.1%) | 180 (60.6%) |
| Chronic disease | |||
| Coronary heart disease (yes) | 48 (12.2%) | 11 (11.2%) | 37 (12.5%) |
| Coronary heart disease (no) | 347 (87.7%) | 87 (88.8%) | 260 (87.5%) |
| Diabetes (yes) | 67 (17.0%) | 11 (11.2%) | 56 (18.9%) |
| Diabetes (no) | 330 (83.0%) | 87 (88.8%) | 241 (81.1%) |
| Chronic gastrointestinal disease (yes) | 74 (18.7%) | 20 (20.4%) | 54 (18.2%) |
| Chronic gastrointestinal disease (no) | 321 (81.3%) | 78 (79.6%) | 243 (81.8%) |
| Chronic pulmonary disease (Yes) | 77 (19.5%) | 14 (14.3%) | 63 (21.2%) |
| Chronic pulmonary disease (no) | 318 (80.5%) | 84 (85.7%) | 234 (78.8%) |
| Rheumatism (yes) | 102 (25.9%) | 18 (18.4%) | 84 (28.3%) |
| Rheumatism (no) | 292 (74.1%) | 80 (81.6%) | 212 (71.7%) |
| Eye diseases (yes) | 114 (28.9%) | 25 (25.5%) | 89 (30.0%) |
| Eye diseases (no) | 281 (71.1%) | 73 (74.5%) | 208 (70.0%) |
| Hypertension (yes) | 177 (44.8%) | 35 (35.7%) | 142 (47.8%) |
| Hypertension (no) | 218 (55.2%) | 63 (64.3%) | 155 (52.2%) |
| Spine disease (yes) | 191 (48.4%) | 51 (52.0%) | 140 (47.1%) |
| Spine disease (no) | 204 (51.6%) | 47 (48.0%) | 157 (52.9%) |
| Osteoporosis (yes) | 199 (50.4%) | 44 (44.9%) | 155 (52.2%) |
| Osteoporosis (no) | 196 (49.6%) | 54 (55.1%) | 142 (47.8%) |
The mean age of older adults was 68.6 years old (range: 60 to 90 years old). Most (77.7%) of the participants were young-old (aged between 60 to 74 years), 76.7% retired, 77.5% currently married, and 38.9% had primary education or below.
Most (78.7%) of the participants had moderate-intensity exercise level in daily life (i.e., ≥600 MET-minutes/week), and 13.7% had high-intensity exercise (i.e., ≥3000 MET-minutes/week). Only one fifth (24.1%) of older adults had sedentary behavior (37), however, 59.7% of them were overweight. Of the nine common diseases, the largest proportion came from osteoporosis (50.4%), spine disease (48.4%), and hypertension (44.8%). The number of chronic diseases reported from two to nine, with a mean of 6.3 (range: 2 to 9) chronic diseases. No vertebral fractures and spine surgery history was reported.
Prevalence of thoracic kyphosis
The mean ± SD angle of kyphosis was 49.0°±10.5°. Two hundred ninety-seven participants had the angle of kyphosis >40°. Thus 75.2% (95% CI 70.6% to 79.4%) of the older adults had thoracic hyperkyphosis.
The relationships between thoracic hyperkyphosis with sociodemographic and health-related factors were reported in Table 3. The unadjusted logistic regression model indicated that those aged ≥75, being female, had a primary education level or below, being widowed/devoiced/single, or having more chronic diseases at higher risk of having thoracic hyperkyphosis.
Table 3.
Relationships between thoracic hyperkyphosis with sociodemographic and health-related factors
| Variables | OR | Unadjusted Model 95% CI | p-value | OR | Adjusted Model 95% CI | p-value |
|---|---|---|---|---|---|---|
| Age | ||||||
| Old-old and the Oldest-old ≥75 | 2.21 | 1.17–4.19 | 0.015* | 2.13 | 1.12–4.06 | 0.022* |
| Young-old 60–75 (ref.) | 1 | 1 | ||||
| Gender | ||||||
| Female | 1.82 | 1.09–3.05 | 0.023* | 1.77 | 1.04–2.99 | 0.035* |
| Male (ref.) | 1 | 1 | ||||
| Education level | 0.005* | - | ||||
| Primary school or less | 3.31 | 1.17–9.36 | 0.024* | - | - | - |
| Middle school or high school | 1.50 | 0.56–4.05 | 0.419 | - | - | - |
| College and above (ref.) | 1 | - | ||||
| Job | 0.082 | - | ||||
| Current working | 1.55 | 0.77–3.14 | 0.223 | - | - | - |
| Homemaker | 2.94 | 1.01–8.58 | 0.049* | - | - | - |
| Retired (ref.) | 1 | - | ||||
| Marital status | ||||||
| Widowed/devoiced/single | 2.78 | 1.41–5.48 | 0.003* | - | - | - |
| Married (ref.) | 1 | - | ||||
| Exercise level | 0.038* | - | ||||
| Low intensity (< 600 MET-minutes/week) (ref.) | 1 | - | ||||
| Moderate intensity (600 to 3000 MET-minutes/week) | 0.85 | 0.33–2.15 | 0.724 | - | - | - |
| High intensity (≥ 3000 MET-minutes/week) | 0.39 | 0.14–1.12 | 0.081 | - | - | - |
| Sitting time | ||||||
| Normal (< 7 hours) (ref.) | 1 | - | ||||
| Long (≥ 7 hours) | 1.68 | 0.94–3.01 | 0.083 | - | - | - |
| Number of chronic diseases | 0.85 | 0.73–0.98 | 0.026* | - | - | - |
| BMI | ||||||
| Overweight (≥23) | 1.15 | 0.73–1.83 | 0.545 | - | - | - |
| Normal or underweight (<23) (ref.) | 1 | - | ||||
— Insignificant variables were removed from the logistic regression with backward selection procedure; * p < 0.05
In the adjusted model, only age group and gender remained significant. People aged ≥75 (adjusted OR=2.13, 95% CI 1.12–4.06) and female (adjusted OR=1.77, 95% CI 1.04–2.99) had higher risks of having thoracic hyperkyphosis, as compared with people aged <75 and male, respectively.
Negative effects of thoracic hypokyphosis
Participants were classified into normal or impaired physical performance according to the corresponding cut-off points (Table 4). In all five physical performance tests, there were more people with thoracic hyperkyphosis having impaired physical performance than those without. In 6MWT, 15 older adults could not participant in this test because they had contraindications.
Table 4.
Five physical performance tests of 395 participants
| Variables | Total (%) N= 395 | No Kyphosis N= 98 | Have Kyphosis N= 297 |
|---|---|---|---|
| OLS | |||
| Normal (≥20s) | 163 (41.3%) | 66 (67.3%) | 97 (32.7%) |
| Impaired (<20s) | 213 (53.9%) | 28 (3.6%) | 185 (62.3%) |
| Refused to complete the test | 19 (4.8%) | 4 (4.1%) | 15 (5.0%) |
| TUG | |||
| Normal (≤10s) | 269 (68.1%) | 87 (88.8%) | 182 (61.3%) |
| Impaired (>10s) | 104 (26.3%) | 7 (7.1%) | 97 (32.7%) |
| Refused complete the test | 22 (5.6%) | 4 (4.1%) | 18 (6.0%) |
| CE | |||
| Normal (≥2.5cm) | 259 (65.6%) | 82 (83.7%) | 177 (59.6%) |
| Impaired (<2.5cm) | 122 (30.9%) | 12 (12.2%) | 110 (37.0%) |
| Refused to complete the test | 14 (3.5%) | 4 (4.1%) | 10 (3.4%) |
| 6 MWT | |||
| Normal (≥375m) | 256 (64.8%) | 81 (82.7%) | 175 (58.9%) |
| Impaired (<375m) | 95 (24.1%) | 7 (7.1%) | 88 (29.6%) |
| Refused or unable to complete the test | 44 (11.1%) | 10 (10.2%) | 34 (11.5%) |
| FGA | |||
| Normal (≥23) | 264 (66.8%) | 85 (86.7%) | 179 (60.3%) |
| Impaired (0–22) | 114 (28.9%) | 8 (8.2%) | 106 (35.7%) |
| Refused to complete the test | 17 (4.3%) | 5 (5.1%) | 12 (4.0%) |
Table 5 shows the unadjusted logistic regression model which found that compared with participants having no hyperkyphosis, those having the angle of kyphosis >40° showed a statistically significant higher risk of performance impairment in all five physical performance tests. In the adjusted model, older adults with thoracic hyperkyphotic still had increased risk of impaired performance in OLS (adjusted OR=4.55, 95% CI 2.18–9.53), TUG (adjusted OR=6.08, 95% CI 2.57–14.40), CE (adjusted OR=3.23, 95% CI 1.63–6.38), 6MWT (adjusted OR=4.64, 95% CI 1.98–10.86), and FGA (adjusted OR=5.18, 95% CI 2.25–11.89).
Table 5.
The risk of having impaired physical performance among older adults with thoracic hyperkyphosis as compared to those without
| Variables | Crude model | Adjusted model# | ||||
|---|---|---|---|---|---|---|
| OR | 95% CI | p-value | OR | 95% CI | p-value | |
| OLS | 5.45 | 2.71–10.96 | < 0.001 | 4.55 | 2.18–9.53 | < 0.001 |
| TUG | 6.62 | 2.95–14.86 | < 0.001 | 6.08 | 2.57–14.40 | < 0.001 |
| CE | 4.25 | 2.22–8.14 | < 0.001 | 3.23 | 1.63–6.38 | 0.001 |
| 6MWT | 5.82 | 2.58–13.13 | < 0.001 | 4.64 | 1.98–10.86 | < 0.001 |
| FGA | 6.29 | 2.93–13.50 | < 0.001 | 5.18 | 2.25–11.89 | < 0.001 |
| # age group, gender, education level, job status, marriage status, exercise intensity, sitting time, chronic disease condition, and BMI were included in the adjusted model. | ||||||
Discussion
The current study was the first one conducted to investigate the prevalence of thoracic hyperkyphosis among Chinese community-dwelling older adults. It filled the gap about the effects of thoracic hyperkyphosis on balance, cardiopulmonary, and gait performance among older adults with an exercise habit.
Our study reported that the prevalence of thoracic hyperkyphosis among Chinese older adults was 75.2%, which was higher than the prevalence of 20% to 50% reported in previous studies (4., 5., 6.). It was even higher than the prevalence of thoracic hyperkyphosis among Chinese adults with primary osteoporosis (56.6%) (8).
A possible reason for the high prevalence may be the sedentary behavior of playing smartphone and mahjong (a Chinese tile-based game). Although, most of the older adults had sitting time less than seven hours, the meantime of sitting was 312 minutes per day approaching the sedentary cutoff. Participants mentioned that when they focused on their phone or mahjong, they were not aware of the posture until feeling stiffness or pain in neck and back. However, the exact time of using smartphones and playing mahjong were not investigated in the current study. As such, we cannot analyze the effects of using smartphones and playing mahjong on thoracic hyperkyphosis prevalence. Mahjong, one of the most popular games in Chinese older adults, was regarded as a benefit to cognitive function and eye-hand-coordination (38, 39). However, no study investigated its possible adverse effects on the thoracic spine. Overuse of smartphones was found to have a negative effect on posture in young adults (40). In 2018, it was reported that 55.1% of Chinese older adults considered smartphones as important to very important, and the percentage has an increasing trend (41). Therefore, using smartphones might also be associated with a higher prevalence of thoracic hyperkyphosis among older adults. Future studies may investigate the potential relationships between using smartphones or playing mahjong with thoracic hyperkyphosis in Chinese older adults.
Another reason for the high prevalence may be a lack of strength exercise. Studies found that strength, mobility, and alignment exercise interventions could effectively reduce the angle of kyphosis (42). Although 78.7% of the Chinese older adults in our sample had moderate-intensity exercise in daily life, and 13.7% had high-intensity exercise in daily life, only two mentioned doing strength exercises, such as pull-up in horizontal bar. The most popular exercise practiced by Chinese older adults were all aerobic exercises, such as fast walking, square dance, and Tai-chi. Therefore, the level of exercise in daily life was found to be an insignificant factor for hyperkyphosis in the adjusted model of the current study. It would be the type of exercise, rather than the intensity of exercise, that was associated with hyperkyphosis. Interventions targeting strength exercise should be developed and promoted to older adults in China.
Consistent with the previous studies, older age and female gender were found as the risk factors of thoracic hyperkyphosis. In the 1980s, studies reported among older adults, the angle of kyphosis increased with age (43, 44). In 2014, Kado and team published a longitudinal study that found the mean angle of kyphosis in older women progressed 7.1° over 15 years (7). Due to a series of physiological changes before and after menopause, women have a greater degree of kyphosis and develop hyperkyphosis earlier than men (2). Schneider and team conducted a cross-sectional study among community-dwelling residents aged 50 to 96 ears old (45). They found for women the mean angle of kyphosis (SD) was 49° (16°), and the mean angle increased 14° [40° (95% CI: 37–42) to 54° (95% CI: 52–56)] from the 60 to 90 years old. For men, the mean angle was 44° (13°), and increased only 8° [39° (95% CI 36–42) to 47° (95% CI 45–49)].
The nine chronic diseases asked by questionnaire or the number of chronic diseases a person have did not show statistically significant association with thoracic hypokyphosis. It was reported that 40.1% of Chinese females aged 50 and above had osteoporosis (46), similar to the current study (50.4% among 60 and above). Although low bone density or osteoporosis were considered as risk factors of thoracic hyperkyphosis (2), an exception existed. By recruiting 189 females aged 50 to 80, Mika and team found that bone mineral density did not associate with thoracic hyperkyphosis, while the back muscle extensor strength had (47). Another study pointed out that the effects of osteoporosis was smaller than the prevalent vertebral fracture (48). As no participants experienced vertebral fracture in the current study, this may also explain the insignificant association between osteoporosis with thoracic hyperkyphosis.
The prevalence of spine disease (48.4%) in the current sample was higher than the previously reported prevalence of cervical spondylosis and lumbar disc herniation (11.4%) in the same population (34). Considering this study included not only cervical spondylosis and lumbar disc herniation but also other spinal diseases, for example, degenerative disc disease, the prevalence difference should not be as large as four times. However, by using convenient sampling, the current study might have attracted more people having spine problems. Previously no studies investigated the effects of chronic disease numbers or chronic disease other than osteoporosis and spinal disease on thoracic hyperkyphosis. Thus, the current results are not a good comparison.
This cross-sectional study found thoracic hyperkyphosis increased the risks of performing impaired in OLS, TUG, CE, and 6MWT in both crude and adjusted models, which was consistent with the studies overseas and in China (8, 10., 11., 12.). Among older adults, age was associated with lower proficiency in body control and more body sway (49), which might be a confounder in examining the relationships between thoracic hyperkyphosis and OLS and TUG. However, in adjusted logistic regression we controlled all sociodemographic factors including age and the results were still robust. The current study also found the thoracic hyperkyphosis had negative effects on gait performance, which has not before been investigated in Chinese older adults with thoracic hyperkyphosis. As gait performance has a close relationship with falling risk (50), which results in negative physical consequences (51), there is a need for future studies to investigate the relationship between thoracic hyperkyphosis with falling in Chinese older adults.
The current study had the strength of using physical measurement in assessing physical performance, and recruited almost 400 older adults. There were some limitations. Usage of convenient sampling may cause sampling bias, resulting in the prevalence of spine disease at a higher level than studies reported before. To minimize the sampling bias, we recruited participants in different communities located in different regions. Nevertheless, the results showed that the spine disease did not have significant association with the thoracic hyperkyphosis. Another limitation was not conducting the radiation method measuring the angle of kyphosis, which is the gold standard. However, to avoid unnecessary radiation exposure, and given the satisfactory validity and reliability of manual inclinometer (20, 21), the spine measurement method in our study was acceptable. Due to the cross-sectional design, the study could not examine the causal relationships, the odds ratios reported in the study could only show thoracic hyperkyphosis may be associated or corroborated with impaired performance in physical performance tests. Nevertheless, this study was conducted in only one city in China which may not represent the whole population in China. It is suggested to repeat this study in other parts of China.
Conclusion
The current study revealed the high prevalence of thoracic hyperkyphosis among Chinese older adults in the community setting. In addition, participants with thoracic hyperkyphosis showed three to six times higher risk of impaired performance in balance tests, cardiopulmonary function tests, and gait performance test, as compared with those without thoracic hyperkyphosis. The findings corroborated that thoracic hyperkyphosis had association with older adults' impaired physical performance. The findings of this study called for the need of exploring a cost-effective intervention on reducing the angle of kyphosis among Chinese older adults with thoracic hyperhyphosis.
Authors contribution
Li, Chau, Dai and Tiwari contributed to the study design, data analysis, results interpretation, and writing the paper. Li also contributed to data collection. All authors contributed to reviewed and approved the final version.
Declaration
This study comply with the current laws of China.
Conflict of interest
The authors has no conflicts.
Funding
Nil
Ethical standards
The study complies with the current laws of the country in which they were performed.
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