Transcendental Meditation in the prevention and treatment of cardiovascular disease and pathophysiological mechanisms: An evidence-based review

Abstract

Objectives:

Despite advances in modern medicine, cardiovascular disease (CVD) is the leading cause of death in Australia and globally. In a recently published scientific statement on alternative methods to lower blood pressure (BP), the American Heart Association (AHA) reported that the Transcendental Meditation (TM) technique may be considered in clinical practice to lower BP. The AHA statement also reported research that TM may reduce heart attack, stroke and death in CVD patients. This article reviews the background and associated evidence for these effects.

Design and methods:

Meta-analyses, systematic reviews and controlled clinical studies on the effects of TM technique on cardiovascular disease and its risk factors were reviewed and the outcomes synthesised.

Results:

Clinical trials indicate that the TM technique has a positive impact on pathophysiological mechanisms of CVD; risk factors for CVD including hypertension, psychosocial stress and smoking; surrogate markers for CVD; and CVD clinical events.

Conclusions:

The wide range of effects of TM practice on cardiovascular health suggests that the TM technique may be considered in clinical applications for both the prevention and treatment of cardiovascular disease.

1. Introduction

Cardiovascular disease (CVD) is the leading cause of death in both developed and developing nations [1]. In 2011, CVD accounted for 31% of all deaths in Australia [2]. Access Economics estimated that in 2009 heart attack and cardiac chest pain cost the nation $18 billion – of which $1.77 billion were direct medical and hospitalisation costs [3].

Psychosocial stress is currently recognised as a major risk factor for coronary heart disease (CHD) [4]. CHD has been linked with stressors such as low socioeconomic status, life events and job stress along with stress responses such as anger, hostility, anxiety and depression. It is interesting to note that positive affect, is protective against 10-year incident CHD, suggesting that preventive strategies may be enhanced not only by reducing depressive symptoms but also by increasing positive affect [5].

Pathophysiological mechanisms by which stress leads to vascular and myocardial damage have been elucidated (see Fig. 1) [6]. They include hyper-activation of the sympathetic nervous system, decreased parasympathetic tone, increased platelet aggregation, oxidative stress, insulin resistance, inflammation and hypothalamic-pituitary-adrenal axis activation. Stress may thus worsen other risk factors and/or directly lead to endothelial damage, vasoconstriction, thrombosis and ultimately myocardial ischaemia and/or infarction and death.

Fig. 1.

Pathophysiological mechanisms for stress in CVD.

2. Design and methods

We conducted a review of the contemporary published literature on effects of stress reduction through meditation, specifically the Transcendental Meditation technique, on CVD, its pathophysiological mechanisms and risk factors. This metasynthesis focused on systematic reviews, meta-analyses, randomised controlled trials and other controlled clinical studies. Search criteria included TM and CVD pathophysiological mechanisms (including cardiovascular reactivity, oxidative stress, insulin resistance neuroendocrine factors); CVD risk factors (including hypertension, smoking, hypercholesterolaemia, stress, anxiety, depression, diabetes, metabolic syndrome); surrogate markers of CVD (including carotid intima media thickness, exercise tolerance test); cardiovascular clinical events (including all cause mortality, CVD mortality, myocardial infarction, stroke, acute coronary syndrome, coronary revascularisation).

3. Results

3.1. Neurophysiological effects of meditation

Evidence suggests that different types of meditation techniques produce differing neurophysiological effects. Neuroscientists propose that meditation techniques may be categorised into three broad sets according to type of practice, degree of cognitive control (mental effort), and EEG characteristics: methods of focused attention, open monitoring and automatic self-transcending [7].

Focused attention involves voluntary and sustained attention on a chosen object such as a mantra, the breath, a specific thought or emotion, e.g., compassion or loving kindness (as in Zen meditations). Open monitoring involves non-reactive monitoring of all thoughts, emotions, breathing and body sensations that pass through the awareness from moment to moment (as in mindfulness meditation). Automatic self-transcending involves the automatic transcending of the procedures of the meditation to a state devoid of mental activity (as in the Transcendental Meditation technique). Focus on a single object of experience and an orientation to monitoring changing objects of experience keeps the meditator involved with the procedures of the technique. In automatic self-transcending the mind effortlessly transcends all mental activity be it thinking, focusing or monitoring and settles to a state of silent wakefulness [7].

Each type of meditation has its own distinctive EEG characteristics. Focused attention is associated with high frequency gamma output (20–50 Hz). Open monitoring is associated with theta two output (4–6 Hz). Automatic self-transcending is associated with alpha one output (8–10 Hz) in the prefrontal cortex and a global phase synchrony or coherence of the EEG [7] (see Fig. 2).

Fig. 2.

Examples of the EEG in 3 main categories of meditation.

During Transcendental Meditation (TM) practice, the mind is allowed to effortlessly experience finer levels of the thinking process until it transcends or goes beyond all thought – described as expanded awareness or pure consciousness. Any attempt to focus, monitor or control the mind is said to increase mental activity and interfere with the transcending process. In the resulting settled state, the mental activity is quiescent but fully awake and at the same time the body is deeply relaxed and rested. It is associated with reduced respiratory rate, reduced plasma lactate, increased galvanic skin response (a measure of sympathetic tone) [8] and reduced plasma cortisol [9] and catecholamines [10]. Neuroscientists propose this state to be a wakeful hypo-metabolic state [11] – a fourth state of consciousness – as necessary for health and wellness as the sleeping, dreaming and waking states.

Brain imaging with positron emission tomography (PET) shows that during TM practice blood flow and corresponding neural activity is increased in the prefrontal cortex (associated with higher cognitive functioning) and reduced in the thalamus and basal ganglia (both associated with sensory-motor processing) – evidence for the theory that TM practice induces a state of restful alertness [12].

3.2. The effects of meditation on the pathophysiological mechanisms of CVD

3.2.1. Stress reactivity

Repeated experience of this restfully alert state has long-term physiological and clinical effects. Functional MRI studies, for example have found reduced brain reactivity to stress in TM practitioners compared to controls [13]. Changes in the hypothalamic-pituitary-adrenal (HPA) axis indicate a more adaptive long-term response to stress in TM practitioners [14]. Neurophysiological measures including EEG preparatory brain responses and electrodermal habituation responses also suggest that long-term TM practitioners react to and recover from stress more efficiently [15].

Reduced stress reactivity in the brain may be associated with reduced cardiovascular reactivity, i.e. reduced surges in sympathetic activation, which affect heart rate and blood pressure. Cardiovascular reactivity to stress is thought to contribute to long-term hypertension, vascular damage and accelerated atherosclerosis [16]. This may help explain the reduced blood pressure and the clinical events found in long-term meditators.

Studies on cardiovascular reactivity in normotensive adults practising TM have had varied outcomes [17,18]. A randomised controlled trial (RCT) in CHD patients showed a trend toward increased high frequency heart rate variability (a measure of increased parasympathetic tone) in the TM group compared with a health education control [19]. In a RCT on 35 adolescents with high normal blood pressure, the TM practitioners exhibited greater decreases in systolic blood pressure, heart rate and cardiac output reactivity to a simulated car driving stressor, and in systolic blood pressure reactivity to a social stressor interview [20].

3.2.2. Insulin resistance

The US National Institutes of Health (NIH) funded a RCT of 103 subjects with CHD that showed a reduction in insulin resistance after 16 weeks practice of TM [19]. This effect on insulin resistance may be a biochemical mechanism for the regression of atherosclerosis found with TM and its clinical cardiovascular effects. This study also indicates that stress reduction through TM may help in the management of metabolic syndrome (the cluster of hypertension, dyslipidaemia, central obesity and insulin resistance) and may mitigate the development of diabetes - both important risk factors for CHD.

3.2.3. Oxidative stress

In a cross sectional study of 41 subjects, significantly lower serum levels of lipid peroxides were found in the TM practitioners compared with controls after controlling for major aspects of diet [21]. Prospective controlled trials are needed to confirm this effect and rule out confounders, such as diet or other lifestyle factors.

3.3. Meditation and cardiovascular risk reduction

3.3.1. Negative emotional states and meditation

Depression is considered a major risk factor for CHD with similar risk as smoking, hypercholesterolemia and hypertension [22]. Chronic and acute stress responses including anger and anxiety are known to precipitate myocardial infarcts and are associated with increased long-term risk for CVD [4].

A study of 300 university students randomly allocated to either TM or wait-list control, over a three month intervention period, found significant improvements in anxiety, depression, anger, hostility, and coping in those practising TM [23].

Meta-analysis of 143 studies in 1989 found that most relaxation and meditation techniques were no better than placebo in reducing trait anxiety. TM, however, was twice as effective as placebo [24]. This was updated in 2013 by a meta-analysis of 16 randomised-controlled trials on TM (total of 1295 subjects) [25].

The 2013 meta-analysis assessed the effects of initial anxiety level, age, duration of practice, regularity of practice, research quality, author affiliation, and type of control group on effect sizes. TM practice was found to be more effective than treatment as usual and most alternative treatments. Progressive muscle relaxation was also found to be effective in reducing anxiety. Greatest effects with TM were observed in individuals with high stress, such as veterans suffering from post-traumatic stress disorder and prison inmates. Studies using repeated measures showed substantial reductions in the first 2 weeks and sustained effects at 3 years.

Another meta-analysis compared the effect of TM, mindfulness and other meditation on a composite index of trait anxiety, negative emotion, neuroticism, perception, self-concept, and selfrealisation and found the effect size was 0.24 for mindfulness and for other meditation compared to 0.37 for TM [26].

3.3.2. Hypertension

In April 2013 the American Heart Association (AHA) published a scientific statement on alternative treatments to lower blood pressure. After systematically reviewing the scientific literature, the AHA scientific committee concluded that TM is recommended for consideration in the treatment plans for individuals with blood pressure >120/80 mm Hg (around 60% of Australians). It was noted that the TM is the only meditation and relaxation technique with sufficient evidence to indicate that it lowers blood pressure [27].

In 1995 the AHA journal, Hypertension, published a classic study on the effects of TM on hypertension in which 102 subjects were randomised to participate in TM, progressive muscular relaxation (PMR) or a health education program and followed over a 12 week period. The health education group was given standard diet and lifestyle instructions i.e. reduce salt, lose weight, do more exercise and avoid stress. The PMR group and TM group were matched for time and attention – they practiced for the same time; and had the same instructional time and follow up. TM was found to be twice as effective as PMR in reducing blood pressure. No significant change was observed in the health education group [28].

Since the 1990’s there have been a total of 11 randomised controlled trials (RCTs) of TM on blood pressure – comprising more than 1200 subjects. A meta-analysis of nine RCTs which met selection criteria for study design [18,19,28–34] found that there was an average reduction of 4.7 mm Hg systolic blood pressure and 3.2 mm Hg diastolic blood pressure for the TM group compared to control [27,35].

Another meta-analysis [36], to which the AHA referred in its statement, compared the effectiveness of different stress reduction techniques in lowering blood pressure. The techniques included TM, PMR, biofeedback and stress management. The 107 studies chosen were selected on the following rigorous criteria: strong experimental design, adequate baseline and blinding measures, and at least one replication study. The study concluded that there was only a significant effect found with TM (see Fig. 3).

Fig. 3.

Effect of TM, relaxation and stress management on blood pressure.

Reduced total peripheral resistance has been found in long-term TM practitioners [37] – indicating reduced vasoconstriction (a function of sympathetic tone). This suggests that decreases in sympathetic nervous system activity during TM practice may be the haemodynamic mechanism responsible for the beneficial influence of TM practice on high blood pressure.

3.3.3. Left ventricular hypertrophy

Increased left ventricular mass, which over time may lead to left ventricular hypertrophy, is a key indicator of hypertensive heart disease [38], and a major risk factor for cardiovascular mortality [39]. In a RCT on 62 prehypertensive African American adolescents, 4 months of TM compared to heath education resulted in a significant decrease in left ventricular mass index, and these changes were maintained at 4-month follow-up [40].

3.3.4. Hypercholesterolaemia

Sympathetic nervous system and hypothalamic-pituitary-adrenal (HPA) axis over-activity has been implicated in the elevation of serum cholesterol levels, independent of diet [41]. In an early study on 23 subjects with high cholesterol, serum cholesterol was reduced by 9% over an 11 month period after learning TM compared to a control group, without any change in diet (p < 0.005) [42]. A more recent RCT, however, found that decreases in total cholesterol and lipoproteins in the TM group were not statistically significant, possibly due to a floor effect due to normal levels at baseline in addition to a 60% statin usage [49].

3.3.5. Cigarette use

A meta-analysis of 131 studies [43] reported that TM was more effective than standard rehabilitation programs and other selfdevelopment techniques, in reducing the tobacco use. As there is no attempt to change health habits in the course of TM instruction, this shift to more positive lifestyle choice is spontaneous – possibly related to the increased brain integration [44] and normalisation of the neurochemistry with regular TM practice [45].

3.4. Meditation and atherosclerotic CVD

A NIH funded RCT [31] investigated the effect of TM practice on carotid artery intima-media thickness as measured by B mode ultrasound. Carotid Intima-media thickness is one of the best noninvasive measures of atherosclerosis – the precursor to myocardial infarction and stroke. In the trial, 60 hypertensive subjects were randomly assigned to either the TM group or a health education group and were followed over 7 months. The outcome was a significant reduction in carotid intima-media thickness in the TM group relative to the control group. This is the first time that a mind-body intervention was shown to have an effect consistent with regressing coronary artery disease without any change in diet or lifestyle.

3.5. Clinical cardiovascular effects of meditation

3.5.1. Exercise tolerance in CHD patients

A quasi-randomised study [46] of 16 subjects with chronic stable angina awaiting surgery for a coronary artery bypass graft showed improvement on exercise stress testing after 8 months practice of TM. This effect was found with key functional measures including improved exercise duration, improved exercise workload and delayed onset of ST-T changes (ECG evidence of myocardial ischaemia).

3.5.2. Mortality, myocardial infarction and stroke in CHD patients

A meta-analysis of individual patient data from 2 RCTs [30,47] found a 23% reduction in all-cause mortality compared to combined controls, a 30% reduction in CVD mortality and 49% reduction in cancer mortality [48].

A larger prospective RCT funded by the NIH was conducted on 201 African American subjects with at least one coronary artery with 50% stenosis on angiography and followed for an average of 5 years. They were randomised to either TM or a health education group and continued their usual medical care (see Fig. 4).

Fig. 4.

Effect of TM on cardiovascular clinical events.

Schneider RH et al, Circulation: CV Quality and Outcomes, 5:750–758, 2012

The study primary outcome showed a 48% reduction in myocardial infarction, stroke and all cause mortality in the TM group compared to the health education controls. This effect is similar if not better than that seen with the standard medications for the secondary prevention of heart disease i.e. prevention of CHD in patents who already have heart disease. It is interesting to note that these patients were already taking the standard medications. So this effect is additional to usual medical care. One might say that this finding is equivalent to the discovery of a whole new class of medication – in this case from the body’s endogenous pharmacy for restoring self repair mechanisms.

The study also found a reduction in systolic blood pressure of 5 mm Hg and a reduction in psychological stress (anger). There was a dose-response relationship - which means the more regular the subjects were in their meditation practice, the greater was their disease-free survival. For those that practised with high regularity, i.e. towards 20 min twice daily, risk reduction was 66%. The majority of people in this study were regular in their practice with at least once a day [49].

3.5.3. Hospitalisations for CVD

A cohort study [50] of 2000 TM practitioners compared with 600,000 matched controls found a 87% reduction in hospitalisation for heart disease and a 56% reduction in hospitalisation for all major categories of disease. There was no difference in the hospitalisation for childbirth – indicating that the TM practitioners attended hospitals when needed (see Fig. 5).

Fig. 5.

The effect of TM on hospitalisations for all disease categories.

4. Conclusion

A review of recent scientific statements, meta-analyses, systematic reviews and controlled clinical studies indicate that the Transcendental Meditation technique demonstrates substantial evidence for reducing CVD risk factors and rates of CVD. This evidence suggests that at least this form of meditation is moving from alternative status to a mainstream healthcare approach. The regular experience of the restful alertness state, evident in TM practice, enhances coherent brain functioning, which in turn is associated with improvements in cardiovascular self-repair and homeostatic mechanisms. The reduced CVD morbidity and mortality, reduced related health care costs and improved quality of life, documented with TM practice, have implications for national health care policy and clearly warrant further investigation and clinical implementation. The next research step is to conduct a phase III multi-centre, multi-national study. However, until those are completed there is reasonable evidence to consider using the TM technique in the clinical prevention and treatment of cardiovascular disease [27].