Yoga for Prevention of Cardiovascular Diseases
Yoga for Prevention of Cardiovascular Diseases
By Yoon-Hang Kim, MD, MPH, DABMA
Dr. Kim practices integrative medicine in San Jose, CA; he reports no consultant, stockholder, speaker’s bureau, research, or other financial relationships with companies having ties to this field of study.
Cardiovascular diseases (CVD) are the most common cause of mortality in the United States. Approximately 70 million people in the United States have some form of CVD, and in 2002 CVD accounted for 38% of all deaths in the United States.1 Despite advances in therapeutic procedures and medications, the morbidity and mortality from CVD continue to burden society. The American College of Cardiology’s sponsorship of its first course on complementary and alternative medicine (CAM) in 2003 is an indication of growing interest among medical professionals in employing various CAM modalities to aid in the effective treatment of cardiovascular diseases.2
Yoga originated in India more than 2,000 years ago. In its original form, yoga was an integrated system of practice including spiritual, moral, and physical dimensions. The word yoga originates from a Sanskrit word meaning to unify or yoke, and implies a connection between body, mind, and spirit.3 The table above lists the major methods of training in yoga described by the ancient Vedic texts.3
In addition to the major methods described in the above table, many specialized styles of yoga exist today. Transcendental meditation can be considered an example of a specialized form of yoga developed by Maharishi Mahesh Yogi as a mind-body method of self-regulation. The protective benefits of transcendental meditation for CVD have been covered in a previous article appearing in this newsletter (see the July 2002 issue of Alternative Medicine Alert).4
The practice of yoga has become extremely popular in the United States. Among the many styles, Hatha yoga is the most popular.5 The practice of Hatha yoga combines postures (asanas) and breathing techniques (pranayama), with meditation often practiced in the beginning and at the end of Hatha yoga classes. A telephone survey conducted in 1998 by Saper et al revealed that an estimated 15 million American adults have used yoga at least once in their lifetime and 7.4 million during the previous year. Yoga was used for both wellness and specific health conditions, often with perceived benefit.6
Mechanism of Action
Western scientific exploration of yoga was stimulated by extraordinary feats achieved by yoga masters. The following are two examples of such feats performed by yoga masters where no scientific explanation exists. The first was documented in 1973; a single yogi remained in an underground pit for eight days, with an absence of electrical activity in the EKG during the period.7 He was then removed and shown upon examination to be in good health. In the second case, documented in 1982, practitioners of a Tibetan form of Buddhist meditation, g-Tum-mo yoga, increased the temperature of their digits by 5-15° C.8 Both examples suggest that yoga training could provide an advanced practitioner voluntary control of the autonomic system. In 2004, Telles et al conducted a clinical trial to investigate the ability to voluntarily reduce the heart rate after one month of yoga practice.9 In this study, the yoga group was given instruction whereas the control group received no instruction. At the end of one month, the yoga group was able to reduce their heart rate by an average of 10.7 beats per minute compared to the control group (P < 0.05). The significance of this study is that the heart rate, an autonomic function, can be modulated in a novice practitioner with one month of yoga training.
A common pathway for the effect of regular yoga practice appears to be the autonomic nervous system; specifically, yoga practice decreases sympathetic activity and increases parasympathetic activity resulting in decreased catecholamine and cortisol secretion.5 It appears that various components of yoga practice, such as meditation, postures, and breathing exercises, individually can result in the described autonomic changes. Telles et al conducted another study investigating the meditative aspect of yoga, comparing a group mentally chanting "om" to a random thinking group.10 The om meditation group had decreased heart rates compared to the random thinking group. Madanmohan et al conducted a study investigating the postural aspects of yoga practice using the shavasana position and demonstrated both decreased sympathetic activity and increased parasympathetic activity.11 Udapa et al conducted a study investigating the effect of yoga breathing vs. no intervention (control group) and also demonstrated decreased sympathetic activity and increased parasympathetic activity.12 Luciano et al conducted a study comparing the effect of yoga mantra recitation vs. Ave Maria prayer.13 The results demonstrated that both recitations of the rosary and yoga mantras slowed breathing to six breaths per minute resulting in enhanced heart rate variability. Lastly, Raghuraj et al described the ability to increase or decrease sympathetic activity by utilizing two different types of yogic breathing known as kapalabhati (breathing at high frequency) vs. nadisuddhi (alternate nostril breathing).14 The kapalabhati was found to increase sympathetic activity while nadisuddhi was found to decrease sympathetic activity.
Clinical Evidence
An early study documenting the benefits of yoga for hypertension was conducted in 1975 by Patel.15 The trial compared an intervention group and an age- and gender-matched control group where 12 hypertensive patients in the intervention group were treated by yoga and biofeedback for 12 months. Results showed a statistically significant reduction in blood pressure in the group using yoga and biofeedback compared to the control group.
There are a large number of non-randomized, uncontrolled studies providing foundational support for the benefits of yoga for cardiovascular risk reduction, particularly in reducing blood pressure. However, many studies lack the rigor of a randomized controlled trial. In 1984, Sundar et al conducted an intervention study demonstrating that six months of yoga practice results in statistically significant reductions in systolic and diastolic blood pressure.16 In 1997, Schmidt et al reported results of an interventional study demonstrating that a comprehensive residential three-month yoga and meditation program where participants lived on a low-fat vegetarian diet reduced body mass index, cholesterol, and blood pressure.17 In 2002, Damodaran et al conducted an intervention study involving three months of yoga practice, which resulted in decreased blood pressure, cholesterol, and blood sugar.18 In addition, decreases in vanillylmandelic acid catecholamine and malondialdehyde levels were documented, suggesting decreased sympathetic activity and decreased oxidative stress. In 2004, Singh et al conducted a yoga intervention study on Type 2 diabetic patients, demonstrating reduction of pulse rate, blood pressure, and fasting glucose level.19 In 2005, Bijlani et al conducted a comprehensive lifestyle education program based on yoga lasting 10 days.20 At trial’s end, the authors reported a reduction in fasting blood glucose and cholesterol. Overall, the results of the studies are consistent for improvement of risk profile for developing CVD in as little as 10 days of yoga training. However, the significance of the studies is reduced as they employ pre-post derandomized, controlled methodology. It is also important to note that the above trials integrated the physical practice of yoga with a more complete yogic lifestyle.
Another non-randomized study that has important implications was conducted by Bharshankar et al comparing 50 sedentary subjects with 50 yoga practitioners age 40 years and older.21 Blood pressure was positively correlated with age in both groups, but results of the study showed that yoga practitioners had a lower pulse rate (P < 0.001) and lower systolic and diastolic blood pressure (P < 0.01). The significance of this study is that yoga appears to reduce the age-related deterioration in cardiovascular functions. However, the groups were not age-matched, which decreases the strength of the authors’ conclusions.
In 2000, Murugesan et al conducted a randomized controlled trial investigating the effect of yoga practice on the management of hypertension.22 Thirty-three subjects were randomly assigned to three groups. The first group participated in yoga practice, the second group received antihypertensive medications, and the third group received no treatment. The results demonstrated that both the yoga and antihypertensive medication groups achieved reduction in blood pressure, heart rate, and body weight compared to the control group receiving no treatment.
In 2000, Manchanda et al conducted a randomized controlled trial investigating the effects of a yoga lifestyle on coronary artery disease.23 The study enrolled 42 men with coronary artery disease who were randomly assigned to a yoga intervention group or a control group, and followed for one year. The yoga lifestyle program included a strict control of risk factors such as smoking, diet control, moderate aerobic physical exercise, breathing and relaxation exercises, stress management, and meditation. The control group was managed by conventional methods, such as risk factor control and a diet plan outlined by the American Heart Association. At the end of one year, the yoga group showed significant improvements including a reduction in the number of anginal episodes, an improved exercise capacity, and decreased body weight. The results also showed the statistically significant regression of coronary artery lesions in the intervention group vs. the control group (20% vs. 2%) as determined by coronary angiography.
Experiencing a Class
A yoga session can vary in content and time depending on the style of yoga, and can be individualized to suit the needs and limitations of any patient. Classes can be extremely gentle as with restorative yoga. A typical session lasts 45-90 minutes, and usually includes breathing exercises characterized by long and deep diaphragmatic breathing. These can be performed either sitting or lying down. Asana practice, or the assuming of various postures in association with breathing exercises, is typically performed next. The postures further facilitate the connection of body, mind, and spirit and help promote relaxation. The end of a yoga class usually employs meditation, visualization, or guided imagery.
Safety
Yoga is a relatively safe activity; however, injuries can result from improper practice. It is important to seek an experienced teacher and to communicate any physical concerns with the teacher prior to beginning the lesson.
Conclusion
There is a small amount of evidence suggesting that yoga lowers blood pressure and protects the practitioner from cardiovascular diseases. The complete practice of yoga and a yoga-based lifestyle including vegetarian diet appears to reduce risk profiles in as short as 10 days. That stated, there is a significant need for additional research if yoga, especially as practiced in the United States, is to be recommended as a therapeutic adjunct to conventional care.
Recommendation
Yoga offers multiple benefits arising from various components including posture, breathing exercises, and meditation. Select patients may benefit from a gentle practice, as data suggest modest improvements in specific cardiovascular parameters, but much of the research focuses on a yogic lifestyle, something not often employed by the majority of yoga practitioners in the United States. As cardiovascular disease is prevalent in our society and commonly employed interventional approaches have associated morbidity and mortality, utilizing yoga practice and yogic lifestyle as a complement to the conventional medical approach is likely to contribute to a positive outcome in select patients with cardiovascular diseases. Identifying a well-trained yoga instructor/therapist with whom the patient can pursue one-on-one instruction can promote individualized programs and allay misperceptions about the practice.
References
1. American Heart Association. Heart and Stroke Statistics—2005 Update. Dallas, TX; 2004.
2. The Second Conference on the Integration of Complementary Medicine into Cardiology; Kohala Coast, HI; Oct. 13-17, 2003. Available at: www.acc.org/education/programs/brochures/vogel3%5Foct03.htm. Accessed June 23, 2005.
3. Ananda S. The Complete Book of Yoga: Harmony of Body and Mind. Delhi, India: Oriental Paperbacks; 1981.
4. Kattapong J. Transcendental meditation and prevention of cardiovascular disease. Altern Med Alert 2002;5:81-83.
5. Frishman WH, et al. Complementary and Integrative Therapies for Cardiovascular Disease. St. Louis, MO: Elsevier Mosby; 2005.
6. Saper RB, et al. Prevalence and patterns of adult yoga use in the United States: Results of a national survey. Altern Ther Health Med 2004;10:44-49.
7. Kothari LK, et al. The yogic claim of voluntary control over the heart beat: An unusual demonstration. Am Heart J 1973;86:282-284.
8. Benson H, et al. Body temperature changes during the practice of g Tum-mo yoga. Nature 1982;295:234-236.
9. Telles S, et al. An evaluation of the ability to voluntarily reduce the heart rate after a month of yoga practice. Integr Physiol Behav Sci 2004;39:119-125.
10. Telles S, et al. Autonomic changes during "OM" meditation. Indian J Physiol Pharmacol 1995;39:418-420.
11. Madanmohan, et al. Modulation of cold pressor-induced stress by shavasan in normal adult volunteers. Indian J Physiol Pharmacol 2002;46:307-312.
12. Udupa K, et al. Effect of pranayam training on cardiac function in normal young volunteers. Indian J Physiol Pharmacol 2003;47:27-33.
13. Bernardi L, et al. Effect of rosary prayer and yoga mantra on autonomic cardiovascular rhythms: Comparative study. BMJ 2001;323:1446-1449.
14. Raghuraj P, et al. Effect of two selected yogic breathing techniques of heart rate variability. Indian J Physiol Pharmacol 1998;42:467-472.
15. Patel C. 12-month follow-up of yoga and bio-feedback in the management of hypertension. Lancet 1975;1:62-64.
16. Sundar S, et al. Role of yoga in management of essential hypertension. Acta Cardiol 1984;39:203-208.
17. Schmidt T, et al. Changes in cardiovascular risk factors and hormones during a comprehensive residential three month kriya yoga training and vegetarian nutrition. Acta Physiol Scand Suppl 1997;640:158-162.
18. Damodaran A, et al. Therapeutic potential of yoga practices in modifying cardiovascular risk profile in middle aged men and women. J Assoc Physicians India 2002;50:633-640.
19. Singh S, et al. Role of yoga in modifying certain cardiovascular functions in type 2 diabetic patients. J Assoc Physicians India 2004;52:203-206.
20. Bijlani RL et al. A brief but comprehensive lifestyle education program based on yoga reduces risk factors for cardiovascular disease and diabetes mellitus. J Altern Complement Med 2005;11:267-274.
21. Bharshankar JR, et al. Effect of yoga on cardiovascular system in subjects above 40 years. Indian J Physiol Pharmacol 2003;47:202-206.
22. Murugesan R, et al. Effect of selected yogic practices on the management of hypertension. Indian J Physiol Pharmacol 2000;44:207-210.
23. Manchanda SC, et al. Retardation of coronary atherosclerosis with yoga lifestyle intervention. J Assoc Physicians India 2000;48:687-694.
Kim YH. Yoga for prevention of cardiovascular diseases. Altern Med Alert 2005;8(8):92-95.Subscribe Now for Access
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