By Nikhil Ramburn and Sat Bir Singh Khalsa, Ph.D.

Hypertension is a condition of abnormally high blood pressure which may eventually damage artery walls and lead to cardiovascular complications. Patients rarely show any symptoms such as headaches and shortness of breath but hypertension remains a major risk factor for heart attack, stroke, chronic heart failure, and chronic kidney disease. Worldwide, hypertension is one of the most important causes of premature morbidity and mortality and is responsible for 7.6 million deaths per year. Hypertension is a major public health concern with estimated direct and indirect annual costs of $76.6 billion in the USA. A diet high in salt along with our modern sedentary and stress-laden lifestyle have in part contributed to the rise in the prevalence of hypertension. Therefore, lifestyle modification, mainly dietary changes and physical activity, are frequently recommended for patients with hypertension along with conventional pharmacological treatments. Unfortunately, poor adherence and the inability of these standard interventions to address underlying causes such as lifestyle stress render these conventional methods of treatment only modestly effective. This is especially the case with this disorder in which patients are not directly experiencing uncomfortable symptoms of the disease and are therefore less motivated to make lifestyle changes.

Since expert panels on hypertension continuously stress the importance of non-pharmacological approaches and lifestyle modifications, it is imperative that we identify alternative strategies that effectively lower blood pressure while addressing the underlying risk factors. Yoga is likely to prove to be one such alternative treatment option since it addresses several of the factors contributing to the development of hypertension, especially lifestyle stress. Indeed, several key mechanisms make yoga a potentially beneficial therapy for hypertension. Yoga practices directly stimulate the vagus nerve, increasing parasympathetic activity and reducing activation of the sympathetic nervous system; they also positively impact neuroendocrine function and inflammatory pathways. These mechanisms are critically beneficial for hypertension because of the stress-induced sympathetic dominance in the autonomic nervous system.

Pranayama, specifically slow breathing practices, are known to have direct and immediate impact on the autonomic nervous system and blood pressure by enhancing baroreflex sensitivity. This significant finding has been particularly well-characterized by the elegant and rigorous studies of pranayama researcher Luciano Bernardi in Italy, which clearly demonstrated the pronounced effects of slow yogic breathing on both the respiratory chemoreflex response as well as the baroreceptor reflex response in both normal and hypertensive subjects. As early as 2001, he concluded that “Enhanced baroreflex sensitivity might be one factor inhibiting the chemoreflex during slow breathing. A slowing breathing rate may be of benefit in conditions such as chronic heart failure that are associated with inappropriate chemoreflex activation.”

More recently, slow pranayama was shown to be effective in reducing blood pressure in an Indian study by yoga researchers Bhavanani, Madanmohan, et al. involving 29 patients with hypertension or prehypertensive conditions. Within only five minutes of practice of Pranava Pranayama, which involves a slow and deep inhale followed by a prolonged chant of AUM (OM), subjects revealed a statistically significant reduction in systolic pressure and supine heart rate, both indicators of cardiovascular function and sympathetic activation. In addition, the immediacy of the results (within 5 minutes) indicates that yogic breathing may also be used in acute clinical interventions when blood pressure needs to be lowered as quickly as possible. These findings also suggest that pranayama should be considered as a key component in yoga interventions.
The first systematic review of the literature on the efficacy of yoga for hypertension was published in 2014 and included 39 cohort studies, 30 nonrandomized controlled trials (NRCTs), 48 randomized controlled trials (RCTs) and 3 case reports. The yoga interventions ranged from 1 week to 4 years and involved a total of 6,693 subjects. Most studies reported favorable outcomes with yoga effectively reducing blood pressure in both normotensive and hypertensive populations. The investigation of yoga as a treatment for hypertension has a long-standing history, and in fact, the very first RCT ever published on yoga was on hypertension. In that early United Kingdom study from 1975, 37 hypertensive patients were randomly allocated to yogic relaxation, breathing, and meditation or to simple relaxation, twice weekly for 60 minutes over the course of 6 weeks. At the end of the trial, the yoga group had a significantly greater reduction in systolic and diastolic blood pressure compared to the control group. Although this early study had a number of methodological short-comings, it was overall of acceptable quality. Since that first research trial, the number of RCTs that have been published on this topic have made hypertension one of the most researched areas of yoga therapy.

More recent studies have since provided similar findings, including a landmark paper published in the Journal of Clinical Hypertension in 2014. This is the first RCT to show the significant effects of yoga when compared with an exercise control group. The participants in both groups were asked to attend two 55-minute classes per week for 12 weeks and to perform 3 sessions of home practice for 20 minutes each week. The study included 84 individuals with prehypertension and stage 1 hypertension between 21 and 70 years of age, with over 90% female and predominantly African American. The results in this high minority population indicated that yoga decreased blood pressure while the active control intervention (nonaerobic exercise) did not. The mean systolic and diastolic blood pressure decreased by approximately 5 mm Hg and 4mm Hg respectively, consistent with values found in other controlled studies of yoga for hypertension and comparable to those obtained from other non-pharmacological strategies such as diet, physical exercise and salt reduction.

Another more recent rigorous study conducted at the University of Pennsylvania by Dr. Debbie Cohen and colleagues was just published in 2016. This 3-armed RCT allocated 137 patients with prehypertension and stage 1 hypertension into one of 3 groups: a dietary intervention with a walking program, a regular, twice-weekly yoga practice, or a combination of these two. This was the first study to directly examine how yoga compared to a dietary intervention. All three interventions had a favorable effect on blood pressure reduction with a significantly greater reduction in systolic blood pressure at 12 weeks in the yoga and combination groups as compared with the control group of diet and walking alone. Although the blood pressure reductions were small, they are still noteworthy since even a 2 mm Hg fall in mean systolic blood pressure results in 7% and 10% decreased risk of death from heart disease and stroke respectively, which is a clinically significant reduction in morbidity and mortality rate.

In summary, studies to date have demonstrated the efficacy of yoga, and especially of pranayama, for lowering blood pressure in hypertension without significant adverse side-effects. Future research should provide more data on safety and address the problem of adherence to long-term practice. Despite the encouraging results from existing studies, the American Heart Association has not yet recommended yoga as a non-pharmacologic intervention because of the lack of high-quality, RCTs. Given the potential efficacy of yoga for hypertension (and its added value in addressing the underlying causes rather than just symptoms) and the likely cost-effectiveness of such interventions, the need for larger, high-quality RCTs with long-term follow-ups is critically important. Future research will further improve our knowledge of the underlying mechanisms of yoga action in hypertension and will facilitate the development of even more effective yoga interventions.

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