Assessing the effect of yoga on hypertensionApril 4, 2020
JNC7 recommends that the adoption of a healthy lifestyle is an essential part of the management of high blood pressure (BP). Yoga, which is increasingly becoming a part of the healthy lifestyle approach, is reported to reduce mean systolic BP by 4.17-9.62 mm of Hg and diastolic BP by 3.62-7.22 mm of Hg in a meta-analysis of published clinical trials. However, the evidence is of low quality, as most studies had high risks of bias. The bias was mainly in the area of study design and conduct, which could impact the ethical and scientific aspects of the studies.
Yoga studies frequently include Asanas (postures), Pranayama (breathing exercises) and Dhyana (meditation). Patients are taught yoga in a classroom setting and are advised to practice these at home. These aspects – training, practice, and compliance – are vital to the planning of the study.
Most clinical studies compare the yoga group to no anti-hypertensive treatment. This could raise questions of safety for patients. A good design would be to compare a combination of anti-hypertensive treatment and yoga to anti-hypertensive treatment alone. In such studies, both groups should receive identical anti-hypertensive drugs in a fixed dose. Changing the dose to control BP would mask the effect of yoga.
Amongst hypertensive patients, 45% don not adhere to drug treatment (JNC7). As such, some of these patients may prefer a healthy lifestyle over drug treatment. Placebo-controlled studies of short duration – 8 to 12 weeks – are acceptable in patients with mild hypertension without any organ damage. Such a study of yoga vs no drug treatment would be useful in estimating the actual efficacy of yoga in hypertension. Of course, the study should be approved by an ethics committee, the patients should consent voluntarily, and the clinician should monitor patient safety throughout the study and take appropriate actions when needed.
Randomization of patients to no drug or no yoga group would be difficult as most patients would want to be in the active yoga group. It would also be challenging to retain patients in no drug or no yoga group for 2-3 months. High dropout rates >15-20% can impact the validity of yoga studies. The investigator should counsel the patients about the need for research, explain the risks and benefits and the randomization procedure, and motivate them to comply with protocol requirements and complete the study.
Blinding participants, study personnel, and outcome assessors is an important component for reducing bias. Concealment of allocation of a patient to yoga or no yoga group from the study personnel, who will measure BP, is critical to reduce measurement bias. However, the blinding of participants and study personnel is not feasible with behavioural intervention such as yoga. However, the use of ambulatory blood pressure monitoring and the blinding of outcome assessors to intervention could improve the validity of yoga studies.
A healthy lifestyle is expected to influence the patient’s outlook and behaviour positively. Yoga could be a good lifestyle option for hypertensive patients if high-quality clinical studies are conducted with rigorous methodology – a statistically valid sample size, adequate randomization, concealment of allocation, intention-to-treat analysis and the blinding of outcome assessors.
Writer is a consultant on clinical research & development from Mumbai.