Current estimates suggest that over 76 million US adults suffer from hypertension [
Yoga is one such alternative healthcare practice thought to improve blood pressure control [
Methods of the analysis and inclusion criteria were specified in advance but were not documented in a publicly available protocol. A systematic literature search was carried out using the databases Academic Search Premier, AltHealthWatch, Biosis/Biological Abstracts, CINAHL Plus with Full Text, Cochrane Library, Embase, MEDLINE, PsycINFO, PsycARTICLES, Natural Standard, and Web of Science. Additional studies were identified by searching bibliographies of reviews, all studies included in this review, and select uncontrolled studies of yoga and blood pressure. Search terms included yoga or yogi* or yama or niyama or pratyaharaor dharana or dhyana or samadhi or asana combined with “blood pressure” or hypertension or hypertensive or systolic or diastolic.
Abstracts were initially examined by a single investigator (MH). Independent extraction of data on potentially eligible articles was performed by two authors (MH/RS) using predefined data fields. Disagreements between reviewers were resolved by discussion to achieve consensus. Blood pressure values with standard deviation or standard error as well as participant health status, type of yoga intervention, type of comparison group, demographic characteristics, number of participants enrolled and completing the study, location of the study, reporting of adverse events, and methods for measurement of blood pressure were gathered from each paper. Systolic and diastolic blood pressures (mmHg) were the only measures of treatment effect investigated by meta-analysis. Mean posttest values, or change scores when available, were used for analysis. Where no standard deviations were available they were calculated from the standard error. For otherwise eligible studies that did not provide blood pressure values, corresponding authors were contacted by email in an effort to obtain the information needed for inclusion in this review.
The risk of bias for each study was determined independently, but unblinded, by the same two authors using the criteria of the Cochrane Risk of Bias Tool. Disagreements were resolved by discussion to achieve consensus [
Reference Manager (RevMan) Version 5.1 from the Cochrane Collaboration [
A primary methodological concern was whether controlled but nonrandomized studies should be included in the meta-analysis given that such studies by definition suffer from selection bias. Consequently, sensitivity analyses were conducted to assess potential variation by presence or absence of random participant allocation. In an effort to be maximally inclusive of relevant data we included studies whose populations were not explicitly hypertensive but was composed of individuals with cardiac health related issues (e.g., diabetes, metabolic syndrome) with a majority of the study participants currently hypertensive. Consequently, sensitivity analyses were conducted to assess potential variation by presence or absence of study inclusion criteria that required participants to be hypertensive.
We hypothesized a priori that variation in intervention practices would likely contribute substantial heterogeneity to the outcomes. Consequently, subgroup analyses were performed based on duration of the yoga intervention and on yoga practice components included in the intervention Yoga interventions were divided into 3 categories: (1) those that incorporated postures, meditation, and breathing (“3-element yoga”); (2) those that included fewer than the 3 yoga practices just described; (3) yoga using any combination of the three elements plus one or more additional intervention(s). We also categorized yoga intervention by total time of practice, distinguishing between studies where total time of practice was shorter or longer than the mean duration across all studies. Finally, we performed a subgroup analysis based on comparison group, as we expected between-group effects to vary depending on the control condition. For this subgroup analysis, we used three categories of comparison groups: (1) usual care, no treatment, or wait list; (2) exercise; and (3) attention control or active, nonexercise comparator.
The initial database searching located 725 potentially eligible articles; an additional 16 papers were identified through other sources, bringing the total number of articles for preliminary review to 741 (Figure
Flow Diagram of article selection.
Characteristics of each study are detailed in Table
Characteristics of studies (
Author/date/ |
Sample size (yoga, control) | % completed (yoga, controls) | Study population (categorization) | Yoga intervention description (categorization) | Comparison group(s) (categorization) | Yoga frequency/duration of session and total sessions | Total time in minutes | BP measure | Adverse events |
---|---|---|---|---|---|---|---|---|---|
Randomized controlled trials | |||||||||
| |||||||||
Cade et al. [ |
34, 26 | 85.3, 80.8 | HIV infected adults with moderate CVD risk, 83% with hypertension, 18–70 yrs., 47% male, most on multiple medications related to HIV status and CVD risk including BP meds, unclear control of changes in BP meds during study | P, M, B; Ashtanga Vinyasa; encouraged to practice at least one time per week at home/no homework compliance measures [ |
usual care [ |
2.5 wk/60 mins/20 wks | 3000 | NR | NR |
| |||||||||
Cohen et al. [ |
14, 12 | 85.7, 100 | Underactive, overweight adults, with metabolic syndrome, 30–65 yrs., 25% males, 59% on at least one BP med., no reported control for BP meds during study | P, M, B; “Restorative” warm up of stretches and breathing exercises followed by 10 poses. Home practice: 3x week for 30 minutes each/home diary for compliance [ |
No treatment [ |
Intro class 180 mins + 2x wk/90 mins/5 weeks + 1x wk/5 wks + reported mean 117 mins |
2700 | S | None |
| |||||||||
Cohen et al. [ |
46, 32 | 56.5, 96.8 | Hypertensive adults, 22–69 yrs., 50% males, none on BP meds by exclusion at recruitment | P, M, B; Iyengar yoga. Home practice during weeks 6–12 one time per day for 25 minutes/home diary for compliance [ |
Enhanced usual care; motivational and behavioral components of life style modifications, for example, reduction of weight and ingestion of sodium and alcohol [ |
2x wk/70 mins/6 wks + 1x wk/6 wks | 1260 | Am | 3 (7%) |
| |||||||||
McCaffrey et al. [ |
32, 29 | 84.4, 93 | Hypertensive adults, age range not reported/mean = 56 yrs., 35% male, none on BP meds by exclusion at recruitment, controlled for those who began BP meds by dropping from study | P, M, B; unspecified type of yoga it appears to be independent practice rather than classes using booklets based on yogic principles for guidance. No information about training in yoga practice. As appears that all practice was at home (no group classes)—no additional home practice [ |
Usual care [ |
3x wk/63 mins/8 wks | 1512 | NR | NR |
| |||||||||
van Montfrans et al. [ |
19, 23 | 94.7, 73.9 | Hypertensive adults, 24–60 yrs., 51% male, none on BP meds by exclusion at recruitment, no reported control for BP meds during study | P, M, B; multimodality program. Hatha yoga plus progressive relaxation and autogenic training for 8 weeks followed by 10 months of independent practice 2x day with cassette tape. All practice was at home except first 8 weeks so no additional home practice [ |
Education about stress and hypertension. Relaxation in comfortable chair [ |
1x wk/60 mins/8 wks plus home practice of 7x/wk/30 mins/40 wks | 480 | Am | NR |
| |||||||||
Murugesan et al. [ |
11, 11, 11 | 100, 100, 100* | Hypertensive adults, 35–65 yrs., gender not reported, none on BP meds by exclusion at recruitment, one comparison group used BP meds | P, M, B; unspecified type of yoga. List of asanas provided plus Om recitation and meditation. No home practice [ |
No treatment [ |
12x wk/60 mins/11 wks | 7920 | S | NR |
| |||||||||
Patel and North [ |
18, 18 | 94.4, 94.4 | Hypertensive adults, 34–75 yrs., 38% male, 94% on BP meds at enrollment, no reported control for BP meds during study | Not reported if P, M, B; multimodality, unspecified type of yoga. Yoga plus education regarding hypertension, “yoga relaxation methods,” “transcendental meditation,” and skin resistance biofeedback. “Instructed to practice relaxation and meditation twice per day.” No homework compliance measures [ |
No treatment [ |
2x wk/30 mins/6 wks | 360 | S | NR |
| |||||||||
Saptharishi et al. [ |
27, 30, 28, 28 | 77.8, 96.7, 96.4, 89.3 | Young pre- and hypertensive adults, age range not reported/mean of all groups 22 yrs., 67% male, BP meds status not a recruitment criterion and not reported | P, B; unspecified type of yoga; postures and breath practices as per reference to previous paper. It appears that only practice is home practice “encouraged to practice yoga.” No compliance measures reported [ |
No treatment [ |
5x wk/45 mins/8 wks | 1800 | S | NR |
| |||||||||
Subramanian et al. [ |
25, 25, 23, 25 | 100, 100, 100, 84 | Young pre- and hypertensive adults, age range not reported/mean of all groups 23 yrs., 65% male, BP meds status not a recruitment criterion and not reported | P, B; unspecified type of yoga; postures and breath practices as per reference to previous paper. It appears that only practice is home practice “encouraged to practice yoga.” No compliance measures reported [ |
No treatment [ |
5x wk/45 mins/8 wks | 1800 | S | NR |
| |||||||||
Non randomized controlled trials | |||||||||
| |||||||||
Deepa et al. [ |
15, 15 | 100, |
Hypertensive adults, 45–65 yrs., 53% male, 100% on BP medication | P, M, B; Yoga Nidra: it begins with single sitting pose and single breath exercise followed by 45 mins of corpse pose meditation led by instructor. No home practice as this occurred 2x/day [ |
Usual care, in this case, continued medication [ |
10x wk/60 mins/12 wks | 7200 | S | NR |
| |||||||||
Hegde et al. [ |
60, 63 | 95, 100 | Adults with Type 2 diabetes, 40–75 yrs., gender not reported, BP meds status and recruitment criterion not reported | P; unspecified type of yoga—19 asanas described only. No home practice described [ |
Usual care [ |
Class length and frequency not reported: class sessions occurred over 3 months | NR | NR | None |
| |||||||||
Jain et al. [ |
57, 30 | 100, |
Adults, hypertension status not described (although mean BP values suggest pre-hypertension of both groups), yoga group 30–60 yrs., age of control group not reported, 60% male in yoga group, gender not reported in control group, BP meds status and recruitment criterion not reported | P, M; unspecified type of yoga, Surya Namaskar + “Sharir Sanchalan”, and “Bhajan Cassette” |
No description of any kind for control group [ |
7x wk/90 mins/18 weeks | 11340 | S | NR |
| |||||||||
Lakkireddy et al. [ |
52, 49 | 94, |
Adults with paroxysmal atrial fibrillation, 39% with known hypertension, (mean BP values across groups suggest pre-hypertension) 18–80 yrs., 47% male, BP meds not a recruitment criteria but reported and controlled for during the interventions | P, M, B: iyengar: home practice encouraged with DVD provided but no compliance measures for homework [ |
Wait list control, same participants for yoga and control group [ |
3x wk (median value)/60 mins/12 wks. | 2160 | NR | None |
| |||||||||
Mizuno and Monteiro |
17, 16 | 100, |
Hypertensive adults, age range not reported/mean(SD) yoga group = 67 (7) and control group = 62 (12) yrs., 15% male, majority of participants on blood pressure medication, meds controlled for in study | P, M, B; Unspecified type of yoga, although reference for asanas is Iyengar text; Pranayama, then asana, end with breathing meditation [ |
Usual care [ |
3x wk/90 mins/16 wks | 4320 | NR | None (PC) |
| |||||||||
Niranjan et al. |
16, 16 | 100, |
Hypertensive adults, age not reported, gender not reported; BP meds status and recruitment criterion not reported | P, M, B: Unspecificed type of yoga, chanting, prayer, asana, breathing exercises, ending with Savasana. No home practice described [ |
Standard exercise, warm up, stationary bike 30 mins, cool down total = 45 mins; intensity not described [ |
4x wk/60 mins/36 wks | 8640 | NR | NR |
| |||||||||
Patel [ |
20, 20 | 100* | Hypertensive adults, age range not reported/mean = 57 yrs., 31% male, 64% on BP meds at enrollment, no reported control for BP meds during study | Not reported if P, M, B; Multimodality, unspecified type of yoga. Yoga plus “psychophysical relaxation exercise based on yogic principles and reinforced by bio-feedback instruments.” No home practice [ |
No treatment [ |
3 |
1080 | NR | NR |
| |||||||||
Selvamurthy et al. [ |
10, 10 | 100, 100 | Hypertensive adults, 100% male, age range not reported/groups divided by age with mean of yoga 50 yrs. and mean of control group 34 yrs., BP meds gradually withdrawn on all participants prior to study onset | P; Unspecified type of yoga; described several specific asanas. No homework practice [ |
Tilt table [ |
Frequency/time in class not reported. Class sessions occurred over 3 weeks | NR | S | NR |
Yoga intervention categorization: P: postures; B: breathing; M: meditation; 1 = P + M + B, 2 = any 2 of these or less; 3 = (±P ±M ±B) ± other interventions.
Comparison group categorization: 1 = no intervention or usual care, 2 = exercise or exercise + additional intervention, 3 = nonexercise intervention.
BP:blood pressure: measurement methods: S: sphygmomanometer; M: machine; Am: ambulatory blood pressure, and NR: not reported.
Males within study based on enrollment data, if not available, data of participants that completed study was used.
Adverse event: NR: not reported; PC: per personal communication with corresponding author.
Categorization of the risk of bias at the individual study level is presented in Figure
Risk of bias summary.
As illustrated in Figures
Forest plots of overall effect of yoga on prehypertension and hypertension: (a) systolic, and (b) diastolic.
Systolic
Diastolic
Sensitivity analysis was performed by comparing the meta-analysis from all 17 studies with a meta-analysis of the RCTs only (
The number of trials, number of participants, and effect sizes for subgroups is reported in Table
Results of subgroup analyses: effect sizes, number of trials, and number of participants per subgroup.
Subgroup category | Number of trials | Number of participants | Effect size (confidence interval), mmHg | |
---|---|---|---|---|
Systolic | Diastolic | |||
Type of yoga intervention* | ||||
(1) P, M, B | 11 | 431 |
|
|
(2) 2 or less of PMB | 8 | 403 |
|
|
(3) ( |
3 | 109 |
|
|
Type of comparison group* | ||||
(1) No intervention or usual care | 13 | 656 |
|
|
(2) Exercise or exercise + additional intervention | 3 | 97 |
|
|
(3) Non-exercise intervention | 6 | 190 |
|
|
Length of yoga intervention | ||||
(1) ≤ mean (58.9 hours) | 16 | 728 |
|
|
(2) > mean (58.9 hours) | 6 | 215 |
|
|
Types of yoga intervention: P: postures; B: breathing; M: meditation; 1 = P + M + B, 2 = any 2 of these or less; 3: (
Length of yoga intervention: 16 trials (12 studies) were categorized as being of short duration as they fell below the mean value across all studies of 58.9 hours; 6 trials (5 studies) were categorized as being of long duration.
When the results of all 17 studies (22 trials) examined in this review are pooled, yoga was associated with a small but significant decline in both systolic and diastolic blood pressure (−4.17 and −3.26 mmHg, resp.). Further, yoga’s effects on blood pressure varied by type of yoga intervention and by comparison group, but not by duration of yoga practice. These subgroup differences may partially explain the high degree of heterogeneity found across all studies. The level of overall blood pressure reduction achieved by yoga is similar to that of other lifestyle modifications advocated by current guidelines, including exercise [
When the analysis was restricted to studies using interventions incorporating three elements of yoga practice (postures, meditation, and breathing), larger reductions of −8.17 (systolic) and −6.14 (diastolic) mmHg were observed. Declines of this magnitude are of clear clinical and prognostic significance [
Yoga was also associated with a significant decline in systolic (−7.96 mmHg) and diastolic blood pressure (−5.52 mmHg) relative to no treatment, but not when compared to exercise or other types of interventions. It is well known that exercise and some of the other active interventions used within the included studies decrease blood pressure relative to no treatment [
The participants of studies included in this report were male and female adults with prehypertension or hypertension with or without cardiovascular disease. The findings of this report are thus applicable to the majority of individuals with elevated blood pressure. Most studies assessed gentle yoga programs of relatively short duration that could be readily implemented in this clinical population.
Unfortunately, overall quality of studies included in this meta-analysis was poor. All had either unclear or high risk of bias on one or more primary domains. The most common risk of bias was the failure to blind (or to report blinding of) participants. However, studies requiring active participation in an instructor-led intervention cannot be blinded and consequently we did not consider this a primary domain reflecting study quality. However, only 2 of the 17 studies reported blinding of outcome assessors, an entirely feasible method for active intervention studies. In addition, 8 of 17 studies had high or unclear risk of attrition bias and 15 of 17 studies had high or unclear risk of selection bias.
This is the first meta-analytic review to examine the effects of yoga on blood pressure. Strengths of this study include the systematic literature search using multiple databases and based on criteria defined a priori, assessment of studies by multiple authors, a priori decisions regarding appropriate subgroup analyses, and use of well-established meta-analysis procedures for our analyses. One limitation of the current study is we did not assess other potentially contributing factors such as style of yoga, qualifications of instructors or teaching styles, practice environment, participant characteristics such as physical fitness and yoga experience, as well as blood pressure assessment procedures, and other methodological issues. Additional limitations are the restriction to English-language publications, to the selected database sources, and to studies that reported complete blood pressure values.
Exclusion of studies that used yogic interventions but did not label the intervention as such may also have introduced bias. Because there are no universally accepted standards for what constitutes yoga practice, reviews such as this one must necessarily create criteria to define yoga for the purposes of analysis. In this review we excluded studies of certain therapies that, while not defined by the authors as “yoga,” could arguably be viewed as yogic practices. These included, for example, studies of certain meditation techniques that, while generally considered yogic practices, were not described as such. Given that there is already considerable evidence suggesting that meditation is effective in lowering blood pressure; [
The current study is the first meta-analysis to examine the effects of yoga on blood pressure among individuals with prehypertension or hypertension. Overall, yoga was associated with a modest but significant reduction in blood pressure (
This work was funded by the National Institute of General Medical Sciences: 1SC3GM088049-01A1.