Introduction. Prehypertension is a precursor for developing hypertension and is a risk factor for cardiovascular diseases. Yoga therapy may have a role in lowering the blood pressures in prehypertension and hypertension. This systematic review aims to synthesize the available literature for the same. Methodology. Databases such as PubMed, Embase, Scopus, and Web of Science were searched for randomised control trials only in the time duration of 2010–2021. The main outcome of interest was systolic and diastolic blood pressures. Articles were screened based on the inclusion criteria, and 8 articles were recruited for the review. Meta-analysis was done for suitable articles. RevMan 5.4 by Cochrane was used for meta-analysis and forest plot construction. Risk of bias was determined using the Downs and Black checklist by three independent authors. Results. The meta-analysis of the articles favoured yoga intervention over the control intervention. Yoga therapy had significantly reduced the systolic pressure (−0.62 standard mean difference, at IV fixed 95% CI: −0.83, −0.41) and diastolic pressure (−0.81 standard mean difference, at IV random 95% CI: −1.39, −0.22). Secondary outcome measures studied were heart rate, weight, BMI, waist circumference, and lipid profile. The main protocol of yoga therapy included postures, breathing exercises, and different meditation techniques. A significant reduction in secondary outcomes was observed, except for HDL values in lipid profile which showed a gradual increase in yoga group in comparison with alternative therapy. Conclusion. Yoga therapy has shown to be significant in the reduction of systolic and diastolic pressure in prehypertensive population. Supporting evidence lacks in providing a proper structured dosage of yoga asanas and breathing techniques. Considering the existing literature and evidence, Yoga therapy can be used and recommended in prehypertensive population and can be beneficial in reducing the chances of developing hypertension or cardiovascular diseases.
Prehypertension and hypertension are one of the treatable diseases in the world. There has been strong evidence on the progression of prehypertension to hypertension, provided by the American Heart Association (AHA) in 2011. One of the studies also gives a probability of prehypertensive adults progressing to hypertension . Prehypertension is defined as systolic blood pressure (SBP) 120–129 mmHg and diastolic blood pressure (DBP) 80–89 mmHg by the 2017 guidelines of AHA . According to the update on the 8th guideline by Joint National Committee (JNC), it was SBP 120–139 mmHg and DBP 80–89 mmHg . Prehypertension is a sign and can give the probability of developing cardiovascular diseases in the future. The Framingham heart study (FRS) has found the epidemiology for developing cardiovascular diseases and has identified elevated cholesterol levels and blood pressures as the important predisposing factors . Elevated stress levels have also been correlated with a rise in blood pressure [4, 5]. Yoga improves flexibility, reduces stress levels, and causes strengthening of muscles. The neurobiological causes for increased stress levels were incorporated in a systematic review by Pascoe et al. in 2017 . This systematic review and meta-analysis included the articles which used MBSR and yoga therapy in reducing stress levels and studied its physiological effects. This review did not solely concentrate on elevated blood pressures as a main outcome measure.
Yoga therapy may prove to be beneficial in hypertensive and prehypertensive population. There was a significant effect of yoga on hypertensive population . As per the review by Park and Hans, yoga therapy and meditation are successful in reducing the systolic and diastolic blood pressures . Yoga therapy has been proven to be more effective in comparison to meditation. This review has focused on both hypertensive and prehypertensive population and has not isolated prehypertension as the primary health condition. Supporting literature also has been found on both hypertension and prehypertensive population [7, 8]. Yoga therapy is proven to be beneficial in reducing the cardiovascular risks as per the review by Chu et al. in 2016 . This review has included all the predisposing comorbidities for developing cardiovascular disease and not solely elevated blood pressures. A review solely focusing on prehypertension was not found.
Therefore, this review aims at providing evidence for stand-alone effect of yoga on prehypertensive population. To ensure high level evidence, this review will also aim to provide a meta-analysis for the blood pressure, systolic and diastolic.
2.1. Literature Search
The protocol of this systematic review was registered in Open Science Framework (OSF) with the registration DOI: 10.17605/OSF.IO/YH2FQ. MEDLINE, Scopus, EMBASE, and Web of Science were screened, and searches were run using various search strategies with a combination of Booleans, AND and OR, separately and later combined to get the desired articles as shown in Table 1 through the search engines of PubMed and Embase. The articles which were unsuitable according to inclusion criteria were excluded. Inclusion criteria and exclusion criteria are given in the following. A total of 126 articles were shortlisted based on the various filters of databases mentioned above and selected for title and abstract screening. 40 articles were identified from sources other than the databases referred to above. After title, abstract and full-text screening, eight appropriate articles were finalised and taken for the systematic review as shown in Figure 1, and then they were reviewed. Synonyms and MeSH terms were identified using Cochrane and PubMed MeSH finders and search strategy builders. The synonyms which were used are described in Table 2.
Basic keyword yoga with ‘OR’
Basic keyword blood pressure with ‘OR’
Basic keyword prehypertension with ‘OR’
Combined searches with ‘AND’
Time span filter (2010–2021)
RCT- Randomised control trial.