introduction: Estrogen begins to decline around the age of 50 while the life expectancy of women is 80 years old. Hormonal changes can lead to central abdominal obesity which has been attributed to increased risk for cardiovascular disease, metabolic disease, diabetes mellitus, and stroke. The prevalence of metabolic syndrome in 2012 was 33% and comparatively higher in women than men (35.6% vs 30.3%) with risks rising with age and hormonal changes. Complementary and alternative medicine (CAM) is gaining popularity among aging women for managing menopausal symptoms. A preliminary literature review revealed that yoga may be a promising CAM for menopausal-aged women to deter risk factors associated with metabolic syndrome. The purpose of this systematic review and meta-analysis is to examine the effectiveness of yoga interventions to reduce metabolic syndrome risk factors in menopausal-aged women.

methods: The guidelines for Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA) were used to conduct this review. PubMed, Medline, and Cochrane Central Register of Controlled Trials were screened through December 2018 for yoga interventions with menopausal-aged women. The outcomes that were of interest included modifiable risk factors for metabolic syndrome. Measures included systolic blood pressure (SBP), diastolic blood pressure (DBP), high-density lipoprotein cholesterol (HDL), triglycerides (TG), fasting blood glucose (FBG), and waist circumference (WC). Effect sizes were calculated using standardized mean differences and 95% confidence intervals for changes from pre to post intervention. Bias was assessed using the Cochrane Risk of Bias Tool.

results: Nine of 266 randomized controlled trials with pre/posttest measures met the inclusion criteria. There were a total cumulative of 310 participants (149 yoga, 161 control) summed from all nine studies at a mean age of 53.4 (SD=8.12). Controls included no exercise standard care in six studies and exercise controls in four studies. Risks of bias were higher in randomization process (n=6), deviations from then intended intervention (n=3), and measurement of outcome (n=4). Significant improvements were reported for BP (n=3), FBG (n=2), and WC (n=1) when compared to non-exercise control groups. When compared with exercise groups, yoga groups showed no significant improvements. Significant posttest improvements occurred within yoga groups for DBP (n=2), SBP (n=1) HDL (n=2), TG (n=1), FBG (n=2), and WC (n=1). However, meta-analysis resulted in modest, though not significant, effects associated with yoga decreasing metabolic risk factors. Because both SBP and DBP had the greatest number of studies, the result of sensitivity analysis after removing outlier studies for SBP (SMD= –0.54; 95% CI –1.15 to 0.07) and DBP (SMD= –0.54; 95% CI –1.15 to 0.07) were only slightly changed but still not significant.

conclusions: The cumulative evidence on the effect of yoga interventions on metabolic syndrome risk factors in menopausal-aged women showed a modest, although not significant, benefit in decreasing BP, dyslipidemia, FBG, and WC. More rigorous research is need for yoga interventions for menopausal-aged women with objective biomarker measures for metabolic syndrome as primary outcomes.