Yoga for Heart Rate Variability: A Systematic Review and Meta-analysis of Randomized Clinical Trials

Area of Science:

• Cardiology
• Integrative Medicine
• Physiology

Background:

• Heart rate variability (HRV) is a key indicator of autonomic nervous system function.
• Yoga is a popular mind-body practice with potential physiological benefits.
• The impact of yoga on HRV requires rigorous scientific evaluation.

Purpose of the Study:

• To systematically review and critically appraise the evidence on yoga's effects on heart rate variability (HRV).
• To assess the quality of existing randomized clinical trials (RCTs) investigating yoga and HRV.

Main Methods:

• Systematic search of nine databases (inception to June 2014) for RCTs comparing yoga to control interventions.
• Inclusion of studies involving healthy individuals or patients with any medical condition.
• Independent review of studies for selection, data extraction, and risk of bias assessment using Cochrane criteria.

Main Results:

• Fourteen RCTs met inclusion criteria, but only two were of acceptable methodological quality.
• Ten RCTs reported favorable effects on HRV, while nine did not; one RCT lacked between-group comparisons.
• Meta-analyses of two trials showed no significant favorable effects of yoga on E:I ratio or 30:15 ratio; remaining data were too heterogeneous for pooling.

Conclusions:

• Current evidence does not convincingly support yoga's effectiveness in modulating HRV in any population.
• Significant methodological weaknesses in existing research limit definitive conclusions.
• Future research should prioritize high-quality RCTs to address the inconsistencies and limitations observed.