Interplay of physical activity and sleep in modulating heart rate variability: insights from adults with major depressive disorder
Background Major depressive disorder (MDD) is a leading contributor to global disability and is increasingly recognised as a significant cardiovascular risk factor mediated through autonomic nervous system (ANS) dysregulation. Methods This cross-sectional comparative study investigated associations between sleep quality, physical activity, and heart rate variability (HRV) including Poincare plot indices (SD1, SD2, SD1/SD2 ratio) in 46 adults with Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) confirmed MDD versus 46 non-depressed controls (aged 18–45 years) recruited at the Dr BC Roy Multi-Speciality Medical Research Centre, IIT Kharagpur, India. Results MDD participants demonstrated markedly reduced HRV across all domains: SDNN (39.2 ± 14.8 vs 58.0 ± 18.6 ms), rMSSD (27.4 ± 12.6 vs 46.2 ± 15.4 ms), SD1 (19.4 ± 8.8 vs 32.6 ± 11.2 ms), SD2 (52.2 ± 18.6 vs 77.4 ± 21.8 ms), and high-frequency power (5.36 ± 0.88 vs 6.56 ± 0.80 ln ms²; all p < 0.001). Poor sleep quality (PSQI ≥ 7) was significantly more prevalent in MDD (82.6% vs 47.8%). PSQI scores were independently associated with reduced HRV in multivariable regression, with associations substantially stronger in MDD participants and particularly in females with MDD. Physical inactivity amplified sleep-related HRV decrements. Conclusion These cross-sectional findings are consistent with the hypothesis that comprehensive HRV assessment, systematic sleep quality screening, and structured physical activity promotion may be beneficial components of MDD management, pending confirmation from longitudinal interventional studies.