Association of Body Composition Parameters With Heart Rate Variability in Healthy Adults: A Cross-Sectional Study

Objective This study aims to investigate associations between body composition and heart rate variability (HRV) in healthy adults and to assess whether body composition provides additional information compared with body mass index (BMI). Methods This cross-sectional study enrolled 400 healthy adults (216 males, 184 females; aged 18–65) who underwent health exams during 2022–2024. Body composition (weight, BMI, fat mass, muscle mass, skeletal muscle mass, protein) was measured by multi-frequency bioelectrical impedance analysis. HRV parameters (standard deviation of all normal-to-normal intervals, percentage of NN50 [pNN50], low-frequency power [LF], high-frequency power [HF], LF/HF) were derived from 24-h ambulatory electrocardiography. Pearson correlations and multiple linear regression (adjusted for age, sex, blood pressure) were used. Results Fat mass negatively correlated with pNN50 ( r = −0.367) and HF ( r = −0.401) and positively with LF/HF ( r = 0.349), all P < 0.001; BMI showed no correlations. Multivariable regression confirmed fat mass was independently associated with lower HF (β = −9.152, 95% confidence interval [CI] −11.144 to −7.160) and higher LF/HF (β = 0.087, 95% CI 0.065–0.109, both P < 0.001); skeletal muscle mass was independently associated with higher HF (β = 1.024, 95% CI 0.006–1.879, P = 0.032). Conclusion Excess fat mass is independently associated with reduced vagal tone and sympathovagal imbalance, while greater skeletal muscle mass is associated with preserved vagal function. BMI did not detect significant associations with HRV indices in this cohort, although it remains a valuable population-level screening tool. Precise body composition quantification may help inform early cardiovascular risk stratification.