Normative Heart Rate Variability Parameters Across Age and Gender in Healthy Adults from an Apex Tertiary Care Centre in Southern India

Background Autonomic regulation of the heart is commonly assessed using heart rate variability (HRV), which reflects beat-to-beat fluctuations in heart rate. Time- and frequency-domain HRV indices are known to vary with age, sex and environmental influences. However, existing reference values are largely derived from Western populations, underscoring the need for region-specific normative HRV data. Purpose This study aimed to develop comprehensive, region-specific reference values for HRV and to examine age- and gender-related differences in HRV indices in a predominantly South Indian population. Methods This cross-sectional observational study recruited 272 healthy adults aged 18–80 years, predominantly from South India. Five-minute resting ECG recordings were obtained for HRV analysis. Standard time- and frequency-domain HRV parameters were calculated. Data normality was assessed prior to analysis. Baseline comparisons were performed across gender and across three predefined age groups, followed by appropriate post hoc analysis. A prior power analysis was also conducted. Results Data from 249 healthy individuals were included in the final analysis. Normative reference values for time- and frequency-domain HRV parameters were established. Males exhibited lower resting heart rate and higher LF/HF ratio, whereas females demonstrated significantly higher root mean square of successive difference and percentage of successive RR intervals differing from the previous interval by more than 50 ms. Age-wise analysis revealed a more pronounced decline in mean RR interval beyond 30 years of age. Compared with individuals younger than 30 years, those older than 30 years showed significant reductions in HRV—particularly in time-domain parameters and frequency-domain indices. Conclusion This study provides 5-min HRV reference data for healthy adults from a predominantly South Indian population. Both age and gender independently influenced HRV indices, with an age-related decline in overall HRV and higher vagal tone observed in women compared to men. The observed deviations from international Task Force reference values suggest population-specific influences, potentially related to ethnicity, lifestyle and environmental factors. We advocate the generation of region-specific HRV data sets by different centres to get a holistic picture of region- and population-specific variations in HRV.