Abstract
BACKGROUND: Heart rate variability (HRV) is a crucial indicator of autonomic nervous system function and cardiovascular health. This study aimed to establish normative HRV data for healthy populations residing at high altitudes (approximately 3500 m) in the Keylong district of Himachal Pradesh, India, and to investigate the influence of age and gender on HRV parameters. METHODOLOGY: A total of 145 healthy subjects (101 females and 44 males) without chronic diseases were recruited for HRV measurement using an Equivital wireless device and LabChart software. Time domain, frequency domain, and non-linear HRV parameters were analyzed. Shapiro-Wilk test, multivariate analysis of variance (MANOVA), aligned rank test, and post-hoc tests were applied for statistical analysis. RESULT: Among time domain parameters, females exhibited significantly higher values of average Mean time duration between two successive R waves in ECG during the period of measurement (RR), root mean square of successive differences (RMSSD), and percentage of successive RR intervals that differ by more than 50 milliseconds (pRR50) compared to males. Age significantly influenced pRR50, with the youngest group (18-30 years) showing higher values than the oldest group (51-70 years). The frequency domain and non-linear parameters showed no significant influence of age or gender. Regression analysis revealed that RMSSD, pRR50, and LF/HF were significantly related to age in females, suggesting a decrease in parasympathetic tone and an increase in sympathetic tone with age. The normative HRV values for high-altitude populations differed from those at sea level. CONCLUSION: These findings provide valuable reference data for assessing cardiovascular health and monitoring disease prognosis in high-altitude populations.