Heart Rate Variability in Adults from Low- and High-Altitude Origins Residing in a High-Altitude City: A...

Ramírez, Esteban, C Alejandro Luzardo, Daniel F Namen, Juan D Rivera, Lina Pérez, Daniela Mora, Nicolás Moncada, Santiago Lopez, and Jaime Guiza. Heart rate variability in adults from low- and high-altitude origins residing in a high-altitude city: A cross-sectional comparison. High Alt Med Biol. 00:00-00, 2026.

Heart rate variability (HRV) is used to assess autonomic regulation, reflecting autonomic nervous system activity through heartbeat interval analysis. HRV can be evaluated using time-domain, frequency-domain, and nonlinear methods. Although acute high-altitude exposure has been studied, the effects of chronic exposure remain less well understood.

This study compared HRV in adults from altitudes ≥2,500 m (group 1) and <1,500 m (group 2), with both groups residing in Bogotá, Colombia (2,600 m) for more than 6 months. HRV was assessed using time domain, frequency domain, and nonlinear metrics.

Participants from low-altitude regions (group 2) exhibited higher resting heart rates (p = 0.002) and lower time domains (standard deviation of normal-to-normal intervals, root mean square of successive differences, number of pairs of successive normal-to-normal intervals differing by more than 50 ms, percentage of NN50 [%]; p < 0.05), frequency domain (total power, high-frequency power; p ≤ 0.004), and nonlinear measures (triangular interpolation of the NN interval histogram, standard deviation of instantaneous beat-to-beat variability, short-term fractal scaling exponent; p < 0.05) than those from high-altitude regions. These results indicate a lower HRV in individuals from low-altitude regions.

Adults raised at low altitudes showed lower HRV when living in Bogotá compared with those raised at high altitudes, suggesting an association with long-term autonomic differences potentially related to early-life altitude exposure, rather than a direct causal effect of chronic hypoxia during childhood. These findings may have physiological and clinical implications, particularly in countries with diverse geography. Further prospective, longitudinal research is needed to confirm these associations and clarify their cardiovascular relevance and the potential contribution of genetic and environmental factors.