Free-living associations between resting heart rate parameters and cardiometabolic health in adults.

This study examined associations between multi-day ultra-short resting heart rate (HR) parameters and cardiometabolic health under free-living conditions. Sixty-seven adults (18-59 years, 53% male) completed seven consecutive days of seated 1-min RR interval recordings after waking using a validated chest strap monitor. Log-transformed root mean square of successive differences (LnRMSSDM) and resting HR (HRM) were averaged across days and standardized. Cardiometabolic health status was defined as the number of metabolic syndrome (MetS) components present. Associations were assessed using Poisson regression adjusted for age and sex, with additional models including HRM and HR-adjusted LnRMSSD. Higher LnRMSSDM was associated with fewer MetS components (IRR = 0.79, 95% CI: 0.64-0.97), whereas higher HRM was associated with greater metabolic burden (IRR = 1.40, 95% CI: 1.10-1.77). When both variables were included, the association between LnRMSSDM and MetS was attenuated and no longer significant (IRR = 0.93, 95% CI: 0.72-1.22), while HRM remained significant (IRR = 1.33, 95% CI: 1.00-1.77). Resting HR parameters obtained through accessible devices were associated with cardiometabolic health, with resting HR accounting for much of the cross-sectional information captured by LnRMSSD. Remote cardiac monitoring may support early cardiometabolic risk identification and longitudinal health surveillance.