Resting Heart Rate as a Non-Cardiovascular Mortality Marker in Young Adults: A Population-Based Cohort Study

Background Elevated resting heart rate (RHR) predicts mortality in older adults, primarily through cardiovascular disease (CVD). Prior cohort evidence suggests that RHR also predicts mortality in younger adults, but whether this association operates through cardiovascular or non-cardiovascular pathways has not been directly tested. Methods and Results We analyzed 3291 adults aged 20 to 49 years from NHANES 1999-2004 linked to mortality data through 2019 (median follow-up, 17.8 years; 120 deaths). RHR and heart rate reserve (HRR) were modeled per 10-bpm increment using Cox regression adjusted for demographic, lifestyle, and comorbidity covariates. Each 10-bpm RHR increase was associated with higher all-cause mortality (hazard ratio [HR], 1.26; 95% CI, 1.07-1.50; P=.007), driven by non-CVD mortality (HR, 1.28; 95% CI, 1.07-1.55; P=.009) rather than CVD mortality (HR, 1.15; 95% CI, 0.77-1.71; P=.51). A behavioral/external composite (accidents and NCHS residual causes, including suicide and liver disease) reached significance (HR, 1.35; P=.02), whereas a disease-oriented composite did not (P=.20). The association was absent before age 35 (HR, 0.98; P=.88) but pronounced at ages 35-39 (HR, 2.60; P=.001). HRR was not associated with any outcome. Conclusions In young US adults, elevated RHR predicted mortality through non-cardiovascular rather than cardiovascular pathways, concentrated among behavioral and external causes. The association emerged at age 35, below current screening thresholds. HRR under submaximal conditions carried no prognostic value. RHR in young adults may reflect global health vulnerability rather than cardiovascular risk alone.