Among 3,291 adults aged 20-49 followed for nearly 18 years, each 10-beat-per-minute increase in resting heart rate raised all-cause mortality risk by 26%, driven entirely by non-cardiovascular deaths rather than heart disease. The association was strongest for behavioral and external causes including accidents, suicide, and liver disease, with no significant link to cardiovascular mortality. Critically, this mortality signal only emerged after age 35, suggesting resting heart rate may serve as an early marker of systemic health vulnerability in midlife. This challenges the traditional view that elevated heart rate primarily signals cardiovascular risk. The finding suggests autonomic dysfunction or metabolic stress may manifest through elevated resting heart rate before overt disease develops. However, important limitations include the observational design preventing causal inference and relatively few deaths limiting statistical power for cause-specific analyses. As an unpeer-reviewed preprint, these results require validation through independent replication. If confirmed, routine heart rate monitoring could identify at-risk individuals decades before conventional screening typically begins, potentially shifting prevention strategies toward addressing broader lifestyle and behavioral factors rather than focusing solely on cardiovascular interventions.