Objective: To examine whether elevated resting heart rate (RHR) is an independent risk factor for mortality or a mere marker of physical fitness (VO2Max).
Methods: This was a prospective cohort study: the Copenhagen Male Study, a longitudinal study of healthy middle-aged employed men. Subjects with sinus rhythm and without known cardiovascular disease or diabetes were included. RHR was assessed from a resting ECG at study visit in 1985-1986. VO2Max was determined by the Åstrand bicycle ergometer test in 1970-1971. Subjects were classified into categories according to level of RHR. Associations with mortality were studied in multivariate Cox models adjusted for physical fitness, leisure-time physical activity and conventional cardiovascular risk factors.
Results: 2798 subjects were followed for 16 years. 1082 deaths occurred. RHR was inversely related to physical fitness (p < 0.001). Overall, increasing RHR was highly associated with mortality in a graded manner after adjusting for physical fitness, leisure-time physical activity and other cardiovascular risk factors. Compared to men with RHR ≤ 50, those with RHR > 90 had an HR (95% CI) of 3.06 (1.97 to 4.75). With RHR as a continuous variable, risk of mortality increased with 16% (10-22) per 10 beats per minute (bpm). There was a borderline interaction with smoking (p = 0.07); risk per 10 bpm increase in RHR was 20% (12-27) in smokers, and 14% (4-24) in non-smokers.
Conclusions: Elevated RHR is a risk factor for mortality independent of physical fitness, leisure-time physical activity and other major cardiovascular risk factors.
Keywords: Cardiac Function; Coronary Physiology.