Resting Heart Rate and Risk of Cancer Mortality.

Background: Increased resting heart rate (RHR) is a predictor of mortality. RHR is influenced by cardiorespiratory fitness (CRF). Little is known about the combined associations of RHR and CRF on cancer mortality. Methods: 50,108 men and women (mean age 43.8 years) were examined between 1974 and 2002 at the Cooper Clinic in Dallas, Texas. RHR was measured by electrocardiogram and categorized as <60, 60-69, 70-79, or =80 beats/minute. CRF was quantified by maximal treadmill test and dichotomized as unfit and fit corresponding to the lower 20% and the upper 80%, respectively, of the age- and sex-specific distribution of treadmill exercise duration. The National Death Index was used to ascertain vital status. Cox regression was used to compute HRs and 95% confidence intervals (CI) for cancer mortality across RHR categories. Results: During a mean follow-up of 15.0 ± 8.6 years, 1,090 cancer deaths occurred. Compared with RHR <60 beats/minute, individuals with RHR =80 beats/minute had a 35% increased risk of overall cancer mortality (HR, 1.35; 95% CI, 1.06-1.71) after adjusting for confounders, including CRF. Compared with "fit and RHR <80 beats/minute", HRs (95% CI) for cancer mortality were 1.41 (1.20-1.66), 1.51 (1.11-2.04), and 1.78 (1.30-2.43) in "unfit and RHR <80," "fit and RHR =80," and "unfit and RHR =80 beats/minute," respectively. Conclusions: RHR =80 beats/minute is associated with an increased risk of overall cancer mortality. High CRF may help lower the risk of cancer mortality among those with high RHR. [ABSTRACT FROM AUTHOR]