Midlife Cardiorespiratory Fitness, Incident Cancer, and Survival After Cancer in Men

IMPORTANCE: Cardiorespiratory fitness (CRF) as assessed by formalized incremental exercise testing is an independent predictor of numerous chronic diseases, but its association with incident cancer or survival following a diagnosis of cancer has received little attention. OBJECTIVE: To assess the association between midlife CRF and incident cancer and survival following a cancer diagnosis. DESIGN, SETTING, AND PARTICIPANTS: This was a prospective, observational cohort study conducted at a preventive medicine clinic. The study included 13 949 community-dwelling men who had a baseline fitness examination. All men completed a comprehensive medical examination, a cardiovascular risk factor assessment, and incremental treadmill exercise test to evaluate CRF. We used age- and sex-specific distribution of treadmill duration from the overall Cooper Center Longitudinal Study population to define fitness groups as those with low (lowest 20%), moderate (middle 40%), and high (upper 40%) CRF groups. The adjusted multivariable model included age, examination year, body mass index, smoking, total cholesterol level, systolic blood pressure, diabetes mellitus, and fasting glucose level. Cardiorespiratory fitness levels were assessed between 1971 and 2009, and incident lung, prostate, and colorectal cancer using Medicare Parts A and B claims data from 1999 to 2009; the analysis was conducted in 2014. MAIN OUTCOMES AND MEASURES: The main outcomes were (1) incident prostate, lung, and colorectal cancer and (2) all-cause mortality and cause-specific mortality among men who developed cancer at Medicare age (≥65 years). RESULTS: Compared with men with low CRF, the adjusted hazard ratios (HRs) for incident lung, colorectal, and prostate cancers among men with high CRF were 0.45 (95% CI, 0.29-0.68), 0.56 (95% CI, 0.36-0.87), and 1.22 (95% CI, 1.02-1.46), respectively. Among those diagnosed as having cancer at Medicare age, high CRF in midlife was associated with an adjusted 32% (HR, 0.68; 95% CI, 0.47-0.98) risk reduction in all cancer-related deaths and a 68% reduction in cardiovascular disease mortality following a cancer diagnosis (HR, 0.32; 95% CI, 0.16-0.64) compared with men with low CRF in midlife. CONCLUSIONS AND RELEVANCE: There is an inverse association between midlife CRF and incident lung and colorectal cancer but not prostate cancer. High midlife CRF is associated with lower risk of cause-specific mortality in those diagnosed as having cancer at Medicare age.