Importance
Cardiorespiratory fitness (CRF) as assessed by formalized incremental exercise testing is a strong independent predictor of numerous chronic diseases but has received little attention as a predictor of incident cancer or survival following a diagnosis of cancer.
Objective
To assess the association between midlife CRF and incident cancer and survival following a cancer diagnosis.
Design
Prospective, observational cohort study.
Setting
Preventive medicine clinic
Participants and Exposures
The prospective, observational cohort 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 utilized age-sex specific distribution of treadmill duration from the overall CCLS population to define fitness groups as low (lowest 20%), moderate (middle 40%), and high (upper 40%) fit groups. The adjusted multivariable model included: age, exam year, body mass index, smoking, total cholesterol, systolic blood pressure, diabetes, fasting glucose.
Main Outcome Measures
(1) Incident prostate, lung, and colorectal cancer, and (2) all-cause mortality and cause-specific mortality among men who developed cancer are Medicare age (on or after age 65 years).
Results
Compared to low CRF, the adjusted hazard ratio (HR) for incident lung, colorectal, and prostate cancer among men with high CRF was 0.45 (95% CI: 0.29-0.68), 0.56 (95% CI: 0.36-0.87), 1.22 (95% CI: 1.02-1.46), respectively. Among those diagnosed with cancer at Medicare age (65 years), high CRF in mid-life was associated with an adjusted 36% (HR 0.64, 95% CI: 0.45-0.93) risk reduction in all cancer related deaths and a 69% reduction in cardiovascular disease mortality following a cancer diagnosis (HR 0.31, 95% CI: 0.15-0.62) compared to low fit men in mid-life.
Conclusions and Relevance
There is a strong inverse relationship between midlife CRF and incident lung and colorectal cancer but not prostate cancer. High mid-life CRF is also protective against the risk of cause-specific mortality in those diagnosed with cancer at Medicare age.