Gymnastik- och idrottshögskolan, GIH

INTRODUCTION: The aim of this prospective cohort study was to investigate the associations between changes in cardiorespiratory fitness (CRF) and the risk of colorectal and prostate cancer in men.

METHODS: Data from men who completed a health assessment both in military conscription in youth and an occupational health profile assessment (HPA) later in life were used. CRF was assessed as estimated V̇O_2max, using a cycle ergometer fitness test at both time points. We linked the assessment data to national register data on colorectal and prostate cancer incidence, and hazard ratios and confidence intervals were estimated using Cox proportional hazard regression.

RESULTS: 139,764 men with a mean age of 18 (SD 0.6) at conscription and 43 (SD 8.9) at HPA were included. The average time between the two assessments was 25.9 (SD 9.0) years and mean follow-up time following HPA test was 10.0 (SD 5.6) years for prostate and colorectal cancer. Annual percentage change in relative and absolute V̇O_2max from conscription to HPA was inversely associated with the risk of colorectal cancer incidence, hazard ratio of 0.83 (95% CI [0.72-0.94]) and 0.88 (95% CI [0.79-0.99]), respectively. These associations were driven by data from individuals in the lowest and moderate level fitness tertials at conscription. Change in CRF was not associated with prostate cancer incidence risk.

CONCLUSIONS: Changes in, not only level of, CRF from youth to adulthood are related to colorectal cancer incidence risk and therefore, improving CRF should be considered as an important colorectal cancer risk reduction strategy.