An Evaluation of the Evidence Relating to Physical Inactivity, Sedentary Behavior, and Cancer Incidence and Mortality

Abstract

This review provides an up-to-date overview of the evidence relating to physical inactivity, sedentary behavior, and cancer, both in terms of risk and mortality. A summary of the postulated biological mechanisms underpinning these associations is also presented. Epidemiologic evidence suggests that physical activity is inversely associated with cancers of the esophagus (adenocarcinoma), liver, lung, kidney, gastric cardia, endometrium, colon, rectum, head and neck, bladder, and breast, as well as myeloid leukemia and myeloma. Physical activity prior to a cancer diagnosis is related to decreased risk of all-cancer mortality, and pre- and postdiagnosis physical activities are both related to lower risk of breast cancer-specific and colorectal cancer-specific mortality. Prolonged sedentary behavior is associated with an increased risk of colorectal, endometrial, lung, and breast cancer. Pre-diagnosis sedentary behavior is associated with increased risk of all-cancer mortality and colorectal cancer-specific mortality. Postulated biological mechanisms underpinning the associations of physical inactivity and sedentary behavior with cancer include body composition (most evidence relates to adiposity), sex hormones, metabolic hormones, and chronic inflammation. Relatively small behavioral changes at a population level would likely decrease cancer-related burden of disease and associated health expenditure. At the individual level, the optimal frequency, duration, and intensity of physical activity or sedentary behavior required for significant risk reduction or increase remain unclear. Future research should integrate objective activity monitoring with multiple assessment time points into large cohort studies for improved assessment of physical activity and sedentary behavior. Such data will help inform more robust and detailed recommendations for cancer control.