Physical activity and endometrial cancer risk: a review of the current evidence, biologic mechanisms and the quality of physical activity assessment methods.

OBJECTIVES: To (1) determine the nature of the association between physical activity and endometrial cancer risk; (2) assess the contribution of variation in the quality of physical activity measurement to inconsistencies in study results; and (3) review the biologic mechanisms that might mediate possible effects of physical activity on risk.
METHODS: We reviewed and summarized all published epidemiologic studies examining physical activity and endometrial cancer risk, and evidence relating to possible biologic mechanisms. We assigned each study a quality score for physical activity measurement.
RESULTS: Fourteen of the 18 studies showed a convincing or possible protective effect of physical activity on endometrial cancer risk, with an average relative risk reduction of around 30%. A dose-response relation was observed in 7 of 13 studies. The quality score was not related to the observed strength of association or the presence of a dose-response relation. There was epidemiologic and biologic evidence that vigorous activity, as well as light and moderate intensity activities, such as housework, gardening or walking for transportation, may reduce risk.
CONCLUSIONS: Physical activity probably has a protective role in endometrial cancer development. More epidemiologic and biologic evidence is needed to make conclusive recommendations on optimal types, characteristics or time periods of physical activity.