Physical activity and risk of breast cancer

Abstract

Breast cancer is the most common cancer in women in the world. The possible protective effect of physical activity on the risk of breast cancer has been gaining increasing attention during the past decade. This paper reviews the current status of research on the possible relation between physical activity and the breast cancer risk, and describes physical activity measurement methods used in published studies. Activity was measured by participation in competetive athletics, recreational and leisure-time activity, occupational tasks, job classification, and home-related activity. Studies of the association between all physical activities and the breast cancer risk have used a great variety of methods in the activity assessment and the recall period for considered activity ranged from a lifetime to the past year. The majority of the studies completed so far in spite of the above mentioned limitations in estimating of physical activity and sometimes incomplete control of potential confounding factors, have shown that increased physical activity has been associated at least with modest reduction of the risk of breast cancer. The strength of the relation appears to be more evident in those studies that had less error in the assessment of physical activity parameters (e.g., intensity, frequency, and duration), that controlled adequately for possible confounders, and that examined the effects within subgroups of the study women (e.g., premonopausal women, postmenopausal women). Complicated nature of the physical activity variable in combination with incomplete understanding of biological mechanisms operating between physical activity and breast cancer causes that further research has to be done.