Moderate physical activity and breast cancer risk: the effect of menopausal status.

INTRODUCTION: It has been suggested that both moderate-and vigorous-intensity physical activity reduces the risk of breast cancer. However, the effect of moderate-intensity physical activity on breast cancer risk has not been consistently evaluated by menopausal status and has not been evaluated in Mexican women.
OBJECTIVE: To evaluate the effect of moderate-intensity physical activity (h/week and MET-h/week) on the risk of breast cancer by menopausal status in Mexican women.
METHODS: A population-based case-control study was conducted in Mexico. One thousand incident cases and 1,074 matched controls to cases by 5 years of age, site and health institution participated in the study. Women provided information on health, diet and physical activity by means of an in-person interview. Anthropometric measurements and blood samples were obtained from all women. A conditional logistic regression model was used to assess this association.
RESULTS: Participating in moderate-intensity physical activity decreased the risk of BC in both pre- and postmenopausal women (OR = 0.96; 95% CI 0.92.-0.99; OR = 0.90; 95% CI 0.86-0.93, respectively) for every 3 h per week of moderate-intensity physical activity. There was a statistically significant modification effect by menopausal status (p = 0.009).
CONCLUSIONS: Strategies need to be identified that will engage women in physical activity programs.