Recreational physical activity and breast cancer risk by menopausal status and tumor hormone receptor status: results from the Nurses’ Health Studies

Physical activity is associated with lower breast cancer risk, especially in postmenopausal women. Associations in premenopausal women are less well established. We evaluated recreational physical activity and breast cancer risk in the Nurses’ Health Study (NHS) and NHSII (187,278 women; n = 12,785 breast cancers; follow-up: NHS = 1986–2016, NHSII = 1989–2017) by menopausal status and estrogen (ER) and progesterone (PR) receptor status. Physical activity was evaluated as updated cumulative average of metabolic equivalent of task (MET)-h/week. Cox proportional hazards models were used to estimate multivariable hazard ratios (HR) and 95