Lifetime exposure to regular physical activity and risk of breast cancer: The Western New York Exposures and Breast Cancer (WEB) study
Sereday, Karen Ann
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Background. Physical activity (PA) has been associated with breast cancer (BrCa) risk; few studies have evaluated lifetime PA and BrCa risk by tumor receptor subtypes and age at first pregnancy. Methods. We examined the association between incident BrCa and PA in the WEB Study, a case-control study of women age 35-79 established in 1996-2001 (310/581 pre and 788/1369 postmenopausal cases/controls). Regular moderate and high intensity PA from age 10 to current was collected. Results. PA of >6 hrs/wk (ORs ranged from 0.66-0.77; 95%CI 0.52-0.95) and percentage of lifetime activity (100 vs 0%: OR 0.52; 95%CI 0.36-0.74) was negatively associated with risk in postmenopausal women. The association was limited to ER+, PR+, ER+/PR+ and ER+/PRtumors. There was no evidence of interaction by age at first pregnancy. Conclusions. Our findings support a protective association of PA with BrCa risk among postmenopausal women and suggest differing effects by tumor receptor status.