Adult weight change and risk of postmenopausal breast cancer

Abstract

Context: Endogenous hormones are a primary cause of breast cancer. Adiposity affects circulating hormones, particularly in postmenopausal women, and may be a modifiable risk factor for breast cancer. Objective: To assess the associations of adult weight change since age 18 years and since menopause with the risk of breast cancer among postmenopausal women. Design, Setting, and Participants: Prospective cohort study within the Nurses' Health Study. A total of 87 143 postmenopausal women, aged 30 to 55 years and free of cancer, were followed up for up to 26 years (1976-2002) to assess weight change since age 18 years. Weight change since menopause was assessed among 49 514 women who were followed up for up to 24 years. Main Outcome Measure: Incidence of invasive breast cancer. Results: Overall, 4393 cases of invasive breast cancer were documented. Compared with those who maintained weight, women who gained 25.0 kg or more since age 18 years were at an increased risk of breast cancer (relative risk [RR], 1.45; 95% confidence interval [CI], 1.27-1.66; P