Gathirua-Mwangi, Wambui G.Palmer, Julie R.Champion, VictoriaCastro-Webb, NelsyStokes, Andrew C.Adams-Campbell, LucileMarley, Andrew R.Forman, Michele R.Rosenberg, LynnBertrand, Kimberly A.2024-04-302024-04-302022Gathirua-Mwangi WG, Palmer JR, Champion V, et al. Maximum and Time-Dependent Body Mass Index and Breast Cancer Incidence Among Postmenopausal Women in the Black Women's Health Study. Am J Epidemiol. 2022;191(4):646-654. doi:10.1093/aje/kwac004https://hdl.handle.net/1805/40353While excess weight is an established risk factor for postmenopausal breast cancer, consideration of maximum body mass index (maxBMI; BMI is calculated as weight (kg)/height (m)2) or BMI at a point in time relevant for breast carcinogenesis may offer new insights. We prospectively evaluated maxBMI and time-dependent BMI in relation to breast cancer incidence among 31,028 postmenopausal women in the Black Women’s Health Study. During 1995–2015, a total of 1,384 diagnoses occurred, including 787 estrogen-receptor (ER)–positive (ER+) cases and 310 ER-negative (ER−) cases. BMI was assessed at baseline and 2, 4, 6, and 8 years before diagnosis. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Compared with women with BMI <25, those with BMI ≥35 had increased risk of ER+ breast cancer but not ER− breast cancer. For BMI assessed 2 years before diagnosis, the HRs for ER+ breast cancer associated with maxBMI ≥35 and time-dependent BMI ≥35 were 1.42 (95% confidence interval (CI): 1.10, 1.84) and 1.63 (95% CI: 1.25, 2.13), respectively. The corresponding HR for time-dependent BMI assessed 6 years before diagnosis was 1.95 (95% CI: 1.45, 2.62). These findings suggest strong associations of BMI with risk of ER+ breast cancer in postmenopausal women, regardless of timing of BMI assessment.en-USPublisher PolicyAfrican AmericansBlack raceBody mass indexBreast cancerLagged analysisObesityArticle