Maximum and Time-Dependent Body Mass Index and Breast Cancer Incidence Among Postmenopausal Women in the Black Women’s Health Study
Menée à partir des données 1995-2015 d'une étude portant sur 31 028 femmes ménopausées afro-américaines (âge : 21-69 ans), cette étude analyse l'association entre l'indice de masse corporelle mesuré sur plusieurs années et le risque de cancer (1 384 cas), en fonction du statut des récepteurs hormonaux
While excess weight is an established risk factor for postmenopausal breast cancer, consideration of maximum body mass index (maxBMI) 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, 1,384 diagnoses occurred, including 787 estrogen receptor (ER) positive and 310 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 confidence intervals (CIs). Compared to women with BMI <25 kg/m2, those with BMI ≥35 had increased risk of ER+, 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% CI 1.10, 1.83) 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.