The relation of body mass index (BMI) and weight gain to breast cancer risk is complex, and little information is available on Black women, among whom the prevalence of obesity is high. We assessed BMI and weight gain in relation to breast cancer risk in prospective data from the Black Women's Health Study. In 1995, 59,000 African American women enrolled in the Black Women's Health Study by completing mailed questionnaires. Data on anthropometric factors were obtained at baseline and every 2 years afterwards. In 10 years of follow-up, 1,062 incident cases of breast cancer occurred. Incidence rate ratios (IRR) were computed in multivariable Cox proportional hazards regression. BMI at age 18 years of z25 relative to <20 was associated with a reduced risk of breast cancer among both premenopausal women (IRR, 0.68; 95% confidence interval, 0.46-0.98) and postmenopausal women (IRR, 0.53; 95% confidence interval, 0.35-0.81). There was an inverse association of current BMI with premenopausal breast cancer but no association with postmenopausal breast cancer, either overall or among never-users of hormone therapy. Weight gain was not associated with postmenopausal breast cancer risk. In analyses restricted to breast cancers that were estrogen and progesterone receptor positive, IRRs for current BMI and weight gain were elevated but not statistically significant. The findings indicate that being overweight at age 18 years is associated with a reduced risk of both premenopausal and postmenopausal breast cancer in African American women. Understanding the reasons for the association may help elucidate the pathways through which adolescent exposures influence breast cancer risk. The lack of association of obesity with receptor-negative tumors in postmenopausal African American women may partially explain why breast cancer incidence in older Black women is not high relative to other ethnic groups in spite of the high prevalence of obesity in Black women. (Cancer Epidemiol Biomarkers Prev 2007;16(9):1795 -802)
Background Estrogen receptor (ER) negative, progesterone receptor (PR) negative breast tumors occur more commonly in women of African ancestry. Recent research indicates that the effects of reproductive factors may differ by hormone receptor status. We assessed the relation of parity and lactation to incidence of ER−/PR− and ER+/PR+ breast cancer in a cohort of African American women. Methods From 1995–2009, 457 incident cases of ER+/PR+ and 318 cases of ER−/PR− breast cancer were confirmed by review of pathology data among 59,000 African American women followed in the Black Women’s Health Study through biennial questionnaires. Hazard ratios (HR) and two-sided 95% confidence intervals (CI) for the incidence of breast cancer subtypes were derived from proportional hazards regression models that controlled for age, reproductive variables, and breast cancer risk factors. Results Higher parity was associated with an increased risk of ER−/PR− breast cancer (HR = 1.48, 95% CI 0.98–1.84 for 3+ versus 0 births, p trend = 0.009), and with a reduced risk of ER+/PR+ cancer (HR = 0.53, 95% CI 0.39–0.73 for 3+ versus 0 births, p trend = 0.0002). Among women who had breastfed, high parity was no longer associated with increased incidence of ER−/PR− breast, but the inverse association with ER+/PR+ cancer persisted. Conclusions The higher incidence of ER−/PR− breast cancer in African American women may be explained in part by their higher parity and lower prevalence of breastfeeding relative to white women. Impact Increased breastfeeding may lead to a reduction in the incidence of this breast cancer subtype.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.