Sexual orientation and benign breast disease in a cohort of U.S. women

Purpose: Several studies indicate that sexual minority (e.g., bisexual, lesbian) women may be at an increased risk for breast cancer. However, we know little about how risk factors, such as benign breast disease (BBD)—which can confer nearly a fourfold breast cancer risk increase—may vary across sexual orientation groups. Methods: Among Nurses’ Health Study II participants followed from 1989 to 2013 (n = 99,656), we investigated whether bisexual and lesbian women were more likely than heterosexual women to have breast cancer risk factors including a BBD diagnosis (self-reported biopsy or aspiration confirmed, n = 11,021). Cox proportional hazard models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI). Results: Compared to heterosexuals, sexual minority participants more commonly reported certain breast cancer risk factors including increased alcohol intake and nulliparity. However, sexual minority participants were more likely than heterosexuals to have certain protective factors including higher body mass index and less oral contraceptive use. When evaluating age- and family history-adjusted rates of BBD diagnoses across sexual orientation groups, bisexual (HR 1.04, 95% CI [0.78, 1.38]) and lesbian (0.99 [0.81, 1.21]) women were just as likely as heterosexuals to have a BBD diagnosis. Results were similar after adjusting for other known breast cancer risk factors. Conclusions: In this cohort of women across the U.S., sexual minorities were more likely than heterosexuals to have some breast cancer risk factors—including modifiable risk factors such as alcohol intake. Heterosexual, bisexual, and lesbian women were equally as likely to have a BBD diagnosis.