Sleep duration and breast cancer risk among black and white women

Abstract

BackgroundSleep has been suggested to influence breast cancer risk; however, the evidence is mixed. Black women have a higher prevalence of both short (<6 h) and long (≥9 h) sleep duration and are more likely to develop more aggressive, hormone receptor-negative breast cancer. No study has examined the relationship between sleep and breast cancer in blacks. We focused on race-specific associations among the blacks. MethodsIn the Southern Community Cohort Study (SCCS), a prospective study of which two-thirds of the population were black, we prospectively investigated self-reported sleep duration in relation to overall breast cancer risk by estrogen (ER) and progesterone receptor (PR) status in all women and in black women alone. ResultsSleep duration was not associated with risk of total or hormone receptor-positive breast cancer. However, we found an inverse relationship between sleep duration and risk of ER− and PR− breast cancer among all women and in black women alone. Compared to the reference group (8 h), black women who reported shorter sleep duration had an increased risk of ER− PR− breast cancer (odds ratios; ORs (95% confidence intervals; CIs): 2.13 (1.15, 3.93), 1.66 (0.92, 3.02), and 2.22 (1.19, 4.12) for <6, 6, and 7 h, respectively, (p for trend, 0.04). ConclusionsShort sleep duration may be a risk factor for hormone receptor-negative breast cancer among black women.