Background: Sleep 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.
Methods: In 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.
Results: Sleep 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).
Conclusions: Short sleep duration may be a risk factor for hormone receptor-negative breast cancer among black women.
Keywords: Black women; Breast cancer; Hormone receptor-negative breast cancer; Hormone receptor-positive breast cancer; Sleep.
Published by Elsevier B.V.