ASPO Abstracts
Sleep duration and risk of invasive breast cancer among Black women
Category: Lifestyles Behavior, Energy Balance & Chemoprevention
Conference Year: 2019
Abstract Body:
Study purpose. It has been suggested that the relation of sleep duration with breastcancer risk is J-shaped, with higher risk for short and long durations of sleep. However,prospective studies have yielded mixed results. Black Americans tend to have shorter sleepdurations than White Americans, but few studies have examined sleep duration and breastcancer within this population. A recent analysis among Black women (n=366 breast cancercases) observed an increased risk of estrogen receptor negative (ER-) breast cancer forshort weekday sleep duration. We assessed sleep duration and breast cancer risk in theBlack Women’s Health Study (BWHS), a large cohort study of Black women.Methods. In 1995, 59,000 women enrolled in the BWHS through mailed questionnaires and arefollowed through biennial questionnaires. Breast cancer cases were identified throughbiennial questionnaires and linkage with cancer registries and confirmed using medicalrecord and cancer registry data. Data on hours of sleep was collected in 2009. Coxproportional hazard regression was used to estimate hazard ratios (HRs) and 95% confidenceintervals (CIs) with control for age, body mass index, education, cigarette smoking,physical activity, and alcohol consumption. Results. Based on 563 incident invasive breast cancer cases that occurred from 2009-2017,of which 74% were postmenopausal, the multivariable-adjusted HRs (95% CI) for ≤5, 6, 7,and ≥9 hours of sleep, relative to 8 hours of sleep (as in the prior study), were 1.03(0.79-1.41), 1.05 (0.84-1.37), 0.99 (0.77-1.29), and 1.07 (0.67-1.72), respectively. TheHRs were similar for ER+ breast cancer (n=394), but elevated for ER- breast cancer(n=150): 1.31 (0.74-2.46), 1.38 (0.84-2.40), 1.39 (0.83-2.47), and 2.14 (0.92-4.84) for≤5, 6, 7, and ≥9 hours of sleep, respectively, relative to 8 hours of sleep. Results wereunchanged with additional control for night shift work, family history of breast cancer,and use of postmenopausal female hormones.Conclusion. Our findings are compatible with a J-shaped association of sleep duration withER- breast cancer, but the results are also compatible with a null association. Largersample sizes are needed to establish whether there is an effect of sleep duration onbreast cancer risk in Black women.
Keywords: breast cancer risk,sleep duration,Black women