Lack of sleep is linked to more aggressive breast cancers, according to new findings published in the August issue of Breast Cancer Research and Treatment by physician-scientists from University Hospitals Case Medical Center’s Seidman Cancer Center and Case Comprehensive Cancer Center at Case Western Reserve University, Cleveland.1
Led by Cheryl Thompson, PhD, the study is the first-of-its-kind to show an association between insufficient sleep and biologically more aggressive tumors as well as likelihood of cancer recurrence.
Study Design
The research team analyzed medical records and survey responses from 412 postmenopausal breast cancer patients treated at UH Case Medical Center. All patients were recruited at diagnosis and asked about average sleep duration in the past 2 years. Researchers found that women who reported 6 hours or less of sleep per night on average before breast cancer diagnosis had higher Oncotype DX tumor recurrence scores (which are based on the expression level of a combination of 21 genes).
“This is the first study to suggest that women who routinely sleep fewer hours may develop more aggressive breast cancers compared with women who sleep longer hours,” said Dr. Thompson, who is Assistant Professor at Case Western Reserve University School of Medicine and lead author. “We found a strong correlation between fewer hours of sleep per night and worse recurrence scores, specifically in postmenopausal breast cancer patients. This suggests that lack of sufficient sleep may cause more aggressive tumors, but more research will need to be done to verify this finding and understand the causes of this association.”
Pre- vs Postmenopausal Women
The authors point out that while the correlation of sleep duration and recurrence score was strong in postmenopausal women, there was no correlation in premenopausal women. It is well known that there are different mechanisms underlying premenopausal and postmenopausal breast cancers. The data suggest that sleep may affect carcinogenic pathway(s) specifically involved in the development of postmenopausal breast cancer, but not premenopausal cancer.
“Effective intervention to increase duration of sleep and improve quality of sleep could be an underappreciated avenue for reducing the risk of developing more aggressive breast cancers and recurrence,” said Li Li, MD, PhD, study coauthor and family medicine physician in the Department of Family Medicine at UH Case Medical Center and Associate Professor of Family Medicine, Epidemiology and Biostatistics at Case Western Reserve University School of Medicine.
The study was supported by NCI grants to Case Western Reserve University School of Medicine. ■
Reference
1. Thompson CL, Li L: Association of sleep duration and breast cancer Oncotype DX recurrence score. Br Cancer Res Treat 134:1291-1295, 2012.
