(ChemotherapyAdvisor) – Data from a first-time study suggest that women who routinely sleep fewer hours may develop more aggressive breast cancers compared with women who sleep longer hours, according to a team of researchers of Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH. This conclusion is based on a study entitled “Association of Sleep Duration and Breast Cancer OncotypeDX Recurrence Score,” which was published in the August issue of Breast Cancer Research and Treatment.  

In this study, the investigators aimed to determine the association between average sleep duration and the diagnosis and aggressiveness of breast cancer. To meet their aim, the investigators conducted an analysis of case-control data of OncotypeDX scores from estrogen receptor-positive, early stage breast cancer patients; these scores are used to guide treatment in this patient population.

“All patients in the parent study were recruited at diagnosis and asked about average sleep duration in the 2 years before diagnosis,” the investigators wrote.  

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The investigators found that recurrence of breast cancer was higher in women whose average sleep duration was lower in the 2 years prior to breast cancer diagnosis (R = −0.30, P = 0.0031), but the effect was limited to postmenopausal women (R = −0.41, P = 0.0011).

“This association remains statistically significant after adjustment for age, physical activity, smoking status, and body mass index in the entire study sample (P = 0.0058) as well as in postmenopausal patients (P = 0.0021),” the investigators reported.