%0 Journal Article
%T Sleep Duration and Breast Cancer Phenotype
%A Ali Khawaja
%A Santosh Rao
%A Li Li
%A Cheryl L. Thompson
%J Journal of Cancer Epidemiology
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/467927
%X Emerging evidence suggests that short sleep is associated with an increased risk of cancer; however, little has been done to study the role of sleep on tumor characteristics. In this study, we evaluated the relationship between sleep duration and tumor phenotype in 972 breast cancer patients. Sleep duration was inversely associated with tumor grade (univariate ), particularly in postmenopausal women (univariate ). This association did not reach statistical significance after adjustments for age, race, body mass index, hormone replacement therapy use, alcohol consumption, smoking, and physical activity in the entire study sample ( ), but it remained statistically significant ( ) among post-menopausal patients. We did not observe a statistically significant association between sleep duration and stage at diagnosis, ER, or HER2 receptor status. These results present a modest association between short duration of sleep and higher grade breast cancer in post-menopausal women. Further work needs to be done to validate these findings. 1. Introduction Breast cancer is the leading cancer in women in the United States and the third leading cause of cancer deaths among women [1]. It was estimated that over 220,000 women will be diagnosed in 2012 with breast cancer, with almost 40,000 women deaths [2]. Women diagnosed with localized breast cancer have a very favorable outcome, with a 99% 5-year survival. However, the survival rate decreases to 84% with regional disease and 23% for women with distant metastases, underscoring the importance of identifying factors associated with the development of more aggressive breast cancers. There is an emerging evidence for the role of sleep deprivation in carcinogenesis, with new research suggesting that disruptions in the circadian rhythm may increase the risk of several types of cancer [3¨C5], including breast cancer (reviewed in [6]). In the few studies of sleep duration and risk of breast cancer, the association of short sleep duration and the incidence of breast cancer has been mixed, with one study suggesting a decreased risk of breast cancer in women who slept longer [7], two other studies showing an inverse association between sleep duration and risk of breast cancer [8, 9], and a fourth study that did not find evidence of this association [10]. However, much less work has been done to investigate whether short sleep duration prior to the diagnosis is associated with breast cancer phenotype. Markers of more aggressive and advanced breast cancer include stage, determined by the size of the tumor and lymph node status or
%U http://www.hindawi.com/journals/jce/2013/467927/