Light Exposure May Raise Breast Cancer Risk

Due to its disruptive effects on circadian rhythms and sleep deprivation at night, shiftworking is generally recognized as a risk factor for breast cancer.  As an extension of this notion, Abraham Haim, from the University of Haifa (Israel), and colleagues studied whether exposure to light during sleep also may contribute to breast cancer risk.  The team studied more than 1,670 Israeli women, finding that those routinely exposed to higher intensity light in their sleeping environment had 22% higher odds of developing breast cancer, as compared to women who slept in full darkness. Sleeping with open window shutters, that admit outside light, or sleeping with the television on, did not significantly predict cancer in the study.  The researchers urge that: “Not only should artificial light exposure in the working environment be considered as a potential risk factor for [breast cancer],  but also [light at-night] in the ‘sleeping habitat.’”