There is a substantial body of evidence suggesting long-term shift work increases the risk of breast cancer. Now comes another study confirming the association.
Researchers in Canada found that the length of the working the night shift is an important risk factor for breast cancer. A duration of 30 years or more was associated with increased risk. The investigators stratified risk by duration: 0-14 years, 15-29 years, and 30 years or more, and compared the breast cancer incidence to a control group.
No association between night shift work and breast cancer risk was observed for the groups, except for the 30+ year one. Those with the longest history of night shift work had a 2.2x risk of developing breast cancer. The greatest proportion of night shift work was in the health field, with such jobs accounting for 44% of the 30+ year group.
My take: Some believe that light at night and melatonin are a cause of breast cancer. Still, other factors might include sleep disturbances, clock gene dysregulation, and lifestyle differences. As for you, I would consider keeping the room dark at night (no outside light seeping in; no clocks emitting low levels of light; no electronics (including TV) for the hour before sleep). For me, I stumble into the bathroom if I need it at night, sans light.
I’m Dr. Michael Hunter.
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Reference: Occup Environ Med. Published online July 1, 2013. Abstract.