Study Links Working the Night Shift to Higher Risk of Breast Cancer

According to the International Agency for Research on Cancer also known as IARC, working during the night shift is a possible carcinogen. In about 15 studies done, a definite link was found between breast cancer and the night shift worker. In this study it was indicated that women working the night shift had a 30% to 80% increase in proportional risk, making the night shift potentially a greater risk of breast cancer. And in another prospective study in Epidemiology, 115,000 women were followed for 12 years and they were found to have an elevated breast cancer risk among women who worked more than 20 years of rotating night shifts.

Why would working the night shift cause breast cancer?

The cause is not entirely clear as of yet, but according to a report in Epidemiology it is believed that it may have something to do with melatonin production and light exposure. Melatonin is a hormone secreted through a part of the brain which aids our bodies to distinguish when to sleep and when it is time to wake up, this is also known as the circadian rhythm. Basically melatonin is inhibited by light and permitted by darkness and this pattern allows us to sleep and wake at different intervals. With the night shift worker the melatonin production is inhibited and not produced at the same interval as a day shift worker. In animal studies done and published in The Lancet it was found that constant light or disruptions in the circadian rhythm led to tumor formation. More than 20 studies were done on animals that involved disrupting the circadian pattern with most showing a major increase in tumor development. And when compared to the studies on animals that did not have the circadian rhythm disrupted there was no clear effect of tumor formation.

According to the journal The Lancet based on "the limited evidence in humans for the carcinogenicity of shift work that involves night work," and "sufficient evidence in experimental animals for the carcinogenicity of light during the daily work period (biological night), it has been concluded that "shift work that involves circadian disruption is probably carcinogenic to humans."

What can be done to prevent the potential of developing breast cancer while working the night shift?

As of today researchers are still trying to gather more information on a definite linkage between working the night shift and developing breast cancer, however it is still important for society to realize that working the night shift may have some other ill effects in the long haul and not only in relation to cancer. There are also other health risks such as cardiovascular disease and gastrointestinal illness. In the meantime there are other ways to try and reduce the risk of developing cancer and other health issues related to working the night shift such as exercising, eating healthy and having continuous follow up with your health care provider. Finally, workers and employers should be made aware of the risks working the night shift and that there should be a concern. And as a precautionary standard there should not be unnecessary night shift work until further research is done.

Resources:

Schernhammer ES, Kroenke CH, Laden F. Night work and risk of breast cancer. Epidemilogy 2006; 17:108-111

http://www.medicinenet.com/script/main/art.asp?articlekey=85584

http://en.wikipedia.org/wiki/Melatonin

http://www.thelancet.com/journals/lanonc/article/PIIS147020450770373X/fulltext