Science has discovered a myriad of breast cancer risks over the years. Genetics, early menstruation, a history of chest x-rays, certain medications, drinking, smoking and environmental factors have all been linked to a higher risk of breast cancer. The latest culprit, however, is certainly an unexpected one: working at night.
As odd as it sounds, a study performed by the International Agency for Research on Cancer seems to indicate that working the night shift – and the circadian rhythm disruption that such schedules cause – may raise a woman’s risk of breast cancer by 30%.
The study involved looking at the medical and work histories of over 3,000 women in France. This is a fairly new area of study, so it’s important to view the results with some skepticism and remember that correlation does not always equal causation, but the theories behind why this could be occurring do give the idea a bit more legitimacy.
Specifically, it relates to melatonin production. We already know that hormone balance plays a very large part in certain aspects of women’s health. Realizing that, it’s easy to see why a relationship between melatonin and breast cancer is not that much of a stretch.
When women work nights, they spend the human body’s normal sleeping hours in well-lit areas. Since darkness is one of environmental factors that triggers melatonin production, being under intense lighting during the night can stop the hormone from being produced. Melatonin is a known anti-carcinogen, so it would seem to make sense that any activity or schedule that interferes with its production could increase cancer risk.
Another interesting point brought out in the study is that the cancer risk was higher among women who had worked nights prior to having their first pregnancy. Since pregnancy causes changes to mammary cells, it would seem that the combination of these undifferentiated cells and disrupted circadian rhythms could be the cause of increased breast cancer risk.
The study’s main author, Pascal Guénel, considers night working a public health risk. Of course, in today’s 24-hour world some women simply have no choice to but to work nights.
Still, the information could be useful to women with nontraditional work schedules. It can make them aware of the risks and more likely to take other dietary and lifestyle precautions to prevent breast cancer.
If you work at night – and even if you don’t – be sure to take proper care of yourself and, most importantly, don’t neglect your monthly self-breast-exam and regular mammograms.
