Night Shift Jobs Up Breast Cancer Risk

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People who work the night or graveyard shift are more susceptible to developing breast cancer, says a new study.

The study, led by researchers from Erasmus University Medical Center, found that people who have irregular sleeping patterns have a higher risk of developing breast cancer, especially in women.

Researchers made use of mice models to find out the effects of irregular sleep patterns. For the study, the mice's circadian rhythms were disrupted by delaying it at 12 hours every week for one year in alternating light-dark cycles.

According to the National Sleep Foundation, the circadian rhythm is our body's natural biological clock. It regulates our body's levels of sleep and wakefulness.

In the findings published online in the journal Biology, the researchers found that mice who were exposed to light/dark periods developed mutations that cause breast cancer. The mice also gained 20 percent more body weight.

According to Bert van der Horst, coauthor of the study, the primary factor for the development of breast cancer and weight gain in the mice is because of the out of sync circadian rhythm. Other factors such as low vitamin D or lack of sunlight exposure are only considered to be secondary factors, according to International Business Times' report.

However, Horst added that more studies need to be conducted in order to test the results of the experiment, as the conditions of human shift workers are different from those of the lab mice.

"One of the questions we often get is to what extent does a mouse resemble humans," Horst explained. "The mechanism of the circadian clock as well as carcinogenesis is comparable in mice and man, and this model opens new avenues for further exploring how circadian disruptions affect the body and how you can intervene to reduce adverse effects."

According to the researchers of the study, there are other lifestyle factors of night shift workers that could also contribute to increased risk for breast cancer.

"Shift work involves many aspects that could be involved in the causal mechanisms that lead to increased health risks: internal desynchronization, melatonin suppression due to light at night, sleep disruption, lifestyle disturbances (such as smoking, [lack of] breastfeeding, unhealthy diet, altered timing of food, etc.), and decreased vitamin D levels due to lack of sunlight exposure," the researchers wrote in their study.

Newsweek reports that the association of disrupted circadian rhythm and increased health risks are not new, in fact, irregular sleeping habits have been found to increase the risk of developing type 2 diabetes, heart attacks and obesity.