Night shift jobs raise man's prostate cancer risk

While working the night shift heightens a man's risk of developing prostate cancer by nearly three times, it also enhances the risk of developing other types of cancers, including those of the bowel, bladder and lungs.

Though previous studies have already established links between female night shift workers and rise in incidence of breast cancer, the study is the first to put forth the risks of night shifts in men.

According to the findings of the study, keeping awake through the night alters the production of melatonin, the hormone responsible for regulating the sleep-wake cycle.

The study
For the purpose of the study, researchers at the University of Quebec and the Centre INRS-Institut Armand-Frappier looked at 3,137 male cancer patients who had had cancer at one of 11 different sites in their bodies, and compared them with 512 non-cancer counterparts.

The participants were typically assessed for their work schedule and job profiles.

Researchers found that men who worked the night shift were 2.77 times more likely to develop prostate cancer. Their risk of developing lung cancer was 1.76 times; colon cancer 2.03 times; bladder cancer 1.74 times; non-Hodgkin's lymphoma 1.31 times; rectal cancer 20.9 times; and pancreatic cancer 2.27 times higher than those working only through the day.

While the researchers are not clear how night shifts affect a man’s cancer risk, “exposure to light at night can lead to a reduced production of the sleep hormone melatonin, inducing physiological changes that may provoke the development of tumors,” study lead researcher Marie-Élise Parent, of the Centre INRS-Institut Armand-Frappier, said.

“This hormone, habitually released in the middle of the night in response to absence of light, plays a pivotal role in hormonal functions and in the immune system.”

The findings of the study are published in the American Journal of Epidemiology.