Night shifts can increase the risk of cancer in men

Men working in night shifts may be at a higher risk of developing various cancers, a new study has claimed. The study is first-of-its-kind to provide evidence of a possible association between night work and the risk of prostate, colon, lung, bladder, rectal, and pancreatic cancer and non-Hodgkin's lymphoma among men.

"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 tumours," said Professor Marie-Elise Parent of Centre INRS-Institut Armand-Frappier, the study's lead investigator. 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," Parent said in a statement.

Despite finding that night work increases the risk of a number of cancers, the researchers are intrigued by the absence of a relationship between duration of night work and cancer risk found in the study. In theory, an increasing duration in the period of night work would be expected to be accompanied by an increase in the risk of cancer, but the results obtained did not confirm such a tendency.

This finding raises questions about the factors that might influence people`s adaptation to night work. More targeted research, including Parent's current research on prostate cancer, will also allow for a detailed study of the consequences of night work on health. For the study, Parent and her team analysed data from a study on occupational exposure and cancer that was conducted between 1970 and 1985, involving 3,137 men aged 35 to 70 years who had been diagnosed with a cancer at 18 hospitals in the Montreal metropolitan area.

The results were compared to a control group of 512 cancer-free individuals from the general population. The study was published in the American Journal of Epidemiology.