Night workers may be more likely to develop cancer, possibly because shift work disrupts normal wake-sleep cycles, new research shows.
A team of Montreal health experts reported the link after analyzing health records for 3,137 men — aged 35 to 70 — diagnosed with cancer at 18 hospitals between 1970 and 1985.
The findings, published in the American Journal of Epidemiology, indicated night-shift workers faced greater risks of developing prostate, colon, lung, bladder, rectal, and pancreatic cancer, and non-Hodgkin's lymphoma, compared to the general population.
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"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,” said lead researcher Marie-Élise Parent, of the Centre INRS–Institut Armand-Frappier.
“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."
Researchers said they were surprised to discover the connection between night work and cancer risk, particularly since there was no link between the number of hours worked at night and disease.
They also noted the findings raise questions about the factors that might influence people’s adaptation to night work.
The study was funded, in part, by Health Canada and the National Cancer Institute of Canada.
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