/publications/issue/2003/2003-08/2003-08-7354

Colorectal Cancer May Be Tied to Women's Work Schedule

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Researchers may have found a link between women who work the graveyard shift and colorectal cancer. Women who worked 15 years or more on night shifts had a 35% greater chance of developing colo-rectal cancers, compared with those whose jobs required more day shifts. The findings were published in the June 4, 2003, issue of the Journal of the National Cancer Institute.

The connection may be related to the hormone melatonin.This molecule has been shown to kill intestinal cancers in laboratory animals; however, it is not produced when people are exposed to light at night. The scientists admit that the study does not prove a connection, and no one has demonstrated melatonin?s anticancer properties in humans.

Data from the Nurses? Health Study were used for this new study. Of the participants, 78,500 provided information about their work schedules. Then they were broken into 8 groups, from those who worked no night shifts to those who worked at least 3 nights a week for >30 years.

"This is one study, and the increase is quite modest," said Francine Laden, ScD, an epidemiologist at Harvard Medical School and coauthor of the study. "More work needs to be done to look at the potential risk."