Magazine article Science News

Cancer Risk Linked to Night Shifts. (Environment)

Magazine article Science News

Cancer Risk Linked to Night Shifts. (Environment)

Article excerpt

Shift work is hard on the body. It's a schedule that reprograms the biological clock every few days. Those adjustments can disturb sleep patterns, impair mental acuity, and foster irritability. In fact, it might be even worse than that. Two new studies find evidence that women who work the graveyard shift also increase their chance of developing breast cancer.

Both reports, published in the Oct. 17 JOURNAL OF THE NATIONAL CANCER INSTITUTE, raise the prospect that the increased risk results from chronic suppression of melatonin. Concentrations of this brain hormone normally peak during darkness, usually around 1 a.m. Previous studies have indicated that in animals, nighttime lighting--which suppresses melatonin release--boosts the growth of cancers (SN: 10/17/98, p. 248).

In the first of the new studies, the working hours of 800 Seattle-area women with newly diagnosed breast cancer were compared with those of an equal number of healthy women their age. Scott Davis of the Fred Hutchinson Cancer Research Center in Seattle and his colleagues also interviewed each woman about her sleeping habits throughout the previous decade.

Among the 1,600 women, only 11.4 percent reported that commonly they weren't asleep during the period around 1 a.m. Davis found that women with breast cancer were more likely to have been among those who sometimes slept at atypical times. Half of the woman who slept during odd hours periodically worked at night. Women who averaged at least 5. …

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