Originally published July 1 2008
Working the Night Shift Promotes Cancer
by David Gutierrez, staff writer
(NaturalNews) The World Health Organization's International Agency for Research on Cancer (IARC) is adding working the night shift to a list of possible carcinogens, after conducting an analysis of the existing research on the topic.
The IARC reviewed studies on night workers, primarily nurses and airline crews, and found that those who worked overnight were more likely to develop cancer than those who worked during the day.
"There was enough of a pattern in people who do shift work to recognize that there's an increase in cancer," said IARC carcinogen classifications unit head Vincent Cogliano.
Animal studies have shown that animals forced to stay awake at night and sleep in the light develop more malignant tumors and die sooner than animals with normal sleep cycles. Research on humans has also linked years of overnight work among women to higher breast cancer rates, with a similar effect on prostate cancer in men.
Once factor behind the link may be melatonin, which a hormone that the body produces primarily at night. Melatonin has a role in regulating the body's internal clock, and also plays a role in the immune system. Because melatonin breaks down when the body is exposed to light, workers who sleep during the day and are active in well-lit places at night may have an excess of melatonin.
In addition, overnight workers tend to be sleep deprived, because it is impossible to fully reverse the body's internal clock.
"Night shift people tend to be day shift people who are trying to stay awake at night," said Mark Rea, director of the Light Research Center at Rensselaer Polytechnic Institute.
Sleep deprivation has been linked to a variety of negative health effects, including suppression of the immune system.
According to Aaron Blair of the National Cancer Institute, switching between day and night work is even harder on the body than only working at night. Blair recommends that anyone who has to work at night make an effort to sleep in a darkened room after work.
"The balance between light and dark is very important for your body," Blair said. "Just get a dark night's sleep."
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