By Melissa Healy, Los Angeles Times/For the Booster Shots blog
5:25 PM EST, December 8, 2011
These days, it's just good to have a job. But remaining gainfully employed can take a toll on health, especially if your work has you up at odd hours and sleeping irregularly. Shift work, say two studies out this week, poses particular problems for women, who appear to be at greater risk of Type 2 diabetes and possibly breast cancer if they maintain work schedules that mess with their internal clocks.
Researchers have uncovered a host of links between humans' respect for their circadian rhythms and their health prospects. Those who toil while their neighbors rest, or who have chronic sleep deficits, are more likely to suffer a wide range of health problems, besides just being tired: They're more likely to be obese and to experience disturbances of metabolism, and to have high blood pressure, heart disease and depression.
In a study published this week in the journal PLoS Medicine, researchers tracked the extent to which more than 175,000 participants in the Nurse's Health Study and its follow-up study, the NHS II, worked "rotating night shifts" over the 18 to 20 years of their participation in the study. (Nurses, of course, attend their patients around the clock, so it is a profession notorious for rotating shifts.)
Those who had spent more than 20 years rotating their work schedules so they sometimes worked nights were almost 60% more likely than women who had never worked rotating shifts to develop Type 2 diabetes. Women who had racked up less time doing shift work also were at higher risk for developing the metabolic disorder, but less so than long-timers (about 20% for women who had donethree to nine years of shift work and 40% for those who had rotated work schedules bewteeen night and day for 10 to 19 years).
The researchers noted that obesity appeared to be a potent contributor to the trend, and that obese shift-working women appeared at greatest risk of diabetes.
Also out this week, a comprehensive Institute of Medicine report on breast cancer and environmental factors cited "growing evidence" that shift work is "probably associated with increase risk for breast cancer," and called for more research to define that link and explore what measures--aside from quitting your night job--might mitigate the effect.
The panel, which prepared the report at the request of the Susan G. Komen for the Cure foundation, speculated about why shift work might boost breast cancer risk, including evidence that irregular sleep patterns disturb the proper function of hormones, and that "clock genes," knocked off-kilter by irregular sleep patterns, may set off cancerous cell growth in breast tissue.
Obesity, of course, is a common factor in Type 2 diabetes and in breast cancer, and shift workers do appear to be at greater risk of weight gain. So if you're working the night shift, making time for exercise and healthful eating might be as important as wedging in some time for shut-eye.
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