Ask the Doctors

Dear Doctor: So many bad things seem to be associated with night shifts -- first an increased breast cancer risk, now an increased risk of obesity. Why is that? Is there any way to lessen the risks?

Dear Reader: You're right -- when it comes to the night shift, there's an ever-growing array of pretty bad outcomes. Research has linked this work schedule to a higher risk of coronary artery disease, a higher incidence of diabetes, and increased risk for several types of cancer, depression, social isolation and all manner of sleep disorders. Now, not that surprisingly, obesity has been added to the list. And although the ill effects of night shift work are diverse and wide-ranging, they all have something in common. That is, a significant and ongoing disruption of the body's innate time-keeping system -- circadian rhythms.

We humans have evolved to be awake and active during daylight, and to spend the dark hours in rest and sleep. During the 24(ish) hours that make up a circadian cycle, the shift from daylight to nighttime and back effects changes in our hormones, body temperature, brain function and other metabolic processes. Also involved are biological clocks -- sets of proteins that interact in cells throughout our bodies. These biological clocks are responsible for circadian rhythms -- and regulate their timing.

All of which is why, when a work schedule forces us to stay awake in the dark and sleep during daylight, it's not only our sleep cycles that get drastically altered. Eating habits, digestion, body temperature, the ebb and flow of hormones, and a host of other vital bodily functions are affected as well. Research has shown that the disruption to patterns of sleep and activity not only suppresses the production of melatonin, it may also affect the regulatory mechanisms of genes that play a role in the development of tumors.

It's possible for a worker to become accustomed to the night shift, but his or her body pays a steep price. And it's not just the traditional night shift that is bad for your health. Ongoing research shows that even a moderate deviation from the traditional 24-hour sleep/wake cycle, as in a swing shift or jobs that require rotating day and night hours, takes a physical toll. In the United States, this affects up to 25 percent of the populace, with the biggest challenge faced by workers whose schedules change week to week. Whether they compensate for those time shifts by powering through a sleepless stretch or by trying to switch to a morning bedtime, the outcome is akin to living in a constant state of jet lag.

For those who can manage it, getting into an unbroken 24-hour cycle for sleep and mealtimes can help, sleep experts say. Some workplaces understand the challenges of the night shift and will schedule workers for months at a time. The key is to control exposure to daylight, which regulates circadian rhythms. Be sure to spend time in bright light during a night shift. Wear sunglasses on the trip home from work. Use blackout curtains, sleep masks, ear plugs and sound machines in the bedroom. And on weekends, spend time with friends and family, but try to keep deviations from the schedule to a minimum.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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