A minor cleans up after a long shift (Jodi Cobb/National Geographic/Getty Images)
A research team at Yale led by epidemiologist Dr. Yong Zhu is currently studying the effect of shifts in circadian rhythms on the risk of certain cancers, including breast, lung, prostate and non-Hodgkin's lymphoma. In 2010, Zhu's team published a paper finding that women who did late-night shift work, which often requires irregular sleeping patterns, had a 50% increase in breast cancer risk.
Interestingly, for shift workers, it isn't just working at night and sleeping during the day that's the problem. Rather, explains Zhu's colleague Dr. Yang, it's the unpredictable nature of shift workers' schedules: sometimes they work at night, other times during the day; the irregularity leads to lost sleep, which can cause long-term health problems. In 2007, the International Agency for Research on Cancer, the cancer arm of the World Health Organization, added overnight shift work to its list of "probable" carcinogens (others include diesel exhaust and UV radiation).
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Once again, it’s time to turn the clocks forward (at 2 a.m. Sunday) for Daylight Saving Time. The yearly change is sure to cause more than a few missed brunch dates, and perhaps some confusion over why the alarm is going off an hour early. But the shift in sleep schedule could have more serious effects on some people’s health, according to experts on circadian rhythm, particularly in people with depression or heart disease.