Sunday, December 2, 2007

Can Working at Night Be a Cause of Cancer?

A report published in The Lancet appears to question whether working the night shift is a good idea. The report comes from several dozen scientists in 10 countries commissioned by the World Health Organization's International Agency on Cancer Research to investigate the idea that breaking one's circadian rhythm could cause cancer.

The report shows "limited" evidence of a connection between cancer and night shift work in people. That evidence included a higher rate of breast cancer in female nurses who work night shifts. While the studies of nurses were purely observational, and didn't prove cause and effect, the scientists also reviewed animal studies.

In this case, animals were exposed to light at night, disrupting the animals' so-called body clocks, or their circadian rhythm. In this case, those studies provided "sufficient evidence" of a connection between circadian rhythm disruption and cancer. This is concerning.

The scientists concluded "shift work that involves circadian rhythm disruption is probably carcinogenic to humans." One of the co-authors speculated that shift work may raise cancer risk by suppressing production of melatonin, a chemical involved in circadian rhythm.



Anonymous said...

Did they rule out natural Vit D/sun exposure?


Dave Jensen said...

Hi S, thanks for your comment. It's a perceptive question, based upon all the positive Vitamin D/Cancer information that has been published lately. I'm afraid that there was no mention of this. Vitamin D and circadian rhythm are not connected (in this research at least).