I read these same results 5 years ago--they evolved from the Women's Health Initiative Studies, yet the American Cancer Society isn't "convinced". I wonder why they are just now making a big deal about it?
http://news.yahoo.com/s/ap/20071129/ap_on_he_me/night_shift_cancerNext month, the International Agency for Research on Cancer, the cancer arm of the World Health Organization, will add overnight shift work as a probable carcinogen. The American Cancer Society says it will likely follow. Up to now, the U.S. organization has considered the work-cancer link to be "uncertain, controversial or unproven."
The higher cancer rates don't prove working overnight can cause cancer. There may be other factors common among graveyard shift workers that raise their risk for cancer.
However, scientists suspect that overnight work is dangerous because it disrupts the circadian rhythm, the body's biological clock. The hormone melatonin, which can suppress tumor development, is normally produced at night.
If the graveyard shift theory eventually proves correct, millions of people worldwide could be affected. Experts estimate that nearly 20 percent of the working population in developed countries work night shifts.