Graveyard Cancer Risk

How could working at night possibly cause cancer? It doesn't seem a likely risk factor, but next month the International Agency for Research on Cancer will classify shift work as a "probable" cause of cancer. While there are plenty of skeptics, it is interesting to note that at one time it was considered heretic to suggest that smoking and lung cancer were linked.

Scientists suspect that working at night is damaging because it disrupts the circadian rhythm, which is the body's biological clock. The production of the hormone melatonin, a tumor suppressor, is normally produced at night.

The theory is based on research that shows higher rates of breast cancer in women and prostate cancer in men who worked during the night. The findings, however, don't yet prove that working overnight can cause cancer as there may be other common factors among night workers accounting for the increased risk.

If the direct link between working at night and cancer development is proven correct, it will affect approximately 20% of the working population worldwide.