Men who alternate between daytime and nighttime shifts on their jobs have triple the normal rate of prostate cancer, according to a Japanese nationwide study.
A variable employment schedule, which can upset daily hormone-production cycles, had previously been linked to breast cancer and, in one study, to colorectal cancer in women. The new finding supports a longstanding expectation that disrupting 24-hour biological rhythms can cause tumors in men too.
The study is the first solid evidence tying shift work to prostate cancer, says neuroendocrinologist David Blask of the Bassett Research Institute in Cooperstown, N.Y.
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