Y’know the joke about how everything causes cancer? Well, the World Health Organization announced today that night causes cancer. Or at least night shifts …
LONDON – It was once scientific heresy to suggest that smoking contributed to lung cancer. Now, another idea initially dismissed as nutty is gaining acceptance: The graveyard shift might increase your cancer risk.
Next month, the International Agency for Research on Cancer, the cancer arm of the World Health Organization, will classify shift work as a “probable” carcinogen.
That will put shift work in the same category as cancer-causing agents like anabolic steroids, ultraviolet radiation, and diesel engine exhaust.
If the shift work theory 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.
It is a surprising twist for an idea that scientists first described as “wacky,” said Richard Stevens, a cancer epidemiologist and professor at the University of Connecticut Health Center. In 1987, Stevens published a paper suggesting a link between light at night and breast cancer.
Back then, he was trying to figure out why breast cancer incidence suddenly shot up starting in the 1930s in industrialized societies, where nighttime work was considered a hallmark of progress. Most scientists were bewildered by his proposal.
But in recent years, several studies have found that women working at night for many years are indeed more prone to breast cancer, and that animals who have their light-dark schedules switched grow more cancerous tumors and die quicker.
Two problems. First, as the article later notes, the studies focused on high-stress occupations like nurses and flight attendants, so there’s not a good control group. Second, the explanation doesn’t really make any sense. They claim that melatonin, which is produced in darkness, is a cancer suppressant; when you’re awake and have lights on all night, then you’re stifling melatonin production, raising your risk level. Well, wait, are the amount of light touching your skin and the time of day perfectly correlated? Probably not. It also fails to explain a detail later in the story: variable sleep schedules are worse for cancer risk than being nocturnal. There is not even a clear hypothesis here, let alone a conclusion. Ergo, bullshit.