Turn Up the Heat (on Your Electric Blanket)

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Nov. 10, 2000 -- Women have nothing to fear from electric blankets, at least when it comes to developing breast cancer. That's the word from researchers at Yale University. In a recent study published in the American Journal of Epidemiology, researchers concluded that using an electric blanket -- even all night and for many years -- did not increase the risk for developing breast cancer.

About 1,200 women participated in the study, half of them breast cancer patients. About 40% in each group reported regular blanket usage. But no matter what important variable was considered -- age, duration of use, whether those with cancer had estrogen-dependent tumors or not -- the answer was the same: Electric blankets did not appear to increase the risk for developing breast cancer.

"The breast cancer hypothesis [with electric blankets] -- and it may be a credible hypothesis -- is that electrical fields reduce melatonin production ... and that melatonin production actually suppresses growth of tumors," says Eugenia Calle, PhD, director of analytical epidemiology for the American Cancer Society. "That may be credible, but it hasn't been substantiated." Melatonin is a hormone produced in the brain that plays a role in sleep regulation, mood, and ovarian cycles.

Calle says that even the basics behind the hypothesis haven't been established: whether electric blankets do, indeed, decrease melatonin production and in turn, whether lowered melatonin levels result in tumor growth.

"There's no reason at this point in time to worry there's a problem here," Calle says.

Still, she finds one potential weakness to the Yale study. "When people develop a disease, they're acutely aware of everything that might be responsible for development of the disease. That's recall bias." The bias, she says, may not be the recall of the diseased group as much as the lack of recall in the healthy one. "Because of this important life event of getting breast cancer and searching their minds for what could have caused this, the [diseased group] may be able to recall better than those who are healthy." That would make the groups, in effect, unequal.

The lack of a connection between breast cancer risk and electric blankets might seem a bit of a surprise, in light of recent reports about the potential danger of cell-phone use. Some researchers have suggested exposure to the phones might lead to breast cancer.

But David Savitz, PhD, professor of epidemiology at the University of North Carolina in Chapel Hill and an expert in the electromagnetic field research, says they are different situations: "The only thing they have in common is they both produce nonionizing radiation. They have very different frequencies and very different patterns of use. So they're very different kinds of exposures."

Savitz says that while it's too early to say what the medical effects of cell phones might be, the electric blanket question is a little clearer: "In absolute terms, I can't say they're harmless. But with the available evidence, one could argue the level of concern is negligible."

That would go, he says, even for the use of older electric blankets, which emit a higher-strength electrical field. "As far as absolute health benefits? It's not a risk or a foolhardy thing to use the old model blanket," he says.

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