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NIH to Require Study of Both Sexes

The US National Institutes of Health is altering its policy to require preclinical research studies to report the sex of the cells, tissues, and animals being used in their studies.

According to a commentary appearing in Nature this week from NIH Director Francis Collins and Janine Clayton, the director of the NIH Office of Research on Women's Health, "[t]he over-reliance on male animals and cells in preclinical research obscures key sex differences that could guide clinical studies." Clinical studies themselves include more women.

Much preclinical work has focused on male cells and animals as researchers have argued that fluctuations in the estrous cycle could confound their experiments. The Nature News Blog notes, though, that some recent meta-studies have cast doubt on this effect.

This emphasis, the New York Times says, has had effects on women as more is known about how certain drugs and diseases affect men. For instance, the Times notes that the US Food and Drug Administration recently said that doses of the sleeping pill Ambien (zolpidem) should be halved for women as they metabolize it more slowly than men.

"One of the underlying assumptions has been that females are simply a variation on a theme, that it isn't a fundamentally different mechanism, that if you've learned about the male you've learned enough to deal with both males and females," the University of Michigan's Jill Becker tells the Times. "We've discovered that's not always the case."

Beginning in October, NIH will roll out policies requiring applicants to report the balance of male and female cells or animals in their studies. First the agency will train staff, those serving on grant-review panels, and applicants, though NIH's Clayton tells the Chronicle of Higher Education that full enforcement will be implemented quickly. She notes to the Nature News Blog that NIH will not require equal numbers of males and females, but both sexes will have to be represented.

The policy, she adds, will allow researchers to explain why it might not make sense for their particular study to include both male and female animals or cells. But aside from reproductive organ-based studies — such as of ovarian or prostate cancer — she said those exceptions should be rare.