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NIH's New Policy: Sex Differences in Research

05/14/2014
Kayt Sukel

With studies showing significant sex differences in response to disease and treatment, the National Institutes of Health (NIH) is calling for biomedical researchers to balance the number of male and female subjects when designing experiments. How will this affect your research? Find out...


While women are more likely to develop multiple sclerosis than men, they tend to get less-severe forms of the disease. Baby aspirin does not appear to have the same protective power against heart attacks in women as it does in men. Even cells studied in vitro show different responses to stressors simply based on whether the cells hail from male or female donors.

A number of studies have now shown that sex differences appear to matter in the prevalence, severity, and treatment of disease. Yet many research projects still rely solely on male participants to avoid the inconveniences of the oestrous cycle.

“We see, by not looking at the different sexes, that we have some serious gaps in our knowledge," said Janine Clayton, Director of the NIH Office of Research on Women’s Health (ORWH). "We really want to fill those gaps, and the NIH is in a position to help everyone understand that sex is a fundamental variable in biomedical research, and it really must be considered from the very start.”

To this end, Clayton and NIH director Francis Collins announced new NIH-wide policies to address sex differences across all biomedical research projects in today’s issue of Nature. Beginning in October 2014, researchers applying for NIH funding will be required to balance the numbers of male and female participants, animals, and cells—as well as to compare and contrast any observed sex differences in their findings.

While this new policy will take some time to implement, researchers will not be left on their own to navigate the change. The NIH is currently developing courses and educational materials to communicate the benefits of considering sex in research and train the scientific community to design experiments balanced by sex.

“I think we have the opportunity to get people thinking differently, to understand how important it is to address sex—and that it’s a fundamental variable that should be considered from the start of any research project,” explained Clayton. “That [way], both men and women can get the full benefit of any medical research project moving forward.”