U.S. Government Will Require Sex Equality for Lab Mice

The U.S. National Institutes of Health has announced that it will require researchers to end gender bias in basic research.

The new policy will have major implications for science, since female animals (like lab rats) and female cells have been underrepresented in many preclinical studies for fear that their reproductive cycles and hormone fluctuations would make results needlessly complicated. One unpublished survey found that only 42% of 1,200 participating neuroscience papers (published in 2011 and 2012) actually reported the sex of the animals used, and of that group, females were include only 24% of the time. That disparity has hindered scientific progress for many years, and has contributed to a lack of consistency in experimental results. In demanding greater equality, the NIH hopes to ensure a better outlook for future health and biomedical studies.

The NIH is requiring that grant applicants have a more even distribution of male and female lab mice in preclinical trials.

A lack of balance between the sexes in animal models makes applying the results to human research a lot trickier. The NIH has already called out researchers for neglecting to include enough women in their clinical experiments, but the new announcement shows a concern for gender biases at a much earlier stage in the experimental process. Here’s Susannah Locke, writing for Vox:

Basic sex differences exist in fundamental ways all the way down to individual cells in a dish in a lab. For example, a male and a female neuron will sometimes use different molecular signaling pathways.

Women and men themselves differ significantly in all sorts of relevant ways. They have different symptoms of heart attacks and depression. Their bodies respond differently to aspirin, Ambien, nicotine patches, and other drugs. Many diseases disproportionately affect one sex or the other, such as multiple sclerosis, which shows differences both in people and animal models.

And researchers using only male animals might miss some of these differences. For instance, a research team that’s mainly testing drugs on male animals might miss drugs that could be beneficial to females. “The over-reliance on male animals and cells in preclinical research obscures key sex differences that could guide clinical studies,” says the Nature piece.

The bias is ironic, considering that there is actually more variability in males than females on several different traits and behaviors. But beginning in October 2014, NIH grant applicants (excerpt in very rare circumstances) will have to outline how they plan to equalize the sexes in their studies. The government still doesn’t have any control over what information is disclosed in journals, but some of their policies on sex and gender are listed here.

Someday we might not need to use animal models in the first place, but the new NIH policy is an initial step in guaranteeing that test subjects yield conclusions that are as thorough as possible.