dr claytonToday in Nature , National Institutes of Health (NIH) Director Dr. Francis Collins and I announce that NIH will be requiring applicants to report their cell and animal inclusion plans as part of preclinical experimental design. By developing this policy, we are promoting a balanced approach to addressing male and female differences in cells and animals — just as we did years ago with women and men in NIH-funded clinical trials.

As biologists, we know that sex is a fundamental variable in biomedical research. As such, it must really be considered from the very start. Every cell has a sex. Every part of the body is made of cells, and each of those has a sex, depending on whether the body is a man's or a woman's. Brain cells, lung cells, skin cells: Each is uniquely male or female.

Although we've made major progress in human studies — women now account for roughly half of the participants in NIH-funded clinical trials — we have not seen a similar pattern in preclinical research. Animal studies have often focused on males, and investigators studying cell models have often ignored the sex of the individual from which the cells were obtained. For the most part, looking for differences between males and females has been a blind spot in biomedical research, leaving gaps in our knowledge. But we can fill those gaps, and this policy will be a first step.

With what we know now, it's time to go beyond business as usual. We have powerful new tools, technologies, and approaches that can uncover knowledge about sex-based influences that will affect the health of women, men, girls, and boys. That's why NIH is asking its grantees to incorporate sex into preclinical experiment design, data collection, and reporting. We are developing policies to have grant applicants report cell and animal inclusions plans, along with training.

Importantly, we recognize that NIH cannot do this alone. The biomedical enterprise is a multifaceted effort with many points of influence. The entire scientific community has a stake in this game. One very serious issue where we need teamwork is reporting of results. Despite the fact that some journals have relevant policies in place, numerous scientific publications continue to neglect sex-based considerations and analyses in preclinical research — and in clinical research, too. We need a stronger commitment to publishing sex-specific results to strengthen the evidence base.

By now requiring researchers to take sex into account, NIH continues to deliver the kind of rigorous science that drives the medical advances we need. We are aiming for research that goes beyond a "unisex" approach that merely tells us about an "average" cell, animal, or person. Each of us is unique, and the science that ultimately informs our health care can and should take that into account.