Women’s participation in medical research studies continues to lag, creating a scientific data gap that has an impact on development of new medicines and treatment protocols, as well as accurate assessment of current treatments.

“This isn’t just a women’s health issue; it’s an everybody’s health issue,” said Nicole Woitowich, director of the Illinois Women’s Health Registry and associate director of the Women’s Health Research Institute at Northwestern University. “We can’t keep claiming we are doing rigorous science if we are excluding important biological variables.”

Woitowich and other scientists and women’s health advocates are working to create more inclusion in research through the Illinois Women’s Health Registry, an online, smartphone-compatible tool that allows women to access information about clinical studies, as well as place themselves in a database of women who are interested in participating in research.

“If we’re not going to be asked to participate in studies,” said Teresa Woodruff, director of Northwestern’s Women’s Health Research Institute, “we should just put our hand in the air. The … registry is a way for us to put our hand in the air.”

For decades, researchers excluded women (and even female research animals) from studies for reasons including the monthly hormonal variation of the menstrual cycle, which they said created another variable that complicated research. In addition, nightmarish cases such as the 1960s Thalidomide disaster prompted scientists to exclude women of childbearing age from early stage clinical trials.

In 1993, the National Institutes of Health, which controls research funding, mandated that both men and women be included in medical research. Since then, the number of women in studies has slowly begun to climb. But the lack of data on women has continued to affect science: “If you look at the basic scientific literature,” said Woodruff, “about 82 percent of it is male or doesn’t describe the sex of the animal or cell being used. So we really have this flawed pipeline in science.”

Today, the NIH requires researchers to address not only how females are being included in the studies they propose, but also how that research will consider sex differences in interpreting data. A recent cancer study, for instance, found that women responded better than men to the treatment protocol for a specific kind of brain tumor. “We need to look at what is it about women that makes that treatment more effective,” said Woitowich, “or maybe why that treatment doesn’t work as well for men.”

Sex-linked data have the potential to provide wide-ranging insights, based on differences in metabolism, body composition, hormone levels and other factors. Women, for instance, absorb some medicines differently than men, though very few medicines are prescribed in sex-linked doses.

In 2014, the U.S. Food and Drug Administration created sex- and weight-specific dosing for zolpidem (sold as Ambien, Edluar and Zolpimist) after it was discovered that the same dose caused two times the level of medication in women as in men. Woitowich said she sees the gap as the legacy of a noninclusive scientific community. “It really has been this kind of pervasive thing in our research culture. This is just how we do things, and that gets passed on to students.”

Woodruff agreed, saying, “Men weren’t being inherently biased. But eventually you’ve jiggered the system toward adverse events that would affect women.”

She sees the registry’s launch as the start of a new chapter in research. “We’re excited about having a tool to create momentum, to fill a gap, to ask women to be a part of studies. At this point, there’s no excuse for not including them.”