The gender gap in science exists but unbeknownst to those outside the scientific community, this gap extends to the scientific test subjects themselves – lab mice.
In 1994, the United State National Institute of Health (NIH) sought to correct the racial and gender homogeneity of white males in clinical trials. Making the inclusion of women and minorities a requirement, the NIH sought to better reflect the population that these trials are created for and represent. And today, approximately 50% of clinical trial participants are women.
But before clinical trials advance to human trials, they must first go through the rigorous preclinical process which begins with testing on lab mice. People may be strongly opposed to testing on lab mice but their sacrifices have been vital to the advancement of science, and as a result, the advancement of the human species. But the problem with past and current trials involving lab mice is the overwhelming preference researchers have had for male mice.
According to the results of a survey by Annaliese K. Beery and Irving Zucker, 8 out of 10 biological disciplines they looked at, male animals outnumbered females. With a breakdown of a 5.5 to 1 male to female ratio in neuroscience, 5 to 1 in pharmacology and 3.7 to 1 in physiology. Of the studies they looked at, 75% of them didn’t state the sex of test animal.
These findings are similar to what’s seen in the behavioral measurement of pain published over the course of 10 years in the journal Pain, with 79% of the studies conducted with male rodents. This is particularly notable because it has been shown that male experimenters induce intense stress in male rodents, dampening pain responses and affecting the rodents’ behavior and potentially confounding the results.
Researchers have used one gender because broadening a study would increase the complexity and cost. With male mice, there are many fields in which there is a significantly larger body of literature and data sets to build upon. Additionally, researchers using male mice don’t have to factor in hormonal cycles as with female mice. The hormonal cycle creates a variability that they don’t want to deal with; this is despite research showing that female mice are no more variable than mice.
As we know, the differences between males and females do exist. Women are 1.5 to 1.7 times more likely to have an adverse reaction to certain drugs and early detection in clinical trials is vital. And there are drugs that have a positive effect on females where early detection in the research process could highlight. Despite the differences in the genders, researchers have been using male mice and applying the findings to both genders.
How do we change this disparity? Simple solutions like disclosing whether male and female animals were used in studies are ongoing. The other, more divisive, response is that funding agencies should favor studies that include both male and female subjects.
Funding and cost of research is a big issue in the scientific community but finding out how drugs could affect both genders would be worth the investment in the long term.