An essay published in Cell Metabolism in early August flagged the scarcity of female participants in clinical trials involving both humans and animals, arguing that men and women are biologically not the same and may therefore react to many drugs in different ways.

Deborah J. Clegg, a Professor of Biomedical Science at Cedars-Sinai Hospital in California who co-authored the essay, explained that:

Right now, when you go to the doctor and you are given a prescription, it might not ever have been specifically tested in females. Almost all basic research – regardless of whether it involves rodent models, dogs, or humans – is predominately [sic] done in males. The majority of research is done with the assumption that men and women are biologically the same.

Women are sometimes excluded from clinical trials due to concerns that hormonal fluctuations throughout their menstrual cycle will affect the results of the trial. A 2014 report by the Mary Horrigan Connors Center for Women’s Health & Gender Biology showed that despite cardiovascular disease killing more women in the US than any other disease, only 35% of participants in related clinical trials are female, and only 31% of relevant trials report outcomes by sex.

The 1993 National Institutes of Health Revitalization Act requires the inclusion of both sexes in NIH-funded clinical research. More recently, the NIH established the Office of Research on Women’s Health. “[N]onetheless, despite these efforts, many publications continue to neglect sex-based considerations, contributions, and analyses in pre-clinical and clinical studies,” the authors of the essay warn.

They conclude that:

There is a bias and tendency to treat all adults as equivalent, drawing conclusions devoid of sex, age, race, and environment. Understanding how these physiological states impact biology is critical for the development of personalized medicine.

The essay entitled “Sex and Gender: Critical Variables in Pre-Clinical and Clinical Medical Research” appeared in Cell Metabolism on 9th August 2016. Its full text is accessible online.