7 July 2021

Covid-19 clinical trials ignore gender differences

Blind spot

Although the coronavirus affects men and women differently, the vast majority of clinical trials do not mention sex/gender, a new analysis of 4,420 studies published in Nature Communications concludes. Ultimately, it can influence the treatment negatively.

Photos: Pexels, Andrea Piacquadio / Edward Jenner
Photos: Pexels, Andrea Piacquadio / Edward Jenner

Most ongoing or just completed clinical COVID-19 trials do not include gender or sex aspects, although the pandemic affects men and women differently.

In fact, only 4 percent of 4,420 registered studies explicitly plan to address sex and gender in their analysis, while 21 percent include gender variables when selecting participants for the trials.

These are some of the findings in a new study, which has been published in the renowned journal Nature Communications with the participation of Danish researchers, including Associate Professor Mathias Wullum Nielsen from the Department of Sociology.

The lack of focus on sex differences is striking considering that men are generally more prone to serious illness. Exactly why this is the case is still being discussed, but an outcome may be that men and women could need different treatments. Moreover, gender is connected to the risk of infection – as when more women are employed in positions where they are exposed to infection during work.

For such reasons, the lack of attention to gender-specific issues is problematic, says Sabine Oertelt-Prigione from Nijmegen's Radboud University Medical Center and Bielefeld University. Together with Mathias Wullum Nielsen as well as Emer Brady and Jens Peter Andersen from Aarhus University, she has co-written the article in Nature Communications.

“We have seen from the beginning that the disease does not have an identical course for women and men. The differences in rates of hospitalisation and death point to this. This means that our care, such as medicines or other interventions, could also have a different outcome depending on whether the patient is a woman or a man,” she says in a press release.

Findings should prompt reflection

The article in Nature is primarily based on an analysis of the COVID-19-related protocols created by researchers from around the world in the US database ClinicalTrials.gov, which records clinical trials in the medical and pharmacological field.

Most experiments are ongoing, but the authors encountered the same blind spot in relation to sex and gender in completed trials.

The results are both surprising and worrying, as statistical analyses of gender differences would give us a better understanding of possible variations in the course of disease and the effectiveness of different forms of treatment,.

Mathias Wullum Nielsen

"In our systematic review of all pharmacological COVID trials, which were published between January 2020 and December 2020, we found that only 8 out of 45 trials reported sex-specific analyses," explains Mathias Wullum Nielsen.

He believes that the new results should prompt reflection in medical research communities.

"It is both surprising and worrying, as statistical analyses of gender differences would give us a better understanding of possible variations in the course of disease and the effectiveness of different forms of treatment," says Wullum Nielsen.

Still, the authors acknowledge that much research during the corona crisis has been under severe time pressure, especially at the beginning of the epidemic. However, as first author Emer Brady from the Department of Political Science at Aarhus University points out in the jointly issued press release, the researchers did not find an increased focus on sex and gender in the study protocols as the pandemic went on.

See the study on the Nature Communications website: Lack of consideration of sex and gender in COVID-19 clinical studies