The exclusion of women from clinical trials

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Although women make up roughly half of the world’s HIV cases, they remain largely excluded from clinical trials testing drugs, vaccines and potential cures for the virus, Reuters Health reports that a research review confirms.

In an analysis spanning several decades that included work done as recently as 2012, researchers found that women typically comprised about 11% of participants in trials investigating cures for HIV. Similarly, drug studies were only about 19% female and just 38% of vaccine trial subjects were women.

“Based on previous studies in other health areas, it wasn’t surprising, but perhaps disappointing given that nearly half of those living with HIV are women,” lead study author Dr Mirjam Curno, said. Research in areas such as heart disease, cancer and depression has also had historically low female participation, as have advanced human trials testing experimental drugs, Curno and colleagues note.

While it may make sense to have fewer women in studies focused on diseases that disproportionately affect men, research findings may overlook gender-specific harms or benefits when the proportion of men and women in the study is wildly different from what happens in the real world, said senior study author Dr Shirin Heidari. That’s because even when the disease is the same, women may have different symptoms than men and respond in unique ways to the treatments being tested. “Failing to systematically study sex and gender differences in health research leads to less evidence-based medicine for one sex or another,” said Heidari, who is chair of the gender policy committee for the European Association of Science Editors.

The analysis of gender disparities in HIV trials included more than 500 studies published in prominent medical journals over several decades. One limitation of the analysis is that by relying on published work, it may not capture any differences in the gender makeup of more recent trials that haven’t yet been completed, the authors acknowledge.

It’s possible that at least some studies in the analysis didn’t set out to favour men, but ended up enrolling fewer female participants due to obstacles that can disproportionately impact women such as lack of child care or elder care or limited transportation or time to participate, noted Mary Foulkes, a biostatistics researcher at George Washington University in Washington, DC.

Introduction: The effect of clinical interventions can differ due to sex/gender. Studies have shown that women are often underrepresented in medical research. The aim of this systematic literature review was to characterize women’s participation in HIV clinical studies of antiretroviral drugs (ARV), prophylactic vaccines (VAX) and curative strategies (CURE).
Methods: Systematic PubMed searches were conducted to identify ARV, VAX and CURE studies. Data were extracted on the number of women, date of publication, sources of funding, country of study, and trial phase. Correlates of female participation were assessed.
Results: Women represented a median of 19.2% participants in ARV studies (387), 38.1% in VAX studies (53) and 11.1% in CURE studies (104). Funding source was not correlated with the proportion of female participants in VAX and CURE studies, but was for ARV studies (p=0.03). ARV trials funded by private non-commercial sources had the highest proportion of women, while publicly-funded trials had the lowest female participation (median 16.7%). The median proportion of women in ARV trials that were fully or partially funded by the National Institutes of Health (NIH) was significantly lower than the median in trials funded by other sources (19.6% vs 22.3%, p=0.001).
Conclusions: Although women comprise nearly half of people living with HIV, they continue to be under-represented in clinical studies. Despite federal policies that have been established to address this, our study shows that publicly-funded ARV trials recruit even fewer women than other trials. There is an urgent need to ensure that HIV clinical studies consider sex/gender dimensions.

Full Reuters Health report
Journal of Acquired Immune Deficiency Syndromes abstract

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