When One Body Stands for All: How Biomedical Bias Endangers Women’s Health
For decades, modern medicine has overlooked women, excluding them from clinical trials and underfunding research into their health conditions. This systemic bias has perpetuated medical inequalities and produced skewed findings that actively endanger women’s health. Medications designed and tested primarily on men often do not work as effectively in women and may even be harmful. Notably, a study shows that women experience adverse drug reactions twice as much as men, largely because data extrapolated from cis male-focused research fails to account for sex differences in metabolism, hormones, and body composition. This example highlights a deeper issue: when medical research ignores half the population, it undermines the very foundations of evidence-based care.
In the 1970s, the U.S. Food and Drug Administration (FDA) advised against including women of childbearing age in clinical trials, arguing the need to protect potential pregnancies. While seemingly ethical, this policy effectively erased women from medical research for decades, leaving an enormous gap in our understanding of how drugs and diseases affect them. In the 1990s this decision was reversed, but the effects of decades of male-centric research continue to shape medicine today. The sex bias embedded in earlier research still influences current disease understanding, diagnostic criteria, and treatment protocols, because scientific knowledge builds cumulatively on past findings.
Even at the preclinical level, sex bias persists. It is still common for preclinical studies to rely exclusively on male animal models, based on the outdated assumption that female hormonal cycles would “complicate” results. For instance, 79% of animal pain studies only used male animals, despite women being 1.5 times more likely to develop pain conditions. This imbalance has led to an incomplete picture of disease biology, one that fails to capture how conditions manifest in women.
This is particularly true for research of immunological diseases. Women generally have stronger immune responses than men, making them more resilient to infections and respond better to vaccines. However, this heightened immune activity also increases vulnerability to autoimmune diseases, including lupus, multiple sclerosis, and rheumatoid arthritis, with women representing up to 80% of all diagnosed cases. To uncover the root causes of these sex differences, preclinical research must include both male and female cell- and animal models, examining how sex chromosomes and hormones shape distinct immune mechanisms. Integrating sex as a biological variable is not just a matter of scientific accuracy, but a necessary step toward more equitable healthcare.
Cardiovascular disease is another example of how sex bias in research can negatively affect women's health outcomes. For instance, women experiencing heart attacks are more likely to present with atypical symptoms such as fatigue, nausea, or lightheadedness, sometimes in the absence of the classic chest and left arm pain reported in men. Even so, diagnostic criteria and awareness campaigns have historically centred on the ‘male’ symptom profile, contributing to missed or delayed diagnoses, with potentially fatal consequences.
Equally concerning is the neglect of reproductive and gynaecological health conditions. Diseases such as endometriosis, which affects roughly one in ten women of reproductive age, remain severely underfunded and understudied. Despite its prevalence and debilitating impact, it still takes an average of nine years to receive a diagnosis and there is no curative treatment yet. Meanwhile, funding has gone toward studying how attractive women with endometriosis are and how endometriosis affects male partners, a stark reminder of where research priorities still lie while millions continue to suffer undiagnosed, untreated, and dismissed.
Efforts to close this gender gap are slowly emerging. In 2016, the U.S. National Institutes of Health (NIH) began requiring researchers to consider sex as a biological variable in their studies; a long-overdue but important step toward more equitable science. Yet progress remains fragile. Under the Trump administration, cuts to biomedical research funding and restrictive policies that discourage the use of words like woman, gender, diversity, or bias in grant proposals actively undermine these gains and silence necessary conversations about equity in science.
Addressing this health inequity requires structural reform in the way medical research is designed and conducted. Clinical trials must include balanced numbers of men and women and perform sex-specific analyses to uncover meaningful differences in disease biology and treatment outcomes. Equally important is that diseases that primarily affect women, such as endometriosis, adenomyosis and PCOS, should receive research funding proportional to their prevalence and burden. Awareness campaigns must also confront the culture of shame and stigma surrounding these conditions, which can discourage women from seeking care and delay diagnosis. Additionally, researchers and clinicians must be trained to systematically integrate sex and gender considerations into research design, diagnostic processes, and treatment decisions. Finally, transparency and accountability are essential. Scientific journals and funding agencies should require sex-based data to be reported and analysed, and they should hold researchers accountable when studies fail to justify sex imbalances.
The underrepresentation of women in biomedical research is not merely an oversight: it is a systemic flaw that endangers people’s health and perpetuates existing inequalities. Science cannot claim to be objective or comprehensive while half the population remains understudied and underrepresented. Inclusive research is not just about fairness; it is about accuracy, safety, and better health for everyone. If modern medicine is truly to serve all of humanity, it must finally account for the forgotten half.