Bias in research – is women’s health being overlooked?

Gender bias is the prejudice against or favouritism towards one gender over another. So, could bias be present within medical research?  

Gender biological bias contributes to health inequity worldwide [1] due to the lack of research into women's health. Historically, for conditions that affect both sexes, women, especially women of colour, have been underrepresented in clinical trials [2].  

Health research has heavily focused on men, with the results applied to women under the assumption that female bodies would react to drugs and medical therapies in the same way [3]. The reasons given for women not being included in these trials has ranged from data inconsistencies due to changing hormones, to safety precautions if a woman becomes pregnant.

The underrepresentation of women in medical research has meant women’s diseases are sometimes missed, misdiagnosed, or simply remain unresearched.

Studies show that women are often less likely than men to receive more advanced diagnostic and therapeutic interventions [4]. The practice of producing biased knowledge through research carried out on men, and then generalising the results has been criticised since the 1970s [5]. 

Without inclusive research that includes sex differences in study design and analysis, both men and women could be missing out on disease risk factors, diagnosis, and treatment. 

Why have women been underrepresented in clinical research?

While there is no straight answer to this question, it’s thought that genetics and hormonal factors play a part.  

In 1977, following the thalidomide scandal, the US Food and Drug Administration (FDA) recommended that women of childbearing age should not be included in future clinical research [6]. Although these initial regulations were put in place to protect women and their babies, exclusion has led to gender misrepresentation in many different areas of research [7].  

Varying hormone levels during a woman’s menstrual cycle are thought to be a big reason why, historically, research has focused on men. Thankfully, today there is growing acknowledgement that understanding the interactions between female hormones and medications is vital.  

Which health conditions are affected by biological bias? 

1. Heart attacks 

Decades of research have positively changed the likely outcome for someone suffering a heart attack. Yet shockingly, women are 50% more likely than men to receive the wrong initial diagnosis for a heart attack. And following a heart attack, women are also less likely to be prescribed medications to help prevent a second [8].  

Women having a heart attack often delay seeking medical help longer than men because many do not recognise the symptoms. As heart disease research has mainly focused on men, it has caused many to automatically think of chest pain as the first sign of a heart attack – which is not always true.  

While chest pain is a well-known indicator of a heart attack, women may also experience dizziness, nausea, or vomiting [9].  

Symptoms of a heart attack women should look out for (as well as chest pain or discomfort): 

• Shortness of breath 
• Nausea/vomiting 
• Back or jaw pain

2. Autoimmune disease 

Around 78% of people affected by an autoimmune disease are women [10]. Thyroid conditions such as Graves’ disease and Hashimoto’s thyroiditis are seven to ten times more common in women than men, while multiple sclerosis (MS) and rheumatoid arthritis (RA) are two to three times more common [11].  

Answering the question of why this gender bias appears so strong is important to explain why more women than men are affected and find better ways to treat different conditions. Two possible reasons are the differences in hormone levels and the presence of two X chromosomes (and their associated genes). 

3. Menopause  

Menopause can be a difficult time for many women. Symptoms can range from mood swings and fatigue to weight gain and hot flushes and affect emotional and physical wellbeing. Despite this, many women feel there is not enough available support for their menopause journey and sometimes feel isolated when trying to find answers to their questions [12].  

A  survey of 1,596 people highlighted a lack of understanding, with only 21% feeling prepared for the menopause, [13]. 

The findings, which featured in the Channel 4 documentary Davina McCall: Sex, Mind and the Menopause, showed many women feel ignored both in the workplace and by healthcare providers. The survey reported that 87% believe the NHS should send all women in their 40s or 50s a list of menopause symptoms to raise awareness.  

More research is needed to ensure perimenopausal and menopausal women have the right information for managing symptoms, understanding therapies, and knowing how to access help instead of being expected to ‘just get on with it’.  

4. Osteoporosis 

Osteoporosis is a condition that weakens bones, making them fragile and more likely to break. Women are more at risk of developing osteoporosis due to menopausal hormonal changes, which affect bone density. While osteoporosis is four times more common in women, the condition also affects men, with research suggesting men tend to have more osteoporosis-related complications [14].  

Compared to other conditions affected by a biological bias, in osteoporosis trials, men appear underrepresented. Because men are poorly studied concerning this condition, often they go underdiagnosed and inadequately treated. The side effects of anti-osteoporotic drugs in men are still poorly known [15]. 

While genetics have a part to play in osteoporosis development and its complications, low vitamin D levels, calcium intake, and physical exercise are all also risk factors [16]. To better understand osteoporosis risk factors, further research is required, which includes equal representation from both genders to create recommendations for population-based interventions. 

5. Drug research and gender bias  

Drug research and development are also affected by gender bias. A lack of female involvement in clinical trials means, historically, women have been at greater risk of adverse side effects from medication, as dosages were often calculated based on male data [17]. 

Research published in the journal Biology of Sex Differences confirmed the drug dose gender gap and highlighted a disregard for the differences between male and female bodies [18].  

Including women earlier in the drug developmental process will increase representation, help reduce gender bias in clinical trials and lead to safer and more accurate recommended dosages [19]. 

6. AI and health advice

As access to healthcare information has moved online, more people are turning to artificial intelligence (AI) tools for health advice, symptom checking, and decision support. While these tools can improve access to information, they are not neutral. AI systems are trained on existing medical data and research — much of which reflects long-standing gender bias in healthcare, including the under-representation of women in clinical trials and the misinterpretation of women’s symptoms (20). 

With medical datasets often prioritising male physiology as the default, AI tools can be less accurate at recognising, assessing, or prioritising women’s health concerns. As a result, AI-driven health advice may inadvertently reproduce the same patterns seen in traditional healthcare settings, such as minimising women’s pain, overlooking sex-specific symptoms, or attributing physical symptoms to psychological causes more readily than in men.

This highlights an important risk. Without deliberate efforts to address bias in medical data and AI development, digital health tools may reinforce — rather than reduce, existing inequalities in women’s healthcare.

What’s being done to reduce the gender gap in clinical trials? 

There has been a shift in attitudes and requirements for who must be included in clinical trials. These changes are helping to positively influence research for the benefit of marginalised groups, including women.  

Scientists must now account for sex as a possible biological variable in animal and human studies. In 1993, the FDA lifted its ban on women participating in clinical research. The European Union’s Clinical Trials Directive also now expects that drug trials reflect the population to be treated once the medicine is on the market. 

Take control of your health 

Despite these changes being implemented to help address the gender divide, a lack of funding for women’s health remains a problem. For example, although one in three women may suffer from a reproductive or gynaecological health issue in their lifetime, it’s estimated that only 2% of UK publicly funded research is dedicated to reproductive health [21,22].  

Discover our range of Women’s Health Checks and Men’s Health Checks, or visit the Test Finder to see how you can take control of your health.

 References 

1. Moretti C, De Luca E, D'Apice C, Artioli G, Sarli L, Bonacaro A. (2023) Gender and sex bias in prevention and clinical treatment of women's chronic pain: hypotheses of a curriculum development. Front Med (Lausanne). (Accessed 19 February 2026)
2. Raleigh, V. (2025). The Health of Women From Ethnic Minority Groups In England. [online] The King’s Fund. 
3. Chhaya VY, Binion CC, Mulles SM, Tannhauser PA, Aziz DZ, Greenwood JD, Barlek MH, Rouan JR, Wyatt TG, Kibbe MR. (2023) Gender Bias in Clinical Trial Enrollment: Female Authorship Matters.   [Accessed 19 February 2026].  
4. McMurray, R.J. (1991). Gender Disparities in Clinical Decision Making. JAMA: The Journal of the American Medical Association. (Accessed 19 February 2026) 
5. Ramasubbu K, Gurm H, Litaker D: Gender bias in clinical trials: do double standards still apply? J. Womens Health Gend. Based Med. 10, 757–764 (2001). 
6. Liu, K. and DiPietro Mager, N., 2016. Women’s involvement in clinical trials: historical perspective and future implications. Pharmacy Practice, 14(1), pp.708-708. 
7. The Pharmaceutical Journal. 2022. Why we need to talk about sex and clinical trials - The Pharmaceutical Journal. [online] Available at: <https://pharmaceutical-journal.com/article/feature/why-we-need-to-talk-about-sex-and-clinical-trials#fn_1> [Accessed 19 February 2026].
8. British Heart Foundation. 2022. Bias and Biology. [online] Available at: <https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/women-and-heart-disease/download-bias-and-biology-briefing> [Accessed 19 February 2026].  
9. Harvard Health. 2022. Gender differences in cardiovascular disease: Women are less likely to be prescribed certain heart medications - Harvard Health. [online] Available at: <https://www.health.harvard.edu/blog/gender-differences-in-cardiovascular-disease-women-are-less-likely-to-be-prescribed-certain-heart-medications-2020071620553> [Accessed 19 February 2026].
10. Fairweather, D. and Rose, N., 2004. Women and Autoimmune Diseases1Emerging Infectious Diseases, 10(11), pp.2005-2011. 
11. Im EO, Lee B, Chee W, Dormire S, Brown A. A national multiethnic online forum study on menopausal symptom experience. Nurs Res 2010; 59:26–33. 
12. University College London (UCL) (2025) Call for nationwide menopause education programme. Available at: https://www.ucl.ac.uk/news/2025/oct/call-nationwide-menopause-education-programme (Accessed: 20 February 2026).
13.  Fawcettsociety.org.uk. 2022. [online] Available at: <https://www.fawcettsociety.org.uk/Handlers/Download.ashx?IDMF=9672cf45-5f13-4b69-8882-1e5e643ac8a6> [Accessed 19 February 2026]. 
14. Khan, M.A., Khan, M.A., Khan, M.A. & Khan, M.A. (2024) Efficacy of methotrexate in rheumatoid arthritis patients: A clinical study. Annals of the Rheumatic Diseases, 83(Suppl 1), p.143. Available at: https://ard.bmj.com/content/83/Suppl_1/143.2 (Accessed: 20 February 2026). 
15. Dy CJ, Lamont LE, Ton QV, Lane JM. Sex and gender considerations in male patients with osteoporosis. Clin Orthop Relat Res. 
16. NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy, 2001. Osteoporosis Prevention, Diagnosis, and Therapy. JAMA: The Journal of the American Medical Association, 285(6), pp.785-795. 
17. Science Connected Magazine. 2022. All of Us: A Lack of Diversity in Medicine. [online] Available at: <https://magazine.scienceconnected.org/2022/04/all-of-us-addresses-lack-of-diversity-in-medicine/> [Accessed 19 February 2026].
18. Zucker, I. and Prendergast, B., 2020. Sex differences in pharmacokinetics predict adverse drug reactions in women. Biology of Sex Differences, 11(1). 
19. Liu, K. and DiPietro Mager, N., 2016. Women’s involvement in clinical trials: historical perspective and future implications. Pharmacy Practice, 14(1), pp.708-708. 
20. GOV.UK. 2022. Survey reveals women experience severe reproductive health issues. [online] Available at: <https://www.gov.uk/government/news/survey-reveals-women-experience-severe-reproductive-health-issues> [Accessed 19 February 2026]. 
21. Criado Perez, C. (2019) Invisible Women: Exposing Data Bias in a World Designed for Men. London: Chatto & Windus.
22. Women’s Health Economics: Investing in the 51 per cent (no date) NHS Confederation. Available at: https://www.nhsconfed.org/publications/womens-health-economics (Accessed: 19 February 2026).