Over the past few decades, we’ve seen progress in including more women in clinical trials—a long-overdue shift after years of male-dominated research. However, while more women are being represented in clinical studies, a major issue persists: many studies still fail to analyze the data collected by sex. This isn’t just a minor oversight—it’s a significant gap that puts women’s health at risk, potentially resulting in treatments that are less effective or even harmful for women.
A 2015 study reviewed 107 NIH-funded clinical trials and found that 72% of them didn’t analyze data by sex. That’s a troubling statistic, especially since it represents a backward slide compared to previous years. In 2004, 67% of studies failed to analyze sex differences; by 2009, it was 64%. Despite growing awareness of the importance of sex differences in medicine, the research community is struggling to keep pace with what we know about men and women’s unique health needs.
Why Are Women Still Overlooked in Clinical Trials?
Historically, women were excluded from many clinical trials—especially in the early stages of drug testing—because researchers were concerned that hormonal fluctuations or the risk of pregnancy could interfere with results or cause unforeseen complications. While well-intentioned, this created a research landscape that treated men’s bodies as the “default” and women’s as outliers. As a result, treatments developed based on male bodies were often assumed to work for women too, which we now know isn’t always the case.
In 1993, the NIH Revitalization Act mandated the inclusion of women in clinical trials, marking a significant shift in policy. However, merely including women isn’t enough. Sex-based differences go far beyond reproductive organs and hormones—they affect how diseases manifest, how medications work, and even the side effects of treatments. Without analyzing data by sex, we risk making dangerous assumptions about women’s health.
The Real-World Consequences of Ignoring Sex Differences
Failing to analyze clinical trial data by sex has tangible, real-world consequences that can put women at risk. A prime example is heart disease. Historically, research focused on men, which skewed the understanding of how heart attacks present in women. Men typically report chest pain as their primary symptom, but women often experience more subtle symptoms like nausea, shortness of breath, and fatigue. These differences often go unrecognized, leading to delayed treatment for women and poorer outcomes overall.
A similar issue arose with the sleep medication zolpidem, better known as Ambien. For years, women were prescribed the same dose as men, even though it became evident that women metabolized the drug more slowly. This oversight led to higher concentrations of the medication in women’s bloodstreams the morning after use, significantly increasing their risk of accidents. It wasn’t until 2013 that the FDA recommended lowering the dose for women, a move that could have been made much earlier if sex differences had been analyzed from the start.
Mental Health Research: A Missed Opportunity
The impact of ignoring sex differences in research isn’t limited to physical health; it also extends into mental health. Women are twice as likely as men to experience depression, yet much of the research on antidepressants has focused on men. This leaves a significant gap in understanding how these medications work for women, who may require different dosages or experience different side effects than men.
Research into post-traumatic stress disorder (PTSD) is another area where sex-based analysis is lacking. Women with PTSD are more likely to experience symptoms like hypervigilance, anxiety, and avoidance, while men may exhibit aggression. However, much of the research on PTSD has focused on male veterans, leaving a gap in understanding how best to treat women with PTSD, especially those who have experienced trauma in civilian life.
Autoimmune Diseases: A Gendered Health Crisis
Autoimmune diseases disproportionately affect women, who make up nearly 80% of those diagnosed with conditions like lupus, multiple sclerosis, and rheumatoid arthritis. Yet clinical trials for these diseases still frequently fail to analyze data by sex, leaving critical gaps in understanding how these diseases progress in women and how best to treat them.
Lupus is a striking example. Hormonal changes during menstruation, pregnancy, and menopause can significantly influence lupus symptoms. Despite this, many clinical trials for lupus treatments fail to consider these hormonal factors in their study designs or data analysis. By not accounting for these sex-based differences, researchers risk developing treatments that are less effective—or even dangerous—for the majority of lupus patients, who are women.
Success Stories: When Clinical Research Gets It Right
While there are plenty of examples of clinical research falling short, there are also cases where sex-based analysis has led to significant breakthroughs. In the field of cardiovascular health, sex-based analysis has resulted in better diagnostic tools and treatment plans for women. After years of focusing primarily on men, researchers have started to study how heart disease presents differently in women, leading to improved outcomes.
In cancer research, sex-based analysis has been crucial in developing targeted therapies for diseases like breast and prostate cancer. By understanding how these cancers behave differently in men and women, researchers have been able to develop treatments that are both more effective and less harmful.
These success stories show that when clinical research takes sex differences into account, everyone benefits. It’s time to apply this approach across the board, in all areas of medicine.
Barriers to Change: Why Aren’t We There Yet?
Despite the clear benefits of sex-based analysis, there are still significant barriers to implementing it across the board. One of the biggest issues is cost. Analyzing data by sex requires larger sample sizes and more complex statistical analyses, which can drive up the cost of clinical trials. For researchers working with limited funding, this can make sex-based analysis feel like an unattainable luxury.
There’s also a lack of training in how to conduct and interpret sex-based research. Many researchers simply don’t have the knowledge or tools to properly analyze data by sex. This points to a broader issue in the research community: the need for better education and training on the importance of sex differences in health and disease.
Finally, there’s a cultural barrier. For too long, men have been considered the “default” in medical research, with women’s health treated as a niche area. Changing this mindset will require a cultural shift within the research community, as well as pressure from policymakers, funding agencies, and the public.
A Global Perspective: Learning from Other Countries
The issue of sex-based analysis isn’t unique to the United States. Countries around the world are grappling with the same problem, though some are doing a better job than others.
Canada has been a leader in promoting sex-based analysis in biomedical research. The Canadian Institutes of Health Research (CIHR) require researchers to explain how they plan to consider sex and gender in their studies or justify why it’s not necessary. This approach has led to more inclusive and effective research that benefits both men and women.
In contrast, many countries in the developing world are still struggling to include women in clinical trials at all. In these regions, women often have less access to healthcare, and cultural barriers can prevent them from participating in research. This leaves women in these countries at an even greater disadvantage when it comes to receiving effective treatments.
Policy and Funding: Driving Change
One of the most effective ways to ensure that clinical trials analyze data by sex is to incentivize researchers through policy and funding. The NIH has made strides in this area by requiring that sex be considered as a biological variable in all research it funds, but more needs to be done to enforce this requirement and to provide researchers with the resources they need to meet it.
Funding agencies should consider offering additional grants or financial incentives to researchers who prioritize sex-based analysis in their studies. Journals could also play a role by refusing to publish studies that don’t analyze data by sex unless there’s a compelling reason for the omission. By creating a system that rewards researchers for conducting inclusive and comprehensive studies, we can start to close the gender gap in medical research.
Advocacy and Education: The Role of Patients and Providers
Patients have a role to play in pushing for better research practices. By asking their healthcare providers about the research behind new treatments or medications, women can demand more transparency and accountability in how their health is addressed. Public awareness campaigns can raise the profile of this issue, while patient advocacy groups can work to ensure that women’s voices are heard in the medical research community.
Healthcare providers also need better training on the importance of sex differences in diagnosis and treatment. By making sex-based analysis a standard part of medical education, we can ensure that future generations of doctors are equipped to provide the best possible care for both men and women.
Conclusion: A Path Forward
We’ve made some progress in addressing gender disparities in clinical trials, but there’s still a long way to go. Analyzing data by sex is not just an option—it’s a necessity. By designing studies with sex-based differences in mind, enforcing stricter publishing standards, and educating both patients and providers, we can move toward a future where treatments are truly personalized. Everyone deserves the best possible care, and we can only achieve that by acknowledging and addressing the unique needs of both men and women.
— Stay Strong! Jaelin —
Additional Reading:
- “Sex Differences in Health and Disease” – National Institutes of Health (NIH)
This page from the NIH offers an in-depth exploration of how sex differences impact health outcomes, the significance of sex as a biological variable, and ongoing efforts to address these disparities in research.
https://www.nih.gov/women-health-research - “The Importance of Sex in Clinical Research” – Harvard Medical School
This article discusses the necessity of including sex-specific analyses in biomedical research and the consequences of neglecting this critical factor in the study of diseases and treatments.
https://hms.harvard.edu/news/why-sex-matters - “Women in Clinical Trials” – U.S. Food and Drug Administration (FDA)
The FDA provides insights into the historical exclusion of women in clinical trials, current policies for including women, and the ongoing need for analyzing clinical data by sex.
https://www.fda.gov/women-clinical-trials - “Gender Bias in Medical Research” – World Health Organization (WHO)
The WHO explores global perspectives on gender bias in medical research, outlining how overlooking sex-based differences can hinder effective healthcare solutions.
https://www.who.int/gender-bias-research - “Addressing Sex and Gender in Health Research” – Canadian Institutes of Health Research (CIHR)
CIHR is a leading organization pushing for the integration of sex and gender in health research, offering practical guidelines and success stories from the field.
https://cihr-irsc.gc.ca/e/8673.html
About the Author:
Jaelin Stickels, CNM, WHNP, is a deeply passionate and highly skilled Certified Nurse Midwife, Women’s Health Nurse Practitioner, and the owner of Holistic Heritage Homebirth in Houston, Texas. With over a decade of experience, Jaelin has had the privilege of helping several hundred women welcome their babies into the world. In addition to her advanced practice licensure training, she has additional advanced training in twin and breech births, making her one of only a few with these skills in her area. Jaelin approaches every birth with expertise, compassion, and a deep respect for the birthing process. Jaelin is finishing her doctorate and looking forward to being Dr. Jaelin in early 2025.
Jaelin’s journey into midwifery began with a profound love for supporting women through the incredible experience of pregnancy, labor, and postpartum. Since 2010, she has been dedicated to walking alongside families during these transformative moments, offering guidance, support, and care tailored to each individual’s unique needs. She is a big believer in informed consent and ensures clients are given the best evidence-based information to make the best decisions for themselves and their families.
Married to her high school sweetheart Ted (aka Chef Ted) since 1984, Jaelin is the proud mother of three grown children and the delighted grandmother of one amazing granddaughter. When she’s not assisting in births, Jaelin finds joy in going to the movies with her husband, quilting, and cherishing time with her family. Known by the other midwives in her practice (Holistic Heritage Homebirth) affectionately as the “Birth Hog,” she brings an unmatched dedication and enthusiasm to her work—no one loves birth quite like she does.