The women's health data gap: what it is and why it persists

The women's health data gap is not a slogan. It is a measurable feature of the evidence base, produced by decisions that were written down at the time, and it is still shaping what your clinician knows when you walk in.

This hub sets out what the gap is, where it came from, and which parts of it are closing.

Key points

• The gap covers research participation, data analysis and clinical application.
• Historic exclusion still shapes the evidence used today.
• Better recruitment and sex-specific analysis can narrow it.

What the gap actually is

It has three layers, and conflating them causes most of the confusion.

A research gap. Fewer studies, smaller samples, less funding relative to disease burden, and analysis that often does not separate results by sex.

A clinical gap. Guidance built on that evidence, applied to bodies it was not derived from. Symptom descriptions in textbooks that describe the presentation in men as the default.

An outcome gap. Longer waits for diagnosis, higher rates of being told symptoms are stress or anxiety, and treatments tested for efficacy in populations that did not look like the patient.

Each layer feeds the next, which is why fixing only the last one does not work.

Where it came from

The formal exclusion is documented. In 1977 the US Food and Drug Administration issued guidance recommending that women of childbearing potential be excluded from early phase drug trials. The NIH Revitalization Act of 1993 later required the inclusion of women and minority groups in NIH-funded clinical research. [1] [2]

Sixteen years of a foundational evidence base built largely without them does not correct itself when the rule changes. Drugs approved before 1993 remained in use. Guidelines derived from those trials remained in guidelines.

The longer history is in why women were left out of clinical trials, and what changed.

Where the gap sits today

Conditions affecting mainly women are under-funded relative to their burden. Endometriosis affects roughly one in ten women and those assigned female at birth of reproductive age, while Endometriosis UK reported an average diagnosis time of 8 years and 10 months in 2024. [3] [4]

Sex-disaggregated analysis is inconsistent. Enrolling women is not the same as analysing them separately. A trial can hit its recruitment target and still publish a single pooled result that hides a different effect by sex.

The menstrual cycle is usually controlled away rather than studied. Hormonal variation is treated as noise to be minimised, which means we know remarkably little about how cycle phase affects drug response, pain thresholds and symptom reporting. See the menstrual cycle is still treated as noise in clinical research.

Symptom reporting is discounted. The evidence on differential treatment of pain reports by sex is substantial and consistent enough to matter clinically. See the gender pain gap.

Women say they are not listened to. The Women's Health Strategy for England, published in 2022, reported that 84% of respondents to its call for evidence said there had been instances when healthcare professionals did not listen to them. [5]

What is changing

The direction is right and the pace is slow. The UK now has a Women's Health Strategy for England and women's health hubs. Funders increasingly require a sex and gender analysis plan. Femtech has brought commercial money into areas that public funders historically ignored, with the mixed quality that commercial money always brings.

The bottleneck that persists across all of it is recruitment. A study that cannot find enough women with the specific condition, at the specific stage, does not run, and the gap stays open by default.

Why this sits on FeFe's blog

FeFe is a research panel for women's health, so we have an interest here and you should read us accordingly. Our position is narrow: the gap will not close through better intentions, it closes when studies that should exist can actually be filled. That is the part we work on.

If you run women's health research, the practical companion to this hub is recruiting for women's health research.

References

1. US Government Accountability Office. Women’s Health: Women Sufficiently Represented in New Drug Testing, but FDA Oversight Needs Improvement. 2001.
2. US Congress. NIH Revitalization Act of 1993. Public Law 103-43.
3. Endometriosis UK. Endometriosis facts and figures.
4. Endometriosis UK. Endometriosis diagnosis times still unacceptably long and getting longer. 2024.
5. Department of Health and Social Care. Women’s Health Strategy for England. 2022.