The gender gap in medical research results in real-life disadvantages for women. Despite women outnumbering men in the U.S. for nearly 80 years, researchers have excluded women from medical studies due to historical and cultural bias, as well as policies that prioritized protecting fetuses. Although policy and social changes in the 1990s helped a bit, women remain underrepresented in research. Growing evidence from clinical research supports that women and men can differ greatly in their susceptibility and presentation of disease and their response to treatment, including adverse effects.
The lack of data about women's health creates a gap to understanding how women experience disease and how best to treat them for many conditions. As Dr. Stacy Sims rightly points out, "women are not small men." Biological sex plays a role in physiological, metabolic, hormonal, and cellular differences that influence how diseases present and the effectiveness of drugs and medical devices. Failure to study medications and other interventions in women has contributed to women experiencing adverse effects from medications at 2x the rate of men. A 2013 study found that women with metal hip replacements were 29% more likely than men to experience implant failure, possibly due to inadequate testing in women. And, despite heart disease being the leading cause of death in the U.S. for both men and women, doctors only fully appreciated that women experience different symptoms than men when the American Heart Association published a Guide to Preventive Cardiology for Women in 1999. Even now, 25 years later, most of the general public is unaware of the prevalence of heart disease among women or of the significant differences in cardiovascular disease presentation in women, which leads to numerous incidences of women not seeking preventative care, not receiving timely diagnoses, and not recognizing their symptoms as life-threatening.
Women were already poorly represented in medical research before the 1970s, but progress was further set back in 1977, when the Food and Drug Administration (FDA) created a policy to exclude women of reproductive age from clinical trials unless they had a life-threatening condition. The FDA was responding (perhaps over-responding) to serious, unexpected side effects of a drug called thalidomide. Although it was never approved for use in the U.S., it caused severe birth defects and deaths in the fetuses of thousands of pregnant European and Australian women, who were taking it to treat morning sickness. FDA’s policy to exclude women of reproductive age from most clinical trials was interpreted broadly and resulted in the exclusion of nearly all premenopausal women, including those who were unlikely to get pregnant. In 1993, Congress passed a law requiring the inclusion of women in clinical research and in 2016, the National Institutes of Health (NIH) instituted a policy that requires researchers with NIH funding to collect data on biological sex differences in pre-clinical research and animal testing, but as recently as 2019, women accounted for only 40% of participants in clinical trials of three of the diseases that affect mostly women despite representing 51% of the U.S. population
Women seeking medical care often have their physical complaints trivialized or misdiagnosed as psychologically based by doctors due to a historically misogynistic cultural view. It is not uncommon that women feel a sense of distrust of medical professionals, with many rightly worrying that their doctors will label them as “anxious” or “depressed” rather than address their physical pain or symptoms. The concept of hysteria as a mental disorder attributable to women goes back 4,000 years and was commonly used to misdiagnose women until the turn of the 20th century; it took until 1980 for hysterical neurosis to be deleted from the Diagnostic and Statistical Manual of Mental Disorders. In the case of multiple sclerosis, which predominately affects women, it took until the 20th century for medical professionals to agree that it is not caused by hysteria. Endometriosis has suffered from lack of funding, in part, because it is stereotyped by doctors as being caused women's life choices. Additionally, some research studies that did focus on endometriosis concluded that the pain was psychological. These stereotypes of women as hysterical, crazy, dramatic, and difficult have real world consequences. A recent study found an average time to diagnosis of endometriosis from first consultation was 4.4 years. As recently as 1983, doctors at Tufts University were attributing menopause symptoms to psychosomatic effects. Recent studies have identified gaps in medical schools and residency programs in preparing doctors to recognize menopause and treat its symptoms as valid as an other medical condition. In one study, approximately 50% of women surveyed felt that their doctor did not recognize the importance of the menopause; 33% reported that their doctors were reluctant to offer treatment options. In a study of 5000 UK women, over 3/4 reported making their doctor aware of their symptoms, more than 25% of women had seen more than 3 doctors about their symptoms and 7% said they had more than 10 visits before getting the help they needed. And the costs extend beyond the literal well-being of the women involved. More than 75% of women at taken at least 2 days off work to attend their appointments.
There also appears to be implicit bias in the funding of research for diseases that predominantly affect women. A recent study of the funding of 18 different types of cancers by the National Cancer Institute found that gynecologic cancers (ovarian, cervical, uterine) ranked 10th, 12th and 14th, respectively, in funding - prostate cancer ranked 1st. Another study found that from 2015-2019, 74% of research funding went to study diseases that are predominately found in men and only 26% went for the study of diseases more common in women.
We know that when focus and funding are available for quality research on women's issues, the results on women's health can be significant. For example, researchers noted in the 1960s that the brains of menopausal women compared with premenopausal women showed significant physical changes - some nerve cells (neurons) in the hypothalamus doubled in size after menopause. By the late 2000s, researchers identified that the increase in size of the cells was accompanied by changes to the neuropeptides in the cells - specifically, their evidence suggested an increase in kisspeptin-1 and neurokinin B (NKB), along with a decrease in dynorphin. Those cells are now referred to as KNDy neurons. These specific neuropeptides were found to regulate sex hormone levels during the menstrual cycle of premenopausal women and have a role in thermoregulation, circadian rhythms, and sleep. NKB also appeared to have a role in causing hot flashes in menopausal women, which led scientists to hypothesize that if they could counteract the increased NKB in KNDy cells of menopausal women, they could reduce their hot flashes. Luckily, NKB has a much greater affinity for one particular neurokinin receptor - the NK-3 receptor - which was important because neurokinin receptors are found not only in KNDy cells in the hypothalamus but also throughout the nervous and immune systems. This specific target, the MK-3 receptor, allowed for development of the first non--hormonal treatment, fezolinetant, for menopausal hot flashes, which was welcomed by women who could not treat their hot flashes with menopausal hormone therapy (MHT), namely women undergoing treatment for breast or other gynecologic cancers and women at high risk for breast cancer or cardiovascular disease.
Research on women's health, if prioritized and supported, can result in development of preventions and treatments for diseases and other conditions that will radically improve outcomes, including quality of life.
