Stroke: Women underrepresented in clinical trials

• A new analysis suggests that while women and men have an equal lifetime risk of stroke, only 37% of participants in clinical trials of stroke treatments are female.
• This gender bias could make the findings of some trials unreliable for female patients, who tend to experience more severe impairment after a stroke.
• The authors of the analysis conclude that researchers should address the barriers that prevent women from enrolling in their studies.

During a stroke, the blood supply to part of the brain is interrupted, or a blood vessel in the brain bursts. This deprives the affected region of oxygen and nutrients, which can result in the death of some brain cells.

Acute symptoms of stroke include numbness or weakness on one side of the body, difficulty speaking and understanding speech, and problems with vision.

The Centers for Disease Control and Prevention (CDC) reports that more than 795,000 people have a stroke every year in the United States. Someone has a stroke every 40 seconds, and every 4 minutes, someone dies from a stroke.

Research suggests the global lifetime risk of stroke from age 25 onwards is approximately 25% among men and women. Women also tend to experience more significant disability and worse quality of life as a result of a stroke.

However, a new study suggests that women are underrepresented in clinical trials of treatments.

“Our findings have implications for how women with stroke may be treated in the future, as women typically have worse functional outcomes after stroke and require more supportive care,” says study author Cheryl Carcel, M.D., of The George Institute for Global Health in Sydney, Australia.

Julie Anne Mitchell, director of health strategy at the National Heart Foundation of Australia, told Medical News Today that the underrepresentation of women in cardiovascular research was a long-standing problem.

“Until recently, the default position has been to conduct studies on male cells, male animals, or male humans, and then apply these findings to women,” she said. She added:

“The risk […] in doing so is that vital pieces of information — such as the influence that hormones, body size, or menstruation might have on treatment options and outcomes — will be missed.”

The research appears in Neurology, the journal of the American Academy of Neurology.

Trials of stroke treatments

The researchers analyzed 281 trials of stroke treatments that took place between 1990 and 2020 and involved a total of 588,887 participants. In the countries where the trials took place, 48% of all strokes occurred in women. But only 37.4% of the total 588,887 trial participants were female.

Women had the worst representation in trials involving a type of stroke known as intracerebral hemorrhage and trials investigating rehabilitation after a stroke.

“Making sure there are enough women in clinical studies to accurately reflect the proportion of women who have strokes may have implications for future treatment recommendations for women affected by this serious condition,” says Dr. Carcel.

“When one sex is underrepresented in clinical trials, it limits the way you can apply the results to the general public and can possibly limit access to new therapies,” she adds.

The representation of women in clinical trials did not appear to have changed over the course of the 3 decades studied.

Access to lifesaving therapy

When researchers design a clinical trial, they may set a goal for the number of women to enroll in order to get statistically significant findings about the treatment in women.

“If the target number of women isn’t enrolled in the trial, then they might not give the medication to women,” said co-first author Katie Harris, Ph.D., of The George Institute for Global Health.

“[T]his may actually preclude women from receiving a new therapy that can save their life or make them live longer,” Dr. Harris told MNT.

In addition, women tend to be older when they have a stroke, so the upper age limits for enrolment in some clinical trials may reduce their representation.

“Researchers could also promote for data to be sex-disaggregated when their work is published in a journal so that such presentation of data becomes the norm rather than the exception,” she said.

She added that longer trials with more follow-ups may be impractical for women who are responsible for the care of children, grandchildren, or partners.

Dr. Sonya Babu-Narayan, a consultant cardiologist at Royal Brompton Hospital and associate medical director at the British Heart Foundation, agreed.

“We know that some requirements for participating in clinical trials, such as repeated visits to hospital for research appointments over months or years, can be difficult for women with commitments to care for children and elderly relatives,” she told MNT.

“The situation may be compounded further by persisting misperceptions that heart disease is a man’s disease,” she added.

In a statement, the American Heart Association told MNT that it now only funds research that is fully inclusive of women. The statement continued:

“In 2019, the American Heart Association launched Research Goes Red […] to engage more women in research and create the world’s most engaged and largest women’s health registry and platform for research. The leadership of the association believes that part of the solution to this is also to engage more women in STEM [science, technology, engineering, and mathematics] careers and research jobs.”

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