Women's period seen as barrier to medical research

Women are badly underrepresented in health research, including sport and exercise studies and even drug trials, and a big reason forthe potentially dangerous disparity is their monthly period, experts say.

An editorial in the British Journal of Sports Medicine looked at the gender gap in sports and exercise research and found menstruation is the major barrier.

"Females undergo a variation in hormone levels through the menstrual cycle. So as a result of this, they appear to be more complex," said lead authorGeorgieBruinvels,a PhD student at University College London in the U.K.

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She points toa review in 2014of more than 1,300 sport and exercise research studies involving more thansixmillion participants.On average, 39 per centof the participants were women and 61 percent were men.

There was a time when women were left out of research because there were concerns drug trials might harm unborn babies.Researchers also didn't want to risk including women, the editorial says, because they were"more physiologically variable than men."

Since men were viewed as adequate proxiesfor women, years of being left out of important research was considered insignificant, the editorial says.

'Not scientifically correct. Period. Full stop'

Dr.JerilynnPrior, a professor of endocrinology at the University of British Columbia,says menare not adequatereplacements for women in research.

"Not scientifically correct. Period. Full stop," shetold CBC News.

Excluding women from drug trialscreates an imbalance, she says.Millions of women and men are prescribed the same drugs every day.Yet some of those drugs were tested only on men.

"Half the human race doesn't have accurate information about the response to whatever the intervention is,"Prior said. "It's like comparing apples and oranges."

This disparity exists, she says, even though a policy of the Canadian Institutes of Health Research requires researchers to say how they are dealing with sex and gender when applying for research grants.

"Rarely ever are half of the participants in trials women,"said Prior,the founder and scientific director of the Centre forMenstrual Cycle and Ovulation Research.

"So how can you apply information that relates only to men, to women whose physiology is different?"

Bruinvelssays there are dangerous consequences to that imbalance because women respond differentlyto drugs.

80% of drugs withdrawn from market

"Evidence actually suggests that women are almost twice as likely to have an adverse reaction to a drug than a male counterpart," she said.

In fact, a U.S. accountability study found "80 per centof drugs there are withdrawn from the market due to unacceptable side-effects on women."

"There are metabolic differences,"Prior said."How the drug iscomplexed[released]or excreted may vary a lot in women versus men.So then you have new risk factors that you didn't even know were a possible risk."

Women not just men with 'boobs and tubes'

In 2013,the U.S. Food and Drug Administrationreleased a safety announcementabout the sleep aid,zolpidem, also knownasAmbien.It recommended the bedtime dose be lowered for men and women. It also warned that women are more susceptible to risks associated with the medicationbecause theymetabolizethe drug at a slower rate than men.

"Women are not just men with boobs and tubes," Dr. Alyson McGregor of Rhode Island said during a recent TED Talk on women's health. "They have their own anatomy and physiology that deserves to be studied with the same intensity."

GeorgieBruinvelsis currently researching how iron deficiency in menstruating women impacts their sports performance. The menstrual cycle can be a barrier for women in sport.Last year, for example, British tennis player Heather Watson blamed "girl things" when shepulled out of the Australian Open.

Bruinvelsis trying to break down the barrier for women in research. She'shopingto foster a greater understanding of the menstrual cycleand to address the ongoing disparity in not only sport and exercise research, but all types of medical research.

"Until we have that," she told CBC News, "there's just going to be this kind of grey cloud over the female."

• Premenstrual mood symptoms questioned
• Sexism in mouse research can lead to medical harm to women, scientists warn