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Why We Need to Study Sex and Gender

March 21, 2019

Count to eight, and somewhere in the United States a baby will be born.

You might imagine that this newborn has an equal chance of being female or male. But that’s not the case.

It’s true that at conception, scientists believe there is a 50 percent chance any given fertilized egg will be female. But a study published in the Proceedings of the National Academy of Sciences in 2015 found that the total mortality of females during gestation outnumbers males. The specific biological causes of this discrepancy remain unclear.

When it comes to this and so many aspects of biology, psychology, and overall health, answers remain elusive. Which is why we must continue asking the right questions. Thankfully, scientists with Women’s Health Research at Yale and our partners around the world are learning more about the influence of sex and gender on health. And we are finding not sameness, but difference.

“As we study women, data show sex and gender differences in the prevalence, risk factors, presentation, and course of diseases and conditions,” said Dr. Carolyn M. Mazure, Director of Women’s Health Research at Yale. “We are also learning that responses to prevention strategies and treatments can vary for women and men. We must continue to explore these differences if we are to improve the health of everyone.”

Historically, women were not widely studied, partly under assumptions — now proven false — that results found in male subjects represent an accurate reflection of what results would be in women.

Now entering our third decade, Women’s Health Research at Yale has driven medical science forward with a focus on studying women and examining health differences between women and men to improve the lives of everyone. The center’s mission is one of scientific inclusivity.

“Some of our core differences — grounded in biology and affected by environment and experience — can significantly impact our health,” Mazure said. “And so we need to study sex and gender in order to better detect and treat diseases that affect women and men differently.”

The health-related differences affecting females more than males stretch from head to toe. For example, women are more likely to:

  • suffer from chronic diseases and disability
  • have acute and chronic pain
  • die following a heart attack
  • develop depression and anxiety
  • develop autoimmune diseases
  • develop Alzheimer’s disease
  • and more rapidly escalate from use to a substance or behavioral addiction with a higher likelihood to relapse after a quit attempt

There’s more. Women with diabetes are more likely to develop cancer than men with diabetes. Women experience stress differently — psychologically and physically. And women are more likely to be blind, even when accounting for the longer average life expectancy of women. Women also:

  • wake faster than men following general anesthesia
  • are more likely to need a repeated hip replacement surgery
  • are more likely to be diagnosed with a more advanced bladder cancer and respond worse to treatment
  • are three times more likely to suffer from migraines are more likely to have shingles and experience a recurrence of this disease’s painful rash
  • are more often affected by anemias such as iron deficiency
  • and are more likely to develop osteoporosis and suffer broken bones

Even when women are included in sufficient numbers, studies are not always analyzed by sex or gender to uncover any significant differences.


“There are so many aspects of health and disease affected by sex and gender,” Mazure said, “that it might well be the case that areas unaffected by sex and gender are a rarity.”

However, despite the clearly demonstrated need for sex-and-gender-focused research, women remain under-enrolled in various studies of cardiovascular disease and cancer — the top two causes of death for women. In addition, women are underrepresented in clinical trials exploring causes, prevention, and treatment of HIV, the virus that causes AIDS. A recent WHRY-led study found that companies applying for government approval to market medical devices rarely determine if or how sex and gender might influence safety and effectiveness.

And even when women are included in sufficient numbers, studies are not always analyzed by sex or gender to uncover any significant differences. It was only in 2016 that the National Institutes of Health, the world’s largest single funder of biomedical research, required the inclusion of female animals, tissues, and cells in laboratory studies, which serve as the necessary basis for human trials.

These unexamined differences have serious consequences for the health care women receive and their outcomes. For example, even though cardiovascular disease (CVD) is culpable for about one in every three female deaths, studies have shown that women suffering heart attack symptoms arrive at a hospital later than men. Moreover, treatment of women for CVD, including heart attacks, is less aggressive than for men and less likely to achieve the best possible results.

It is because of such life-diminishing repercussions that Women’s Health Research at Yale exists. We are funding researchers and training others to overcome this gap in knowledge and to make sure everyone has the best chance possible to live a long and healthy life.

WHRY’s pilot projects and interdisciplinary research partnerships have focused on sex and gender differences in heart attacks, chronic urinary tract infections, skin cancer, autism spectrum disorder, neurological aging, domestic violence, cognitive dysfunction, autoimmune disorders, addiction, and depression, among many other diseases and conditions.

And there is so much more to do.

“We are so grateful for our supporters who share our commitment to fully exploring all aspects of how sex and gender influence health,” Mazure said. “Because there will always be a need to study women. And not just the differences between women and men, but also the differences among populations of women and men.”

For more news from Women's Health Research at Yale, like WHRY on Facebook, follow WHRY on Twitter, or visit WHRY's website.

For questions, please contact Rick Harrison, Communications Officer at or 203-764-6610.

Submitted by Carissa R Violante on March 22, 2019