Women and girls make up 50% of the population, yet most health and physiology research is conducted in men.
This is especially true for fundamental research (which creates knowledge but has no application yet) and pre-clinical (animal) research. This type of research often focuses only on male humans, animals, and even cells.
In our discipline of exercise physiology, 6% of research studies only included female participant groups.
So why do so many scientists seem oblivious to the existence of half the world’s population?
Read more: Equal but not equal: a male bias reigns in medical research
Women, women, trans men and non-binary people
First, it is important to understand the key terminology in society and research. As noted throughout this article, “male” and “female” are categories of sex, defined by a set of biological properties associated with physical and physiological characteristics.
In comparison, “men”, “female” and “non-binary people” are categories of gender: a social construct that includes attitudes, power relationships, roles, and identities.
Here we discuss research on specific genders, but further considering gender-diverse groups, such as transgender people, is also a gap in science.
Why are women not studied?
The main argument is that females are more “complex” model organisms than males.
The physiological changes associated with the menstrual cycle add a lot of complications when it comes to understanding how the body may respond to external stimuli, such as taking medication or performing a specific type of exercise.
Read more: From energy levels to metabolism: Understanding your menstrual cycle may be key to achieving exercise goals
Some women use contraception, and those who use different types of contraception. This adds to the variability between them.
Women also go through menopause around the age of 50, another physiological change that fundamentally affects the way the body functions and adapts.
Even when research is done properly with women, the findings may not apply to all women. This includes whether a female person is cisgender or gender nonconforming.
Overall, this makes women’s research more time-consuming and expensive – and research is almost always limited by time and money.
does it really matter?
Yes, because males and females are physically different.
This includes not only apparently obvious differences (so-called primary sexual characteristics, such as body size or genitalia), but also a whole range of hidden differences in hormones and genetics.
There is also emerging evidence from our research team that gender differences affect epigenetics: how your behavior and environment affect the expression of your genes.
Researching health and physiology in men particularly disregards these differences. So our knowledge of the human body, inferred from what has been observed mostly in men, may not always be true for women.
Some diseases, such as heart disease, present differently in men and women.
Read more: Women who suffer heart attacks receive less care than men
Males and females may also metabolize drugs in a different way, which means they may require different amounts or formulations. These drugs can have sex-specific side effects.
The way we treat our diseases or the preferred drugs we use in the clinic can have big consequences.
Take COVID-19, for example. The severity and mortality rate of COVID-19 is higher in men than in women. Gender differences in immune and hormonal pathways may explain this, so researchers are advocating for sex-specific research to aid in viral treatment.
We’re finally starting to see some changes
No matter the cost or added complexity, research should be for everyone and apply to everyone. International medical research bodies are now beginning to accept this.
A March 2021 statement from the Endocrine Society, the international body for doctors and researchers who study hormones and treat related problems, recognizes:
Before the mechanisms behind sex differences in physiology and disease can be elucidated, a fundamental understanding of gender differences present at baseline is needed.
The United States’ largest medical research board, the National Institutes of Health (NIH), recently asked researchers to account for “sex as a biological variable.”
Unless a strong case can be made for studying only one gender, studies of both sexes are now required to receive NIH research funding.
The Australian counterpart, the National Health and Medical Research Council (NHMRC), indirectly recommends the collection and analysis of sex-specific data in animals and humans.
However, it is not yet necessary to include both sexes to receive money in Australia.
But researchers can start now
Because sex matters, we’ve created a freely available infographic based on our research that aims to make it easier to design female health and physiology research.
It presents it as a simple flow through diagram that researchers can use before starting their project and prompts them to consider questions such as:
Is the phenomenon I am investigating influenced by female hormones?
Should all women in my cohabitation use the same contraception?
On what day of the menstrual cycle should I test my participants for the most reliable results?
Based on the answers, our infographic proposes strategies for designing research taking into account the complexity of the female body (which may be practical – such as who to recruit and when – or statistical).
It is easy to follow and accessible to all. And, while initially designed for exercise physiology research, it can be applied to any type of female health and physiology research.
Read more: Medicine’s gender revolution: how women stopped being perceived as ‘little men’
Based on our infographics, we have designed a four-year research project only to map the process of muscle aging in women. Women live longer than men, but paradoxically, are more vulnerable to some of the consequences of aging. Despite a lot of research into aging in men, we still know very little about the female-specific characteristics at play.
So yes, the future is female – so is our research. And we hope to inspire health and physiology researchers around the world to do the same.