Why are there research studies for men or women, not both?

medical research studiesSometimes medical research studies require that participants include only males while others may be only for females. A variety of reasons are behind this type of selection criteria, based on what the clinical trial is for, what phase it’s in, and what other studies may have already been completed. First, let’s take a look at some of the differences between men and women.

The Difference Between “Sex” and “Gender”

In addition to the obvious physical differences between males and females, there are additional biological and physiological differences which determine “sex”—male or female. For example, the levels and types of hormones men and women have are different. Women have more estrogen and progesterone; men have more testosterone.

There are other physical differences that may not be so apparent. Generally speaking, women have a higher body fat percentage than men, whereas men generally have more muscle tissue mass. Women have lower blood pressure but their hearts beat faster. Adult men have approximately 5.2 million red blood cells per cubic millimeter of blood; women have about 4.6 million; but females have more white blood cells, more granulocytes, and more B and Tlymphocytes. Women produce more antibodies at a faster rate than males. And women have a higher orbitofrontal-to-amygdala ratio (OAR) in the brain than men.

“Gender” takes into consideration gender identity, role in society, socio-economic status, and interpersonal relationships. The World Health Organization (WHO) describes it like this: “Gender refers to the socially constructed characteristics of women and men—such as norms, roles and
relationships of and between groups of women and men. It varies from society to society and can be changed.” Both sex and gender can affect health symptoms, risk factors, and outcomes. Males and females experience higher or lower risks of certain diseases, illnesses, or conditions based on
their genetics and their environments; may react and report symptoms differently or seek medical care at different times based on their culture or societal norms; and may respond in various ways to medications or treatments based on a variety of factors from current health status to the rate of their metabolism.

Sex-Related Illnesses

Some diseases and conditions occur only in people of one sex, such as ovarian and prostrate cancers, or uterine fibroids. Certain diseases and conditions also are clearly sex related, because they are caused by the same chromosomes that determine sex. Some are just more common in one than the other. And some occur at similar rates, but manifest differently in men and women.

Some examples of sex-related illnesses and disorders:

  • 99% of breast cancer occurs in women.
  • Endometriosis almost always occurs in women; it has been found in men, but only rarely when they are undergoing estrogen treatment for prostate cancer.
  • Osteoporosis is female-dominant.
  • 75% of autoimmune diseases such as Sjögren’s syndrome and scleroderma occur in women.
  • Alzheimer’s has a higher rate in women than men.
  • Autism is four times more prevalent in males than in females.
  • Women are more likely to suffer from unipolar clinical depression.
  • Hemophilia occurs almost exclusively in men.
  • Cluster headaches and gout are more prevalent in men.
  • Migraine, carpal tunnel syndrome, Multiple Sclerosis, and IBS are more prevalent in women.

Study Bias

In the past, research has been biased towards males; so some female studies may be trying to make up for this fact and gather female-only research. According to the Gendered Innovations project at Stanford University, “science, medicine, and engineering often take the young, white, able-bodied 70kg male as the norm. When studied at all, other segments of the population— women, the elderly, and non-white groups—are frequently considered as deviations from that norm.”

According to “Reporting Sex, Gender, or Both in Clinical Research,” an article published by Drs. Janine Austin Clayton and Cara Tannenbaum in 2016, there are three important reasons to report data by sex, gender, or both:

1. To see sex/gender specific results that might be hidden by combined results.
2. To provide robust raw data for large, diverse combinations of study results.
3. To avoid the need to repeat a trial for sex/gender specific matters that may arise later in the trial process.

For all of these reasons, certain studies may require participants be male or female. It may be to supplement prior research completed on one gender only; it may be due to the prevalence of the indication in one or the other; or it may simply be all about sex.

Meridien Research is currently conducting studies related to several of the illnesses and conditions mentioned here, including Alzheimer’s, depression, gout, low T, migraines, uterine fibroids, and Multiple Sclerosis, at several of our locations. For more information or to see if
you or someone you know – male or female – may qualify to participate, please contact us today at 1-888-777-8839.