Sometimes studies will require that participants include only females. A variety of reasons are behind this type of selection criteria, based on what the trial is for, what phase it’s in, and what other studies may have already been completed.
1—Differences in the Sexes. 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 and less muscle tissue mass. Women have lower blood pressure but their hearts beat faster. Women have about 4.6 million red blood cells per cubic millimeter of blood compared to 5.2 million in men; but females have more white blood cells, more granulocytes, and more B and T lymphocytes. Women produce more antibodies at a faster rate than males.
Sex 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.
“The lack of clinical trial data for women means we don’t fully understand if drugs are as safe and effective in women as they are in men,” says Dr. Natalie DiPietro Mager, an associate professor of pharmacy practice at Ohio Northern University. An example: After its release, the sleeping pill zolpidem (Ambien) was found to clear much slower in women than in men, leading the FDA to cut the recommended dosage for women in half.
2—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 illnesses and disorders that are female-biased:
• 99% of breast cancer occurs in women.
• Endometriosis almost always occurs in women.
• Osteoporosis is female-dominant.
• 75% of autoimmune diseases such as Sjögren’s syndrome and scleroderma occur in women.
• In the U.S., twice as many women than men suffer from depression.
• Migraine, carpal tunnel syndrome, Multiple Sclerosis, and IBS are also more prevalent in women.
3—Underrepresentation. “Sex-Specific Medical Research: Why Women’s Health Can’t Wait,” a report from the Mary Horrigan Connors Center for Women’s Health & Gender Biology at Brigham and Women’s Hospital, also reports the following:
• Cardiovascular disease is the number one killer of women in the U.S, yet only one-third of cardiovascular clinical trial subjects are female.
• More women die each year of lung cancer than of breast, ovarian, and uterine cancers combined; it is the leading cause of cancer death in women. Yet most lunch cancer studies enroll more men than women.
• Two-thirds of Alzheimer’s patients are women and women are almost twice as likely to develop it than men; yet the impact of hormonal changes and sex differences in gene expression are only beginning to emerge as potential explanations.
4—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.”
5—You are Needed! Adequate numbers of women volunteers in clinical trials is crucial for the discovery of new and improved methods of prevention, diagnosis, and treatment that can improve the health and well being of women everywhere.
Meridien Research is currently conducting studies related to several of the illnesses and conditions mentioned here, including Alzheimer’s, depression, migraines, uterine fibroids, and Multiple Sclerosis, at several of our locations. For more information or to see if you or someone you know may qualify to participate, please contact us today at 1-888-777-8839.