Women are underrepresented in clinical trials for heart failure, coronary artery disease and acute coronary syndrome but proportionately or overrepresented in trials for hypertension, 

Heart disease is the No. 1 killer of women and men. It represents a very significant health concern for women because it is often overlooked as a health issue, plus the sex and gender differences in cardiovascular disease pathophysiology, clinical presentation and outcomes mean that treatments for men may not always work as well in women. Women being well-represented in clinical trials is essential to determine possible gender differences in treatment responses.

In this study, researchers looked at the numbers of women and men who participated in cardiovascular trials submitted to the US Food and Drug Administration supporting new drug application approvals. Between Jan. 1, 2005 and Sept. 15, 2015, 36 approvals for 35 drugs for acute coronary syndrome / myocardial infarction, atrial fibrillation, coronary artery disease including angina, heart failure, hypertension, and pulmonary arterial hypertension, were looked at for the percentage of women enrolled.

Clinical trials

"As we move into the era of precision medicine, that is assessing the impact of a wide range of patient and disease characteristics on drug effects, it is imperative that clinical trial participants represent the full spectrum of patients for whom the drug will be prescribed, "said Janet Woodcock, MD, senior author of the study and director of the FDA Center for Drug Evaluation and Research. "This will move closer to our goal of providing the best possible information about the use of drugs for every patient."

Estimates for the participation of women were calculated by dividing the percentage of women among participants by the rate of women in the disease population, with a range between 0.8 and 1.2 reflecting proportional representation. In total, the proportion of women enrolled ranged from 22 to 81 percent, with a mean of 46 percent.

The ratio for atrial fibrillation was 0.8-1.1, for hypertension; it was 0.9, and for pulmonary arterial hypertension, it was 1.4 – all within or above the desirable range. Heart failure, coronary artery disease and acute ischemic syndrome / myocardial infarction were all under the ratio level, at 0.5-0.6, 0.6 and 0.6, respectively. Researchers also looked at the gender differences in efficacy or safety and found little indication of clinically meaningful differences.

According to the researchers, previous studies have suggested that clinical trial inclusion and exclusion criteria disproportionately exclude women from  cardiovascular studies ; However, data in this latest study show that the lower enrollment of women reflects the smaller number of women referred for pre-trial participation screening. Factors before testing, such as the identification of potential trial participants and the ability of the candidate to participate, may be more likely reasons for low enrollment of women.