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Too few women take part in many CVD clinical trials

Poor representation of women in studies limits ability to draw conclusions from outcomes

Louise Prime

Tuesday, 01 May 2018

Women make up a lower than expected proportion of participants in many clinical trials for cardiovascular disease, US researchers have found. The authors of the study*, published today in the Journal of the American College of Cardiology, said it is imperative that participants in a drug trial represent the full spectrum of patients for whom it will be prescribed.

The research team noted that heart disease is the most common cause of death for women as well as men, but is ‘often overlooked as a health issue’. They pointed out that because there are sex differences in cardiovascular disease pathophysiology, clinical presentation and outcomes, meaning that treatments might work differently in women and men, it is important in trials to be able to determine possible sex differences in response to treatment. They set out to assess how well current trials are meeting this goal.

They first calculated the proportion of women enrolled in the trials behind 36 submissions to the US Food and Drug Administration (FDA) for 35 drugs, between 1 January 2005 and 15 September 2015. The drugs were to be used to treat acute coronary syndrome/myocardial infarction, atrial fibrillation, coronary artery disease including angina, heart failure, hypertension and pulmonary arterial hypertension.

For each cardiovascular disease type, they then estimated women’s participation – they did this by dividing the percentage of women among trials participants, by the percentage of women in the population with each disease.

They found that overall, the proportion of women enrolled in trials varied hugely, from 22% to 81% (mean 46%). They then calculated that women’s participation was 0.8-1.1 for atrial fibrillation, 0.9 for hypertension and 1.4 for pulmonary arterial hypertension; these figures, they said, were either within or above the desirable range of 0.8-1.2.

However, women’s participation in trials for heart failure, coronary artery disease and acute coronary syndrome/myocardial infarction were all under the ratio level – at 0.5-0.6, 0.6 and 0.6, respectively.

The study authors said their data showed that women’s underrepresentation went right back to referral for preparticipation screening, and suggested that factors prior to screening, such as the identification of potential trial participants and the ability of a candidate to participate, might be likely reasons for low enrolment of women.

They commented: “Based on this work, future research is needed to identify factors leading to under participation of women in cardiovascular clinical trials, particularly those occurring before screening. Research is needed to better define barriers that limit participation of diverse populations, not only of women but of minority and older populations.”

They added: “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.”


*Scott PE, Unger EF, Jenkins MR, et al. Participation of women in clinical trials supporting FDA approval of cardiovascular drugs. Journal of the American College of Cardiology May 2018, 71 (18) 1960-1969; DOI: 10.1016/j.jacc.2018.02.070

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