Women under-represented in cardiac-related clinical trials, says study

Toronto, ON – Women have successfully broken the glass ceiling in the boardroom, in politics, and on the home front. Is it now time for women to lobby for equal representation in research trials?

According to the Heart and Stroke Foundation, more than 50% of deaths caused by heart disease and stroke – the leading cause of death in Canada – are women.

But that’s a fact you would never guess if you looked at the gender balance in the crucial clinical trials that study cardiovascular disease, Dr Wendy Tsang told the Canadian Cardiovascular Congress 2008 co-hosted by the Heart and Stroke Foundation and the Canadian Cardiovascular Society.

Dr Tsang reviewed landmark clinical trials between January 1, 1997 and December 31, 2007 in leading medical journals The Journal of the American Medical Association (JAMA), The Lancet and the New England Journal of Medicine.

“These are major trials published in the world’s leading medical journals,” says Dr Tsang who is a cardiology resident at the University of Toronto. “Trials published in these journals undergo rigorous peer and editorial review.”

Dr Tsang’s study found that although women comprise 53% of patients in the general population with cardiovascular disease, in clinical trials they represented only 29% of subjects with coronary artery disease, 25% with congestive heart disease, and 34% with arrhythmias. Interestingly, they represented 61% of the subjects in prevention trials.

“Our study shows the proportion of women enrolled in landmark cardiovascular clinical trials is substantially lower than you would find in the general disease population. What is even more of a shock is that this under-representation has not drastically changed over the past decade,” she says.

“This study shows why it’s important to put a gender lens on research,” says Dr Beth Abramson, Heart and Stroke Foundation spokesperson. “Although women should not get the wrong message – as cardiac care and treatments are proven in female patients – optimally women should be better represented in trials.”

Dr Abramson adds that in addition to making sure women are well represented in clinical trials, we need ongoing evaluation into possible gender differences in cardiovascular disease and how to address them.

The Heart and Stroke Foundation and CIHR’s multi-provincial GENESIS research initiative – which explores the differences in how men and women experience heart disease – is a good example of how this issue can be addressed.

“A trial may show that a drug or therapy benefits patients enrolled in the trial – but if women are under-represented in the trial, it makes it difficult to tell if the outcomes of the trial can be applied to women,” says Dr Tsang. She says that the next step in this research is to figure out what factors affect female enrollment in clinical trials in order to help address this issue.

Addressing this issue may be more difficult than it sounds. In the United States in the early 1990s the National Institutes of Health put in place a policy that said there should be a fair representation of women in trials as long as it was reasonable.

“The results of this study are even more surprising because in 1993 in the US Congress passed an act to increase enrollment of women and minorities in trials,” says Dr Tsang. “You would have thought that between then and 2007 there would have been a change. But we didn’t find that.”

The under-representation of women in clinical trials could be because they are asked to participate less often than males. Women get heart disease later in life than men and a lot of trials have an age rule that says nobody 70 or over can enroll. However, Dr Tsang’s research does show women make up 61% of trials that investigate exercise and diet. Could this be due to gender stereotyping?

That could be next on the research agenda.