Women are less likely to be included in clinical trials on cardiovascular disease, even though women suffer more than half of deaths caused by heart disease and stroke, a review suggests.

At the Canadian Cardiovascular Congress in Toronto on Tuesday, Dr. Wendy Tsang said women were underrepresented in key clinical trials on cardiovascular disease published in leading medical journals between 1997 and 2007.

"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," Tsang said.

While women make up 53 per cent of patients in the general population with cardiovascular disease, the review suggested they represented:

• 9 per cent of subjects with coronary artery disease.
• 25 per cent of subjects with congestive heart disease.
• 34 per cent of subjects with arrhythmias.
• 61 per cent of subjects in prevention trials.

"Every drug and intervention that I give my female patients has been proven effective in women," Dr. Beth Abramson, a cardiologist in Toronto and spokeswoman for the Heart and Stroke Foundation said in an interview.

"Having said that, the study does show that women still are underrepresented in clinical research. "We need to … change the statistic to make sure we have better information for our female patients and women."

Many reasons for gender gap

The clinical trials for cardiovascular disease involved thousands of subjects, including thousands of women, so researchers still receive answers from women, Abramson said.

It's the older, frailer woman who is less likely to enter a clinical study and that doctors need more information on, she added.

In 1993, the U.S. Congress passed an act to increase enrolment of women and minorities in trials.

"You would have thought that between then and 2007 there would have been a change," said Tsang. "But we didn't find that."

Women may be underrepresented because they are asked to participate less often than men — an issue that both physicians and the general public need to be aware of, Abramson said.

Many trials also have an age rule preventing anyone over 70 from enrolling. Since women without diabetes develop cardiovascular disease on average seven to 10 years later than men, that could also be leading to under-representation in trials.

Women were overrepresented in prevention studies involving diet and exercise, though the reason for this wasn't clear.

The meeting is co-hosted by the Heart and Stroke Foundation and the Canadian Cardiovascular Society and ends on Wednesday.