Duke Study Highlights Failure to Improve Representation of Women and Elderly in Cardiovascular Clinical Trials
DURHAM, N.C. – Despite efforts during the past decade to reverse the situation, women and the elderly remain significantly underrepresented in cardiovascular clinical trials, according to a new study by Duke University Medical Center researchers.
"Because safety and efficacy can vary as a function of sex and age, these enrollment biases undermine efforts to provide evidence-based care to all cardiac patients," the researchers wrote in their study report, which was published in the Aug. 8, 2001 issue of the Journal of the American Medical Association (JAMA).
The study examined 593 cardiovascular randomized clinical trials investigating myocardial infarction (heart attack) and unstable angina published between January 1966 and March 2000. Of these trials, 528 reported distributions by gender. The percentage of participants aged 75 or older, which was established as the definition of elderly, was reported in 268 trials of the trials and calculated in another 139, for a total of 407.
"Between 1966 and 1990, patients aged 75 years or older accounted for only 2 percent of all patients enrolled in acute coronary syndrome trials," said Dr. Eric Peterson, associate professor of medicine and senior author of the study. "This rose to 9 percent in trials after 1990. While these are positive trends, this remains far below their representation of nearly 40 percent of all heart attack patients in the United States."
From 1966 through 1990, 81 percent of cardiac trials failed to enroll a single patient aged 75 or older. After 1990, enrollment of elderly patients improved, but still 60 percent still did not include any elderly patients.
The percentage of women in these clinical trials rose from 20 percent during the 1966-1990 period to 25 percent in trials between 1990 and 2000. For those trials enrolling patients after 1995, women comprised 29 percent of the total participants. As with the elderly, these numbers pale considering that 43 percent of heart attack patients are women, Peterson said.
"The universal extension of trial results from a younger, mostly male population to women and elderly patients may be inappropriate," Peterson said. "This paucity of information regarding the safety and efficacy of therapies in women and elderly patients may lead some physicians to withhold treatment in these subgroups."
Beyond their high prevalence in the heart attack population, elderly persons and women also fare worse following cardiac events and experience more complications including heart failure, shock and ventricular rupture.
Despite a series of guidelines and funding criteria enacted by U.S. regulatory agencies beginning in 1989 designed to reverse these age and sex biases, women and the elderly remain underrepresented relative to their disease prevalence, Peterson said. It may take many years for these regulations to have an effect, he said.
The authors noted that studies published in the United States were not significantly better than those from sites outside the United States at enrolling elderly persons and women. Government sponsorship also was not a predictor of more inclusive trial enrollment.
"This further casts doubts on whether regulatory recommendations and U.S. funding may influence enrollment patterns," Peterson said. "Furthermore, we noted that much of the sex disparity in trial enrollment appears to be a byproduct of underenrollment of elderly persons. If efforts to increase enrollment of elderly persons in trials were successful, this may simultaneously eliminate sex disparities."
The authors called for continued monitoring by regulatory agencies of enrollment practices in trials to ensure that future studies involve representative populations. Agencies that fund clinical trials also should provide additional resources to promote enrollment of representative patient populations, the authors said.
"These efforts are urgently needed if we are to provide evidence-based care to all cardiac patients," Peterson said.
Joining Peterson in the study were Patrick Lee, Dr. Karen Alexander, Bradley Hammill and Sara Pasquali from the Duke Clinical Research Institute.