Treatment studies that exclude the homeless, illicit drug users or people with mental problems disproportionately curb the number of African-Americans and/or women eligible to participate in medical research, according to a new study from investigators at Stanford University.
Lead researcher Keith Humphreys says the findings should encourage scientists who design studies to consider the unintended consequences of eligibility criteria.
“When you start to push on certain levers, you move some other variables you may not have anticipated, particularly how many women and African-Americans end up in the study,” Humphreys said. “I assume the best of my colleagues: I don't think they are racist or sexist, but I do think they underestimate the downside of restrictive study enrollment rules in terms of inclusion and fairness.
“Scientists share a basic social justice viewpoint that we all contribute to medical research when we pay our taxes, so the benefits of it and the burdens of it should be shared throughout society,” said Humphreys, a professor of psychiatry at Stanford and the Veteran Affairs Health Care System in Palo Alto, Calif.
The National Institutes of Health, the largest public funding source for medical research, shares the same philosophy and has guidelines to promote diversity in NIH-supported medical trials.
In the June issue of Alcoholism: Clinical and Experimental Research , Humphreys and colleagues write, “In designing treatment studies with many eligibility criteria, researchers may therefore inadvertently be thwarting their own good-faith efforts to ensure that a range of vulnerable populations are able to participate in research.”
The ACER investigation explores the effect of participant prohibitions in five alcohol treatment studies that enrolled more than 100,000 people.
Trials that disqualified patients with mental health problems — such as depression or an anxiety disorder — disproportionately whittled down the number of female participants, the study found. Studies that barred prospective patients based on social and residential instability or trials with drug-use prohibitions had the greatest effect on African-Americans.
Across a range of studies in different parts of the country, African-Americans had, on average, a 23 percent higher risk of being prohibited from alcohol treatment studies that excluded drug-using patients and 46 percent higher risk of exclusion from studies that disallowed participation by patients with unstable housing and employment situations.
“In other words, if you were an African-American showing up saying you wanted to be in the study, you'd be much more likely than a white person to have a treatment researcher say, ‘Well, you can't,'” Humphreys explained.
Eligibility criteria are especially problematic because their consequences are so difficult to counter.
“If you have a criterion that disproportionately excludes people in some group — blacks, women, whoever — over-sampling will not correct the problem. If the women in the study are less representative of all women, then simply adding more, less-representative women doesn't fix the problem. You just end up with a bigger unrepresentative group,” Humphreys said.