A new study led by researchers at the Yale School of Public Health finds that Alzheimer’s disease clinical trials in the United States have consistently failed to reflect the nation’s racial and ethnic diversity, raising important concerns about whether new treatments are equally safe and effective for all patients.
Published in JAMA Network Open, the study offers one of the most comprehensive reviews to date of diversity in late-stage Alzheimer’s clinical trials. The research team examined 88 U.S.-based phase 3 drug trials conducted between 1997 and 2023, focusing on how race and ethnicity were reported and how well participants represented the broader population.
The findings revealed persistent and widespread gaps. Nearly half of published trials did not report participants’ race or ethnicity at all. Among those that did, reporting was often inconsistent and incomplete. White participants made up the overwhelming majority of enrollees — more than 90% in a typical trial — while Black, Hispanic, Asian, and Native American populations were included at much lower rates.
These disparities are especially troubling given the unequal burden of Alzheimer’s disease. In the United States, older Black adults are nearly twice as likely to develop Alzheimer’s as their white counterparts, and Hispanic adults also face a significantly higher risk. Yet these same groups were underrepresented in clinical trials used to evaluate new treatments.
The study also found major gaps in how data are analyzed and reported. Only a small fraction of trials — just over 4% — examined whether treatments worked differently across racial or ethnic groups. None reported detailed findings on differences in safety or effectiveness, limiting researchers’ ability to understand how therapies may perform in diverse populations.
“Clinical trials are the foundation for determining whether new treatments are safe and effective,” said Dr. Xi Chen, PhD, associate professor of health policy and management at the Yale School of Public Health and the study’s senior author. “Aligning clinical trial demographics with disease prevalence is essential for scientific integrity and clinical utility.”
Despite growing awareness of health disparities and increased calls for inclusive research, the researchers found diversity in Alzheimer’s trials has remained largely unchanged over the past two decades.
The authors say the findings highlight the need for stronger reporting standards and more intentional trial design. Strategies such as expanding eligibility criteria, increasing the number of trial sites in diverse communities, and reducing barriers to participation like transportation costs or language differences could help improve representation.
The authors acknowledged their study had several limitations. The analysis focused only on U.S.-based phase 3 trials, which are critical for regulatory decision-making but do not capture diversity challenges in earlier-stage or global studies. In addition, trials that failed to report race or ethnicity may have enrolled even fewer participants from underrepresented groups, meaning the true extent of disparities could be even greater than reported.
In addition to Chen, senior collaborators included Dr. Joseph S. Ross, MD, MHS, of Yale School of Medicine. The study’s lead author, Zhuoer Lin, PhD, is affiliated with the University of Illinois Chicago, with additional co-authors from the University of Pennsylvania and Yale University.