Minorities underrepresented in U.S. neuroimaging Alzheimer’s research

Racial, ethnic minorities have disproportionally high risk for disease

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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Racial and ethnic minority groups in the U.S. are underrepresented in Alzheimer’s disease neuroimaging research, but the gap may be starting to close, according to a review study.

Efforts to address the issue in recent years have been associated with small increases in minority inclusion, but much work remains to address the issue adequately, according to the scientists.

“As far as we know, this is the most comprehensive review of representation in the Alzheimer’s disease neuroimaging literature,”  Duke Han, PhD, the study’s senior author and a professor at the Keck School of Medicine, University of Southern California, said in a university news release. “It gives us a good sense of the current state of the literature and what needs to be addressed moving forward.”

The study, “Quantification of race/ethnicity representation in Alzheimer’s disease neuroimaging research in the USA: a systematic review,” was published in Communications Medicine.

Research shows racial and ethnic minorities are at a disproportionally high risk for Alzheimer’s in the U.S., with Hispanic Americans being about 1.5 times and African Americans about two times more likely to develop the neurodegenerative disease relative to white Americans.

Such disparities could be related to a wide range of factors, including genetics, environmental exposures, and socioeconomic, educational, or healthcare inequities. Yet numerous studies suggest minority patients are underrepresented in research.

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Improving minority representation in Alzheimer’s research

Without adequate representation, study findings might not be generalizable to all patients, leaving scientists to know less about how the disease manifests and responds to treatment in nonwhite patients.

The issue is particularly important given the fact that the minority population in the U.S. is growing and is expected to continue to do so in the coming years.

Han and colleagues sought to learn more about this representation gap in Alzheimer’s research by examining race and ethnicity data from 2,464 U.S. studies related to brain imaging in Alzheimer’s.

Among the 719 studies that directly reported on ethnicity and race, a median 87.4% of study participants were non-Hispanic white, 7.3% were Black/African American, 3.4% were Hispanic/Latino, and 0% were Asian American, Native Hawaiian/Pacific Islander, American Indian/Alaska Natives, multiracial or other race.

A larger group of 1,745 studies indirectly reported on race, meaning they drew the information from 44 external databases or larger multicenter studies. Again, more than eight in 10 participants (83.7%) were non-Hispanic white, 11.6% were Black/African American, 4.7%, Hispanic/Latino, and 1.75%, Asian American.

While these indirect studies were slightly more diverse, their proportions still didn’t reflect the makeup of the U.S. population, where less than 60% are white. All racial and ethnic minority groups were underrepresented relative to the percentage of the population they make up.

“This is a pretty big deal, especially as we look toward the future, where an increasing proportion of the U.S. will be ethnic minority groups,” said Aaron Lim, PhD, the study’s first author and a postdoctoral fellow in Han’s research lab. “If their representation isn’t adequately captured, then this disparity in research will grow and grow.”

Nearly all the indirect studies in the analysis (94%) drew their information from 10 shared databases, including about 70% that used data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), one of the largest Alzheimer’s studies.

This means that, to address this representation gap, these large, multisite studies need to recruit more diverse participants “to adequately represent the communities they are recruiting from,” Lim said.

Efforts are already underway to make that happen. For example, ADNI launched a new effort to recruit minority participants in 2020 and numerous other large studies are aimed at registering specific minority groups.

Part of these efforts include relationship-building between the scientific and Alzheimer’s minority communities. Also, funding agencies like the National Institute on Aging, which supported this study, are starting to offer grants aimed at bolstering diversity.

In the past, some researchers were so focused on recruiting large groups of participants, that it took priority over the importance of representation. Now, there’s an increasing focus on balancing numbers with representation.

Smaller Alzheimer’s studies also have a role to play, the researchers said. These types of studies are good for getting a more detailed picture of patients’ lived experiences, such as how healthcare inequities and socioeconomic status influence disease risk.

“In the past, some researchers were so focused on recruiting large groups of participants, that it took priority over the importance of representation,” Han said. “Now, there’s an increasing focus on balancing numbers with representation. This increased emphasis on diversity in neuroimaging is a welcome sight.”

Such efforts have started to pay off. In their analysis, the scientists found that Black/African American participation in Alzheimer’s studies increased from 3.39% between 1994-2017 to 8.29% between 2018-2022.

Still, “median representation of all other racial groups … has been consistently low,” the researchers wrote, adding a “small, but growing” number of studies with less than 50% [white] participants was observed.

“Understanding the landscape of Alzheimer’s disease representation in studies is necessary to contextualize progress in correcting these imbalances and historical failures,” they said.