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The Medical Issue

Why are Black Americans twice as likely to have Alzheimer’s or other dementias as white Americans?

New research into a “silent epidemic” suggests experiencing racism may damage the brain.

Dr. Lisa L. Barnes is a professor of gerontology and geriatric medicine at Rush University Medical Center in Chicago.
Dr. Lisa L. Barnes is a professor of gerontology and geriatric medicine at Rush University Medical Center in Chicago.From Rush University Medical Center

It’s a chilling statistic: Black Americans are twice as likely as white Americans to have Alzheimer’s and other dementias, according to the Alzheimer’s Association. And researchers still don’t fully understand why. The Alzheimer’s Association calls the effect of the disease on the Black population “the silent epidemic.”

Even as people of color are disproportionately affected by the disease — some studies suggest Hispanics are up to one-and-a-half times as likely to have Alzheimer’s or other dementias as older white people — they are severely underrepresented in clinical trials and Alzheimer’s research. For example, a 2017 meta-analysis found that across 18 Alzheimer’s observational studies and clinical trials, only 7 percent of the participants were Black.

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Fortunately, a growing body of research is exploring the links between racial inequities and dementia. “It is becoming clear that . . . the health of our most vulnerable populations will reflect the health of our entire nation, so we need to be focused on better brain health for all of our communities,” says Dr. Lisa L. Barnes, a professor of gerontology and geriatric medicine at the Rush Alzheimer’s Disease Center at Chicago’s Rush University Medical Center, who has been calling attention to this issue for more than 20 years.

Some newer research suggests that Black people are more vulnerable to long-term neurodegenerative effects of chronic stress due to factors such as socioeconomic status, discrimination, and psychological stress. A study from the University of Wisconsin-Madison School of Nursing found that Black Americans reported having 84 percent more stressful life events than white Americans report, and those events took a greater toll on memory function. For white participants, each stressful event added six months of aging. But for Black participants, each stressful event aged them an extra year-and-a-half.

Few epidemiologic studies have assessed the effect of racial discrimination on cognition. The largest and most recent, from Boston University, found that higher levels of perceived discrimination were associated with worse subjective cognitive ability (based on participant responses to questions about memory and other aspects of cognition). In explaining the higher rates of dementia among Black Americans, experts have also pointed to the correlation between increased risk of dementia and diabetes, hypertension, stroke, elevated cholesterol, and heart disease — all of which disproportionately affect Black Americans (and, in a vicious cycle, can also be exacerbated by chronic stress).

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One result of the Black Lives Matter activism of the past year is that American society is becoming more aware of the prevalence and pernicious impact of systemic racism. “The effects on the body are real, and research has shown that over and over again,” says Patricia Coogan, epidemiologist and lead author of the BU study, as well as co-investigator on the Black Women’s Health Study. “Now we need to devote attention and resources to looking at how racism affects aging.”

That may happen, as brain research becomes more representative. “Funding for Alzheimer’s dementia is at an all-time high,” says Barnes, “and there is a particular interest at the National Institute on Aging on funding studies that support inclusion of racial and ethnic populations.” She urges people of color to seek out and participate in clinical trials (the national POINTER study is focused on recruiting participants from different racial, ethnic, and socioeonomic backgrounds). “We are in desperate need of diverse populations in our research,” Barnes says, “so that when we find a cure for this devastating disease, it will be a cure for everyone.”

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Corrie Pikul is a health writer and editor in the Boston area. Send comments to magazine@globe.com.