Racial Discrimination in Midlife Linked to Biomarkers of Alzheimer’s Disease
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“Black Americans have a higher risk of Alzheimer’s disease and other dementias compared to non-Hispanic white Americans, but we still don’t fully understand the factors that contribute to this disproportionate risk,” says coauthor Michelle Mielke, PhD, professor of epidemiology and prevention at Wake Forest University School of Medicine in Winston-Salem, North Carolina.
— Negar Fani, PhD
Although that difference is likely caused by a variety of different reasons, including genetic factors and a higher rate of other diseases that impact brain health (such as heart disease), many experts believe that exposure to racism and the acute and chronic stress that causes may be a key driver of the disparity.
“The study provides compelling evidence of how racial discrimination is contributing to health disparities and further validates the importance of racism as a problem on a global public health level,” says Negar Fani, PhD, neuropsychologist and associate professor in the department of psychiatry and behavioral sciences at Emory University in Atlanta, who was not involved in this study. Dr. Fani conducts research on trauma, including racial trauma, and accessible interventions for trauma-related problems.
“Hopefully the findings are also validating to Black Americans and other minoritized communities who sometimes experience self-doubt about what they’ve experienced and how it impacts them,” says Fani.
“You’re not being ‘too sensitive.’ This is a real thing, and it can contribute to real damage to the brain,” she says.
Exploring What Racism Does to the Brain
But researchers are still trying to understand the different brain pathways that racism affects, says Dr. Mielke. “For example, is it related to the cerebral vascular pathology in your brain or more related to Alzheimer’s pathology? Or could it be related to general brain atrophy? Those are some of the questions that we were trying to start getting at in this particular study,” she says.
By looking at biomarkers of brain health, this study aimed to answer some of those questions, she says. “This could allow us to better identify those individuals that are at highest risk and possibly intervene to improve outcomes,” says Mielke.
How the Study Was Conducted
Study participants were a sample of 255 Black Americans who were part of the Family and Community Health Study, which started in 1996 and included more than 800 families in the United States. For this new study, investigators used blood samples collected every to to three years as well as three interviews over a 17-year period.
Researchers analyzed serum biomarkers (molecules made by normal and abnormal cells) that are associated with Alzheimer’s disease and related dementias. These biomarkers are a potential measure of the disease process, but their presence doesn’t automatically mean that the person is going to develop Alzheimer’s, explains Mielke.
The biomarkers included the following:
- Serum phosphorylated tau181 (p-Tau181), marker of Alzheimer’s pathology
- Neurofilament light (NfL), a nonspecific marker of neurodegeneration
- Glial fibrillary acidic protein (GFAP), a marker of brain inflammation
To measure racial discrimination, the study team surveyed the participants about how often — on a scale of “never” to “frequently” — they experienced discriminatory events during the preceding year.
Examples of such events included instances where they were the victim of disrespectful treatment by a store owner or salesclerks, racial slurs, or being hassled by the police, as well as exclusion from social activities, and not being expected to do well because of being a Black American.
What the Researchers Found
When the researchers measured serum biomarkers in 2008 (when the participants were an average age of 46) there were no correlations between racial discrimination and increased levels of the serum biomarkers.
That would be expected, says Mielke. Although brain changes can appear decades before a person develops Alzheimer’s symptoms (if they develop symptoms at all), that would still be a relatively young age for the increase in biomarker levels, she says.
However, in 2019 — 11 years later — researchers found that increased discrimination during middle age significantly correlated with higher levels of both p-Tau181 and NfL.
“An average age of 57 is still quite young; we didn’t necessarily expect to see changes this early on,” says Mielke.
The findings provide evidence that the chronic stress of racial discrimination experienced between the ages of 40 and 50 years old can become biologically embedded and contribute to Alzheimer’s disease pathology and neurodegeneration later in life, says Mielke.
This highlights the importance of continuing to research “the everyday challenges and circumstances experienced by Black Americans as a strategy for identifying the factors that explain their increased risk for dementia,” the authors wrote.
The Evidence Is Clear: Chronic Stress Negatively Impacts the Brain
“This study is an important look into the potential cumulative impacts of racialized stress on health for minoritized individuals,” says Nathaniel Harnett, PhD, director of the Neurobiology of Affective and Traumatic Experiences Laboratory at McLean Hospital in Belmont, Massachusetts, and assistant professor of psychiatry at Harvard Medical School. Although not involved in this trial, Dr. Harnett has conducted research on trauma’s impact on the brain.
The evidence for the impacts of chronic stress on the brain and body is “pretty overwhelming” at this point, he says. “And I think researchers now are starting to realize what other scholars of racism have known for a while, which is that racism — in its many forms — can be a chronic stressor,” says Harnett.
This particular study adds to a growing knowledge base by highlighting potential long-term effects about new ways racial discrimination can affect neurobiology, he says.
RELATED: Mental Health Resources for Black Americans
Screening for Experiences of Racism May Help Identify People at Risk
Researchers hope the findings will be used to help create policies and interventions to reduce racial disparities and reduce dementia risk.
What would this look like in “the real world”? Fani believes accumulating evidence is enough to warrant screening for racism in a medical setting.
“Just like we screen for factors such as family history or psychiatric issues like depression, I think screening for the experiences of racism is critical to help identify people at risk for certain health conditions,” she says.
“I hope that this study and others like it will help create positive change through public policy and increase spending to research the effects of racism on health and have more resources allocated to detecting racism in institutional settings and eliminating it,” says Fani.
Harnett agrees, saying, “The American Public Health Association named racism as a public health crisis several years ago. So, I think there is understanding that systemic interventions — rather than purely individually focused ones — are needed to address the issues of racism in the United States,” he says.
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