Some Alzheimer's Biomarkers Differ by Race
A new study funded by the National Institute on Aging (NIA) points to differences in some biological markers underlying Alzheimer's disease in African Americans and non-Hispanic Whites.
The results, published recently in JAMA Neurology, add to growing evidence of different biological mechanisms when considering race and Alzheimer's. An accompanying editorial emphasizes that gathering biological data from African Americans is essential to furthering research in Alzheimer's health disparities.
It's been difficult to explain why Alzheimer's disproportionately affects African Americans, in part because they are under-represented in studies of dementia. The new study from researchers at Washington University School of Medicine, St. Louis, looked at biomarkers, using the largest set of fluid biomarker data from African Americans to date, collected for more than a decade.
Researchers analyzed biomarker data for 1,255 participants (average age 70), including 173 African Americans, who enrolled in studies at the Washington University's Knight Alzheimer's Disease Research Center.
In each racial group, 67% of participants had normal cognition, and the rest were mildly impaired. All had undergone at least one Alzheimer's biomarker test, including brain scans to measure brain shrinkage and harmful forms of the amyloid protein, as well as lumbar punctures to collect cerebrospinal fluid (CSF), which reveals levels of amyloid and another protein, tau, indicating the disease processes.
Although there were no differences between African Americans and Whites on some measures, including amyloid levels in the brain and CSF, other test results showed differences. Compared with Whites, African Americans with a family history of dementia had a smaller hippocampus, a brain structure important for learning and memory.
Also, African Americans had significantly lower levels of tau in CSF than Whites when both had the APOE ɛ4 gene form, a genetic risk factor for Alzheimer's. Generally, lower tau, which forms damaging tangles inside neurons, means a person is less likely to be cognitively impaired, but African Americans were just as impaired as Whites.
It's possible that CSF tau levels found to be abnormal in Whites are not abnormal in African Americans because APOE ɛ4 exerts a weaker effect in African Americans, the authors suggested.
To encourage aging researchers to explore racial and ethnic differences in aging-related outcomes, NIA developed the NIA Health Disparities Research Framework. Since 2015, NIA has awarded more than $100 million to explore the environmental, sociocultural, behavioral, and biological determinants of health disparities related to aging.
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