Race is a biological variable for Alzheimer’s risk that scientists are still working to understand. In the meantime, experimental diagnostic methods, like blood tests, are being found to be less effective in diagnosing the disease in different racial ethnicities as they are in white people.
This, researchers say, is because these forthcoming Alzheimer’s tests were predominantly developed through clinical trials populated disproportionately by white people.
Most medical research is conducted in white people, a sample that isn’t representative of diversity within the population. When researchers study diseases — and test their potential treatments — in only a tiny sliver of the population, it means they only get a tiny sliver of the full view. That’s why, moving forward, a major goal for Alzheimer’s advocates is to boost diversity in clinical trials, through methods like community advocacy and trial diversity quotas.
The need for improving diversity in clinical trials is urgent. Researchers also need to take a closer look at the design of the tests used to diagnose Alzheimer’s and other neurological diseases. Cognitive tests are already under scrutiny for their racist roots. Case in point: An April 2022 study published in Neurology has found that three of four Alzheimer’s blood diagnostic tests are also inaccurate at diagnosing Alzheimer’s in African Americans.
“When you use a limited study population — as, unfortunately, scientists have traditionally done in Alzheimer’s research — and then try to apply the results to everyone, including people of diverse backgrounds, you could exacerbate health inequities,” Dr. Suzanne Schindler, an associate professor of neurology at Washington University and an author on the study, said in a news release.
Some blood biomarkers aren’t predictive in African Americans
The researchers compared the performance of four different blood tests on 152 participants who were either non-hispanic white or who identified as African American. The participants were grouped into 76 matched pairs — people in the pair would have a similar age, ApoE4 status and cognitive ability — so that the largest difference within any pair would be their race.
Blood diagnostic tests are purported to work by finding proteins in the blood that strongly associate with either amyloid levels in the cerebrospinal fluid or in a PET scan. This can help someone understand their risk of developing the disease, helping them get screened earlier.
“The fact these risk models have not been tested in a lot of populations makes me wary, because Alzheimer’s is a global disease,” Dr. Thomas K. Karikari, a co-author on the study and an assistant professor in the University of Gothenburg, said in the news release.
Different tests focused on different biomarkers in the blood. While the value of certain biomarkers like p-tau181, p-tau231 or neurofilament light chain were predictive of amyloid in white participants, they were inaccurate in the African American participants. This means these blood biomarkers don’t work well across all ethnic and racial groups.
The only test that performed equally well in the white and Black participants was the PrecivityAD test, developed by C2N Diagnostics, which measures the levels a couple kinds of Alzheimer’s biomarker beta-amyloid protein in the blood to predict the levels of these same proteins in the cerebrospinal fluid — which indicates its presence in the brain.
Why does race matter in an Alzheimer’s diagnosis?
“My hope is that this paper will help illustrate the need to increase the diversity of participants in Alzheimer’s studies,” Schindler said. “My colleagues and I are working to develop a much larger, multicenter study to better evaluate racial differences in Alzheimer’s-related blood biomarkers.”
While people may be of different races, the proteins their bodies produce are structurally identical. Yet, African Americans may face double the risk of developing Alzheimer’s than white individuals. More experts are beginning to study the role of environmental factors and policies that sprung from racist lines of thinking that may affect brain health. These contributing factors include the differences in cognitive development attributed to racially segregated education in the Jim Crow era, the higher exposure to air pollution, and a tangle of other interrelated factors.
Even when an individual is being tested for Alzheimer’s, they continue to encounter these racial disparities: The way cognition is measured is often rooted in racism, which may impact diagnosis.