A team of researchers from the USC Mark and Mary Stevens Neuroimaging and Informatics Institute at the Keck School of Medicine of USC has identified meaningful differences in how early brain changes linked to Alzheimer’s disease appear across racial and ethnic groups. The findings highlight the importance of using more inclusive approaches when studying and diagnosing Alzheimer’s, particularly as current knowledge has largely been based on more limited populations. The study has been published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
The research drew on a large and diverse group of older adults who did not have dementia. It found that Black and Hispanic participants showed higher levels of tau, a protein associated with Alzheimer’s disease, in key areas of the brain involved in memory. Notably, these higher tau levels were observed even before the buildup of amyloid plaques, which are typically considered an early sign of Alzheimer’s. This suggests that the sequence or pattern of brain changes may differ across populations.
At the same time, the study found that the link between these brain changes and memory performance was not the same for all groups. While higher levels of tau were generally associated with poorer memory, the role of amyloid in strengthening this relationship varied. In particular, amyloid appeared to intensify the connection between tau and memory decline in non-Hispanic white and Hispanic participants, but not in Black participants. This indicates that common Alzheimer’s biomarkers may not fully explain cognitive changes in every population.
The data came from the Health and Aging Brain Study–Health Disparities (HABS-HD), one of the largest and most diverse brain imaging studies of ageing in the United States. Researchers used advanced PET scans to detect abnormal protein buildup in the brain years before symptoms appear. They analysed brain scans and memory test results from more than 1,500 participants who were either cognitively healthy or experiencing mild cognitive impairment.
The findings also suggest that factors beyond amyloid and tau may play a larger role in cognitive changes for some groups. These may include vascular health, other medical conditions, long-term exposure to stress, and broader social influences. In addition, researchers noted that some differences in tau levels might be linked to technical limitations in imaging methods, as certain scans can produce signals that are not directly related to tau. This reinforces the need to validate diagnostic tools across diverse populations.
Overall, the study points to the possibility that Alzheimer’s disease may develop through different biological pathways in different groups. This has important implications for how the disease is detected, monitored, and treated. Future research will continue to follow participants over time to better understand how biological, genetic, and social factors interact to shape cognitive ageing across communities, to improve care and prevention for all populations.
More information: Koral V. Wheeler et al, The relationships between ethnoracial identity, Aβ positivity, APOEε4, and medial temporal lobe tau PET, Alzheimer’s & Dementia. DOI: 10.1002/alz.71226
Journal information: Alzheimer’s & Dementia Provided by Keck School of Medicine of USC
