Population disparities in Alzheimer's disease: A systematic review of fluid and neuroimaging biomarkers.

Alzheimer's disease manifests differently across ancestral groups, with African populations showing distinct fluid biomarker levels, neuroimaging patterns, and post mortem pathology. These differences may compromise diagnostic accuracy and exacerbate health disparities. This systematic review, examined studies published from 2015 to 2025 assessing amyloid-β and tau via fluid assays and neuroimaging. Findings reveal ancestry-linked variation where African populations exhibit lower cerebrospinal fluid/plasma Aβ42/Aβ40 and p-tau181 ratios, with neuroimaging showing broadly similar reduced positron emission tomography patterns but slightly elevated amyloid and reduced tau signals. Limited post mortem data suggest reduced plaque and tangle densities despite comparable dementia severity. Genetic, environmental, and sociocultural factors contribute to these disparities. Diagnostic thresholds derived from non-African cohorts risk underdiagnosing AD in African individuals. There is an urgent need to recalibrate and validate biomarker protocols to ensure equitable and accurate dementia diagnosis across diverse populations.