Ethnic and racial influences on blood biomarkers for Alzheimer's disease: A systematic review

Background: Little is known about confounding factors influencing Alzheimer's disease (AD) blood biomarker concentrations. Objective The objective of this systematic review was to explore the available evidence for the influences of ethnicity and race on AD blood biomarker concentrations. Methods: We conducted a comprehensive systematic search in PubMed and Web of Science databases spanning from inception until 15 June 2023. We included studies that utilized plasma or serum biomarkers (amyloid-beta [A beta], total tau [t-tau], phosphorylated tau [p-tau], neurofilament light [NfL], and glial fibrillary acidic protein [GFAP]), compared individuals with AD to healthy controls, and included a minimum of two ethnic or racial groups for comparison. A total of 10 studies were included in the qualitative synthesis. All studies were conducted in the US. Results: Seven studies reported differences in blood biomarker concentrations between ethnic or racial groups. However, after adjusting for medical conditions and social determinants of health, the differences became non-significant in two of the studies. The included studies differed in their included covariates and their statistical approaches, which complicated the interpretation of the observed differences. Conclusions: The available evidence suggests that ethnicity and race may influence blood biomarker concentrations. However, it remains unclear to what extent these differences are mediated by differences in social determinants of health and medical conditions. Future studies are needed to explore ethnic and racial differences in blood biomarkers, including studies in diverse samples outside the US.