Neurodegenerative plasma biomarkers for prediction of hippocampal atrophy in older adults with suspected Alzheimer's disease in Kinshasa, Democratic Republic of Congo

Background Hippocampal atrophy is a key feature of Alzheimer's disease (AD), but neuroimaging is often inaccessible in low-resource settings. Blood-based biomarkers such as amyloid-β (Aβ 42/40 ), phosphorylated tau-181 (p-tau181), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) may offer a practical alternative, though their utility in African populations remains understudied. Objective This study investigated the ability of plasma biomarkers of AD and AD-related dementias—Aβ 42/40 , p-tau181, NfL, and GFAP—to predict hippocampal atrophy in older adults in Kinshasa, Democratic Republic of Congo. Methods Eighty-five adults aged over 65 (40 healthy; 45 suspected AD) were recruited. Core AD (Aβ 42/40 , p-tau181) and non-specific (NfL, GFAP) biomarkers were analyzed. Hippocampal volumes were measured using MRI. Linear and logistic regressions assessed biomarker differences by age, sex, and neurological status, and predicted hippocampal atrophy. Results Elevated p-tau181 was associated with left hippocampal (LH) atrophy (p = 0.020), with 4.2-fold increased odds [OR = 4.2 (1.5–18.4)] of LH atrophy per standard deviation increase. The areas under the curve of plasma biomarkers without clinical covariates to discriminate LH, right hippocampal (RH), and total hippocampal (TH) atrophy ranged from 90%–94%, 76%–82%, and 85%–87%, respectively. Models including clinical covariates and biomarkers improved discrimination to 94%–96% (LH), 81%–84% (RH), and 88%–90% (TH). Conclusions Consistent with findings from other settings, core AD plasma biomarkers can effectively predict hippocampal atrophy in a Sub-Saharan African population, supporting their potential for scalable dementia screening where imaging is limited.