Plasma biomarkers identify older adults at risk of Alzheimer's disease and related dementias in a real-world population-based cohort.

ABSTRACT

INTRODUCTION: Plasma biomarkers-cost effective, non-invasive indicators of Alzheimer's disease (AD) and related disorders (ADRD)-have largely been studied in clinical research settings. Here, we examined plasma biomarker profiles and their associated factors in a population-based cohort to determine whether they could identify an at-risk group, independently of brain and cerebrospinal fluid biomarkers. METHODS: We measured plasma phosphorylated tau181 (p-tau181), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and amyloid beta (Aß)42/40 ratio in 847 participants from a population-based cohort in southwestern Pennsylvania. RESULTS: K-medoids clustering identified two distinct plasma Aß42/40 modes, further categorizable into three biomarker profile groups normal, uncertain, and abnormal. In different groups, plasma p-tau181, NfL, and GFAP were inversely correlated with Aß42/40, Clinical Dementia Rating, and memory composite score, with the strongest associations in the abnormal group. DISCUSSION: Abnormal plasma Aß42/40 ratio identified older adult groups with lower memory scores, higher dementia risks, and higher ADRD biomarker levels, with potential implications for population screening. HIGHLIGHTS Population-based plasma biomarker studies are lacking, particularly in cohorts without cerebrospinal fluid or neuroimaging data. In the Monongahela-Youghiogheny Healthy Aging Team study (n = 847), plasma biomarkers associated with worse memory and Clinical Dementia Rating (CDR), apolipoprotein E ε4, and greater age. Plasma amyloid beta (Aß)42/40 ratio levels allowed clustering participants into abnormal, uncertain, and normal groups. Plasma Aß42/40 correlated differently with neurofilament light chain, glial fibrillary acidic protein, phosphorylated tau181, memory composite, and CDR in each group. Plasma biomarkers can enable relatively affordable and non-invasive community screening for evidence of Alzheimer's disease and related disorders pathophysiology.