Associations of blood biomarkers of glial cell dysfunction and neuronal injury with future cognitive decline and incident dementia.

INTRODUCTION: Prospective studies of blood-based biomarkers reflecting pathogenic processes, other than Alzheimer-specific pathologies, that contribute to dementia in diverse cohorts are lacking. METHODS: We jointly fitted linear mixed-effect models and proportional hazards models to examine associations of midlife glial fibrillary acidic protein (GFAP), chitinase-3-like protein 1 (YKL-40), soluble cluster of differentiation-14 (sCD14), neurofilament light chain (NfL), total tau (t-tau), and ubiquitin C-terminal hydrolase L1 (UCHL1) levels in serum (collected in 1993 to 1995) with cognitive decline and incident dementia (ascertained over 29 years through 2022) in the community-based Atherosclerosis Risk in Communities Study. sCD14 and YKL-40 were measured in 3082 participants and the other four biomarkers in 1766 participants. RESULTS: Higher serum GFAP, YKL-40, sCD14, and NfL were associated with faster cognitive decline and elevated dementia rate (e.g., 1 standard deviation [SD] higher log-base2 YKL-40 was associated with -0.11SD faster 25-year cognitive decline (95% confidence interval [CI]: -0.15,-0.07) and 45% higher dementia hazard (hazard ratio [HR]: 1.45 [95% CI: 1.25, 1.68]). Higher t-tau and UCHL1 were also associated with faster cognitive decline. DISCUSSION: Midlife blood biomarkers reflecting glial and neuronal dysfunction and neuroinflammation are associated with early cognitive impairment.