Plasma inflammatory biomarker profiles across the Alzheimer's disease spectrum in the Bio-Hermes cohort.

INTRODUCTION

Inflammation contributes to Alzheimer's disease (AD), but its stage-specific and amyloid-dependent patterns remain unclear.

METHODS

We analyzed 964 participants from the Bio-Hermes cohort (cognitively normal [CN] = 404, mild cognitive impairment [MCI] = 302, mild AD = 258). Plasma levels of 32 cytokines, neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) were quantified alongside core AD biomarkers. Associations with cognition, amyloid, apolipoprotein E (APOE) ε4, and clinical outcomes were assessed using analysis of covariance, partial correlations, and regression models.

RESULTS

Twenty-four cytokines, NfL, and GFAP differed across cognitive groups. Amyloid stratification revealed a core amyloid-independent profile (14 cytokines + NfL) and a broader amyloid-specific profile including GFAP, interleukin (IL)-1β, and IL-18, implicating microglial inflammasome and astrocytic activation. Stage-dependent patterns suggested inflammation may act as early driver, concurrent process, or late amplifier. Paradoxical associations (e.g., eotaxin-2, IL-2R with better memory) and APOE ε4-linked immune differences indicated context-dependent roles.

DISCUSSION: This exploratory study reveals biologically plausible, inflammatory heterogeneity in AD and highlights plasma cytokine profiles as candidate biomarkers and therapeutic targets, warranting investigation.