Association Between Plasma GFAP and Medial Temporal Atrophy and Cognition in Amyloid-Negative Cerebrovascular Disease

BACKGROUND AND OBJECTIVES: Plasma glial fibrillary acidic protein (GFAP), a marker of astrocyte reactivity, is elevated across multiple neurodegenerative conditions, including Alzheimer disease. However, its role in neurodegeneration and cognitive decline driven by cerebrovascular pathology, independent of β-amyloid (Aβ) copathology, remains poorly characterized. We investigated whether plasma GFAP is associated with medial temporal atrophy and cognition across a spectrum of cerebrovascular burden in Aβ-negative cognitively impaired individuals. METHODS: In this cross-sectional multicenter study, Aβ PET-negative cognitively impaired participants were recruited from South Korean memory clinics. Plasma GFAP was measured using ultrasensitive Simoa assays. White matter hyperintensity burden was graded using the Fazekas scale and stratified into low (LVP: Fazekas 1) and high (HVP: Fazekas 2-3) cerebrovascular burden groups. Medial temporal gray matter density was assessed using voxel-based morphometry, and hippocampal and amygdalar volumes were derived from T1-weighted MRI adjusted for intracranial volume. Linear regression, interaction, and bootstrap mediation models were used to assess associations among GFAP, brain structure, and cognition. RESULTS: = 0.016). Vascular comorbidities (diabetes, dyslipidemia, hypertension) did not modify the GFAP-cognition association. DISCUSSION: In Aβ-negative cognitively impaired individuals with high cerebrovascular burden, elevated plasma GFAP is associated with medial temporal atrophy and cognitive decline, suggesting GFAP may capture astrocyte-reactivity relevant to vascular cognitive impairment beyond amyloid pathology. These cross-sectional findings require confirmation in longitudinal and ethnically diverse cohorts.