APOE4 and cognition in intracranial atherosclerosis: beyond Alzheimer's pathology.

INTRODUCTION: The apolipoprotein E ε4 (APOE ε4) allele is a major genetic risk factor for Alzheimer's disease, but its relevance to cognition in intracranial atherosclerosis (ICAS) remains unclear. We investigated the association between APOE ε4 and cognition in ICAS. METHODS: Baseline data from a multicenter cohort were analyzed. Patients with radiologically confirmed ICAS underwent APOE genotyping, plasma biomarker assays, magnetic resonance imaging assessment of cerebral small vessel disease (CSVD) and brain atrophy, and standardized cognitive testing. RESULTS: Among 409 patients (mean age 60 years, 55% male), 16% carried APOE ε4. Carriers showed more frequent cognitive impairment (63% vs 48%), greater stenosis burden, and lower plasma amyloid beta (Aβ)42/40 ratios, whereas other Alzheimer's biomarkers, CSVD burden, and atrophy scores showed no difference. After adjustment, APOE ε4remained associated with cognitive impairment (odds ratio [OR] 1.86). The association was pronounced in women (OR 4.43) but absent in men. DISCUSSION: APOE ε4 is linked to cognitive impairment in ICAS, particularly in women, through mechanisms beyond Alzheimer's pathology. HIGHLIGHTS: In patients with ICAS, cognitive impairment was more prevalent in carriers than in non-carriers. Carriers showed greater stenosis burden and lower plasma Aβ42/40 ratios. After full adjustment (stroke, CSVD, and AD biomarkers), APOE ε4 remained associated with cognitive impairment. Female carriers had substantially higher odds of cognitive impairment.