Age‐at‐Onset and APOE Related Heterogeneity in the Clinical, Plasma Biomarker, and Neuropathologic Presentation of Alzheimer’s Disease (AD)

Patients with sporadic early‐onset AD (EOAD) show less pronounced memory impairment, faster cognitive decline, and greater likelihood of focal cortical syndromes than those with later onset (LOAD), while often lacking the APOE ε4 allele classically associated with younger onset. This heterogeneity could arise from differences in the distribution of AD pathology or presence of concomitant pathologies.