Process-level eye-movement dynamics enhance sensitivity to early Alzheimer's disease-related cognitive vulnerability

BackgroundEarly Alzheimer's disease (AD)-related cognitive vulnerability is characterized by subtle disruptions in attentional and executive processing that may precede overt declines in global cognitive scores. Identifying process-sensitive behavioral markers capable of capturing these early alterations remains a major challenge in psychogeriatric assessment.ObjectiveTo examine whether eye-movement-derived process-level measures, particularly fixation-shift dynamics, are associated with early cognitive vulnerability in older adults and whether they provide incremental value beyond conventional cognitive screening scores in an AD-related context.MethodsThis cross-sectional study enrolled 109 adults aged ≥65 years, categorized as cognitively normal (CN, n = 33), mild cognitive impairment (MCI, n = 35), and dementia due to AD (ADD, n = 41). Participants completed a standardized online interactive cognitive task while eye movements were recorded using a non-head-fixed, desktop-based eye-tracking system. Cognitive-only, eye-movement-only, and combined multimodal models were compared using receiver operating characteristic (ROC) analysis and area under the curve (AUC).ResultsThe combined multimodal model consistently outperformed single-modality approaches. Discriminative performance was high for CN versus ADD (AUC = 0.925) and for CN versus cognitively impaired participants overall (AUC = 0.897). Fixation-shift dynamics emerged as a robust process-level marker, demonstrating particular sensitivity in distinguishing CN individuals from those with MCI.ConclusionsFixation-shift eye-movement dynamics capture early AD-related cognitive vulnerability beyond conventional total cognitive scores. This multimodal framework may support psychogeriatric screening and clinical triage by detecting subtle cognitive inefficiencies that precede measurable declines on standard cognitive tests.