Recognition memory as a neuropsychological marker of progression in early-stage Alzheimer's disease: a 24-month prospective cohort study.

INTRODUCTION: Alzheimer's disease (AD) is the leading cause of dementia, and amnestic mild cognitive impairment (a-MCI) is considered its prodromal stage. Recognition memory is commonly assessed with yes/no tasks, although conventional scoring often overlook false alarms. Signal Detection Theory (SDT) measures, particularly discriminability (d-prime), may better detect early recognition deficits and predict progression to AD dementia. METHOD: In this prospective cohort study, 278 older adults with a-MCI were followed for 24 months. Participants underwent clinical and neuropsychological assessment, including the Rey Auditory Verbal Learning Test. Recognition was decomposed into hits, false alarms, and d-prime. A subsample underwent amyloid and tau biomarker assessment by cerebrospinal fluid and/or imaging. Mixed-effects models examined longitudinal change and prediction of conversion to AD dementia. RESULTS: Delayed recall, recognition hits, and d-prime declined significantly over time, with steeper trajectories among converters. Converters showed an early and marked d'prime reduction during the first 12 months, mainly related to increased false alarms. Lower baseline d-prime and greater early decline independently predicted conversion after adjustment for demographic, global cognition, and AD biomarkers. CONCLUSIONS: SDT-derived recognition indices, especially d'prime, provide clinically relevant prognostic information in a-MCI. Adding d' to delayed recall and biomarkers may improve risk stratification, follow-up planning, and selection for disease-modifying trials.