Neuropsychological performance and conversion to Alzheimer's disease in early- compared to late-onset amnestic mild cognitive impairment: CREDOS study.

BACKGROUND: Amnestic mild cognitive impairment (aMCI) is regarded as a prodromal stage of Alzheimer's disease (AD). Given that patients with early-onset AD (EOAD) and with late-onset AD (LOAD) are known to have different clinical courses, symptoms and neuroimaging findings, early-onset (EOMCI) and late-onset aMCI (LOMCI) might be expected to have similar differences as EOAD versus LOAD.
METHODS: Our study involving 425 patients with aMCI (124 EOMCI, 301 LOMCI), who were followed for around 1.5 years, and 958 normal control subjects (NC) investigated neuropsychological characteristics and prediction of progression to AD in patients with EOMCI versus LOMCI. Neuropsychological scores were compared between EOMCI, LOMCI and NC with analyses of covariance controlling age, gender, education and disease duration. The risk of AD conversion was evaluated by Cox proportional hazard analyses.
RESULTS: The baseline neuropsychological performances were comparable between EOMCI and LOMCI. Visuospatial memory for EOMCI and verbal memory scores for LOMCI were significant predictors of AD conversion.
CONCLUSION: Our study indicates that EOMCI with visuospatial memory impairment, which implies underlying right predominant pathology, and LOMCI with poor verbal memory, which suggests underlying left predominant pathology, are individual conditions at an increased risk of conversion to AD.