Neuropsychological subtypes of incident mild cognitive impairment and mild neurocognitive disorder in a population-based cohort of older adults

Background: Mild cognitive impairment (MCI) is a heterogenous condition which places individuals at higher risk for Alzheimer's disease, yet it is not well understood. Studies of primarily prevalent MCI have identified different subtypes characterized by different neuropsychological profiles, while a recent incident MCI study empirically identified four neuropsychological subtypes (amnestic, dysexecutive, dysnomic, and subtle cognitive impairment (SCI) subtypes). Objective: We aimed to identify whether four distinct neuropsychological subtypes could be empirically derived in a sample of a) incident MCI and b) DSM5 mild neurocognitive disorder (mNCD). Methods: We used data from the Personality and Total Health Through Life study. Participants were aged 72–78, with a diagnosis of incident MCI (n = 117), and/or mNCD (n = 161). We undertook a cross-sectional cluster analysis on neuropsychological data from participants from four domains: executive, memory, language, and visuospatial. Results: For incident MCI, cluster analysis derived four subtypes, (dysexecutive, SCI, mixed dysnomic/visuospatial and mixed dysexecutive/visuospatial). For mNCD, the resulting four cluster solution included dysexecutive, SCI-amnestic/dysnomic, SCI-dysexecutive and mixed/global impairment. Discriminant function analysis revealed that 94% and 91% of MCI and mNCD participants respectively were correctly classified based on the cognitive domain scores, and further analysis confirmed the SCI groups showed reduced cognitive performance compared with matched cognitively unimpaired participants. Conclusions: Neuropsychological subtypes were empirically derived in both incident MCI and mild NCD samples, with both SCI and dysexecutive clusters most reliably detected and consistent with previous studies. The early identification of these MCI/mNCD subtypes may help to identify patient groups for targeted early intervention in clinical settings.