Cognitive dispersion is elevated in amyloid-positive older adults and associated with regional hypoperfusion.

ABSTRACT

OBJECTIVE: Cognitive dispersion across neuropsychological measures within a single testing session is a promising marker predictive of cognitive decline and development of Alzheimer's disease (AD). However, little is known regarding brain changes underlying cognitive dispersion, and the association of cognitive dispersion with in vivo AD biomarkers and regional cerebral blood flow (CBF) has received limited study. We therefore examined associations among cognitive dispersion, amyloid-beta (Aß) positivity, and regional CBF among older adults free of dementia. METHOD: One hundred and forty-eight Alzheimer's Disease Neuroimaging Initiative (ADNI) participants underwent neuropsychological testing and neuroimaging. Pulsed arterial spin labeling (ASL) magnetic resonance imaging (MRI) was acquired to quantify CBF. Florbetapir positron emission tomography (PET) imaging determined Aß positivity. RESULTS: Adjusting for age, gender, education, and mean cognitive performance, older adults who were Aß+ showed higher cognitive dispersion relative to those who were Aß-. Across the entire sample, higher cognitive dispersion was associated with reduced CBF in inferior parietal and temporal regions. Secondary analyses stratified by Aß status demonstrated that higher cognitive dispersion was associated with reduced CBF among Aß+ individuals but not among those who were Aß-. CONCLUSIONS: Cognitive dispersion may be sensitive to early Aß accumulation and cerebrovascular changes adjusting for demographics and mean neuropsychological performance. Associations between cognitive dispersion and CBF were observed among Aß+ individuals, suggesting that cognitive dispersion may be a marker of brain changes among individuals on the AD continuum. Future studies should examine whether cognitive dispersion predicts brain changes in diverse samples and among those with greater vascular risk burden.