Predicting cognitive decline: Which is more useful, baseline amyloid levels or longitudinal change?

The use of biomarkers for early detection of Alzheimer disease (AD) is crucial for potential therapeutic treatments. Positron Emission Tomography (PET) is a well-established tool used to detect ß-amyloid (Aß) plaques in the brain. Previous studies have shown that cross-sectional biomarkers can predict cognitive decline (Schindler et al 2021). However, it is still unclear whether longitudinal Aß-PET may have additional value for predicting time to cognitive impairment in AD. The current study aims to evaluate the ability of baseline- versus longitudinal rate of change in- 11C-Pittsburgh compound B (PiB) Aß-PET to predict cognitive decline. 153 Participants with unimpaired cognition, very mild dementia, or mild dementia were included in this study. All participants underwent PiB-PET scans and comprehensive clinical assessments. Analyses demonstrate that baseline Aß is significantly associated with the rate of change in cognitive composite scores. Cognition declines more rapidly when baseline PiB Aß levels are high. In contrast, the rate of change in PiB-PET Aß is not significantly associated with cognitive decline. Additionally, the predictive ability of the rate of change in the PiB-PET measures on cognitive decline was significantly influenced by APOE ε4 carrier status. These results suggest that a single PiB-PET scan is sufficient to predict cognitive decline and that longitudinal measures of Aß accumulation do not improve prediction of cognitive decline once someone is amyloid positive.