CROSS-SECTIONAL AND LONGITUDINAL EXAMINATION OF FLORBETAPIR-PET AMYLOID IMAGING AND COGNITIVE PERFORMANCE IN THE OLDEST-OLD
- Claudia Kawas, Professor of Neurology, University of California, Irvine
- Maria Corrada, Associate Professor of Neurology, University of California, Irvine
Florbetapir imaging has been developed as part of the effort to understand the amyloid cascade hypothesis, which theorizes that amyloid deposition is the first event in the Alzheimer’s disease course. The purpose of this examination was to study the relationship between amyloid deposition and cognitive performance in non-demented oldest-old, as an extension of a preliminary examination done by The 90+ Study. We asked thirty-five non-demented oldest-old subjects from The 90+ Study to undergo a florbetapir amyloid PET scan. Amyloid deposition was quantified by standard uptake value ratio (SUVr), which compares the radioactive signal from cortex to the signal from the whole cerebellum as a reference point. Since the cerebellum is known to be less affected by amyloid than the cortex, SUVr allows us to account for baseline radioactivity in our quantification. Data from seven of these participants, who participated in our preliminary study, was used in a longitudinal examination. Our cross-sectional analysis exhibited a significant association between higher SUVr and cognitive performance on the Mini-Mental State Examination (MMSE). Our longitudinal examination revealed little change between our amyloid positive and amyloid negative participants in both SUVrs or MMSE scores over a two-year period. While we present evidence that measurement of amyloid via florbetapir PET can be used to predict performance on the MMSE, our longitudinal examination also suggests that more research is needed to determine how amyloid deposition progresses in the oldest-old over time. Considering that the oldest-old is currently the fastest growing age group in our society and the incidence of Alzheimer’s increases with age, determining the predictive ability of in-vivo amyloid imaging in this cohort is crucial for the future of Alzheimer’s disease diagnosis and prevention.