Abstract
119
Objectives Beta-amyloid (Aβ) deposition has been detected in vivo in a significant portion of non-demented older adults, but the time course, regional distribution and cognitive consequences of this deposition is unclear.
Methods We prospectively examined Aβ across a lifespan sample of healthy adults and assessed its impact on cognition. Participants (N = 137, aged 30-89) underwent PET with 18Florbetapir and were administered a range of cognitive tests. Cognitive construct composites were calculated for speed of processing, working memory, reasoning, and crystallized intelligence. SUVRs (relative to cerebellum) were obtained from ROIs including anterior and posterior cingulate, precuneus, lateral temporal, dorsolateral and orbital frontal, parietal, and occipital cortices.
Results There was a differential pattern of amyloid distribution across region and age. Some regions showed small, but significant increases with aging, such as prefrontal and parietal cortices, whereas other regions displayed steeper increases with age and greater variability in amyloid deposition in adults age 60 and over (e.g., anterior and posterior cingulate, precuneus). These age-associated increases in amyloid burden were correlated with decreases in processing speed. Subanalysis of the group of older participants with the highest amyloid burden showed a dose-response effect where higher amyloid burden predicted poorer processing speed, working memory and fluid abilities.
Conclusions Amyloid burden appears to exert an effect on the most basic of cognitive measures (processing speed), whereas higher-order cognitive operations such as working memory and fluid reasoning are only affected in those with markedly elevated amyloid. Cognitive abilities which rely upon expertise, such as verbal abilities or crystallized intelligence, were unaffected by Aβ deposition.
Research Support Supported by NIH grants 5R37AG-006265-25, 3R37AG-006265-25S1, and Alzheimer’s Association grant IIRG-09-135087. Radiotracer was generously provided by Avid Radiopharmaceuticals