. Beta-amyloid in healthy aging: regional distribution and cognitive consequences. Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;

Abstract:

Beta-amyloid 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. To address these questions, we prospectively examined beta-amyloid across a lifespan sample of healthy adults and assessed its impact on cognition. Participants (N = 137, aged 30-89) were scanned by PET using 18Florbetapir and were administered a range of cognitive tests. Cognitive construct composites with two or more measures each were calculated for speed of processing, working memory, reasoning, and crystallized intelligence. Standardized uptake value ratios (SUVRs) were obtained from a priori masked regions of interest including anterior and posterior cingulate, precuneus, lateral temporal, dorsolateral and orbital frontal, parietal, and occipital cortices. Our results revealed 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 differences in behavior. Specifically, across the entire sample increases in mean cortical amyloid burden were associated with decreases in processing speed. Subanalysis of the group of older participants with the highest amyloid burden showed stronger amyloid-cognitive associations. In the high-amyloid individuals, a dose-response effect was observed where higher amyloid burden predicted poorer processing speed, working memory and fluid abilities. Thus, beta-amyloid burden appears to first 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, are impervious to the effects of As deposition, at least in healthy adults. Supported in part by NIH grants 5R37AG-006265-25, 3R37AG-006265-25S1, and Alzheimer's Association grant IIRG-09-135087. Radiotracer was generously provided to the study by Avid Radiopharmaceuticals.

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