Effects of age and β-amyloid on cognitive changes in normal elderly people

Age-related decline is common in multiple cognitive domains. beta-amyloid (A beta) deposition, a pathological hallmark of Alzheimer's disease, is also associated with cognitive changes in many older people. In this study, we examined a wide range of cognitive function in order to differentiate the effect of age and A beta on cognition during aging. Using positron emission tomography (PET) imaging with the radiotracer Pittsburgh Compound B (PIB), we classified normal older subjects as High PIB-Old and Low PIB-Old and applied sequential multivariate analyses (i.e., principal components analysis [PCA] and discriminant analysis) to obtain summary measures of cognitive tests encompassing multiple cognitive domains. Among 5 cognitive components, a significant age effect was observed in component scores of visual memory and executive functions, regardless of the level of A beta. Discriminant scores (weighted scores of the 5 cognitive components) revealed a significant effect of both age and A beta and were further associated with quantitative PIB counts. The results of the current study highlight both effects of age and A beta on cognitive changes in normal elderly. (C) 2012 Elsevier Inc. All rights reserved.