Aβ and cognitive change: Examining the preclinical and prodromal stages of Alzheimer's disease

Background: High beta-amyloid (A beta) is associated with faster memory decline in healthy individuals and adults with mild cognitive impairment (MCI). However, longer prospective studies are required to determine if A beta-related memory decline continues and whether it is associated with increased rate of disease progression. Methods: Healthy controls (HCs; n = 177) and adults with MCI (n = 48) underwent neuroimaging for A beta and cognitive assessment at baseline. Cognition was reassessed 18 and 36 months later. Results: Compared with low-A beta HCs, high-A beta HC and MCI groups showed moderate decline in episodic and working memory over 36 months. Those with MCI with low A beta did not show any cognitive decline. Rates of disease progression were increased in the high-A beta HC and MCI groups. Conclusions: In healthy individuals, high A beta likely indicates that Alzheimer's disease (AD)-related neurodegeneration has begun. Once commenced, the rate of decline in cognitive function remains constant across the preclinical and prodromal stages of AD. (C) 2014 Published by Elsevier Inc. on behalf of The Alzheimer's Association.