Association of plasma β-amyloid with MRI markers of structural brain aging the 3-City Dijon study

Cerebral beta-amyloid (A beta) deposition and atrophy are central features of Alzheimer disease. Studies of Alzheimer disease biomarkers have largely focused on A beta in cerebrospinal fluid (CSF), and there is uncertainty as to what plasma A beta may be a marker. We examined the association of A beta levels in the plasma with magnetic resonance imaging (MRI)-markers of brain aging, including longitudinal changes in global and regional brain volumes, in dementia-free persons. We studied 1530 participants of the Three-CityDijon cohort, aged 65-80 years. Plasma A beta measurement and magnetic resonance imaging were performed at baseline and after a 4-year follow up. Total brain, gray matter, and hippocampal volume were estimated using voxel-based morphometry, and annualized change in brain volumes was calculated. Increased plasma A beta(1-40) was associated with lower baseline hippocampal volume. Although baseline plasma A beta levels were not associated with longitudinal change in brain volumes, consistently high plasma A beta(1-40) levels were associated with faster total brain atrophy and consistently low plasma A beta(1-42)/A beta(1-40) ratio, with increased total brain atrophy and gray matter atrophy. In dementia-free older adults, high plasma A beta(1-40) and low plasma A beta(1-42)/A beta(1-40) ratio were associated with smaller hippocampal volume and accelerated global and regional brain atrophy respectively. (C) 2015 Elsevier Inc. All rights reserved.