Amyloid-associated depression: A prodromal depression of Alzheimer disease?

Abstract

Context: A high ratio of plasma amyloid-β peptide 40 (Aβ40) to Aβ42, determined by both hig hAβ40 and low Aβ42 levels, increases the risk of Alzheimer disease. In a previous study, we reported that depression is also associated with low plasma Aβ42 levels in the elderly population. Objective: To characterize plasma Aβ40: Aβ42 ratio and cognitive function in elderly individuals with and without depression. Design: Cross-sectional study. Setting: Homecare agencies. Participants: A total of 995 homebound elderly individuals of whom 348 were defined as depressed by a Center for Epidemiological Studies Depression score of 16 or greater. Main Outcome Measures: Cognitive domains of memory, language, executive, and visuospatial functions according to levels of plasma Aβ40 and Aβ42 peptides. Results: Subjects with depression had lower plasma Aβ42 levels (median, 14.1 vs 19.2 pg/mL; P=.006) and a higher plasma Aβ40:Aβ42 ratio (median, 8.9 vs 6.4; P