Depression is associated with low plasma Aβ42 independently of cardiovascular disease in the homebound elderly

Background: Depression often the onset of Alzheimer's disease before the of precedes (AD) appearance cognitive symptoms. Plasma Amyloid-β peptide 42 (Aβ42) declines before and soon after the onset of AD, yet the relationship between plasma Aβ42 and depression is unclear. Methods: We used 515 homebound elders aged 60 and older in a population-based, cross-sectional study to investigate associations between plasma Aβ levels and depression with and without cardiovascular co-morbidities. Depression was evaluated by using the Center for Epidemiological Studies Depression (CES-D) scale. Plasma Aβ40 and Aβ42 were measured. Results: The elderly with depression had lower plasma Aβ42 (median: 15.3 vs. 18.9, p=0.008) than those without depression. The CES-D score was inversely associated with plasma Aβ42 (p=0.001) in subjects with no cardiovascular disease (CVD); however, in the presence of CVD, this association did not exist. Low plasma Aβ42 (OR = 0.41, p = 0.007) and the presence of CVD (OR = 1.84, p = 0.005) were independently associated with depression after adjusting for the confounders of age, stroke and apolipoprotein FA. Conclusions: Depressive symptoms are associated with low plasma Aβ42 independently of CVD. Prospective studies are needed to determine whether depression associated with low plasma Aβ42 is a separate depression subtype that could predict the onset of AD.