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

Background Depression often precedes the onset of Alzheimer's disease (AD) before the appearance of 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 E4. 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. Copyright © 2006 John Wiley & Sons, Ltd.