Background: Depression may increase the risk of developing Alzheimer's disease (AD). Recent large cohort studies have also shown that a low plasma amyloid beta (Abeta)-42 level combined with a high Abeta40 level increases the risk of developing AD, suggesting plasma Abeta42/40 ratio as useful for identifying risk of developing mild cognitive impairment and AD. Although several studies have examined Abeta levels in the peripheral blood of elderly individuals with depression, results have been inconsistent. Furthermore, no results have been described for younger depression.
Methods: Serum Abeta40, Abeta42 level and Abeta40/42 ratio were evaluated using enzyme-linked immunosorbent assay in 60 patients with major depressive disorder (MDD) and 60 healthy controls. The results were analyzed in two age groups (young, <60 years; elderly, >or=60 years).
Results: Serum Abeta40 level was significantly higher in young MDD patients compared to young controls (P < 0.001), but it was not significantly deferent in the elderly group. Serum Abeta42 level did not differ significantly in both young and elderly groups. Abeta40/42 ratio was significantly higher in both young (P < 0.001) and elderly (P < 0.001) patients with MDD compared to controls.
Conclusions: Serum Abeta40/42 ratio was significantly higher in MDD patients than in controls, and this difference was seen for both elderly and young subjects. This may suggest that even young subjects with MDD undergo pathological changes in the very early stage of amyloid deposition.