Elevation in plasma Abeta42 in geriatric depression: a pilot study.

Elevated plasma amyloid beta 1-42 (Abeta42) level has been linked to increased risk for incident AD in cognitively-intact elderly. However, plasma Abeta levels in individuals with late-life depression (LLMD), especially those with a late age of onset of first depressive episode, who are at a particularly increased risk for Alzheimer's disease, have not been studied. We compared plasma Abeta in 47 elderly with LLMD with 35 controls and examined its relationships to age of onset of first depressive episode, antidepressant treatment (paroxetine or nortriptyline), and indices of platelet activation (platelet factor 4 and beta-thromboglobulin) and brain abnormalities. Results indicated that plasma Abeta42 levels and the Abeta42/40 ratio were elevated in the LLMD group relative to controls in the overall group analyses and in the age- and gender-matched groups. MRI data indicated that higher Abeta42/40 ratio was associated with greater severity of total white matter hyperintensity burden in LLMD. Plasma Abeta levels in LLMD were not influenced by age of onset of first depressive episode or antidepressant treatment and were not related to indices of platelet activation. Our preliminary results suggest that increased plasma Abeta42 and Abeta42/40 ratio are present in geriatric depression, and future studies should be done to confirm these findings and to determine their relationship to cognitive decline and brain abnormalities associated with LLMD.