Clinical course and serum amyloid β levels in elderly patients with major depressive disorder.

Background: Depression is known to be a risk factor for Alzheimer's disease (AD). Changes in amyloid β protein (Aβ) metabolism have been speculated as a factor contributing to the transition from depression to AD. The aim of this study is to reveal the time course and state-dependency of Aβ metabolism.

Methods: Serum Aβ levels in 277 elderly (≥60 years) patients with depression (both early- and late-onset) were measured at admission, immediately after remission, and 1 year after remission, and compared them with 178 healthy subjects.

Results: The analysis revealed decreased Aβ42 levels and increased Aβ42/40 ratios in elderly patients with depression at admission compared with healthy subjects. These changes in the acute phase of depression were not normalized immediately after remission; however, they recovered to healthy levels 1 year after remission.

Limitations: There is a possibility that the results may be influenced by antidepressants.

Conclusions: These results suggest that altered Aβ metabolism caused by depression may ameliorate, although after a lengthy period of time after remission. Our findings also suggest that the AD-related pathological changes caused or increased by depression can be reduced by maintaining remission for an extended period of time.