Prospective longitudinal study of depression and anosognosia in Alzheimer's disease

BACKGROUND: The aim was to examine the longitudinal evolution of depression and anosognosia in patients with probable Alzheimer's disease (AD). METHOD: Sixty-two of a consecutive series of 116 AD patients that were examined with a structured psychiatric interview had a follow-up evaluation between one and two years after the initial evaluation. RESULTS: At the initial evaluation 19% of the 62 patients had major depression, 34% had dysthymia, and 47% were not depressed. After a mean follow-up of 16 months, 58% of patients with major depression at the initial evaluation were still depressed, whereas only 28% of patients with initial dysthymia and 21% of the non-depressed patients were depressed at follow-up. During the follow-up period, all three groups showed similar declines in cognitive status and activities of daily living. At the initial evaluation, 39% of the patients had anosognosia, and there was a significant increment of anosognosia during the follow-up period. CONCLUSIONS: While dysthymia in AD is a brief emotional disorder, major depression is a longer-lasting mood change. Anosognosia is another prevalent disorder among AD patients, and increases with the progression of the illness.