Dexamethasone suppression in dementia, depression, and normal aging.

Dexamethasone suppression tests (DSTs) were performed for 18 moderately demented elderly patients, 66 depressed elderly outpatients, and 25 age- and sex-matched healthy elderly control subjects. Seventeen percent of the demented patients and 4% of the normal subjects were DST nonsuppressors, compared to 38% of the total depressed group. The postdexamethasone plasma cortisol levels of the dementia group fell between those of the normal and the depressed subjects. In addition, demented patients had postdexamethasone cortisol levels significantly lower than those of depressed patients with high Hamilton depression scores. Older subjects in all diagnostic categories, including normal subjects, had higher postdexamethasone plasma cortisol levels.