Mild cognitive impairment in old-age depression is associated with increased EEG slow-wave power.

Reversible dementia in geriatric depression is known to be a risk factor for irreversible dementia. Whether just mild cognitive deficits in elderly depressed patients hold a similar risk is not known yet. It may be suggested that elderly depressed patients with mild cognitive deficits, who are prone to develop dementia, show EEG alterations similar to those observed in demented patients. We studied the relationships between cognitive performance, severity of depressive symptoms and quantitative EEG parameters in 31 unmedicated, nondemented, depressed patients aged 60 years or more. Twenty-one of the patients showed a cognitive performance characteristic of mild cognitive impairment. In these patients, the mean delta and theta power was significantly higher than in the patients without cognitive impairment. Total delta power was negatively correlated with cognitive performance. There was no relationship between cognitive performance or EEG parameters and the severity of depression.