Late-life depression can be dementia prodrome

Elderly patients with acute depression who show deficits on brief structured tests of memory and executive function are the high risk for developing Alzheimer’s disease within the next few years, mounting evidence indicates.

“The study suggests that latelife depression with documented memory and executive function impairment is just the tip of a very bad neuropsychiatric iceberg and that there is more to come,” said the annual meeting of the American Association for Geriatric Psychiatry.

It’s unclear as yet whether depression in the elderly is a risk factor for dementia or a prodrome of the disorder. That’s an ongoing debate in the field. The two possibilities are not mutually exclusive, according to the professor and chairman of the psychiatric department at the University of Connecticut, Farmington.

What is clear is that the subsequent course of elderly depressed patients with comorbid mild cognitive impairment is highly variable, as illustrated in a study in which they followed 69 such patients for two years. Seventeen ended up cognitively unimpaired, six developed subsyndromal Alzheimer’s disease, six had possible Alzheimer’s disease, two had probable Alzheimer’s, two had dementia of undetermined etiology, 13 still met criteria for mild cognitive impairment without dementia, and 23 had cognitive impairment which during follow-up became attributable to a more specific cause, such as cerebrovascular disease or another medical condition.

In an effort to find a means of predicting which patients with late-life major depressive disorder are most likely to go on to develop dementia, the investigators turned to baseline neuropsychologic testing. He presented recently published highlights of the NCODE (Neurocognitive Outcomes of Depression in the Elderly) trial, a longitudinal outpatient’s depression treatment study. In this phase of NCODE, 179 not demented, acutely depressed older adults underwent baseline neuropsychologic testing, received active treatment for their depression, and were followed for a mean of 5.5 years. During follow-up diagnosed 30 subjects as having incident dementia, while the other 149 were deemed cognitively normal.

Of course, completing an extensive battery of neuropsychological test is a lot to ask of an elderly patient with late-life depression. Fortunately, two of the neuropsychologic test – the CERAD (Consortium to Establish a Registry of Alzheimer’s Disease) Recognition Memory and the Trail Making B-proved to be the best predictors of subsequent conversion to dementia. That’s good news, because focusing on just two tests for prognostication is practical in everyday clinical practice, whereas administering a lengthy battery of neuropsychologic tests really isn’t observed.

In a multivariate analysis, deficits on CERAD Recognition Memory and Trail Making B were associated with 6.8-fold increased risk of developing dementia during follow-up, compared with elderly acutely depressed patients who scored in the normal range.