Patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD) often experience depression, but the link between the two remains unclear.
Edo Richard, M.D., Ph.D., of the University of Amsterdam in the Netherlands, and colleagues investigated the association of late-life depression with MCI and dementia in a multiethnic group of 2,160 Medicare recipients ages 65 and older.
The study, published in the journal Archives of Neurology, found that people with depression were 40 percent more likely to show mild cognitive impairment and more than twice as likely to have full-blown dementia.
“Traditionally, cognitive complaints and impairment in the presence of depression has been considered to be caused by the depression. Our study suggests that depression is not a cause of dementia but accompanies the onset of cognitive impairment,” said José Alejandro Luchsinger, M.D., M.P.H., associate professor of medicine and epidemiology at Columbia University Medical Center.
“Depression could be a risk factor for dementia, an early dementia symptom, a reaction to cognitive and functional disability, or a symptom of a related risk factor, such as cerebrovascular disease,” said Luchsinger and colleagues.
Although depression was associated with a greater risk for incident dementia, it was not associated with incident problems with thinking and memory.
The researchers reported that individuals who suffer from both mild cognitive impairment and depression were at increased risk for developing dementia, especially vascular dementia. They added, however, that these patients were not at greater risk for Alzheimer’s disease, the most common form of dementia.
“Our finding … suggests that depression develops with the transition from normal cognition to dementia,” said the authors.
Depression affects many people with mild cognitive impairment, and prior research has shown that those with a history of depression are at greater risk for dementia.
“There has now been an accumulation of enough studies and enough data to say that people with a history of depression do have increased rates of cognitive decline and dementia in late life,” said Meryl Butters, Ph.D., neuropsychologist and associate professor of psychiatry, University of Pittsburgh School of Medicine. Butters was not involved in the study.
“This is a very active area of investigation. It’s likely that different mechanisms are at work in different people.”
Source: Archives of Neurology