People who develop depression and mild cognitive impairment (MCI) after age 65 are more vulnerable to accelerated brain aging, according to a new study.
Older adults with major depression have double the risk of developing dementia compared with those who have never had the mood disorder, according to senior investigator Meryl A. Butters, Ph.D., an associate professor of psychiatry at the University of Pittsburgh School of Medicine.
But she noted there’s no clear explanation for why a treatable mood disorder like depression leads to increased risk for dementia. “Until now, most studies have examined only one or two biomarkers,” she said.
“Our study represents a significant advance because it provides a more comprehensive and integrated view of the neurobiological changes related to mild cognitive impairment in late life,” she said.
“Better understanding of the neurobiology of cognitive impairment in depression can provide new targets for developing more specific treatments, not only for its prevention and treatment, but also for its downstream negative outcomes, including the development of dementia and related disorders.”
For the study, published in Molecular Psychiatry, the researchers collected blood samples from 80 adults in remission after being treated for major depression. Of the group, 36 had MCI and 44 had normal cognitive function.
The blood was tested for 242 proteins involved in biologic pathways associated with cancer, cardiovascular diseases, and metabolic disorders, as well as psychiatric and neurodegenerative disorders.
The researchers also performed PET and MRI brain scans to look for indicators of cerebrovascular disease, brain atrophy or shrinkage, and beta-amyloid, which is the protein that makes up the brain plaques associated with Alzheimer’s disease.
The researchers found that the participants in the MCI group were more likely to have differences in the biologic activity of 24 proteins that are involved in the regulation of immune and inflammatory pathways, intracellular signaling, cell survival, and protein and lipid balance.
Brain scans also revealed a greater propensity for cerebrovascular disease — for example, small strokes — in the MCI group, but there was no difference in the amount of beta-amyloid deposition, according to the researchers.
“If you take these results altogether, they suggest that people with depression and cognitive impairment may be more vulnerable to accelerated brain aging, which in turn puts them at risk for developing dementia,” Butters said.
“Ultimately, if we can understand what happens in the brain when people are depressed and suffer cognitive impairment, we can then develop strategies to slow or perhaps stop the impairment from progressing to dementia.”
“The next step in the research is to assess the protein panel in older people with normal cognitive function who have not experienced depression,” she noted.