Depression in a group of Medicare recipients was associated with prevalent mild cognitive impairment and an increased risk for dementia, researchers reported online in the Archives of Neurology. However, the mechanisms linking depression to dementia remained unclear.
“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,” the researchers wrote.
Edo Richard, MD, PhD, of the University of Amsterdam, and colleagues examined the link between late-life depression, mild cognitive impairment (MCI) and dementia in 2,160 Medicare recipients aged 65 years or older from northern Manhattan, New York City. Depression was assessed using the Center for Epidemiological Studies Depression Scale, a 10-item questionnaire.
Results showed that baseline depression was associated with prevalent MCI (OR=1.4; 95% CI, 1.1-1.9) and dementia (OR=2.2; 95% CI, 1.6-3.1). Baseline depression was also associated with an increased risk for incident dementia (HR=1.7; 95% CI, 1.2-2.3). However, depression was not associated with incident MCI (HR=0.9; 95% CI, 0.7-1.2), indicating that the disorder develops along with cognitive decline, but does not precede it, according to the researchers.
Those with MCI and coexisting depression at baseline had a higher risk for dementia (HR=2; 95% CI, 1.2-3.4), particularly vascular dementia (HR=4.3; 95% CI, 1.1-17), but not Alzheimer’s disease (HR=1.9; 95% CI, 1-3.6). According to Richard and colleagues, this relationship suggests that cerebrovascular disease plays a role in the association.
“We could not address the exact mechanism linking depression and dementia,” the researchers wrote, “but our results support the hypothesis that late-life depression accompanies the occurrence of cognitive decline and does not precede it. Our findings that the association of depression with probable [Alzheimer’s disease] was weaker compared with all [Alzheimer’s disease] (probable and possible) and [vascular dementia] suggest that other pathologic conditions with [Alzheimer’s disease] may be more likely to manifest as depression.”
Disclosure: The researchers report no relevant financial disclosures.