New research provides the clearest demonstration yet that depression is a risk factor for cognitive decline in patients with type 2 diabetes, investigators say.
The decline happens relatively quickly and needs to be monitored, they add.
"Our study demonstrates depression-induced cognitive decline in diabetic patients occurs over a relatively short time period (40 months)," Mark Sullivan, MD, PhD, professor of psychiatry and behavioral sciences at University of Washington, Seattle, told Medscape Medical News.
"This cognitive decline affects multiple domains: psychomotor speed, verbal memory, executive function. This cognitive decline affects all patient subgroups: by age, gender, previous cardiovascular disease, baseline cognition, getting intensive or standard glucose, blood pressure, or lipid control," he added.
The findings suggest that a "potentially reversible factor may be promoting general cognitive decline in the broad population of patients with type 2 diabetes. Since dementia is one of the fastest growing and most dreaded complications of diabetes, our findings may be important for public health," Dr. Sullivan and colleagues conclude.
The study is published in the October issue of JAMA Psychiatry.
Modifiable Risk Factor
This report was a 40-month substudy of 2977 middle-aged and older adults with long-standing type 2 diabetes participating in the Action to Control Cardiovascular Risk in Diabetes–Memory in Diabetes (ACCORD-MIND) trial.
At baseline, 531 participants (18%) had scores indicative of depression (10 or greater) on the 9-item Patient Health Questionnaire (PHQ-9) Depression Scale.
During 40 months of follow-up, depression was associated with accelerated decline on a battery of cognitive tests, the researchers say.
Specifically, they saw significant differences between depressed and nondepressed groups on the Digit Symbol Substitution Test (DSST) (P = .003), the Rey Auditory Verbal Learning Test (RAVLT) (P = .001), and the modified Stroop test (P = .02).
This effect of depression on cognitive decline did not differ with respect to any of the factors examined: previous cardiovascular disease; baseline cognition or age; or intensive vs standard glucose lowering treatment, blood pressure treatment, lipid treatment, or insulin treatment. The addition of demographic and clinical covariates to models also did not significantly change the cognitive decline associated with depression.
"Our study," Dr. Sullivan said, "suggests that it is important to diagnose and treat depression in patients with diabetes to preserve their cognition, but we need a separate treatment trial to prove that depression treatment really prevents dementia in diabetic patients."
There have been "persistent questions" about whether depression represents a risk factor for cognitive decline or whether depression represents an early manifestation of dementia, the researchers note in their article.
"In our study, no patients had dementia at baseline and the effect of depression did not differ by baseline cognitive impairment, also suggesting that depression is not simply an early manifestation of dementia," they say.
"Unique and Important" Findings
This result "strongly suggests that depression or the factors that lead to depression accelerate cognitive decline," Joshua Barzilay, MD, from Kaiser Permanente of Georgia in Duluth, told Medscape Medical News. Dr. Barzilay is part of the ACCORD-MIND study team but did not participant in this substudy.
He said the new data are "unique and important."
He added, "When interpreting the study findings, one should keep in mind, as the authors suggest, that depression may be an early sign of cognitive impairment or that depression and cognitive impairment arise from common factor(s)."
The ACCORD-MIND study was funded through an intra-agency agreement between the National Institute on Aging and the National Heart, Lung, and Blood Institute and the National Institute on Aging Intramural Research Program. The original article contains a complete list of author disclosures.
JAMA Psychiatry. 2013;70:1041-1047. Abstract
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Cite this: Depression Accelerates Cognitive Decline in Type 2 Diabetes - Medscape - Oct 17, 2013.
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