Chances of dementia higher for diabetics with major depression

Kathleen Blanchard's picture
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Diabetics with major depression are more than twice as likely to develop dementia compared to individuals with diabetes alone, found in a new study. The link between major depression diabetes and dementia is discovered from an analysis of the Pathways Epidemiological Follow-Up Study that included adults from the Group Health Cooperative's diabetes registry. Researchers calculated a 2.7 percent increased risk of dementia for diabetics who also suffer from major depression.

"Diabetes alone has shown to be a risk factor for dementia, as has major depression by itself," says lead author of the study, Dr. Wayne Katon, University of Washington (UW) professor of psychiatry and behavioral sciences. We wanted to determine the effects of both conditions – diabetes and major depression--occurring together. Our analysis suggests that major depression more than doubles the risk of dementia in adults with diabetes."

Patients were enrolled in the study between2000 and 2002 and followed for five years. Of 455 patients, 7.9 percent of patients with major depression and diabetes were also diagnosed with dementia. Diabetes alone increases the odds of cognitive decline 40 to 100 percent.

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The findings also showed that among 3,382 patients with diabetes and no symptoms of major depression, only 4.8 percent developed dementia.

Researchers are not certain how depression contributes to dementia, or how diabetes, depression and dementia are linked. High levels of the stress hormone cortisol may lead to endocrine dysfunction that can affect heart rate, blood clotting, and inflammatory responses. In the general population, depression doubles the chances of cognitive decline that can progress to Alzheimer’s disease. Diabetics with depression also suffer more complications and poorer outcomes.

Negative health behaviors such as smoking, poor dietary and sleep habits and obesity might also raise the risk of dementia linked to depression and diabetes, but for the current study the researchers controlled other risk factors, finding that major depression combined with diabetes still more than doubled the chances of dementia.

The study authors suggest, "It seems prudent for clinicians to add effective screening and treatment for depression to other preventive measures such as exercise, weight control, and blood sugar control to protect against the development of cognitive deficits in patients with diabetes." Depression is common among diabetics, Poor blood vessel health from the combination of diabetes and major depression may accelerate tissue damage that can lead to dementia.

Journal of General Internal Medicine

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