HealthDay News — Patients with diabetes who have comorbid depression are at increased risk for developing dementia compared with those with diabetes alone, study results indicate.

“Given that depression is potentially modifiable, future studies are needed to further evaluate whether effective depression interventions reduce the risk of dementia and identify the mechanisms that may explain our observation,” Wayne Katon, MD, from the University of Washington in Seattle, and colleagues wrote in the Archives of General Psychiatry.

They surveyed a random sample of 19,239 patients with type 2 diabetes, aged 30 to 75 years, from the Diabetes and Aging Study to identify prevalent cases of depression. Dementia diagnoses were identified based on International Classification of Diseases, Ninth Revision-clinical modification [ICD-9-CM] criteria three to five years post-baseline to ensure that depression was not a prodrome of dementia. The researchers then estimated dementia risk for patients with depression and diabetes relative to patients with diabetes alone using Cox proportional hazard regression models adjusted for sociodemographic, clinical, risk factors and healthcare use.

Continue Reading

One or more dementia diagnosis occurred in 2.1% of 3,766 patients with diabetes and comorbid depression, and in 1% of the 15,473 patients with diabetes alone (incidence rate=5.5 and 2.6 per 1,000 person-years, respectively), the researchers found. A 100% increased risk of dementia was observed in patients with comorbid depression  (adjusted HR=2.02).

Previous studies have associated depression with poorer adherence to diet and exercise regimens, increased rates of cigarette smoking and higher HbA1c levels, according to the researchers, which could  “worsen the course of diabetes and increase the risk of dementia associated with depression.”

However, controlling for these potential confounding factors did not significantly change the risk for dementia among these patients. “These data suggest that biologic factors associated with depression may be important risk factors for dementia in patients with type 2 diabetes,” the researchers wrote. They called for more studies to further examine potential mechanisms of action.

One of the study researchers disclosed financial ties to the pharmaceutical industry.

Katon W et al. Arch Gen Psychiatry. 2011; doi:10.1001/archgenpsychiatry.2011.154.