Depression Increases Risk of Dementia in Patients with Type 2 Diabetes

Patients with type 2 diabetes who have depression are significantly more like to develop dementia than those with diabetes alone, according to research published in the Archives of General Psychiatry.

In the study, lead author Wayne Katon, MD, of the University of Washington, and colleagues found that the risk of developing dementia 3 to 5 years after initial screening was doubled among individuals with type 2 diabetes who also had depression. The research was supported by the National Institutes of Health-funded Diabetes & Aging Study and its parent study, Diabetes Study of Northern California (DISTANCE), which collected surveys from more than 20,000 adults with diabetes who are listed under the Kaiser Permanente Northern California Diabetes Registry.

“Prior research has shown that both depression and diabetes are risk factors for dementia. This study suggests that having both of these illnesses occurring together is associated with an even greater risk,” said senior author Rachel Whitmer, PhD, of Kaiser Permanente.

“Since depression affects up to 20% of diabetic patients, it is critical to understand this relationship and further evaluate whether depression interventions have an impact on dementia risk in patients with diabetes,” said Andrew J. Karter, PhD, principal investigator for the Diabetes & Aging and DISTANCE Studies, in a statement. “Earlier onset of diabetes in patients with depression and greater risk of dementia in younger compared to older patients with depression and diabetes underscore the importance of evaluating the potential for early depression interventions to reduce the incidence of dementia.”

Of the 20,188 consenting adults in the DISTANCE Study, 19.6% of the patients with diabetes met criteria for clinically significant depression.

Among patients with diabetes, depression is associated with poorer adherence to diet and exercise programs, increased smoking and poorer blood sugar control, and psychobiologic changes such as increases in cortisol and increased sympathetic nervous system tone, which could worsen the course of diabetes and increase the risk of dementia associated with depression, the authors noted.