This article is more than 5 years old. Information may no longer be current.

Depression, diabetes increase risk for dementia

Results from a national population-based study suggested that depression and diabetes independently increased risk for dementia and further increased risk when the conditions coexisted.

To assess how depression, diabetes or both affected risk for all-cause dementia, researchers reviewed data from national registries for 2,454,532 Danish adults aged 50 years or older that had no signs of dementia as of January 2007. Study participants were followed through December 2013. Dementia was determined by physician diagnosis; depression was determined psychiatrist diagnosis; and diabetes was identified via medical records.

About twenty percent of the study cohort had depression, 9.1% had diabetes and 3.9% had comorbid depression and diabetes.

During the study period, 2.4% of the study cohort developed dementia. Of these, 26.4% had depression, 10.8% had diabetes and 6.7% had comorbid depression and diabetes.

When adjusting for age, sex, calendar period and marital status, diabetes was associated with a 20% greater risk for all-cause dementia (HR = 1.2; 95% CI, 1.17-1.23). Depression was associated with an 83% greater risk for dementia (HR = 1.83; 95% CI, 1.8-1.87) and comorbid diabetes and depression was associated with a 117% greater risk for dementia (HR = 2.17; 95% CI, 2.1-2.24).

During the first year following depression diagnosis, the associated HR for dementia increased nearly sevenfold (HR = 6.75; 95% CI, 6.55-6.95), according to researchers, but decreased thereafter to approximately twofold.

Wayne Katon

Study participants with early onset diabetes had a significantly higher risk for dementia (HR = 1.82; 95% CI, 1.73-1.91) vs. participants with late-onset diabetes (HR = 1.3; 95% CI, 1.24-1.36; P < .001).

Depression (HR = 1.39; 95% CI, 1.34-1.44), diabetes (HR = 1.06; 95% CI, 1.01-1.11) and comorbid depression and diabetes (HR = 1.46; 95% CI, 1.37-1.55) increased risk for Alzheimer’s disease.

“We found that depression and [diabetes mellitus] were both associated with a greater risk for all-cause dementia, Alzheimer disease and vascular dementia. These associations appeared to be stronger among those individuals with depression alone compared with those with [diabetes mellitus] alone,” study researcher Wayne Katon, MD, of the University of Washington School of Medicine, in Seattle, and colleagues wrote. “Persons with comorbid [diabetes mellitus] and depression appeared to have the highest relative risk for dementia, and this association tended to be stronger than additive. The interaction between [diabetes mellitus] and depression tended to be particularly strong for individuals younger than 65 years.”

These study findings highlight the need for further research on how to promote healthy brain aging and cognitive fitness in old age, according to Charles F. Reynolds III, MD, of the University of Pittsburgh Medical Center.

“The convergence of expertise from epidemiology, behavioral and basic science in the biology of aging, and brain health are all necessary to ‘move the needle’ in the demographic challenge that confronts the entire globe,” Reynolds wrote in an accompanying editorial. – by Amanda Oldt

Disclosure: Katon reports no relevant financial disclosures. Reynolds reports receiving pharmaceutical support for NIH-sponsored research studies from Bristol-Myers Squibb, Forest, Pfizer and Lilly. Please see the full study for a list of all other authors’ relevant financial disclosures.