February 18, 2010 — Nonsevere, persistent, and untreated depression may lead to the development of diabetes in people older than 55 years, according to results from a 5-year longitudinal study.
In addition, clinically significant depression was linked to a 65% increased risk of incident diabetes mellitus, write the investigators, led by Antonio Campayo, MD, Instituto Aragonés de Ciencias de la Salud, Zaragoza, Spain.
"In view of the epidemic nature of both diabetes and depression, we believe our results have important public health as well as clinical implications," the investigators write.
This study was published online February 1 in the American Journal of Psychiatry.
Study Not Limited to MDD
Previous research has shown that depressed individuals have a 60% increased risk of developing diabetes. "However, most of these studies used rather weak methods to document depression, such as self-reports or general physicians' diagnoses," the study authors write.
They note that other studies have focused specifically on major depression disorder (MDD), which may not be the type that most affects the general population and older age groups.
The aim of the study was to examine the association between clinically significant depression (not limited to MDD) and risk of diabetes development. The investigators also examined diabetes risk with respect to nonsevere depression, first-ever depression, persistent depression, and untreated depression.
A random sample of 4803 adults from the Zaragoza Dementia and Depression Project were identified and interviewed at baseline. After excluding patients with dementia and those with diabetes at baseline, a total of 3521 participants older than 55 years were included in this study. Of these, 379 were diagnosed as having depression (80.5% female; mean age, 73.6 years), and 3142 were found to be nondepressed (51.9% female; mean age, 71.8 years).
Diabetes was assessed using a risk factors questionnaire, and follow-up evaluations 2.5 and 5 years later were completed to determine the incidence of diabetes.
Results showed that "the risk of incident diabetes mellitus was higher among those with depression when compared with nondepressed subjects, and the association remained significant after controlling for potential confounders, including diabetes risk factors (P = 0.04)."
The incidence rate was 19.70 per 1000 person-years for the depressed patients compared with 12.36 per 1000 person-years for the nondepressed patients.
Although the community characteristics of nonsevere, persistent, and untreated depression were associated with a significantly increased risk of diabetes compared with nondepression (hazard ratios = 1.66, 2.09, and 1.83, respectively), treatment with antidepressants was not.
Overall, "the population attributable risk percentage for diabetes," comparing depressed and nondepressed patients and based on adjusted hazard ratios, was 6.87% (95% confidence interval, 1.04% – 11.64%).
In other words, "the estimated rate of diabetes mellitus attributable to depression was 6.87%."
The investigators note that their results reinforce previous reports of a "robust association" between depression and incidence of diabetes mellitus. "However, whether interventions in depression lower the increased risk of diabetes has yet to be examined," they conclude.
This study was funded by grants from the Fondo de Investigación Sanitaria, Ministerio de Sanidad, Madrid, Spain, and the Dirección General de Investigación Científica y Téchnica, Secretaría General de Universidades, Madrid, Spain. The study authors have disclosed no relevant financial relationships.
Am J Psychiatry. Published online February 1, 2010.
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