Aims/hypothesis: Although several studies have reported on the association between diabetes and depression, none have used both formal psychiatric criteria and a prospective, population-based design. Therefore, it remains unclear whether diabetes is a risk factor for the development of depression. Moreover, it is not clear if this effect is influenced by other chronic diseases and functional disabilities.
Methods: A large (n=4,803) representative community-based study in Spanish elderly subjects (at least 55 years of age) was conducted. The presence of major depression was assessed by means of a standardised psychiatric diagnostic interview (Automated Geriatric Examination for Computer Assisted Taxonomy). Subjects underwent a baseline assessment and a follow-up assessment after 2 and 5 years to determine the incidence of depression.
Results: At baseline 597 subjects (12.5%) were identified as having diabetes. Prevalence and incidence of depression in cases of diabetes were 15.4% and 16.5% respectively. Diabetes was associated with an increased risk of prevalent (odds ratio [OR]=1.47; 95% CI: 1.16-1.83) and incident (OR=1.40; 95% CI: 1.03-1.90) depression. Controlling for potential confounders did not essentially change these findings (prevalent depression: OR 1.41, 95% CI: 1.08-1.83; incident depression: OR 1.26, 95% CI: 0.90-1.77).
Conclusions/interpretation: In a large, representative prospective population-based sample using strict psychiatric criteria, we confirmed previous findings that diabetes is associated with an increased risk of depression. The effect on the incidence of depression suggests that diabetes may play a role in the development of depression in the elderly. The presence of comorbid medical diseases seems to decrease the effects of diabetes on the risk of prevalent depression, but to increase the risk of incident depression.