gms | German Medical Science

Aim: There is sufficient evidence for an association between diabetes and depression in cross sectional studies. However, only few prospective studies estimated the incidence of depression in diabetes, and results are conflicting. This is particularly true for undetected diabetes, where data are lacking at all. We examined the development of depressive symptoms or depression in subjects with diagnosed and undetected diabetes, each compared to nondiabetic subjects.

Methods: We used baseline and 5-year follow up data from the population-based German Heinz Nixdorf Recall study. Diabetes was assessed by self report (diagnosis or medication) as well as blood glucose levels. Depressive symptoms or depression were assessed using CES-D scale or self report of a physician diagnosis. In individuals without depression at baseline (n=2,634, 53.5% male, mean age 58.9 (SD 7.6) years, 7.0% known diabetes, 5.8% unknown diabetes), we estimated 5-year cumulative incidences with 95% confidence intervals (CI) and fitted multiple logistic regression models to calculate odds ratios (OR) for depressive symptoms in subjects with diagnosed and undetected diabetes versus nondiabetic individuals (separate models).

Results: The cumulative incidence of depression was 14.1% (95% CI 9.4-19.9) in persons with known diabetes, 10.5% (95% CI 6.1-16.5) in persons with unknown, and 10.0% (95% CI 8.8-11.3) in those without diabetes at baseline. Participants with known compared to those without diabetes had a significantly increased risk to suffer from depression after 5 years (OR 1.61 (1.04-2.50) adjusted for age and sex). After adjustment for further covariates (myocardial infarction, stroke, asthma, BMI, education, physical activity, and depression-inducing drugs), the OR decreased to 1.44 (0.90-2.30). We found no differences between participants with undetected and those without diabetes (age-sex adjusted OR 1.21 (0.70-2.08; full adjusted OR 1.04 (0.59-1.85). Co-morbidities were significantly associated with the development of depression.

Conclusions: We found a 60% increased risk to develop depression in individuals with diagnosed diabetes compared to individuals without diabetes, which decreased to 44% after adjustment for potential confounders including comorbidities. Individuals with undetected diabetes did not show an increased risk after adjustment for relevant confounders. The development of depression in individuals with undetected diabetes has not been investigated in prospective studies so far; however, our finding is in line with findings from cross sectional studies. Large prospective studies are warranted to examine associated and possibly explaining factors in more detail.