Depression and incident diabetic foot ulcers: a prospective cohort study.

Objective: To test whether depression is associated with an increased risk of incident diabetic foot ulcers.

Methods: The Pathways Epidemiologic Study is a population-based prospective cohort study of 4839 patients with diabetes in 2000-2007. The present analysis included 3474 adults with type 2 diabetes and no prior diabetic foot ulcers or amputations. Mean follow-up was 4.1 years. Major and minor depression assessed by the Patient Health Questionnaire-9 were the exposures of interest. The outcome of interest was incident diabetic foot ulcers. We computed the hazard ratio and 95% confidence interval (CI) for incident diabetic foot ulcers, comparing patients with major and minor depression with those without depression and adjusting for sociodemographic characteristics, medical comorbidity, glycosylated hemoglobin, diabetes duration, insulin use, number of diabetes complications, body mass index, smoking status, and foot self-care. Sensitivity analyses also adjusted for peripheral neuropathy and peripheral arterial disease as defined by diagnosis codes.

Results: Compared with patients without depression, patients with major depression by Patient Health Questionnaire-9 had a 2-fold increase in the risk of incident diabetic foot ulcers (adjusted hazard ratio 2.00; 95% CI, 1.24-3.25). There was no statistically significant association between minor depression by Patient Health Questionnaire-9 and incident diabetic foot ulcers (adjusted hazard ratio 1.37; 95% CI, 0.77-2.44).

Conclusion: Major depression by Patient Health Questionnaire-9 is associated with a 2-fold higher risk of incident diabetic foot ulcers. Future studies of this association should include better measures of peripheral neuropathy and peripheral arterial disease, which are possible confounders or mediators.