Introduction: Patients with COPD are believed to have a high risk for the development of depression. However, it remains unclear whether or not there is a temporal relation between COPD and depression, and if the higher risk for depression is a result of having a chronic disease, or is specific for COPD. The aim of this study is to compare the risk for physician-diagnosed depression in patients with COPD, patients with diabetes mellitus (DM), and control subjects without chronic conditions.
Methods: The study was a prospective cohort study based on the Continuous Morbidity Registration database. Cox proportional hazards analysis was used to identify the risk of a first episode of depression in patients with COPD compared to patients with DM and matched control subjects without chronic conditions. The following covariates were added to the model: age, the general practice the patient was listed with, socioeconomic status, comorbidity, and gender. All patients with a diagnosis of depression preceding the date of first diagnosis of COPD or DM (dummy date in control subjects) were excluded.
Results: The hazard ratios for a first episode of depression in the COPD group compared to the DM group and healthy controls subjects were 1.80 (95% confidence interval [CI], 1.16 to 2.81) and 1.68 (95% CI, 1.20 to 2.35), respectively.
Discussion: We found a temporal relation between COPD and physician-diagnosed depression. Patients with COPD are more likely to have depression diagnosed than patients with DM and control subjects without chronic conditions.