Risk of bipolar disorder in patients with COPD: A population-based cohort study

Bakcground: Few studies have investigated the relationship between chronic obstructive pulmonary disease (COPD) and bipolar outcomes in the world. We sought to investigate the association between COPD and risk of bipolar disorder in a large national sample. Methods: The insured aged 15 years or more with a new primary diagnosis of COPD (ICD-9: 491, 492, 494 and 496) between 2000 and 2007 were identified from Taiwan's National Health Insurance Research Database. We included individuals with an inpatient diagnosis of COPD and/or at least 1 year of two diagnoses of COPD in outpatient services. These 35,558 cases were compared to 35,558 sex-, age-, residence- and insurance premium-matched controls. We followed both groups until the end of 2008 for incidence of bipolar disorder, defined as ICD-9 codes 296.0-296.16, 296.4-296.81 and 296.89. Competing risk-adjusted Cox regression analyses were applied with adjusting for sex, age, residence, insurance premium, prednisone use, Charlson comorbidity index, diabetes, hypertension, hyperlipidemia, cardiovascular diseases, hospital admission days, outpatients' visits and mortality. Results: Of the total 71,116 subjects, 202 were newly diagnosed with bipolar disorder during the study period. The mean follow-up time was 6.0 (SD=2.2) years. COPD, younger age, lower economic status, lower dose of prednisone use, higher hospital admission days and higher outpatient visits were independent predictors of bipolar disorder. Conclusions: COPD was associated with increased risk of bipolar disorder independent of a number of potential confounding factors in this study.