Association of asthma and bipolar disorder: A nationwide population-based study in Taiwan

Background The relationship between asthma and bipolar disorder has received little research. We sought to investigate this in a large national sample. Previous studies have found mood changes after prednisone use in asthma patients, and we therefore also investigated this exposure in relation to bipolar disorder. Methods Cases were identified from Taiwan's National Health Insurance Research Database with a new primary diagnosis of asthma (ICD-9:493) between 2000 and 2007. Case status required the presence of any inpatient diagnosis of asthma and/or at least one year diagnosis of asthma in outpatient service. These 46,558 cases were compared to 46,558 sex-, age-, residence- and insurance premium-matched controls and both groups were followed until the end of 2008 for first diagnosis of bipolar disorder (ICD-9 codes 296.0 to 296.16, 296.4 to 296.81 and 296.89). Competing risk adjusted Cox regression analyses were applied, adjusting for sex, age, residence, insurance premium, prednisone, hyperthyroidism, COPD (chronic obstructive pulmonary disease), Charlson comorbidity index, and hospital admission days for any disorder. Results Of the 93,116 subjects, 161 were ascertained as having bipolar disorder during a mean (SD) follow-up period of 5.7 (2.2) years. Asthma was an independent risk for bipolar disorder in the fully adjusted model. Higher daily dose of prednisone was a risk factor in asthma cases. Limitations The severity of asthma and bipolar disorder, and the route/duration of prednisone treatment were not evaluated. Conclusions Asthma was associated with increased risk of bipolar disorder. Higher daily dose of prednisone was associated with a further increased risk.