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

Background Few studies have investigated the bidirectional relationship between asthma and anxiety; we sought to investigate asthma and anxiety in a large national sample. Methods Cases were identified from Taiwan's National Health Insurance Research Database with a new primary diagnosis of asthma (ICD-9:493) aged more than 15 years 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 22,797 cases were compared to 22,797 sex-, age-, residence- and insurance premium-matched controls and both groups were followed until the end of 2008 for instances of anxiety, defined as ICD-9 codes 300.0, 300.01, 300.02, 300.2, 300.21, 300.23, 300.3. Competing risk adjusted Cox regression analyses were applied, adjusting for sex, age, residence, insurance premium, prednisone use, Charlson comorbidity index, cardiovascular disease, diabetes, depression disorder, and hospital admission days for any disorder. The effect of asthma on the risk of panic disorder and the effect of anxiety disorder on the risk of later asthma were also examined as competing risk adjusted Cox regression analyses Results Of the 45,594 subjects, 2792 were ascertained as having anxiety during a mean (SD) follow-up period of 5.3 (2.5) years. Asthma, females, older age, rural residence, depression disorder, and prednisone use were independent risks on anxiety in the fully adjusted model. Anxiety, older age, rural residence, and prednisone use were independent risks on asthma in the fully adjusted model. Limitations The severity of asthma and anxiety disorder, the duration of prednisone treatment and adherence, stressful life events, smoking, family history and relationship were not evaluated. Conclusions Bidirectional relationship between asthma and anxiety disorder was confirmed in this population, in dependent of a number of potential confounding factors.