Coexisting Respiratory Comorbidities Increase Mortality in Patients with Asthma: A National Cohort Study

Background: Asthmatic patients are generally considered to have an increased risk of mortality compared with subjects without asthma. However, this issue has not been fully evaluated using nationally representative data. In addition, it is unclear whether respiratory comorbidities other than chronic obstructive pulmonary disease (COPD) are associated with increased mortality in asthmatic patients compared with subjects without asthma. Methods: Using a nationally representative sample database, we performed a retrospective cohort study of patients with asthma and age- sex-matched control cohort. We estimated hazard ratio (HR) and 95% confidence interval (CI) for mortality. We also stratified the asthma cohort based on respiratory comorbidities. Results: During a median 8.9-year follow-up, the overall mortality rate was higher in the asthma cohort than in the control cohort (p < 0.001). The HR for mortality in the asthma cohort compared with the control cohort was 1.13 (95% CI = 1.07–1.19). The effects of asthma on mortality were more evident in males, patients under medical aid, and subjects with COPD. Respiratory comorbidities were significantly associated with increased risk of mortality in asthmatic patients compared with controls (COPD, adjusted HR, aHR = 1.49, 95% CI = 1.39–1.59; bronchiectasis, aHR = 1.43, 95% CI = 1.18–1.73; lung cancer, aHR = 4.11, 95% CI = 2.59–6.52; pneumonia, aHR = 1.59, 95% CI = 1.46–1.74). Conclusion: Patients with asthma had a higher mortality rate compared with subjects without asthma. Coexisting pulmonary comorbidities were the primary cause of higher mortality in patients with asthma