Abstract Background Bronchiectasis frequently coexists with asthma and may worsen disease control and healthcare burden. However, large-scale evidence on its impact in real-world populations remains limited. This study evaluated the influence of bronchiectasis on asthma exacerbations, comorbidities, and medical costs using a nationwide claims database. Methods This population-based, retrospective cohort study used data from the Health Insurance Review and Assessment Service (HIRA) of South Korea from 2015 to 2019. Adults (≥18 years) with asthma were identified by International Classification of Diseases, 10th Revision (ICD-10) codes J45-J46 as the principal or up to four additional diagnoses, and prescriptions for asthma-related medications. Bronchiectasis was defined by at least one claim with code J47, excluding cystic fibrosis (E84). Asthma exacerbations were classified based on healthcare utilization. Hospitalization and emergency room (ER) visits were defined as asthma-related claims with systemic corticosteroid use for ≥1 day and nebulizer treatment (ER visits additionally required an ER code). Outpatient exacerbations were identified by asthma-related claims with systemic corticosteroid use for ≥2 days. Propensity score matching (1:5) by age and sex was performed, and incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were calculated. Results A total of 530,358 patients were included: 88,393 with both asthma and bronchiectasis, and 441,965 with asthma alone. Patients with bronchiectasis had higher rates of comorbidities, including gastroesophageal reflux disease (83.1% vs. 77.8%), chronic obstructive pulmonary disease (75.6% vs. 56.6%), nontuberculous mycobacterial infection (6.1% vs. 1.1%), and depression (31.2% vs. 28.0%) (all p 0.001). Acute exacerbations occurred in 42,006 patients (47.5%) with bronchiectasis and in 203,944 patients (46.1%) with asthma alone. The overall exacerbation rate was slightly higher in the bronchiectasis group (IRR = 1.03, 95% CI 1.02-1.04). Hospitalizations (IRR = 1.44, 95% CI 1.42-1.47) and ER visits (IRR = 1.42, 95% CI 1.39-1.46) were significantly more frequent, while outpatient events were slightly lower (IRR = 0.98, 95% CI 0.97-0.99). In subgroup analyses, the risk of exacerbations was higher among older adults (≥65 years), males, and those with diabetes, hypertension, malignancy, or depression. Conclusion Asthmatic patients with coexisting bronchiectasis experienced more severe exacerbations and higher comorbidity burden. These findings highlight the importance of individualized management and close monitoring in asthma, particularly in elderly and those with multiple comorbidities. This abstract is funded by: None
An et al. (2026) studied this question.