Clinical Characteristics and Outcomes of Patients with Asthma–COPD Overlap in Japanese Patients with COPD

PURPOSE: Asthma–COPD overlap (ACO) has been reported as an association with a lower quality of life, frequent exacerbations, and higher mortality than those with COPD alone. However, clinical characteristics and outcomes of ACO remain controversial. PATIENTS AND METHODS: We conducted a prospective observational study analyzing data of patients with stable COPD enrolled from the Ishinomaki COPD Network Registry. Patients with features of asthma who had a history of respiratory symptoms that vary over time and intensity, together with documented variable expiratory airflow limitation, were identified, and then defined as having ACO. The characteristics, frequency of exacerbations, and mortality during the 3-year follow-up were compared between patients with ACO and patients with COPD alone. RESULTS: Among 387 patients with COPD, 41 (10.6%) were identified as having ACO. Patients with ACO tended to be younger, have higher BMI, have a shorter smoking history, and use more respiratory medications, especially inhaled corticosteroids. Inflammatory biomarkers including fractional exhaled nitric oxide, blood eosinophil count, total immunoglobulin E (IgE) level, and presence of antigen-specific IgE were significantly higher in patients with ACO than in those with COPD alone. Lung function, mMRC score, CAT score, and comorbidity index were not different between the groups. The annual rate of all exacerbations and severe exacerbations required hospital admission were not different between ACO and COPD alone (0.20 vs 0.14, 0.12 vs 0.10, events per person, respectively). Mortality was significantly higher in patients with COPD alone compared with those with ACO during the study period (P=0.037). CONCLUSION: The results of our study indicate that ACO is not associated with poor clinical features nor outcomes in an outpatient COPD cohort receiving appropriate treatment.