Asthma-COPD Overlap Shows Favorable Clinical Outcomes Compared to Pure COPD in a Korean COPD Cohort

PURPOSE Comparisons of the characteristics of chronic obstructive pulmonary disease (COPD) and asthma-COPD overlap syndrome (ACOS) have been the focus of several studies since the diseases were defined by the Global Initiative for Asthma and Global Initiative for Chronic Obstructive Lung Disease guidelines. However, no consensus is available yet. In this study, we aimed to compare the characteristics of asthma-COPD overlap (ACO) and COPD. METHODS We retrospectively reviewed 1,504 patients with COPD in a Korean COPD Subtype Study cohort. The occurrence of ACO was defined as a positive response to a bronchodilator (an increase in forced expiratory volume in 1 second [FEV1] of 12% and 200 mL). RESULTS Among 1,504 patients with COPD, 223 (14.8%) were diagnosed with ACO. Men (95.5%) and current smokers (32.9%) were more prevalent in the ACO group compared with the pure COPD group (90.5% and 25.3%, respectively; P=0.015 and P=0.026, respectively). Patients with ACO had a better quality of life (St. George's Respiratory Questionnaire for COPD score=31.0±18.0 [mean±standard deviation]) than those with pure COPD (35.3±19.1) (P=0.002). Although the prevalence of acute exacerbation was not different between the 2 groups, patients with severe exacerbation required hospital admission significantly more frequently in the pure COPD group than in the ACO group. Patients with ACO showed a higher likelihood of FEV1 recovery than those with pure COPD (P<0.001). CONCLUSIONS We suggest that ACO is characterized by less severe symptoms, and therefore it might lead to rare severe exacerbation and the possibility of lung function recovery.