Heterogeneity of asthma and COPD overlap

BACKGROUND: Asthma and COPD are heterogeneous diseases. Patients with both disease features (asthma–COPD overlap [ACO]) are common. However, clinical characteristics and socio-economic burden of ACO are still controversial. The aim of this study was to identify the heterogeneity of ACO and to find out the subtypes with clinical impact among ACO subtypes. METHODS: In the Korean National Health and Nutrition Examination Survey (KNHANES) conducted between 2007 and 2012, subjects who were ≥40 years and had prebronchodilator FEV(1)/FVC <0.7 and FEV(1) ≥50% predicted were included. The presence or absence of self-reported wheezing was indicated by W+ or W− and used as an index of airway hyper-responsiveness. S+/S− was defined as subjects who were smokers/never smokers. The subjects were divided into the following four groups: W−S−, W−S+, W+S−, and W+S+. W+S− and W+S+ were asthma-predominant ACO and COPD-predominant ACO, respectively. KNHANES and linked National Health Insurance data were analyzed. RESULTS: The asthma-predominant ACO group showed the lowest socioeconomic status, FEV(1), FVC% predicted, and quality of life (QoL) levels. The COPD-predominant ACO group showed the highest hospitalization rate, outpatient medical cost, and total and outpatient health care utilization. COPD-predominant ACO was associated with exacerbations compared to the W−S− group (adjusted odds ratio [aOR], 1.79; 95% confidence interval [CI], 1.12–2.85; P=0.015) and W−S+ group (OR 2.11; 95% CI 1.43–3.10; P<0.001). COPD-predominant ACO was associated with increased medical cost. CONCLUSION: Asthma-predominant ACO individuals displayed poorer socioeconomic status and QoL compared to the COPD-predominant ACO group. The COPD-predominant ACO group displayed more frequent exacerbations and greater medical costs. Considering the heterogeneity of ACO, it is desirable to identify subtypes of ACO patients and appropriately allocate limited medical resources.