The Asthma–COPD Overlap Syndrome (ACOS): What Is the Significance COPD Associated with Asthma?

Abstract

Asthma is characterized by inflammation involving eosinophils and Th2 cytokines of the central to peripheral airways, with high reversibility of the airflow obstruction (hereafter simply, airflow reversibility). On the other hand, chronic obstructive pulmonary disease (COPD) is characterized by inflammation involving neutrophils and inflammatory cytokines of the peripheral airways to the alveoli, with low or no airflow reversibility. The asthma-COPD overlap syndrome (ACOS) is characterized by features of both and associated with moderate airflow reversibility. ACOS does not uniformly have the features of asthma or COPD, and its features depend on the type and major site of airway inflammation. The medical costs of ACOS are higher than those of either asthma or COPD. Under such circumstances, the Global Initiative for Asthma (GINA) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) have provided guidelines for the management of ACOS. It is important to combine treatments for both COPD and asthma and not use treatment for either alone in patients with AOCS.