ABSTRACT
Asthma and chronic obstructive pulmonary disease (COPD) are common diseases that affect a substantial proportion of individuals worldwide. The structured and formalized definitions and diagnostic criteria for both asthma and COPD have allowed focused analysis and characterization of subgroups or special populations with some standardization and reproducibility. 1,2 However, without a clearly accepted consensus definition and known heterogeneous criteria for defining patients with asthma-COPD overlap (ACO), it is not completely certain how ACO relates to specific patient populations. 3 Available data suggest that ACO reflects a mixture of features, characteristics, and subsequent special-population effects of those seen in individuals with both asthma and COPD. In this chapter, we will explore current knowledge on special populations with asthma, COPD, and ACO.
