Concept of Asthma COPD Overlap: Japanese Guideline and Global Trends—How Was the Concept of Asthma COPD Overlap Developed and Moving Forward?

Bronchial asthma and chronic obstructive pulmonary disease (COPD) are two of the most frequent respiratory diseases. These two are independent diseases that differ in their pathogenesis and treatment. However, because both diseases often occur in a patient, partly due to the increased incidence of each, and because patients with both diseases may have different medical conditions from those with COPD or asthma alone, the combined condition has been attracting attention from physicians. In light of this situation, the term asthma-COPD overlap (ACO) was introduced by international committees to describe patients with both conditions. However, although many clinical studies on ACO had been published since then, there was no unified definition or diagnostic criteria, which has been a barrier to a true understanding of this condition. Therefore, to provide a uniform definition and diagnostic criteria, the Japanese Respiratory Society published “The JRS Guidelines for the Management of ACO” in December 2017. In this chapter, we will outline the concept of ACO, focusing on the Japanese guidelines, and discuss the future approach to ACO, including developments in other countries, including the international committees.