Summary of the Japanese Respiratory Society guidelines for the diagnosis and treatment of asthma and chronic obstructive pulmonary disease overlap 2023 (2nd edition)

Many patients have overlapping features of asthma and chronic obstructive pulmonary disease (COPD), but not all of them receive appropriate treatment for both conditions. The Japanese Respiratory Society published the guidelines on the diagnosis and treatment of asthma and COPD overlap (ACO) to promote its awareness. This English summary of the revised edition highlights the concepts, definitions, clinical features, diagnosis, and management of ACO based on recent evidence from observational studies. It also discusses the updates to the evaluation of ACO severity, workflow of management, and pharmacological treatment strategy. ACO is characterized by chronic airflow limitation with features of both asthma and COPD, and its diagnostic algorithm based on the clinical features and multidimensional evaluation, including imaging and functional tests, is provided. The classification of ACO severity based on exacerbations and symptoms is also advocated. There is no consensus on the treatment strategy for ACO, but the guidelines propose a pharmacotherapy strategy based on this classification to prevent under- or over-treatment. ACO requires a comprehensive approach that includes tailored pharmacological and non-pharmacological therapies. These guidelines will contribute to advancing research on the characteristics and pathophysiology of ACO and facilitate discussions on its management.