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Clinical Review State of the Art Review

Asthma-COPD overlap syndrome: pathogenesis, clinical features, and therapeutic targets

BMJ 2017; 358 doi: (Published 25 September 2017) Cite this as: BMJ 2017;358:j3772
  1. Janice M Leung, assistant clinical professor of respiratory medicine,
  2. Don D Sin, professor of respiratory medicine
  1. Division of Respiratory Medicine and Centre for Heart Lung Innovation, St Paul’s Hospital, University of British Columbia, Vancouver, BC, Canada
  1. Correspondence to: D Sin don.sin{at}


Asthma-COPD overlap syndrome (ACOS) or asthma-COPD overlap captures the subset of patients with airways disease who have features of both asthma and chronic obstructive pulmonary disease (COPD). Although definitions of ACOS vary, it is generally thought to encompass persistent airflow limitation in a patient older than 40 years of age with either a history of asthma or large bronchodilator reversibility. ACOS affects about a quarter of patients with COPD and almost a third of patients who previously had asthma. Compared with their counterparts with asthma or COPD alone, patients with ACOS have significantly worse respiratory symptoms, poorer quality of life, and increased risk of exacerbations and hospital admissions. Whether this condition emerges after gradual shifts in airway remodelling and inflammation in a patient with COPD, as the result of noxious exposures in a patient with asthma, or even as a de novo disease with its own pathology is yet to be determined. Nevertheless, using treatments developed for asthma or COPD that target eosinophilic, neutrophilic, or paucigranulocytic airway inflammation may be a helpful approach to these patients until further clinical trials can be performed.


  • Series explanation: State of the Art Reviews are commissioned on the basis of their relevance to academics and specialists in the US and internationally. For this reason they are written predominantly by US authors

  • We thank Cheng Wei Tony Yang and Chloe Chih Ya Huang for their contribution to the figures.

  • Contributors: Both authors were involved in the conception, writing, and editing of the manuscript. Both are guarantors.

  • Competing interests: We have read and understood BMJ policy on declaration of interests and declare the following interests: DDS has received honorariums for speaking engagements with AstraZeneca and Boehringer Ingelheim and for participating in COPD advisory boards of Sanofi, Regeneron, AstraZeneca, Boehringer Ingelheim, Novartis, and Merck and has received research funding for investigator initiated COPD studies from Merck, AstraZeneca, and Boehringer Ingelheim. DDS is supported by a Tier 1 Canada research chair award in COPD.

  • Provenance and peer review: Commissioned; externally peer reviewed.

  • Patient involvement: No patients were involved in the creation of this article.

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