The Asthma–Chronic Obstructive Pulmonary Disease Overlap Syndrome

Pharmacotherapeutic Considerations

Samuel Louie; Amir A Zeki; Michael Schivo; Andrew L Chan; Ken Y Yoneda; Mark Avdalovic; Brian M Morrissey; Timothy E Albertson


Expert Rev Clin Pharmacol. 2013;6(2):197-219. 

In This Article

Abstract and Introduction


Asthma–chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) is a commonly encountered yet loosely defined clinical entity. ACOS accounts for approximately 15–25% of the obstructive airway diseases and patients experience worse outcomes compared with asthma or COPD alone. Patients with ACOS have the combined risk factors of smoking and atopy, are generally younger than patients with COPD and experience acute exacerbations with higher frequency and greater severity than lone COPD. Pharmacotherapeutic considerations require an integrated approach, first to identify the relevant clinical phenotype(s), then to determine the best available therapy. The authors discuss the array of existing and emerging classes of drugs that could benefit those with ACOS and share their therapeutic approach. A consensus international definition of ACOS is needed to design prospective, randomized clinical trials to evaluate specific drug interventions on important outcomes such as lung function, acute exacerbations, quality of life and mortality.


The asthma–chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) is poorly recognized in part because clinical trials have consistently ignored this condition, as evidenced by strict inclusion and exclusion criteria that exclude either asthma patients from COPD studies or COPD patients from asthma studies. Asthmatic bronchitis was a term used to describe the overlapping conditions of asthma and COPD by the American Thoracic Society (ATS) in 1962,[1] but no further attempts were made to expound on this clinical phenotype until recently.[2–4] Guidelines from Canada, Japan and Spain attempt to describe this clinical phenotype and establish treatment options.[5–7]

Asthma is a syndrome consisting of similar phenotypes with characteristic but nonspecific symptoms. COPD is a syndrome akin to asthma but with important differences, including tobacco smoke-induced pathobiology and pulmonary emphysema. An exploration of how best to define ACOS is beyond the scope of this article. However, a clinical definition is a necessary starting point for a review of potential pharmacotherapeutic approaches.