The asthma-COPD overlap syndrome : what is it and how should we treat it? : guest review

Asthma and COPD are two distinct diseases but may overlap, especially in older patients. Typically, asthma patients have marked variability in their airflow obstruction with significant reversibility in response to both bronchodilator and corticosteroid therapy. However, it has become increasingly clear that many patients with asthma may develop fixed airflow obstruction, whereas many patients with COPD exhibit some bronchodilator reversibility. The term 'Asthma-COPD Overlap Syndrome' (ACOS) has been coined to describe patients who have features of both but, as yet, there is no validated definition for the combination of features. Patients with ACOS have worse outcomes than those with asthma or COPD alone: more frequent exacerbations, poorer quality of life, more rapid decline in lung function, higher mortality and greater healthcare use. The Global Initiative for Asthma (GINA) and the Global Initiative for Chronic Obstructive Lung Disease (GOLD) have recently published guidelines for the diagnosis and treatment of patients with asthma, COPD or ACOS.