Severe asthma: Epidemiology, burden of illness, and heterogeneity

Background: Patients with severe persistent asthma comprise only 5-10 % of the total asthma population, but account for a large proportion of asthma morbidity and health care expenditures. Among patients with severe asthma, higher costs can be expected in association with not well or poorly controlled asthma. Objective: To summarize the evidence concerning the epidemiology, burden, and heterogeneity of severe asthma. Methods: A literature search was performed to identify citations using the terms "severe asthma" and "epidemiology", "asthma control", "asthma" and "heterogeneity". Results: Successful management of patients with severe asthma continues to be a major unmet need. One of the barriers to successful management is the heterogeneity of asthma. Asthma is not one disease; it is a disorder that can be subdivided into a number of different phenotypes and endotypes. A revised paradigm for asthma management, that entails categorization of asthma patients via use of "biomarkers", and prescribing targeted therapy, will supplant what has been a "one size fits all" approach to asthma management. Conclusion: The novel approach to asthma management, in which therapy will be more mechanism-specific based on phenotype/endotype, offers the potential for improved asthma care outcomes - particularly for patients with severe persistent asthma who are not well or poorly controlled.