Integrating evidence for managing asthma in patients who smoke.

Cigarette smoking among asthma patients is associated with worsening symptoms and accelerated decline in lung function. Smoking asthma is also characterized by increased levels of neutrophils and macrophages, and greater small airway remodeling, resulting in increased airflow obstruction and impaired response to corticosteroid therapy. As a result, smokers are typically excluded from asthma randomized controlled trials (RCTs). The strict inclusion/exclusion criteria used by asthma RCTs limits the extent to which their findings can be extrapolated to the routine care asthma population and to reflect the likely effectiveness of therapies in subgroups of particular clinical interest, such as smoking asthmatics. The inclusion of smokers in observational asthma studies and pragmatic trials in asthma provides a way of assessing the relative effectiveness of different treatment options for the management of this interesting clinical subgroup. Exploratory studies of possible treatment options for smoking asthma suggest potential utility in: prescribing higher-dose ICS; targeting the small airways of the lungs with extra-fine particle ICS formulations; targeting leukotreines, and possibly also combinations of these options. However, further studies are required. With the paucity of RCT data available, complementary streams of evidence (those from RCTs, pragmatic trials and observational studies) need to be combined to help guide judicious prescribing decisions in smokers with asthma.