Background
Asthma affects approximately 300 million people world- wide and is responsible for 250,000 deaths each year [1]. In addition, there is evidence that the prevalence of asthma is increasing. Asthma furthermore accounts for a significant percentage of public health budgets [1, 2].
There is accordingly a pressing need for studies to re- veal strategies to better control this disease, particularly severe and difficult-to-treat cases [2].
In this perspective, smoking plays an important role since the group of asthmatic smokers has special charac- teristics compared with nonsmokers (e.g., increased morbidity and mortality, more severe symptoms, much more difficult asthma control, higher frequency of exac- erbations, worse quality of life, and increased number of life-threatening asthma attacks [1]. Decline of lung