Background
Asthma is a chronic inflammatory airway disease in which a variety of inflammatory cells and mediators play a role. Inhaled corticosteroids (ICS) are the cornerstone of treatment, since they exert broad anti-inflammatory effects. They have been shown to improve symptoms and lung function as well as bronchial hyperresponsiveness and markers of airway inflammation in blood, induced sputum and bronchial biopsies. In addition, the use of ICS reduces the number of asthma exacerbations.
About 20-30% of asthma patients smoke and another 20-40% are ex-smokers. Current-smokers appear to have a different airway inflammatory profile than never-smokers, with less eosinophilic and more neutrophilic inflammation. Thus far, very little is known about the inflammatory profile of ex-smokers.
The few studies investigating the effects of smoking on the short-term efficacy of oral or inhaled corticosteroid treatment in asthma, demonstrate that the forced expiratory volume in one second (FEV1) improves significantly in never-smokers, but not in current-smokers. However, none of these studies found statistically significant differences in improvement in FEV1 when directly comparing never- and current-smokers. The only study that included ex-smokers, showed no improvement in FEV1 or asthma control after 2-week oral corticosteroid treatment in ex- and current-smokers.
We aimed to investigate whether ex-, current- and never-smokers with asthma have different inflammatory profiles and if current number of cigarettes or packyears smoked affect this. Furthermore, we assessed whether the short- and long-term responsiveness to corticosteroids after 2-week and 1-year treatment is different between ex-, current- and never-smoking asthmatics. We have analyzed this in a relatively large group of 114 well-characterized patients with allergic, mild to moderately severe asthma.