Asthma and smoking: A review.

Asthma occurrence is often associated with cigarette smoking. Surprisingly, active smokers are excluded from most clinical studies. Prevalence of asthma associated with smoking appears to be similar to asthma in the general population. However, in active smokers, asthma tends to be more difficult to manage and more severe. Several studies have demonstrated a poor response to inhaled corticosteroids (ICS) and an accelerated decline of lung function. Smoking decreases exhaled NO rate and down-regulates ICS receptors, which is associated with increased oxidative stress. Data on biologic therapies are scarce. Finally, nicotine dependence seems higher in asthmatic patients and smoking cessation is thus more difficult.