Influence of cigarette smoking on airway inflammation and inhaled corticosteroid treatment in patients with asthma

Abstract

Background: Cigarette smoking induces neutrophilic airway inflammation and relative resistance to inhaled corticosteroids (ICS).

Objective: We evaluated the influence of cigarette smoking on airway inflammation in patients with asthma and also compared the effect of ICS between smoking and nonsmoking in patients with asthma.

Methods: Smokers with asthma (n = 81) and nonsmokers with asthma (n = 52) were recruited for the study. We examined lung function, fractional exhaled nitric oxide (FeNO) concentration, induced sputum, and acetylcholine inhalation before and 6 months after inhaling budesonide at 800 μg/day. Thirty-four healthy volunteers were included as controls.

Results: Smokers with asthma showed a lower forced expiratory volume in 1 second (FEV1) to forced volume capacity (FVC) ratio (p < 0.05), a lower FeNO (p < 0.01), a lower eosinophil proportion (p < 0.05), and a higher neutrophil proportion (p < 0.05) in induced sputum than nonsmokers with asthma. Bronchial hyperresponsiveness (the provocative concentration of acetylcholine [Ach] that produced a 20% fall in FEV1 [PC20-Ach]) was increased in smokers with asthma compared with nonsmokers with asthma (p < 0.05). Both smokers with asthma and nonsmokers with asthma exhibited more prominent airway obstruction, a higher FeNO, and a higher percentage of sputum eosinophils than the controls (p < 0.05 to p < 0.001, each). After 6 months of treatment with inhaled budesonide at 800 μg/day, the improvement in lung function (FEV1 to FVC ratio, flow at 50% forced vital capacity [V50% predicted] and flow at 25% forced vital capacity [V25% predicted]), the eosinophil proportion in induced sputum and PC20-Ach were lower in smokers with asthma than nonsmokers with asthma (p < 0.05).

Conclusion: Smokers with asthma showed neutrophilic airway inflammation in addition to eosinophilic inflammation, and cigarette smoking impaired the efficacy of ICS treatment in mild-to-moderate asthma. These findings have important implications for the management of patients with asthma and who smoke.