Assessment of airway inflammation and disease burden in moderate to severe asthmatic smokers

BACKGROUND: Conflicting results have been found among studies assessing the effect of smoking on airway inflammation among asthmatic subjects. OBJECTIVE: We sought to compare the inflammatory and clinical characteristics of active smokers and nonsmokers with uncontrolled moderate-to-severe asthma. Methods: We conducted a cross-sectional study comparing active-smoker and nonsmoker subjects with uncontrolled moderate-to-severe asthma. Sociodemographic and clinical data were collected. FeNO levels and spirometry were measured. We obtained sputum and blood cell counts and measured the cotinine level. The clinical data were linked to 3 Quebec administrative databases. RESULTS: A total of 40 active smokers and 39 nonsmokers were included. Uncontrolled asthmatic smokers and nonsmokers had the same clinical characteristics. Although, blood eosinophil counts were similar between groups, the number of subjects with a high sputum eosinophil count (> 10%) was higher in nonsmokers. Asthmatic smokers had lower levels of FeNO than nonsmoker asthmatics. The nonsmoker group showed a higher number of total asthma exacerbations (1.9 +/- 0.7) than the smoker group (1.0 +/- 1.2) (p<0.01) in the year preceding their assessment. The annual costs related to asthma care tended to be higher in uncontrolled asthmatic nonsmokers (352.05 +/- 813.45CAD) than in smokers (263.38 +/- 684.00CAD), whereas the annual cost for health care of all causes tended to be lower in nonsmokers (1617.57 +/- 1736.53 CAD) than in smokers (2575.07 +/- 3453.30 CAD). INTERPRETATION: The clinical characteristics of uncontrolled moderate-to-severe active asthmatic smokers and nonsmokers were similar. Although the FeNO levels were profoundly affected by smoking, the impact of smoking on airway eosinophilic inflammation appeared marginal.