Inflammation and corticosteroid responsiveness in ex-, current- and never-smoking asthmatics

Background: It has been suggested that smoking asthmatics benefit less from corticosteroid treatment than never-smoking asthmatics. We investigated differences in blood and sputum inflammatory profiles between ex-, current-, and never-smokers and assessed their ICS treatment response after 2-week and 1-year treatment.

Methods: We analyzed FEV1, PC20 methacholine and PC20 AMP, (differential) cell counts in sputum and blood in ex-, current-and never-smokers at baseline (n=114), after 2-week treatment with fluticasone 500 or 2000 mu g/day (n=76) and after 1-year treatment with fluticasone 500 mu g/day or a variable dose of fluticasone based on a self-management plan (n=64).

Results: A total of 114 patients were included (29 ex-, 30 current-and 55 never-smokers. At baseline, ex-and current-smokers had less eosinophils in sputum and blood than never-smokers. Blood neutrophil counts were higher in current-than in never-smokers. A higher number of cigarettes smoked daily was associated with lower blood and sputum eosinophils. After 2-week ICS treatment, FEV1 % predicted improved less in current-smokers than never-smokers (2.4% versus 8.1%, p=0.010) and ex-smokers tended to improve less than never-smokers (4.1%, p=0.067). In contrast, no differences in ICS treatment response in lung function or inflammatory cells were found between the three groups after 1 year.

Conclusions: Ex-and current-smokers have less eosinophils and more neutrophils in their sputum and blood than never-smokers. Although ex-and current-smokers have a reduced short-term corticosteroid treatment response, we did not find a difference in their long-term treatment response.