Introduction Tobacco smoking has been associated with reduced response to inhaled corticosteroids (ICS) in asthma treatment. However, little is known about how smoking affects lung function response after initiation of ICS treatment in new-onset asthma.

Aims and objectives To evaluate the sub-acute ICS response on lung function in new adult-onset asthma in steroid-naïve patients.

Methods In the Seinäjoki Adult Asthma Study, 203 patients with new adult-onset asthma were followed for 12 years. Patients who were dispensed ICS during the first two years of the follow-up were included (n=174). Lung function was evaluated at the baseline and the maximum lung function point during the first 2.5 years (Max_0-2.5). Patients were divided into groups by smoking status (never/ex/current smokers) and smoking history (never vs. ever or <10 vs. ?10 smoked pack-years).

Results At diagnosis half of the patients (n=87) were ex- or current smokers with a median of 13 pack-years smoking history. The median point of Max_0-2.5 was at 0.65 (0.36-1.40) years. The increase of FVC % predicted from baseline to Max_0-2.5 was significantly higher (p=0.025) in current smokers compared to never- and ex-smokers. No other differences were observed. No differences in lung function between never vs. ever smokers or in patients with <10 vs. ?10 smoked pack-years were found after ICS initiation. No differences between the groups were found when lung function change was normalized with daily use of ICS.

Conclusion The result indicates that sub-acute lung function responses to ICS treatment in adult-onset asthma do not differ according to smoking status. The result suggests similar start of ICS therapy regardless of smoking history.