Introduction: Smoking has been shown to increase the incidence of asthma in young adults, worsen the disease severity and impair its control. However, these observations were mainly derived from cross-sectional or case-control studies.Aims: To prospectively study asthma incidence as a function of smoking habits in the Italian adult population.Methods: In the frame of the Gene Environment Interactions in Respiratory Diseases study, two surveys were done in Verona and Sassari in 1998-2000 and 2007-2009 (follow-up period of 9.1±0.8 years, follow-up response rate=60.3%). Among 5,204 non-asthmatic at baseline, 3,182 of them participated in the follow-up, and answered a screening questionnaire on smoking habits, asthma, chronic bronchitis and allergic rhinitis.Results: During the follow up, the prevalence of smoking decreased from 31.6% (95% CI 30.4-32.8%) to 21.7% (20.2-22.9%) while the prevalence of current asthma increased from 5.2% (4.7-5.8%) to 7.9% (7.0-8.9%). Nine-year cumulative incidence of asthma was 4.6% (145/3182). The incidence was higher in ex-smokers at baseline (5.3%=30/566) than in never smokers (4.5%=76/1687) and current smokers (4.3%=39/909). A Cox regression model, assuming asthma onset as terminal event, did not find a significant influence of baseline smoking on asthma, while allergic rhinitis was associated with a higher risk of asthma incidence (Hazard ratio=2.91, 2.06-4.10).Conclusion: In this prospective study active smoking was not a risk factor for asthma. The higher incidence of asthma observed in ex-smokers was likely due to reverse causation. As expected, we found an association between asthma onset during the follow-up and allergic rhinitis at baseline.
File in questo prodotto:
Non ci sono file associati a questo prodotto.