Asthma phenotypes according to the timing of smoking onset in young adults.

Setting: Whether and how cigarette smoking influences asthma are still matters of debate.

Objective: To identify risk factors associated with asthma according to whether individuals began active smoking before or after asthma onset.

Design: A sample of 544 individuals was examined using the protocol of the European Community Respiratory Health Status, Phase 1.

Results: Current active smoking (43.6%) was associated with wheezing during the past year (15.2%, OR 3.7; 95% CI 1.7-8.4), but not with asthma (17.6%, OR 0.78; 95% CI 0.48-1.26). However, active smoking modulated risk factors for asthma. Asthma that developed before smoking and asthma without smoking were both significantly related to nasal allergy, parental asthma and atopy (as assessed by skin prick test positivity and increased total and specific IgE levels). Only a lower FEV1 level was significantly associated with asthma that initiated after beginning smoking.

Conclusions: Our data put forward different phenotypes of asthma according to the timing of smoking onset and suggest that asthma either never accompanied by smoking or followed by smoking onset might be characterised by an allergic pattern. Longitudinal studies are warranted to further clarify the relationships among asthma phenotypes according to the sequence of disease onset and smoking.