Effect of active smoking on asthma symptoms, pulmonary function, and BHR in adolescents.

Background: Active smoking is known to increase asthma symptoms and bronchial hyper-responsiveness (BHR) while decreasing pulmonary function in adults, but few studies have addressed these issues in adolescents.
Methods: We conducted a cross-sectional survey involving questionnaires and assessment of urinary cotinine levels among 1,492 adolescents from three urban areas of South Korea. Current smoking was defined as having smoked more than 1 day in the prior 30 days or having urine cotinine levels >or=100 ng/ml. Spirometry, skin tests, and methacholine challenge tests were performed on adolescents in Seoul (n = 724).
Results: The prevalence of current smoking was 8.2% in boys and 2.4% in girls. Reports of wheeze and exercise-induced wheeze in the previous 12 months were more frequent in smokers than nonsmokers (15.2% vs. 8.5%, P = 0.024, and 20.4% vs. 10.7%, P = 0.004, respectively). In multiple logistic regression analysis, current smoking was found to be a significant risk factor for having wheezed in previous 12 months (OR = 4.5, 95% CI 1.5-13.2) and having exercise-induced wheezing in previous 12 months (OR = 8.7, 95% CI, 3.7-20.9). The subgroup analysis revealed that the FEV(1)/FVC was lower in smokers than nonsmokers (mean +/- SD, 105.1 +/- 8.6% vs. 107.8 +/- 7.8%, P = 0.019). In contrast, there was no significant difference in BHR. The effect of smoking on asthma symptoms were more pronounced in non-atopic compared with atopic adolescents.
Conclusion: Current smoking was significantly associated with symptoms of asthma, such as having recent wheezing and recent exercise-induced wheezing, especially for non-atopics, in Korean adolescent population. Current smoking was further associated with lower pulmonary function, but not BHR.