title: Impact of airway lability, atopy, and tobacco smoking on the development of asthma-like symptoms in asymptomatic teenagers.
abstract: OBJECTIVE
  To investigate the impact of airway lability, atopy, and tobacco smoking on the development of asthma-like symptoms in asymptomatic subjects.
  
  
  METHODS
  In this prospective, community-based study, 271 asymptomatic adolescents with an average age at inclusion of 13.9 years were followed for 6.4 years. Airway lability was assessed at baseline by three tests, including exercise challenge, airway provocation with methacholine, and monitoring of peak expiratory flow. Atopy was defined by one or more positive reactions (> or = 3-mm weal) to 10 common aeroallergens by skin prick testing. The influence of airway lability, atopy, and smoking on the development of asthma-like symptoms was assessed by logistic regression.
  
  
  RESULTS
  During the 6-year study period, 68 of the previously asymptomatic teenagers (25%) developed asthma-like symptoms. Among those, 50% reported cough only, 29% reported wheezing only, and 21% reported both wheezing and coughing. Hyperresponsiveness to methacholine (odds ratio [OR], 3.5; 95% confidence interval [CI], 1.1 to 11.6), smoking (OR, 2.1; 95% CI, 1. 2 to 3.8), and atopy (OR, 3.5; 95% CI, 1.8 to 6.8) each contributed independently to explain symptom development (wheezing and cough together). Girls, but not boys, with airway lability were less likely to take up smoking, compared with subjects of that set with no airway lability (32% vs 51%; p < 0.05). No effect of airway lability on the likelihood of giving up smoking could be demonstrated, nor did the presence of atopy have any significant impact on smoking behavior.
  
  
  CONCLUSIONS
  Hyperresponsiveness to methacholine, atopy, and smoking were independent risk factors for the development of asthma-like symptoms during adolescence. The presence of airway lability may prevent girls from taking up smoking.
authors.affiliation: Department of Respiratory Medicine, Odense University Hospital, Denmark. fn.rasmussen@winsloew.ou.dk
authors.forename: F
authors.initials: F
authors.lastname: Rasmussen
authors.forename: H C
authors.initials: HC
authors.lastname: Siersted
authors.forename: J
authors.initials: J
authors.lastname: Lambrechtsen
authors.forename: H S
authors.initials: HS
authors.lastname: Hansen
authors.forename: N C
authors.initials: NC
authors.lastname: Hansen
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology*; D016535:Bronchial Hyperreactivity / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D011446:Prospective Studies; D012130:Respiratory Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology*; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*