title: Bronchial responsiveness is related to increased exhaled NO (FE(NO)) in non-smokers and decreased FE(NO) in smokers.
abstract: BACKGROUND
  Both atopy and smoking are known to be associated with increased bronchial responsiveness. Fraction of nitric oxide (NO) in the exhaled air (FE(NO)), a marker of airways inflammation, is decreased by smoking and increased by atopy. NO has also a physiological bronchodilating and bronchoprotective role.
  
  
  OBJECTIVE
  To investigate how the relation between FE(NO) and bronchial responsiveness is modulated by atopy and smoking habits.
  
  
  METHODS
  Exhaled NO measurements and methacholine challenge were performed in 468 subjects from the random sample of three European Community Respiratory Health Survey II centers: Turin (Italy), Gothenburg and Uppsala (both Sweden). Atopy status was defined by using specific IgE measurements while smoking status was questionnaire-assessed.
  
  
  RESULTS
  Increased bronchial responsiveness was associated with increased FE(NO) levels in non-smokers (p = 0.02) and decreased FE(NO) levels in current smokers (p = 0.03). The negative association between bronchial responsiveness and FE(NO) was seen only in the group smoking less <10 cigarettes/day (p = 0.008). Increased bronchial responsiveness was associated with increased FE(NO) in atopic subjects (p = 0.04) while no significant association was found in non-atopic participants. The reported interaction between FE(NO) and smoking and atopy, respectively were maintained after adjusting for possible confounders (p-values<0.05).
  
  
  CONCLUSIONS
  The present study highlights the interactions of the relationship between FE(NO) and bronchial responsiveness with smoking and atopy, suggesting different mechanisms behind atopy- and smoking-related increases of bronchial responsiveness.
authors.affiliation: Department of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden. Andrei.Malinovschi@medsci.uu.se
authors.forename: Andrei
authors.initials: A
authors.lastname: Malinovschi
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Marieann
authors.initials: M
authors.lastname: Högman
authors.forename: Giovanni
authors.initials: G
authors.lastname: Rolla
authors.forename: Kjell
authors.initials: K
authors.lastname: Torén
authors.forename: Dan
authors.initials: D
authors.lastname: Norbäck
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Olin
mesh_terms: D000328:Adult; D016535:Bronchial Hyperreactivity / Q000175:diagnosis*; D001985:Bronchial Provocation Tests; D045853:Exhalation; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis*; D012907:Smoking; D011795:Surveys and Questionnaires
chemical_list: D016210:Methacholine Chloride; D009569:Nitric Oxide