title: Geographic variations in the effect of atopy on asthma in the European Community Respiratory Health Study.
abstract: BACKGROUND
  Atopy has long been related to asthma. The prevalences of both atopy and asthma have shown substantial variation.
  
  
  OBJECTIVE
  We sought to assess geographic variations in the fraction of asthma attributable to IgE sensitization to specific allergens in the European Community Respiratory Health Survey.
  
  
  METHODS
  A cross-sectional study was undertaken during the years 1991 and 1992 on 13,558 individuals in 36 centers in 16 countries. Asthma was defined in several ways, variously incorporating reported symptoms, bronchial responsiveness to methacholine, and physician diagnosis. Specific IgE against house dust mite (Dermatophagoides pteronyssinus), cat, timothy grass, Cladosporium herbarum , and a local allergen (birch, Parietaria judaica , or ragweed) were measured.
  
  
  RESULTS
  The overall attributable fraction (AF) of asthma symptoms caused by atopy was 30% but varied widely between centers, ranging from 4% to 61%. The overall AF increased to 43% when asthma was based on wheezing and bronchial responsiveness, to 45% with a physician diagnosis of asthma, and to 48% when the patient reported more than 12 attacks in the last year. Between centers, the AF for atopy was significantly correlated with the prevalence of atopy among the asthmatic patients ( r = 0.91) and with the sensitization to house dust mite ( r = 0.64), as well as with the prevalence of asthma among atopic individuals ( r = 0.43) and the prevalence of asthma among nonatopic individuals ( r = -0.51).
  
  
  CONCLUSIONS
  The effect of atopy on the prevalence of asthma varies widely between centers, probably because of variations in factors related to the expression of asthma and to the prevalence of sensitization, particularly to house dust mite.
authors.affiliation: Environmental Respiratory Research Unit, Institut Municipal d'Investigació Mèdica (IMIM), C. Doctor Aiguader 80, 08003 Barcelona, Spain. jsunyer@imim.es
authors.forename: Jordi
authors.initials: J
authors.lastname: Sunyer
authors.forename: Deborah
authors.initials: D
authors.lastname: Jarvis
authors.forename: Juha
authors.initials: J
authors.lastname: Pekkanen
authors.forename: Susan
authors.initials: S
authors.lastname: Chinn
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Benedicte
authors.initials: B
authors.lastname: Leynaert
authors.forename: Christina
authors.initials: C
authors.lastname: Luczynska
authors.forename: Raquel
authors.initials: R
authors.lastname: Garcia-Esteban
authors.forename: Peter
authors.initials: P
authors.lastname: Burney
authors.forename: Josep M
authors.initials: JM
authors.lastname: Antó
mesh_terms: D000485:Allergens / Q000276:immunology*; D001249:Asthma / Q000453:epidemiology* / Q000276:immunology; D003430:Cross-Sectional Studies; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology*; D007073:Immunoglobulin E / Q000097:blood*; D015995:Prevalence
chemical_list: D000485:Allergens; D007073:Immunoglobulin E