title: International variations in bronchial responsiveness in children: findings from ISAAC phase two.
abstract: BACKGROUND
  Bronchial responsiveness is an objectively measurable trait related to asthma. Its prevalence and association with asthma symptoms among children in many countries are unknown.
  
  
  OBJECTIVE
  To investigate international variations in bronchial responsiveness (BR) and their associations with asthma symptoms and atopic sensitization.
  
  
  METHODS
  Bronchial challenge tests were conducted in 6,826 schoolchildren (aged 8-12 years) in 16 countries using hypertonic (4.5%) saline. FEV(1) was measured at baseline and after inhalation for 0.5, 1, 2, 4, and 8 min. BR was analyzed both as a dichotomous (bronchial hyperreactivity, BHR, at least 15% decline in FEV(1)) and as a continuous variable (time-response slope, BR slope, individual decline in FEV(1) per log(min)).
  
  
  RESULTS
  Prevalence of wheeze last year ranged from 4.4% in Tirana (Albania) to 21.9% in Hawkes Bay (New Zealand) and of BHR from 2.1% in Tirana to 48% in Mumbai (India). The geometric mean BR slope varied between 3.4%/log(min) in Tirana and 12.8%/log(min) in Mumbai and Rome (Italy). At the individual level, BHR was positively associated with wheeze during the past 12 months both in affluent countries (OR = 3.6; 95% CI: 2.7-5.0) and non-affluent countries (OR = 3.0; 1.6-5.5). This association was more pronounced in atopic children. There was a correlation (rho = 0.64, P = 0.002) between center-specific mean BR slope and wheeze prevalence in atopic, but not in non-atopic children.
  
  
  CONCLUSIONS
  BR to saline in children varied considerably between countries. High rates of BR were not confined to affluent countries nor to centers with high prevalences of asthma symptoms. The association between wheeze and BHR at the individual level differed across centers and this heterogeneity can be largely explained by effect modification by atopy. Pediatr. Pulmonol. 2010; 45:796-806. (c) 2010 Wiley-Liss, Inc.
authors.affiliation: Institute of Epidemiology, University of Ulm, Ulm, Germany. gisela.buechele@uni-ulm.de
authors.forename: Gisela
authors.initials: G
authors.lastname: Büchele
authors.forename: Jon
authors.initials: J
authors.lastname: Genuneit
authors.forename: Gudrun
authors.initials: G
authors.lastname: Weinmayr
authors.forename: Bengt
authors.initials: B
authors.lastname: Björkstén
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gehring
authors.forename: Erika
authors.initials: E
authors.lastname: von Mutius
authors.forename: Alfred
authors.initials: A
authors.lastname: Priftanji
authors.forename: Renato T
authors.initials: RT
authors.lastname: Stein
authors.forename: Emmanuel O
authors.initials: EO
authors.lastname: Addo-Yobo
authors.forename: Kostas N
authors.initials: KN
authors.lastname: Priftis
authors.forename: Jayant R
authors.initials: JR
authors.lastname: Shah
authors.forename: Francesco
authors.initials: F
authors.lastname: Forastiere
authors.forename: Vija
authors.initials: V
authors.lastname: Svabe
authors.forename: Julian
authors.initials: J
authors.lastname: Crane
authors.forename: Wenche
authors.initials: W
authors.lastname: Nystad
authors.forename: Luis
authors.initials: L
authors.lastname: García-Marcos
authors.forename: Yildiz
authors.initials: Y
authors.lastname: Saraçlar
authors.forename: Nuha
authors.initials: N
authors.lastname: El-Sharif
authors.forename: David P
authors.initials: DP
authors.lastname: Strachan
mesh_terms: D000415:Albania / Q000453:epidemiology; D001249:Asthma / Q000453:epidemiology* / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000453:epidemiology*; D001985:Bronchial Provocation Tests; D002648:Child; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D009520:New Zealand / Q000453:epidemiology; D015995:Prevalence; D012135:Respiratory Sounds / Q000175:diagnosis; D012384:Rome / Q000453:epidemiology; D012462:Saline Solution, Hypertonic; D012882:Skin Tests
chemical_list: D012462:Saline Solution, Hypertonic