title: Wheezing in relation to atopy and environmental factors in Estonian and Swedish schoolchildren.
abstract: BACKGROUND
  The prevalence of asthma and allergic diseases is significantly lower in post socialist Eastern Europe than in Western industrialized countries. The reason for this difference is largely unknown. Different types of childhood wheezing could be related to different risk factors.
  
  
  OBJECTIVE
  To compare the prevalence of respiratory symptoms, asthma and atopic diseases among Estonian and Swedish schoolchildren and to evaluate characteristics for wheezing in the two countries.
  
  
  METHODS
  In a prevalence study, population-based random samples of 10-11-year-old schoolchildren in Tallinn (n = 979), Estonia and in Linköping (n = 911) and Ostersund (n = 1197), Sweden were studied by a parental questionnaire and skin prick tests (SPT). All 275 children with wheeze in the past 12 months and 710 randomly selected controls within the original cohorts were invited to a case-control study involving a parental questionnaire, examination for flexural dermatitis and bronchial challenge with hypertonic saline. The study adhered to the International Study of Asthma and Allergies in Childhood (ISAAC) Phase II protocol.
  
  
  RESULTS
  The prevalence of current wheezing was similar (8-10%) in the three centres, while diagnosed asthma and atopic symptoms were more common in Sweden and cold-related respiratory symptoms were more prevalent in Estonia. Frequent wheezing was more common in Sweden than in Estonia (but significantly so only in Ostersund). Wheezing children in Sweden had a high rate of positive SPT (49% in Linköping and 58% in Ostersund) bronchial hyper-responsiveness (BHR) (48% in Linköping and Ostersund) and anti-asthmatic treatment (63% in Linköping and 81% in Ostersund). In Estonia, the proportion of wheezing children with positive SPT, BHR and anti-asthmatic treatment was only 26%, 13% and 17%, respectively. Domestic crowding was inversely related to wheezing in one of the study areas (Ostersund). The mean baseline forced expiratory volume in one second (FEV1) was higher in Estonia than in Sweden, both in wheezing and non-wheezing children.
  
  
  CONCLUSIONS
  Our study suggested that although wheezing symptoms were equally common in Estonia and Sweden, they were less severe in Estonia. More frequent symptoms and a high rate of atopy, BHR and anti-asthmatic medication characterized wheezing children in Sweden. In contrast, BHR, atopy and medication were uncommon among wheezing children in Estonia.
authors.affiliation: Tartu University Children's Hospital, Tartu, Estonia.
authors.forename: T
authors.initials: T
authors.lastname: Annus
authors.forename: B
authors.initials: B
authors.lastname: Björkstén
authors.forename: X M
authors.initials: XM
authors.lastname: Mai
authors.forename: L
authors.initials: L
authors.lastname: Nilsson
authors.forename: M A
authors.initials: MA
authors.lastname: Riikjärv
authors.forename: A
authors.initials: A
authors.lastname: Sandin
authors.forename: L
authors.initials: L
authors.lastname: Bråbäck
mesh_terms: D016535:Bronchial Hyperreactivity / Q000209:etiology; D001985:Bronchial Provocation Tests; D016022:Case-Control Studies; D002648:Child; D002669:Child Welfare; D004781:Environmental Exposure / Q000009:adverse effects*; D004957:Estonia / Q000453:epidemiology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000209:etiology*; D008297:Male; D015995:Prevalence; D012135:Respiratory Sounds / Q000209:etiology*; D012307:Risk Factors; D012572:School Health Services; D012882:Skin Tests; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology