title: Does migration affect asthma, rhinoconjunctivitis and eczema prevalence? Global findings from the international study of asthma and allergies in childhood.
abstract: BACKGROUND
  Immigrants to Westernized countries adopt the prevalence of allergic diseases of native populations, yet no data are available on immigrants to low-income or low-disease prevalence countries. We investigated these questions using data from the International Study of Asthma and Allergies in Childhood.
  
  
  METHODS
  Standardized questionnaires were completed by 13-14-year-old adolescents and by the parent/guardians of 6-7-year-old children. Questions on the symptom prevalence of asthma, rhinoconjunctivitis and eczema, and a wide range of factors postulated to be associated with these conditions, including birth in or not in the country and age at immigration, were asked. Odds ratios for risk of the three diseases according to immigration status were calculated using generalized linear mixed models. These were adjusted for: world region; language and gross national income; and individual risk factors including gender, maternal education, antibiotic and paracetamol use, maternal smoking, and diet. Effect modification by gross national income and by prevalence was examined.
  
  
  RESULTS
  There were 326 691 adolescents from 48 countries and 208 523 children from 31 countries. Immigration was associated with a lower prevalence of asthma, rhinoconjunctivitis and eczema in both age groups than among those born in the country studied, and this association was mainly confined to high-prevalence/affluent countries. This reduced risk was greater in those who had lived fewer years in the host country.
  
  
  CONCLUSIONS
  Recent migration to high prevalence/affluent countries is associated with a lower prevalence of allergic diseases. The protective pre-migration environment quickly decreases with increasing time in the host country.
authors: Respiratory Medicine and Allergy Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain, Murdoch Children's Research Institute, Melbourne, Australia, MRC Centre for Environment and Health, St George's, University of London, London, UK, Department of Paediatrics: Child and Youth Health, University of Auckland, Auckland, New Zealand, Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK and Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. The ISAAC Phase Three Study group are listed under Supplementary data at IJE online lgmarcos@um.es.
authors: Luis
authors: L
authors: Garcia-Marcos
authors: Respiratory Medicine and Allergy Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain, Murdoch Children's Research Institute, Melbourne, Australia, MRC Centre for Environment and Health, St George's, University of London, London, UK, Department of Paediatrics: Child and Youth Health, University of Auckland, Auckland, New Zealand, Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK and Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. The ISAAC Phase Three Study group are listed under Supplementary data at IJE online.
authors: Colin F
authors: CF
authors: Robertson
authors: Respiratory Medicine and Allergy Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain, Murdoch Children's Research Institute, Melbourne, Australia, MRC Centre for Environment and Health, St George's, University of London, London, UK, Department of Paediatrics: Child and Youth Health, University of Auckland, Auckland, New Zealand, Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK and Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. The ISAAC Phase Three Study group are listed under Supplementary data at IJE online.
authors: H
authors: H
authors: Ross Anderson
authors: Respiratory Medicine and Allergy Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain, Murdoch Children's Research Institute, Melbourne, Australia, MRC Centre for Environment and Health, St George's, University of London, London, UK, Department of Paediatrics: Child and Youth Health, University of Auckland, Auckland, New Zealand, Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK and Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. The ISAAC Phase Three Study group are listed under Supplementary data at IJE online.
authors: Philippa
authors: P
authors: Ellwood
authors: Respiratory Medicine and Allergy Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain, Murdoch Children's Research Institute, Melbourne, Australia, MRC Centre for Environment and Health, St George's, University of London, London, UK, Department of Paediatrics: Child and Youth Health, University of Auckland, Auckland, New Zealand, Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK and Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. The ISAAC Phase Three Study group are listed under Supplementary data at IJE online.
authors: Hywel C
authors: HC
authors: Williams
authors: Respiratory Medicine and Allergy Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain, Murdoch Children's Research Institute, Melbourne, Australia, MRC Centre for Environment and Health, St George's, University of London, London, UK, Department of Paediatrics: Child and Youth Health, University of Auckland, Auckland, New Zealand, Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK and Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. The ISAAC Phase Three Study group are listed under Supplementary data at IJE online.
authors: Gary Wk
authors: GW
authors: Wong
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000453:epidemiology*; D002648:Child; D003233:Conjunctivitis, Allergic / Q000453:epidemiology*; D004485:Eczema / Q000453:epidemiology*; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data*; D004641:Emigration and Immigration; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D015995:Prevalence; D065631:Rhinitis, Allergic / Q000453:epidemiology*; D011795:Surveys and Questionnaires
keywords: Asthma; ISAAC; eczema; epidemiology; migration; rhinoconjunctivitis