title: Childhood environment and atopic conditions, with emphasis on asthma in a Chilean agricultural area.
abstract: BACKGROUND
  An explanation of the etiology of atopic conditions based on the hygiene hypothesis remains controversial.
  
  
  OBJECTIVE
  To analyze exposure variables in childhood to assess their impact on hay fever, asthma, and sensitization.
  
  
  METHODS
  Data were collected on 1,232 young Chilean adults born between 1974 and 1978. Information was available on consultations for infections early in life, number of siblings, sharing a bedroom, nursery school attendance, and contact with animals in the first 5 years of life. Information on asthma symptoms and rhinitis were obtained from a standardized questionnaire. Sensitization to eight allergens and bronchial hyper responsiveness (BHR) to methacholine were assessed. The study design was non-concurrent longitudinal for infectious episodes and nutritional status in the first year and cross-sectional for the other outcomes.
  
  
  RESULTS
  Number of siblings was associated with sensitization only (p = 0.0048). Nursery school attendance was negatively associated with positive BHR (odds ratio (OR) 0.54, 95% CI 0.30-0.95). A severe respiratory infection early in life was protective of sensitization and wheeze combined (OR 0.29, 95%CI 0.12-0.74). Contact with dogs in the first year was a protective factor of rhinitis (OR 0.47, 95%CI 0.28-0.80), but contact with poultry and cats early in life increased the risk of rhinitis (OR 1.42, 95%CI 1.06-1.88; 1.82, 95%CI 1.06-3.14).
  
  
  CONCLUSIONS
  The pattern of associations between environmental exposure in early life and atopic conditions was inconsistent. The significant associations were evenly distributed as protective and risk factors of atopic conditions.
authors.affiliation: Department of Nutrition, Faculty of Medicine, University of Chile, Chile.
authors.forename: Claudio
authors.initials: C
authors.lastname: Vargas
authors.forename: Patricia
authors.initials: P
authors.lastname: Bustos
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Diaz
authors.forename: Hugo
authors.initials: H
authors.lastname: Amigo
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Rona
mesh_terms: D000328:Adult; D000383:Agriculture; D001249:Asthma / Q000453:epidemiology*; D002648:Child; D002677:Chile / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology*; D008137:Longitudinal Studies; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology*; D012307:Risk Factors; D011795:Surveys and Questionnaires