title: Not all farming environments protect against the development of asthma and wheeze in children.
abstract: BACKGROUND
  In recent years, studies have shown a protective effect of being raised in a farm environment on the development of hay fever and atopic sensitization. Inconsistent data on the relation of farming to asthma and wheeze have raised some doubt about a true protective effect.
  
  
  OBJECTIVE
  We sought to study the differential effects of farm-associated exposures on specific asthma-related health outcomes.
  
  
  METHODS
  The cross-sectional Prevention of Allergy Risk Factors for Sensitization in Children Related to Farming and Anthroposophic Lifestyle study included 8263 school-age children from rural areas in 5 European countries. Information on farm-related exposures and health outcomes was obtained by using questionnaires. In subsamples allergen-specific IgE and RNA expression of CD14 and Toll-like receptor genes were measured, and dust from children's mattresses was evaluated for microbial components.
  
  
  RESULTS
  Inverse relations with a diagnosis of asthma were found for pig keeping (odds ratio [OR], 0.57; 95% CI, 0.38-0.86), farm milk consumption (OR, 0.77; 95% CI, 0.60-0.99), frequent stay in animal sheds (OR, 0.71; 95% CI, 0.54-0.95), child's involvement in haying (OR, 0.56; 95% CI, 0.38-0.81), and use of silage (OR, 0.55; 95% CI, 0.31-0.98; for nonatopic asthma) and in Germany for agriculture (OR, 0.34; 95% CI, 0.22-0.53). Protective factors were related with higher expression levels of genes of the innate immunity. Potential risk factors for asthma and wheeze were also identified in the farm milieu. Levels of endotoxin and extracellular polysaccharides were related to the health outcomes independently of the farm exposures.
  
  
  CONCLUSIONS
  The protective effect of being raised in a farm environment was ascribed to distinct exposures.
  
  
  CONCLUSIONS
  The development of atopic sensitization and atopic and nonatopic asthma is most likely determined by different environmental factors, possibly reflecting distinct pathomechanisms.
authors.affiliation: University Children's Hospital Munich, Germany.
authors.forename: Markus Johannes
authors.initials: MJ
authors.lastname: Ege
authors.forename: Remo
authors.initials: R
authors.lastname: Frei
authors.forename: Christian
authors.initials: C
authors.lastname: Bieli
authors.forename: Dieneke
authors.initials: D
authors.lastname: Schram-Bijkerk
authors.forename: Marco
authors.initials: M
authors.lastname: Waser
authors.forename: Marcus R
authors.initials: MR
authors.lastname: Benz
authors.forename: Gertraud
authors.initials: G
authors.lastname: Weiss
authors.forename: Fredrik
authors.initials: F
authors.lastname: Nyberg
authors.forename: Marianne
authors.initials: M
authors.lastname: van Hage
authors.forename: Göran
authors.initials: G
authors.lastname: Pershagen
authors.forename: Bert
authors.initials: B
authors.lastname: Brunekreef
authors.forename: Josef
authors.initials: J
authors.lastname: Riedler
authors.forename: Roger
authors.initials: R
authors.lastname: Lauener
authors.forename: Charlotte
authors.initials: C
authors.lastname: Braun-Fahrländer
authors.forename: Erika
authors.initials: E
authors.lastname: von Mutius
mesh_terms: D000293:Adolescent; D000383:Agriculture; D000818:Animals; D000829:Animals, Domestic; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D005260:Female; D015870:Gene Expression; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology / Q000209:etiology; D007073:Immunoglobulin E / Q000097:blood; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008297:Male; D012135:Respiratory Sounds / Q000209:etiology*; D051193:Toll-Like Receptors / Q000378:metabolism
chemical_list: D018950:Lipopolysaccharide Receptors; D051193:Toll-Like Receptors; D007073:Immunoglobulin E