title: Endotoxin exposure and childhood wheeze and asthma: a meta-analysis of observational studies.
abstract: BACKGROUND
  Exposure to endotoxin has been widely investigated as a potential factor for asthma and associated symptoms in children with different results. To clarify a potential relationship, we performed the present meta-analysis to integrate the results of studies examining the association of endotoxin exposure with wheeze and asthma in children.
  
  
  METHODS
  A search for relevant studies and reviews was conducted in MEDLINE, Highwire, CINAHL, and The Cochrane Library databases. Adjusted odds ratio (OR) with corresponding 95% confidence interval (CI) for endotoxin exposure and wheeze or asthma were retrieved and pooled to generate summary effect estimates in STATA 11.1.
  
  
  RESULTS
  Nineteen studies were included in the meta-analysis. The summary estimates suggested that endotoxin was positively associated with wheeze in infants and toddlers (meta-OR: 1.48, 95% CI: 1.10-1.98), but negatively related to asthma in school-aged children (meta-OR: 0.82, 95% CI: 0.69-0.97 for endotoxin concentration and 0.68, 95% CI: 0.50-0.93 for endotoxin load).
  
  
  CONCLUSIONS
  Based on the studies evaluated, endotoxin is a risk factor for wheeze in younger children, but a protective factor for asthma in older children. Thus, this study supports the "hygiene hypothesis."
authors: Robert Stempel School of Public Health, Florida International University, Miami, FL 33199, USA.
authors: Angelico
authors: A
authors: Mendy
authors: Janvier
authors: J
authors: Gasana
authors: Edgar Ramos
authors: ER
authors: Vieira
authors: Erick
authors: E
authors: Forno
authors: Jasmin
authors: J
authors: Patel
authors: Prasad
authors: P
authors: Kadam
authors: Gilbert
authors: G
authors: Ramirez
mesh_terms: D001249:Asthma / Q000209:etiology*; D004731:Endotoxins / Q000009:adverse effects*; D004781:Environmental Exposure; D006801:Humans; D006920:Hygiene; D015201:Meta-Analysis as Topic; D012135:Respiratory Sounds / Q000209:etiology*; D012307:Risk Factors
chemical_list: D004731:Endotoxins