title: Early life microbial exposure and fractional exhaled nitric oxide in school-age children: a prospective birth cohort study.
abstract: BACKGROUND
  Inflammation is a key factor in the pathogenesis of respiratory diseases. Early life exposure to microbial agents may have an effect on the development of the immune system and on respiratory health later in life.In the present work we aimed to evaluate the associations between early life microbial exposures, and fractional exhaled nitric oxide (FeNO) at school age.
  
  
  METHODS
  Endotoxin, extracellular polysaccharides (EPS) and β(1,3)-D-glucan were measured in living room dust collected at 2-3 months of age in homes of participants of three prospective European birth cohorts (LISA, n = 182; PIAMA, n = 244; and INMA, n = 355). Home dampness and pet ownership were periodically reported by the parents through questionnaires. FeNO was measured at age 8 for PIAMA and at age 10/11 for LISA and INMA. Cohort-specific associations between the indoor microbial exposures and FeNO were evaluated using multivariable regression analyses. Estimates were combined using random-effects meta-analyses.
  
  
  RESULTS
  FeNO at school age was lower in children exposed to endotoxin at age 2-3 months (β -0.05, 95% confidence interval (CI) -0.10;-0.01) and in children with reported dog ownership during the first two years of life (GM ratio 0.82, CI 0.70-0.96). FeNO was not significantly associated with early life exposure to EPS, β(1,3)-D-glucan, indoor dampness and cat ownership.
  
  
  CONCLUSIONS
  Early life exposure to bacterial endotoxin and early life dog ownership are associated with lower FeNO at school age. Further studies are needed to confirm our results and to unravel the underlying mechanisms and possible clinical relevance of this finding.
authors.affiliation: Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain. lcasas@creal.cat.
authors.forename: Lidia
authors.initials: L
authors.lastname: Casas
authors.forename: Christina
authors.initials: C
authors.lastname: Tischer
authors.forename: Inge M
authors.initials: IM
authors.lastname: Wouters
authors.forename: Maties
authors.initials: M
authors.lastname: Torrent
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gehring
authors.forename: Raquel
authors.initials: R
authors.lastname: Garcia-Esteban
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Thiering
authors.forename: Dirkje S
authors.initials: DS
authors.lastname: Postma
authors.forename: Johan
authors.initials: J
authors.lastname: de Jongste
authors.forename: Henriëtte A
authors.initials: HA
authors.lastname: Smit
authors.forename: Alícia
authors.initials: A
authors.lastname: Borràs-Santos
authors.forename: Jan-Paul
authors.initials: JP
authors.lastname: Zock
authors.forename: Anne
authors.initials: A
authors.lastname: Hyvärinen
authors.forename: Joachim
authors.initials: J
authors.lastname: Heinrich
authors.forename: Jordi
authors.initials: J
authors.lastname: Sunyer
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D001419:Bacteria / Q000737:chemistry; D002648:Child; D002675:Child, Preschool; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000633:toxicity*; D005260:Female; D005858:Germany; D006801:Humans; D006813:Humidity; D007223:Infant; D008297:Male; D009426:Netherlands; D009569:Nitric Oxide / Q000378:metabolism*; D010067:Ownership; D057805:Pets; D011135:Polysaccharides, Bacterial / Q000633:toxicity*; D011446:Prospective Studies; D013030:Spain; D047071:beta-Glucans / Q000633:toxicity*
chemical_list: D004391:Dust; D004731:Endotoxins; D011135:Polysaccharides, Bacterial; D047071:beta-Glucans; D009569:Nitric Oxide; C033363:beta-1,3-glucan