title: Meta-analysis of the effects of indoor nitrogen dioxide and gas cooking on asthma and wheeze in children.
abstract: BACKGROUND
  Since the meta-analysis on the association between indoor nitrogen dioxide (NO2) and childhood respiratory illness in 1992, many new studies have been published. The quantitative effects of indoor NO2 on respiratory illness have not been estimated in a formal meta-analysis since then. We aimed to quantify the association of indoor NO2 and its main source (gas cooking) with childhood asthma and wheeze.
  
  
  METHODS
  We extracted the association between indoor NO2 (and gas cooking) and childhood asthma and wheeze from population studies published up to 31 March 2013. Data were analysed by inverse-variance-weighted, random-effects meta-analysis. Sensitivity analyses were conducted for different strata. Publication bias and heterogeneity between studies were investigated.
  
  
  RESULTS
  A total of 41 studies met the inclusion criteria. The summary odds ratio from random effects meta-analysis for asthma and gas cooking exposure was 1.32 [95% confidential interval (CI) 1.18-1.48], and for a 15-ppb increase in NO2 it was 1.09 (95% CI 0.91-1.31). Indoor NO2 was associated with current wheeze (random effects OR 1.15; 95% CI 1.06-1.25). The estimates did not vary much with age or between regions. There was no evidence of publication bias.
  
  
  CONCLUSIONS
  This meta-analysis provides quantitative evidence that, in children, gas cooking increases the risk of asthma and indoor NO2 increases the risk of current wheeze.
authors: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands and Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Weiwei
authors: W
authors: Lin
authors: Bert
authors: B
authors: Brunekreef
authors: Ulrike
authors: U
authors: Gehring
mesh_terms: D016902:Air Pollution, Indoor / Q000706:statistics & numerical data*; D001249:Asthma / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003296:Cooking / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D009585:Nitrogen Dioxide; D016017:Odds Ratio; D012135:Respiratory Sounds
chemical_list: D009585:Nitrogen Dioxide
keywords: Asthma; gas cooking; indoor pollution; infant; review; wheeze