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.

Asthma, wheeze, gas cooking, indoor pollution, infant, review