Meta-analysis of the association between secondhand smoke exposure and physician-diagnosed childhood asthma

Nicotine Tob Res. 2013 Sep;15(9):1475-83. doi: 10.1093/ntr/ntt033. Epub 2013 Mar 28.


Introduction: Studies suggest an association between secondhand smoke exposure and the development of childhood asthma. Several countries are considering legislation to protect children from exposure.

Methods: A systematic review was conducted using MEDLINE, Embase, PubMed, and Web of Knowledge databases and a random effects meta-analysis was undertaken. Heterogeneity was assessed using the I (2) test. Publication and small study biases were examined visually using a funnel plot and tested formally using Egger test. Univariate and multivariate meta-regression analyses were undertaken, including a subgroup analysis of cohort studies to examine the effect of duration of follow-up.

Results: Twenty relevant studies were identified (14 cross-sectional, 4 cohort, and 2 case-control) and provided 31 estimates of effect size. The pooled odds ratio was 1.32 (95% CI: 1.23, 1.42, p < .001). There was moderate heterogeneity (I (2) = 74.2%, p < .001). On multivariate meta-regression analysis, effect size estimates were significantly higher for case-control studies (p = .042) and those using self-reported exposure to secondhand smoke (p = .050). There was no evidence of significant publication or small study bias (Egger test, p = .121).

Conclusions: There is now consistent evidence of a modest association between secondhand smoke and physician-diagnosed childhood asthma. These results lend support to continued efforts to reduce childhood exposure to secondhand smoke.

Publication types

  • Meta-Analysis
  • Review
  • Systematic Review

MeSH terms

  • Adolescent
  • Asthma / chemically induced
  • Asthma / epidemiology*
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Male
  • Odds Ratio
  • Tobacco Smoke Pollution / adverse effects*


  • Tobacco Smoke Pollution