The Relationship Between Tobacco Smoke Exposure and Airflow Obstruction in US Children: Analysis of the National Health and Nutrition Examination Survey (2007-2012)

Background: It has been difficult to determine the individual impact of prenatal and postnatal tobacco smoke exposure (TSE) on childhood lung function, as children are often exposed to both.

Objective: The goal of this study was to determine the association between current TSE and airflow obstruction while adjusting for self-reported prenatal TSE.

Methods: Children aged 6 to 11 years who participated in the National Health and Nutrition Examination Survey (2007-2012) who had serum cotinine levels measured and spirometry performed were included. Logistic regression was used to determine the association between log-transformed serum cotinine level and airflow obstruction while adjusting for confounders; the analysis was then stratified according to asthma status. The final model included both log-transformed serum cotinine level and prenatal exposure as covariates.

Results: The sample consisted of 2,070 children; 9.6% had airflow obstruction. The association between cotinine levels and airflow obstruction was significant in an unadjusted analysis (OR, 1.12 [95% CI, 1.02-1.23]). In the multivariate analysis with both exposures included as covariates, serum cotinine level was not significantly associated with airflow obstruction (OR_adj, 1.07 [95% CI, 0.94-1.21]), and no association was seen in children with asthma and nonasthmatic children. Prenatal smoking was associated with airflow obstruction in children with asthma (OR_adj, 2.51 [95% CI, 1.08-5.79]) but not in nonasthmatic children (OR_adj, 1.08 [95% CI, 0.53-2.18]).

Conclusions: Current TSE was not independently associated with airflow obstruction in school-aged children. Prenatal TSE was associated with airflow obstruction in children with asthma. Repeated studies into potential mediators and confounders of this relationship are needed.