A recent study published in CHEST found that current tobacco smoke exposure (TSE) was not independently associated with airflow obstruction in school-age children, but prenatal TSE may be associated with airflow obstruction in children with asthma.
Stacey-Ann Whittaker Brown, MD, of the division of pulmonary, critical care and sleep medicine, Icahn School of Medicine at Mount Sinai in New York City, and colleagues used logistic regression to determine the association between log-transformed serum cotinine and airflow obstruction in a sample of 2070 children between the age of 6 and 11 who had participated in the National Health and Nutrition Examination Survey between 2007 and 2012.
Airflow obstruction was found in 9.6% of children and was associated with higher body mass index, poorer health, asthma history, higher serum cotinine levels and a history of prenatal TSE exposure. However, after adjusting for confounders, no significant relationship was found between cotinine levels and airflow obstruction.
A total of 262 children (14.4%) had a history of prenatal maternal smoking. Prenatal TSE was associated with airflow obstruction in both the unadjusted and multivariate analyses (odds ratio [OR], 1.67 and 1.69, respectively). Furthermore, in the stratified multivariate analyses, the association was seen in children with asthma (OR, 2.59), but no significant association was found in children who did not have asthma (OR, 1.33). However, the researchers noted that the association between prenatal TSE and overall asthma was considerably weaker and did not reach significance. The association between prenatal TSE and obstruction appears to be primary, with a distinct subset of those patients having asthmatic symptoms.
The researchers argued that although prenatal TSE is not strongly associated with asthma overall, it may define a phenotypic subgroup of individuals who develop asthma as the result of relatively smaller airways.
Study limitations included the inability to determine temporality; incomplete data on birth weight history, which may mediate the relationship between prenatal TSE and airflow obstruction; and the possibility of misclassification bias as prenatal exposure was measured by self-report and collected retrospectively.
Whittaker Brown S-A, Liu B, Taioli E. The relationship between tobacco smoke exposure and airflow obstruction in US children — analysis of the National Health and Nutrition Examination Survey (2007-2012) [published online October 13, 2017]. CHEST. doi:10.106/j.chest.2017.10.003