Prenatal tobacco smoke exposure tied to airflow limitation in asthmatic children
Current tobacco smoke exposure (TSE) is not related to airflow obstruction in school-aged children, a study suggests. On the other hand, an association exists between prenatal TSE and airflow obstruction in asthmatic children.
The study included 2,070 children aged 6 to 11 years who participated in the National Health and Nutrition Examination Survey (2007 to 2012). Serum cotinine was used to measure TSE, while spirometry was performed to detect airway obstruction, defined as the ratio of forced expiratory volume in one second and the forced vital capacity (FEV1/FVC) less than the lower limit of normal.
A total of 9.6 percent children had airflow obstruction, which was associated with log-transformed cotinine levels in an unadjusted logistic regression analysis (odds ratio [OR], 1.12; 95 percent CI, 1.02 to 1.23).
In a multivariate analysis including both exposures as covariates, the association between log-transformed cotinine levels and airflow obstruction lost its significance (adjusted OR, 1.07; 0.94 to 1.21). This was observed regardless of asthma status.
On the other hand, self-reported prenatal smoking was associated with airflow obstruction among paediatric asthma patients (adjusted OR, 2.51; 1.08 to 5.79) but not among those without asthma (adjusted OR, 1.08; 0.53 to 2.18).
“The presence of asthma seems to be a significant mediator of the association between prenatal TSE and airflow obstruction … [suggesting that] while prenatal TSE is not strongly associated with asthma overall, it may define a phenotype [seen in those] who develop asthma as a result of relatively smaller airways,” researchers explained, adding that such a theory is supported by previous studies reporting that prenatal TSE is associated with smaller sized airways, and less consistently with airway reactivity. [Am J Respir Crit Care Med 2005; 171:78-82; Pediatr Pulmonol 2001; 32:418-427]
Additional studies exploring potential mediators and confounders of the relationship between prenatal TSE and airflow limitation are warranted, researchers said.