In utero smoke exposure and impaired response to inhaled corticosteroids in children with asthma

Background: Few studies have examined the effects of in utero smoke exposure (IUS) on lung function in children with asthma, and there are no published data on the impact of IUS on treatment outcomes in children with asthma. Objectives: To explore whether IUS exposure is associated with increased airway responsiveness among children with asthma and whether IUS modifies the response to treatment with inhaled corticosteroids (ICSs). Methods: To assess the impact of parent-reported IUS exposure on airway responsiveness in childhood asthma, we performed a repeated-measures analysis of methacholine PC20 data from the Childhood Asthma Management Program, a 4-year, multicenter, randomized, double-masked, placebo-controlled trial of 1041 children age 5 to 12 years comparing the long-term efficacy of ICS with mast cell stabilizing agents or placebo. Results: Although improvement was seen in both groups, children with asthma and IUS exposure had on average 26% less of an improvement in airway responsiveness over time compared with unexposed children (P = .01). Moreover, while children who were not exposed to IUS who received budesonide experienced substantial improvement in PC20 compared with untreated children (1.25-fold increase; 95% CI, 1.03-1.50; P = .02), the beneficial effects of budesonide were attenuated among children with a history of IUS exposure (1.04-fold increase, 95% CI, 0.65-1.68; P = .88). Conclusion: In utero smoke exposure reduces age-related improvements in airway responsiveness among children with asthma. Moreover, IUS appears to blunt the beneficial effects of ICS use on airways responsiveness. These results emphasize the importance of preventing this exposure through smoking cessation counseling efforts with pregnant women. (J Allergy Clin Immunol 2010;126:491-7.)