Association of Autism Spectrum Disorders with Secondhand Smoke Exposure

Abstract

Objectives: Second Hand Smoke (SHS) exposure has been associated with neurobehavioral disorders among children. Our objective was to evaluate relationship between SHS and Autism Spectrum Disorders (ASD) in children in the United States (US) and to assess sex distribution of ASD when exposed to SHS. Methods: Parent-reported postnatal SHS exposure inside and outside the house and ASD was examined in children younger than 12 years using the 2011-2012 National Survey on Children's Health. The physician diagnosis of current ASD as reported by the parents was used as the outcome variable. Multiple logistic regression models adjusted for potential confounders and complex survey designs were used to assess associations. Results: Of the 61,076 children (equivalent to weighted 49 million children), 20% had SHS exposure, and 4% were exposed to SHS inside the house, corresponding to a weighted 10 million and 2 million children, respectively. For all children irrespective of SHS exposure status, ASD weighted prevalence and 95% confidence interval was 1.81% (1.56, 2.05) equivalent to 1 in 55 children. Weighted prevalence of ASD in children exposed to SHS outside the house was 2.26% (1.64, 2.87), and 2.57% (1.26, 3.88) with SHS inside the house, compared to 1.67% (1.39, 1.93) in those without SHS exposure (p<0.01). Girls constituted 48% of the total sample. Girls exposed to SHS had 21% higher risk of age adjusted ASD compared to unexposed girls (OR=1.21, 95% CI: 1.01, 1.44, p=0.038). With covariate adjustment, girls had 22% higher risk of ASD when exposed to SHS in comparison to unexposed girls (OR=1.22, 95% CI: 1.02, 1.46, p=0.034). In addition, increasing age of the child, unstable family structure (step or single parent) and mother's age were significantly related to ASD in girls. In boys, increasing age was the only variable significantly associated with ASD and no relationship with SHS was noted. Conclusions: US girls experience a higher prevalence of SHS related ASD.