Attention deficit hyperactivity disorder among children exposed to secondhand smoke: a logistic regression analysis of secondary data

Background: A growing body of literature examines the association of postnatal secondhand smoke exposure with attention deficit hyperactivity disorder (ADHD) in children, but the findings are mixed.

Objective: We compare prevalence of ADHD in children aged 4-15 years who were exposed to postnatal secondhand smoke with prevalence in those who were not exposed, and examine the association of postnatal secondhand smoke exposure with ADHD using both reported and cotinine-measured secondhand smoke exposure.

Design and setting: We analyze secondary data from the 1999-2004 U.S. National Health and Nutrition Examination Surveys.

Participants: Analyses using reported secondhand smoke exposure and cotinine-measured exposure included 6283 and 6033 children aged 4-15 respectively, including 419 and 404 children who either had a reported physician diagnosis of ADHD or were taking stimulant medications.

Methods: The association of secondhand smoke exposure with ADHD was examined by two multiple logistic regression models that differ in the secondhand smoke measurement used.

Results: After controlling for maternal smoking during pregnancy, gender, age, race/ethnicity, preschool attendance, health insurance coverage, and exposure to lead, children with reported secondhand smoke exposure at home were more likely to have ADHD (adjusted odds ratio=1.5, 95% confidence interval: 1.1-2.0) than those who were not exposed. After controlling for these covariates, children with detectable cotinine levels were more likely to have ADHD (adjusted odds ratio=1.8, 95% confidence interval: 1.3-2.5) than those with non-detectable levels.

Conclusions: Our findings suggest that secondhand smoke exposure in children is strongly associated with ADHD independent of other risk factors and this association is robust using both measurements of secondhand smoke exposure. Further research is needed to understand the mechanism underlying this association. Nurses and other healthcare professionals can play an important role in encouraging parents to quit smoking to reduce children's exposure to secondhand smoke and their risk of ADHD.