Association between household secondhand smoke exposure and ADHD in US children aged 4–15 years: Evidence from NHANES 1999–2004
INTRODUCTION Household tobacco smoke (or secondhand smoke, SHS) exposure is a common type of environmental exposure among children, and it may be associated with the development of attention deficit hyperactivity disorder (ADHD); however, current findings remain inconsistent. This study aimed to examine the association between household SHS exposure and ADHD among US children, and to provide an epidemiological foundation for ADHD prevention and tobacco-control interventions targeting pediatric populations. METHODS This is a secondary analysis of pooled secondary data from the National Health and Nutrition Examination Survey (NHANES) 1999–2004. ADHD cases were identified through questionnaire-based assessments, and participants were categorized into exposed and non-exposed groups according to whether or not any household member smoked inside the home. Weighted multivariate logistic regression models were employed to evaluate the association between household SHS exposure and ADHD. In addition, subgroup and sensitivity analyses were conducted. RESULTS A total of 6790 children were included in the analysis, of whom 452 (7.97%) were classified as having ADHD. The prevalence of household SHS exposure was significantly higher among children with ADHD compared to those without (36.25% vs 22.77%, p<0.001). After adjustment for multiple confounding variables, household SHS exposure remained significantly associated with ADHD (OR=1.583; 95% CI: 1.166–2.150). Subgroup analyses stratified by sex, age, race, poverty–income ratio (PIR), body mass index (BMI), and birth weight showed that the association remained generally consistent across all strata (all p for interaction >0.05). Sensitivity analyses further confirmed the positive association between household SHS exposure and ADHD (all p<0.05). CONCLUSIONS Household SHS exposure was significantly associated with ADHD among US children within our cross-sectional analysis. Future prospective investigations are required to clarify the causal relationship underlying this association.