Association between long-term ambient ozone exposure and attention-deficit/hyperactivity disorder symptoms among Chinese children

Background: Although ozone exposure has neurological toxicity, it remains unclear whether it was associated with an increased risk of attention-deficit/hyperactivity disorders (ADHD) among childhood. Methods: We matched the four-year average ozone concentration with questionnaire data for 35,103 children aged 3–12 years from seven cities in Liaoning, China, 2012–2013. Using mixed-effect logistic regression models, we assessed the association of ozone concentration with multiple ADHD indicators using the Conners Abbreviated Symptom Questionnaire (C-ASQ), including explicit attention-deficit/hyperactivity symptoms (ADHD; score ≥15), attention-deficit/hyperactivity disorder tendencies (ADHD-T; 11 ≤ score ≤14), and attention-deficit/hyperactivity problems (ADHP; score ≥11). Results were also stratified by sociodemongraphics. Results: After adjusting for covariates, we found that each interquartile range (IQR) increase in ozone concentration was associated with an increased risk of ADHD, ADHD-T, and ADHP (P < 0.001) with an odds ratio of 1.12 (95% confidence interval, 1.04–1.21), 1.08 (1.03–1.13), and 1.09 (1.05–1.14), respectively. Additionally, we found greater effect estimates in children who reported longer exercise time (vs those with limited exercise time) with odds ratio of 1.18 (1.07–1.31) vs 1.06 (0.96–1.17) for ADHD, 1.13 (1.06–1.21) vs 1.03 (0.96–1.10) for ADHD-T, and 1.15 (1.08–1.21) vs 1.04 (0.98–1.10) for ADHP. Non-breastfed children were also shown to be more vulnerable to ADHD with an odds ratio of 1.22 (1.09–1.36) compared with 1.06 (0.96–1.16) among the rest. Conclusions: Long-term ozone exposure may be associated with increased ADHD among children. Additional studies are needed to validate our findings and support policies and interventions to address this growing public health concern.