Hyperactivity disorder in children related to traffic-based air pollution during pregnancy

Abstract Background Attention-deficit hyperactivity disorder (ADHD) is one of the most common neurobehavioral disorders in childhood globally. Between the two components of ADHD, hyperactivity disorder is more prevalent than inattention during early childhood. Although some investigations have implied a relationship between childhood ADHD and gestational exposure to air pollution, the evidence is limited. The aim of this study was to investigate the association between gestational exposure to air pollution exposure and hyperactivity disorder in childhood in a population-based birth cohort. Methods The Taiwan Birth Cohort Study started from all deliveries of Taiwan in 2005 by the birth registry, and recruited representative 12% of all mother–infant pairs by two-stage stratified sampling. At age of 8 years in each child, their main caretaker was inquired whether the child had ever received a hyperactivity diagnosis from a physician or other specialist, like special needs educator. Exposure to air pollutants during gestation was estimated through ordinary kriging based on data from air monitoring stations of Environmental Protection Administration, Taiwan. Logistic regression was used to determine adjusted odds ratios (aORs) of hyperactivity disorder in relation to air pollutants. Results A total of 16,376 mother–infant pairs were included in the final analysis; 374 (2.3%) of the children had received a diagnosis of hyperactivity before 8 years of age. The occurrence of hyperactivity was significantly related to prenatal nitrogen oxide (NOx), but not to particulate matter 10 μm or less in diameter or sulfur dioxide. Further analysis to separate effects by nitrogen dioxide (NO2) and/or nitric oxide (NO) showed that only NO was significantly related to hyperactivity [aOR per interquartile range (3.14 ppb): 1.26, 95% confidence interval: 1.09–1.46]. Conclusions In conclusion, our study found childhood hyperactivity disorder to be positively associated with prenatal NO exposure. Further confirmation on potential hazardous effects of NO and investigation on potential mechanisms are warranted.