Long-term exposure to ozone and sleep disorders in children: A multicity study in China

Evidence regarding the link between long-term ambient ozone (O₃) exposure and childhood sleep disorders is little. This study aims to examine the associations between long-term exposure to O₃ and sleep disorders in children. We conducted a population-based cross-sectional survey, including 185,428 children aged 6-18 years in 173 schools across 14 Chinese cities during 2012 and 2018. Parents or guardians completed a checklist using Sleep Disturbance Scale for Children, and O₃ exposure at residential and school addresses was estimated using a satellite-based spatiotemporal model. We used generalized linear mixed models to test the associations with adjustment for factors including socio-demographic variables, lifestyle, meteorology and multiple pollutants. Mean concentrations of O₃, particulate matter with diameters ≤2.5 mm (PM_2.5) and nitrogen dioxide (NO₂) were 89.0 μg/m³, 42.5 μg/m³ and 34.4 μg/m³, respectively. O₃ and NO₂ concentrations were similar among provinces, while PM_2.5 concentration varied significantly among provinces. Overall, 19.4% of children had at least one sleep disorder. Long-term exposure to O₃ was positively associated with odds of sleep disorders for all subtypes. For example, each interquartile increment in home-school O₃ concentrations was associated with a higher odds ratio for global sleep disorder, at 1.22 (95% confidence interval: 1.18, 1.26). Similar associations were observed for sleep disorder subtypes. The associations remained similar after adjustment for PM_2.5 and NO₂. Moreover, these associations were heterogeneous regionally, with more prominent associations among children residing in southeast region than in northeast and northwest regions in China. We concluded that long-term exposure to O₃ is positively associated with risks of childhood sleep disorders. These associations varied by geographical region of China.