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

Evidence regarding the link between long-term ambient ozone (O) exposure and childhood sleep disorders is little. This study aims to examine the associations between long-term exposure to O 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 O 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 O, particulate matter with diameters ≤2.5 mm (PM) and nitrogen dioxide (NO) were 89.0 μg/m, 42.5 μg/m and 34.4 μg/m, respectively. O and NO concentrations were similar among provinces, while PM concentration varied significantly among provinces. Overall, 19.4% of children had at least one sleep disorder. Long-term exposure to O was positively associated with odds of sleep disorders for all subtypes. For example, each interquartile increment in home-school O 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 and NO. 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 O is positively associated with risks of childhood sleep disorders. These associations varied by geographical region of China.