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 3 ) exposure and childhood sleep disorders is little. This study aims to examine the associations between long-term exposure to O 3 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 3 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 3 , particulate matter with diameters <= 2.5 mm (PM 2.5 ) and nitrogen dioxide (NO 2 ) were 89.0 mu g/m 3 , 42.5 mu g/m 3 and 34.4 mu g/m 3 , respectively. O 3 and NO 2 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 O 3 was positively associated with odds of sleep disorders for all subtypes. For example, each interquartile increment in home-school O 3 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 NO 2 . 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 3 is positively associated with risks of childhood sleep disorders. These associations varied by geographical region of China.