Associations of Long-Term Exposure to Ambient Air Pollution, Physical Activity and Insomnia in China's Adults

Abstract

Background: Insomnia is linked with poor quality of life and many adverse health outcomes. Air pollution is a potential environmental risk for sleep disturbance. However, the evidence is very limited in China. On the other hand, physical activity (PA) is a preventive behavior that can improve insomnia, but whether PA mitigates the negative impact of air pollution on insomnia is unknown. Therefore, we examined the association between air pollution and insomnia, as well as PA’s modification effect of on this association. Methods: We obtained data from the baseline of China Multi-Ethnic Cohort (CMEC) survey, conducted from 2018 to 2019. We included 70668 respondents (out of 99,556). We assessed insomnia symptoms using any of the following self-reported symptoms, 1) difficulty initiating sleep or staying asleep, 2) waking up early in the morning, and 3) taking medication to help with sleep. Using satellite data, we estimated the residence-specified, three-year average PM1, PM2.5, PM10 (particulate matter with aerodynamic diameters of ≤1 μm, ≤2.5 μm and 10 μm, respectively), O3 (ozone), and NO2 (nitrogen dioxide) concentrations. We established the associations between air pollutants and insomnia symptoms through logistic regression. We evaluated the modification impact of total and domain-specific PA (leisure, occupation, housework, transportation) by introducing an interaction term into the model. Findings: After adjusting for potential confounders, we found that long-term exposure to PM1, PM2.5, PM10, and O3 is significantly associated with insomnia symptoms, with ORs (95% confidence interval [CI]) of 1.09 (1.03-1.16), 1.11 (1.07-1.15), 1.07 (1.05-1.10) and 1.15 (1.11-1.20), respectively. As total PA increased, the ORs of air pollution for insomnia tended to decrease and then rise. We observed varying modification effects of domain-specific PA. Transportation PA generally had no significant modification impact on the association between air pollution and insomnia. With an increase in leisure PA, the ORs for PM2.5 and PM10 significantly declined. However, we detected increased ORs of air pollutants in relation to insomnia among participants with higher levels of occupational and housework PA. Interpretation: Long-term exposure to higher concentrations of PM1, PM2.5, PM10, and O3 increases the risk of insomnia symptoms. Moderate to high levels of leisure PA alleviate the harmful effects of air pollution on insomnia, while high levels of occupation and housework PA intensify the effects. Funding Statement: The National Key Research and Development Program of China (Grant No. 2017YFC0907303), the Sichuan Science and Technology Program (Grant No. 2019YFS0274), and the National Natural Science Foundation of China (Grant No. 81773548). Declaration of Interests: The authors declare that they have no conflicts of interests. Ethics Approval Statement: We received approval from the Sichuan University Medical Ethical Review Board (K2016038).