Exposure to Ambient Air Pollution and Myopia Among Children and Adolescents: An Exposure Study Across Three Cities in North-Western China

Abstract

Background: In north-western China, the potential effects of exposure to air pollution on myopia is not clear. The present study aimed at assessing the associations between exposure to ambient air pollution and myopia among children and adolescents living in north-western China.

Methods: This is a population-based, cross-sectional study. Participants included children and adolescents aged four to 22 years who had lived at their current address for no less than three years. Parameters of air pollution included air quality index (AQI), particulate matter (PM2.5, PM10), SO2, NO2, CO, and O3. All the data were obtained from China National Environmental Monitoring Center. The main outcomes were prevalence of myopia and value of SEs and were measured through cycloplegic autorefraction.

Findings: A total of 96,636 individuals (mean [SD] age, 10.835 [3.223] years, 51.6% boys) were included in our study. Among these participants, 62,713 (64.9%) were diagnosed with myopia. Our results indicated that exposure to air pollutants were significantly associated with higher risk of myopia and poorer SEs. Specifically, the ORs for myopia were 1.126 (95%CI: 1.106, 1.145), 1.145 (95%CI: 1.131, 1.159), 1.118 (95%CI: 1.101, 1.133), 1.079 (95%CI: 1.068, 1.091), 1.162 (95%CI: 1.148, 1.177), 1.167 (95%CI: 1.153, 1.181) and 1.019 (95%CI: 1.001, 1.035) for an interquartile range (IQR) increase in AQI, PM2.5, PM10, SO2, NO2, CO and O3, respectively. In SE of right eye, an IQR increase in AQI, PM2.5, PM10, NO2, and CO was associated with a change of -0.207 (95%CI: -0.222, -0.192), -0.179 (95%CI: -0.192, -0.167), -0.146 (95%CI: -0.159, -0.134), -0.110 (95%CI: -0.122, -0.097), and -0.201 (95%CI: -0.213, -0.189), however, associations of poorer SE with SO2 (β=-0.019; 95%CI: -0.066, 0.002) and O3 (β=0.110; 95%CI: -0.007, 0.122) showed little statistical significance. SE of left eye exhibited similar results. In addition, these associations of exposure to air pollutants with prevalence of myopia and value of SEs remained significant after adjusting for covariate factors. Moreover, these associations were only seen in non-high myopia, but not in high myopia. Furthermore, these associations were magnified in participants being girls, living in urban, elder, higher grade, lacking aware of wearing glasses, and living in Xi’an city (provincial capital of Shaanxi).

Interpretation: Our findings suggest that exposure to air pollution was associated with higher risk of myopia and poorer SEs. The negative associations were only seen in non-high myopia, but not in high myopia, and might be modified by participant’s age, sex, grade level, residential area, aware of wearing glasses, and living city. More efforts should be taken to reduce air pollution to protect vision health.

Funding: National Natural Science Foundation of China, China Postdoctoral Science Foundation, Natural Science Foundation of Shaanxi Province, the Key Research Plan of Shaanxi Province, Science and Technology Plan Project of Xi’an, and relative projects in XJTU.

Declaration of Interest: All other authors declare no competing interests.

Ethical Approval: Participants and their guardians were emphasized the noncompulsory nature of participation and signed informed consent forms. The study protocol received approval for research ethics from the Medical Ethics Committee of Xi’an Jiaotong University. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline and was conducted in compliance with the Declaration of Helsinki

Keywords: Air pollution, myopia, North-western China, Children and adolescents, Cross-sectional study