Outdoor Activity and Myopia among Primary Students in Rural and Urban Regions of Beijing

Objective To assess associations among outdoor activity, ocular biometric parameters, and myopia among grade 1 and grade 4 primary students in Beijing. Design School-based, cross-sectional study. Participants A total of 382 grade 1 and 299 grade 4 children participated in the study. Methods The children underwent a comprehensive eye examination, including ocular biometry by optical low-coherence reflectometry and noncycloplegic refractometry. Parents and children participated in a detailed interview, including questions on time spent indoors and outdoors. Main Outcome Measures Factors associated with myopia. Results The study included 681 children, with 382 (56.1%) students from grade 1 (mean age, 6.3±0.5 years; range, 5–8 years) and 299 students from grade 4 (mean age, 9.4±0.7 years; range, 8–13 years); 370 students (54.3%) lived in the urban region. The mean daily time spent outdoors was 1.6±0.8 hours (range, 0.5–5.1 hours). In multivariate analysis, axial length was significantly associated with older age (P<0.001; standardized β coefficient, 0.28), taller body height (P = 0.001; β, 0.18), maternal myopia (P = 0.03; β, 0.09), and urban region of habitation (P<0.001; β, −0.21), or alternatively to the region of habitation, with less time spent outdoors (P = 0.001; β, −0.16) and more time spent indoors studying (P = 0.02; β, 0.10). The axial length-to-corneal curvature radius ratio was associated with older age, urban region of habitation, maternal and paternal myopia, and paternal level of education. Presence of myopia (defined as refractive error ≤−1 diopters in the right eye) was associated with older age (P<0.001; odds ratio [OR], 1.45; 95% confidence interval [CI], 1.24–1.69), maternal myopia (P<0.001; OR, 2.99; 95% CI, 1.94–5.35), and urban region of habitation (P<0.001; OR, 0.17; 95% CI, 0.11–0.26), or alternatively to the region of habitation, with less time spent outdoors (P<0.001; OR, 0.32; 95% CI, 0.21–0.48) and more time spent indoors studying (P<0.001; OR, 1.38; 95% CI, 1.09–1.75). Conclusions Less outdoor activity, more indoor studying, older age, maternal myopia, and urban region of habitation were associated with longer ocular axial length and myopia in grade 1 and grade 4 primary school children in Greater Beijing. Remaining outdoors more (e.g., during school) may reduce the high prevalence of myopia in the young generation in Beijing. Financial Disclosure(s) The author(s) have no proprietary or commercial interest in any materials discussed in this article. To assess associations among outdoor activity, ocular biometric parameters, and myopia among grade 1 and grade 4 primary students in Beijing. School-based, cross-sectional study. A total of 382 grade 1 and 299 grade 4 children participated in the study. The children underwent a comprehensive eye examination, including ocular biometry by optical low-coherence reflectometry and noncycloplegic refractometry. Parents and children participated in a detailed interview, including questions on time spent indoors and outdoors. Factors associated with myopia. The study included 681 children, with 382 (56.1%) students from grade 1 (mean age, 6.3±0.5 years; range, 5–8 years) and 299 students from grade 4 (mean age, 9.4±0.7 years; range, 8–13 years); 370 students (54.3%) lived in the urban region. The mean daily time spent outdoors was 1.6±0.8 hours (range, 0.5–5.1 hours). In multivariate analysis, axial length was significantly associated with older age (P<0.001; standardized β coefficient, 0.28), taller body height (P = 0.001; β, 0.18), maternal myopia (P = 0.03; β, 0.09), and urban region of habitation (P<0.001; β, −0.21), or alternatively to the region of habitation, with less time spent outdoors (P = 0.001; β, −0.16) and more time spent indoors studying (P = 0.02; β, 0.10). The axial length-to-corneal curvature radius ratio was associated with older age, urban region of habitation, maternal and paternal myopia, and paternal level of education. Presence of myopia (defined as refractive error ≤−1 diopters in the right eye) was associated with older age (P<0.001; odds ratio [OR], 1.45; 95% confidence interval [CI], 1.24–1.69), maternal myopia (P<0.001; OR, 2.99; 95% CI, 1.94–5.35), and urban region of habitation (P<0.001; OR, 0.17; 95% CI, 0.11–0.26), or alternatively to the region of habitation, with less time spent outdoors (P<0.001; OR, 0.32; 95% CI, 0.21–0.48) and more time spent indoors studying (P<0.001; OR, 1.38; 95% CI, 1.09–1.75). Less outdoor activity, more indoor studying, older age, maternal myopia, and urban region of habitation were associated with longer ocular axial length and myopia in grade 1 and grade 4 primary school children in Greater Beijing. Remaining outdoors more (e.g., during school) may reduce the high prevalence of myopia in the young generation in Beijing.