The increasing prevalence of myopia in junior high school students in the Haidian District of Beijing, China: a 10-year population-based survey

Abstract

Background: Myopia is a leading cause of preventable blindness. Although, multiple cross-sectional epidemiological studies have confirmed that there is a high prevalence of myopia in high school-aged students in China. However, few longitudinal studies have been performed to assess junior high school students. In the present study, we investigate changes in the prevalence of myopia in third year junior high school (grade 9) students in the Haidian District of Beijing, China, from 2006 to 2015.

Methods: A retrospective, longitudinal cohort study was performed over 10 years. A total of 37,424 third-year middle school (grade 9) students from 8 junior high schools in Haidian district, Beijing, were included. Participants underwent a comprehensive ophthalmic examination in which they were evaluated using autorefraction under cycloplegia and submitted to retinoscopy to assess accuracy. According to the spherical equivalent refraction (SER) of the right eye, subjects were separated into the following groups: non-myopia, -0.5 ≤ SER diopters (D); low myopia, -3.0 ≤ SER < -0.5 D; moderate myopia, -6.0 ≤ SER < -3.0 D; and high myopia, SER > -6.0 D. The following characteristics were measured: refractive error; the proportion of subjects with non- myopia, low myopia, moderate myopia and high myopia; and the difference in the prevalence of myopia between male and female subjects.

Results: From 2006 to 2015, the prevalence of non-myopia (from 44.05% to 34.52%) and low myopia (from 32.27% to 20.73%) decreased, while the prevalence of moderate myopia (from 19.72% to 38.06%) and high myopia (from 3.96% to 6.69%) significantly increased. For refractive error, the worse eye was -2.23 ± 2.42 D (median, -1.75; range - 12.75 to +8.50) in 2006 and -3.13 ± 2.66 D (median, -2.75; range - 12.75 to +8.50) in 2015. When the entire population was considered, the overall prevalence of myopia increased from 55.95% in 2005 to 65.48% in 2015. There was a significant positive relationship between the year and the prevalence of myopia in both girls and boys. Girls were more likely than boys to have myopia (odds ratio, 1.43 [95% CI, 1.14-1.96]), especially moderate myopia, and the prevalence of moderate and high myopia were higher in girls than in boys.

Conclusions: During the last 10 years, the prevalence of myopia significantly increased on an annual basis among third-year junior high school students in the Haidian District of Beijing, China. The total prevalence of myopia was significantly higher in girl than in boy participants. The refractive status of this age group deserves particular attention.

Keywords: Beijing; Haidian District; Junior high school; Myopia; Prevalence.

Fig. 1

Prevalence of non-myopia and myopia in the whole group. a The incidence of non-myopia, low myopia, moderate myopia, and high myopia are presented. The total myopia group was defined using a refractive error > −0.50 diopters and included students with low myopia, moderate myopia, and high myopia. Overall, the prevalence of myopia increased significantly. b The total myopia group was defined using a refractive error > −3.0 diopters and included the moderate myopia and high myopia groups

Fig. 2

Prevalence of myopia in boys and girls. In a univariate analysis, girls were significantly more myopic and more likely to have myopia than boys from 2006 to 2015

Fig. 3

Prevalence of myopia in each myopic group in boys and girls. a and b, the prevalence of non-myopia, low myopia, moderate myopia, and high myopia in boys. c and d, the prevalence of non-myopia, low myopia, moderate myopia, and high myopia in girls

Fig. 4

The prevalence of each myopia subgroup in girls and boys. a, b, c and d represent non-myopia, low myopia, moderate myopia, and high myopia prevalence separately in boys and girls. The results indicate that females are more likely than males to develop moderate myopia