The influence of near work on myopic refractive change in urban students in Beijing: a three-year follow-up report

To investigate the influence of daily activities on myopic refractive change and myopic onset in Chinese urban students. The Beijing Myopia Progression Study was a 3-year cohort study. Cycloplegic refraction and a daily activity questionnaire were assessed at baseline and at follow-up examinations. Refractive change was defined as the difference in cycloplegic spherical equivalent (SE) between the final follow-up and baseline. 386 students were initially enrolled in the baseline study. At the final follow-up, 222 students (57.5 %) with completed refractive error and daily activity data were analyzed. These students spent 0.32 +/- 2.33 h/day more on near work (p = 0.04), and 0.21 +/- 1.31 h/day less on outdoor leisure (p = 0.02), than they did at baseline. In the multivariate analysis, the younger among the secondary students (beta = 0.06, p < 0.001), and those with more near work hours at baseline (beta = -0.028, p = 0.033), exhibited more myopic refractive change. However, myopic refractive change was not found to be significantly associated with near work hours in the primary students, or with time spent outdoors, in either school level. After stratifying the activity hours into quartile groups, students with a greater near work load at baseline (trend P = 0.03) exhibited a greater myopic refractive change and had a higher risk to develop myopia (hazard ratio, 95 % confidence interval: 5.19, 1.49-18.13), after adjusting for the confounders. However, no significant association was found related to outdoor activity. In this cohort, children with a greater near work load at baseline exhibited more myopic refractive change and were also more likely to develop myopia. The protective effect of outdoor activity on myopic refractive change was not observed.