Baseline Characteristics of Children in the Intervention and Control Groups
myopia
REGRESSION, EVENTS, MYOPIA
Distributions of continuous (age, height, weight, and sleep time), binary (sex), and ordered categorical (outdoor time, screen time, and study or reading time) variables between the intervention and control groups were compared using linear, logistic, and ordinal logistic regression models, respectively. All analyses took cluster effects within schools into account.Missing values were outdoor time and screen time (n = 2), study or reading time (n = 23), and sleep time (n = 18).Overall, 4548 (96.3%) of the 4724 scheduled extracurricular physical activity sessions were successfully implemented. Some sessions could not be implemented due to inclement weather (144 [3.0%]) or school events (32 [0.7%]). A total of 3626 sessions (79.7%) were implemented outdoors, whereas 518 sessions (11.4%) were implemented in semiopen spaces and 404 (8.9%) occurred indoors (eTables 1 and 2 in At baseline, mathematics scores (mean difference, −0.59; 95% CI, −5.13 to 3.95), overall physical fitness scores (mean difference, 0.73; 95% CI, −0.86 to 2.33), and myopia prevalence (mean difference, −0.57; 95% CI, −19.64 to 18.49) were similar in the 2 groups (