Outdoor activity and myopia progression in children: A follow-up study using mixed-effects model.

Purpose The purpose of this study was to determine the influence of outdoor activity on myopia progression. Methods It was a hospital-based longitudinal prospective observational study. Children between 7 and 14 years of age with a myopia of - 0.5 D or worse were included. Myopia progression was evaluated by cycloplegic refraction, every 6 months for 18 months. Parents were asked to record the daily outdoor activity of the child in hours per day at school and at home during weekdays and at weekends separately, based on which the daily outdoor activity score was calculated. The independent variables measured included age and gender of the participant, degree of myopia, and the daily outdoor activity score. Progression of myopia was defined as an increase in the spherical equivalent (SE) over 18 months. The magnitude of the association was determined by two mixed-effects models. Results A total of 495 participants (250 males and 245 females) completed three visits during the study period. On taking age groups and paired observations as a random effect and adding SE at the last visit as the random slope in Model 1, each unit increase in outdoor activity had a negative effect on change in SE of - 0.01 (-0.02 to 0.00; P = 0.045). The same inverse relationship between outdoor activity and absolute SE as - 0.06 (-0.07 to - 0.03; P < 0.001) is estimated in Model 2. Conclusion The study demonstrates a statistically significant inverse relationship between outdoor activity and myopia.