A study on the association between uncorrected visual acuity and 24-h activity behaviors among middle school students in Tianjin

Objective This study aims to investigate the independent and combined effects of 24-h activity behaviors—including sedentary behavior, light-intensity physical activity, moderate-to-vigorous physical activity (MVPA), and sleep—on myopia among middle school students in Tianjin. The findings are intended to inform strategies for myopia prevention and control, as well as the development of evidence-based physical activity prescriptions for children and adolescents. Methods A stratified cluster sampling method is used to recruit 1,212 middle school students from five districts in Tianjin. Participants wore accelerometers (ActiGraph GT3X+) for seven consecutive days to objectively monitor their 24-h activity patterns. Ophthalmologic examinations are conducted to assess Uncorrected Visual Acuity. LASSO regression analysis is employed to explore the associations between activity behaviors and uncorrected visual acuity. Given the inherent interdependence and multicollinearity among time-based 24-h activity behaviors, LASSO regression was employed to enable robust variable selection and improve model stability compared with traditional regression approaches. Results (1) Prevalence of Myopia: the overall myopia detection rate is 73.3%, with a higher prevalence among girls. Severe visual impairment accounted for the highest proportion (38.0%), and the prevalence increased significantly with grade level, reaching 39.2% in the third year of middle school. (2) 24-h Activity Behaviors: Daily sedentary time (572.08 ± 51.16 min) significantly exceeded recommended guidelines. Both MVPA (38.74 ± 15.36 min) and sleep duration (453.10 ± 47.18 min) are below the recommended levels. (3) Associations with Uncorrected Visual Acuity: LASSO regression indicated that MVPA (β = 0.162) and sleep duration (β = 0.131) are positively associated with uncorrected visual acuity, suggesting protective effects against myopia. In contrast, sedentary behavior (β = −0.106) and light-intensity physical activity (β = −0.078) are negatively associated with uncorrected visual acuity, implying an increased risk of myopia. Conclusion Twenty-four-hour activity behaviors are significantly associated with uncorrected visual acuity in middle school students. Higher MVPA and longer sleep are associated with better visual acuity, whereas greater sedentary behavior and light-intensity physical activity are associated with poorer visual outcomes.