The association between time spent outdoors and myopia in children and adolescents: a systematic review and meta-analysis.

OBJECTIVE: To summarize relevant evidence investigating the association between time spent outdoors and myopia in children and adolescents (up to 20 years). DESIGN: Systematic review and meta-analysis. PARTICIPANTS: Results from 7 cross-sectional studies were pooled in a meta-analysis. A further 16 studies (8 cross-sectional not meeting criteria for meta-analysis; 7 prospective cohort studies; 1 randomized, controlled trial [RCT]) were reported in the systematic review. METHODS: The literature search included 4 databases (Medline, Embase, Web of Science, and Cochrane Central Register of Controlled Trials [CENTRAL]), and reference lists of retrieved studies. Estimates of association were pooled using random effects meta-analysis. We summarized data examining the association between time spent outdoors and prevalent myopia, incident myopia, and myopic progression. MAIN OUTCOME MEASURES: Pooled odds ratios (ORs) and 95% confidence intervals (CIs) for myopia for each additional hour spent outdoors per week from a meta-analysis. RESULTS: The pooled OR for myopia indicated a 2% reduced odds of myopia per additional hour of time spent outdoors per week, after adjustment for covariates (OR, 0.981; 95% CI, 0.973-0.990; P