Exposure-response association between outdoor activity time and myopia risk in Chinese children and adolescents: a systematic review and meta-analysis

Clinical Snapshot

Key Findings

• P Value: Not reported in abstract

• Effect Size: Pooled OR = 0.75 (25% risk reduction)

• Primary Outcome: Myopia risk reduction with increased outdoor activity

• Nnt Or Sensitivity: Exposure >2 hours daily: OR = 0.74 (95% CI = 0.69-0.80)

• Confidence Interval: 95% CI = 0.71-0.80

Clinical Application

Two hours daily outdoor activity may be challenging within current educational systems but represents achievable target Relevant for Australian children given rising myopia rates, though cultural and environmental differences from Chinese context require consideration. Aligns with existing Australian guidelines promoting outdoor activity for children's health Children and adolescents at risk of myopia development, particularly in high-prevalence populations

Abstract

BACKGROUND: The prevalence of myopia among Chinese children and adolescents has increased sharply over recent decades, raising concern about modifiable environmental risk factors. Although outdoor activity is widely recognised as protective, the quantitative exposure-response relationship within the Chinese educational context remains incompletely defined. METHODS: A systematic review and meta-analysis were conducted following PRISMA guidelines. Studies examining the association between daily outdoor activity time and myopia risk among Chinese youth were identified from major English and Chinese databases (Web of Science, PubMed, CNKI, and Wanfang) through October 2025. Random-effects meta-analysis was conducted to pool odds ratios (ORs). Prespecified subgroup and sensitivity analyses examined exposure thresholds, study design, and geographic latitude. RESULTS: We included 31 studies comprising 380 215 participants. Greater outdoor activity was consistently associated with lower myopia risk (pooled OR = 0.75; 95% confidence interval (CI) = 0.71-0.80), although substantial heterogeneity was observed (I2 = 94%). Compared with <1 hour per day, outdoor exposure of 1-2 hours (OR = 0.85; 95% CI = 0.79-0.92), 2-3 hours (OR = 0.86; 95% CI = 0.78-0.95), and > 3 hours (OR = 0.74; 95% CI = 0.63-0.87) was associated with reduced risk. When dichotomised at two hours, exposure >2 hours yielded an OR of 0.74 (95% CI = 0.69-0.80). Findings were directionally consistent across study designs and latitude strata. CONCLUSIONS: Greater outdoor activity time is associated with lower myopia risk among Chinese children and adolescents. An approximate daily exposure of around two hours appears to represent a pragmatic benchmark under current educational conditions.

References

1. 1.Dai, J., Wang, J., Bao, Y. H., & Zhang, Y. (2026). Exposure-response association between outdoor activity time and myopia risk in Chinese children and adolescents: a systematic review and meta-analysis. Journal of Global Health, 16, 04122. https://doi.org/10.7189/jogh.16.04122