Modifiable Behavioral Determinants of Myopia Occurrence and Severity among Primary Schoolchildren in Vietnam

Introduction Childhood myopia has become a major public health concern worldwide. This study investigated the prevalence, severity, and behavioral factors associated with myopia among primary schoolchildren in Nghe An province, Vietnam. Methods A school-based cross-sectional study was conducted among 9,498 boys and girls aged 6-10 years from 10 primary schools. Distance visual acuity screening was followed by refractive assessment using autorefractometry and retinoscopy. Behavioral and familial information was collected using structured questionnaires. Multivariable and ordered logistic regression models accounting for school clustering were used to identify factors associated with myopia and its severity. Results The prevalence of myopia was 20.7% (1,966/9,498); 68.9%, 25.1%, and 6.0% had low, moderate, and high myopia, respectively. A near-work distance ≥30 cm was associated with lower odds of myopia (adjusted odds ratio [aOR] 0.22, 95% CI 0.19-0.26), whereas extra study time >2 hours/day (aOR 1.63, 95% CI 1.32-2.00) and screen exposure ≥2 hours/day (aOR 1.44, 95% CI 1.26-1.65) increased the risk. Outdoor activity ≥3 hours/day was protective (aOR 0.48, 95% CI 0.40-0.57). The same behavioral factors were also independently associated with greater myopia severity. Discussion These findings support previous evidence that modifiable lifestyle behaviors influence both myopia occurrence and severity. However, causal relationships cannot be inferred because of the cross-sectional design. Conclusion Reading distance, extra study time, screen exposure, and outdoor activity were independently associated with myopia occurrence and severity. Promoting healthy visual habits and increasing outdoor activity should be prioritized in school-based myopia prevention programs.