Translational Pediatrics · 5 authors, 4 centres
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Higher serum 25-hydroxyvitamin D levels and more leisure-time exercise are associated with lower rates of myopia in children and adolescents. Female gender, higher poverty income ratio, and higher body mass index are linked to increased myopia risk. These findings support the vitamin D hypothesis and highlight the importance of outdoor activity for myopia prevention.
**Background:** Myopia is a multifactorial vision disorder with increasing global prevalence, projected to affect over 5 billion people by 2050. Prior studies on the relationship between vitamin D levels and myopia in children have been inconsistent and limited by small sample sizes. This study aimed to clarify the association using a large, nationally representative sample.
**Methods:** Data were extracted from the National Health and Nutrition Examination Survey (NHANES) database for participants under 19 years old from 2001 to 2008. Myopia was defined as spherical equivalent ≤ -1.0 D measured by autorefractor. Serum 25-hydroxyvitamin D [25(OH)D] was quantified using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Covariates included age, sex, race, education, body mass index (BMI), poverty income ratio (PIR), and leisure-time exercise (minutes/week). Stepwise logistic regression was used in three models: Model 1 (unadjusted), Model 2 (adjusted for sex, age, education, ethnicity), and Model 3 (further adjusted for leisure-time exercise). Subgroup analyses by sex were also performed.
**Key Results:** A total of 6,814 children (49.5% girls; mean age 14.9±1.85 years) were included. The myopia group (n=2,905) had significantly lower mean serum 25(OH)D levels (54.1±20.5 ng/mL) compared to the non-myopia group (56.0±21.1 ng/mL, P<0.001). In Model 1, there was a negative dose-response relationship: compared to the lowest quartile (Q1), the odds ratio (OR) for myopia in Q4 was 0.78 (95% CI: 0.65–0.95, P for trend=0.02). After full adjustment (Model 3), the highest quartile remained significantly associated with lower myopia risk (OR=0.98, 95% CI: 0.77–0.99, P<0.05), though the dose-response trend was no longer significant (P for trend=0.14). In sex-stratified analyses, high serum 25(OH)D was negatively correlated with myopia in both males (OR=0.88, 95% CI: 0.6–0.99) and females (OR=0.97, 95% CI: 0.68–0.99). Additional covariates associated with higher myopia risk included female sex (OR=1.12, 95% CI: 1.01–1.24, P=0.03), higher PIR (OR=1.08, 95% CI: 1.04–1.11, P<0.001), and higher BMI (OR=1.19, 95% CI: 1.11–1.27, P<0.001). White ethnicity (OR=0.78, 95% CI: 0.68–0.90, P<0.001) and more leisure-time exercise (OR=0.94, 95% CI: 0.92–0.97, P=0.02) were protective.
**Clinical Implications:** These findings suggest that higher serum 25(OH)D levels and increased leisure-time exercise are associated with lower myopia rates in children and adolescents, supporting the vitamin D hypothesis for myopia prevention. The study also identifies female sex, higher socioeconomic status (PIR), and higher BMI as risk factors. While the cross-sectional design precludes causal inference, the results reinforce public health recommendations for outdoor activity and adequate vitamin D status to potentially reduce myopia burden. Further prospective studies are needed to confirm causality and explore underlying mechanisms.