Association between serum 25-hydroxyvitamin D level and myopia in children and adolescents: a cross-sectional study

Background: Prior reports have indicated an inconsistent relationship between vitamin D levels and myopia in children and adolescents with limited sample size. This study was undertaken to further clarify this relationship with a repeated cross-section study. Methods: The National Health and Nutrition Examination Survey (NHANES) database with samples <19 years old was utilized. Data on rates of myopia (spherical equivalent less than or equal to -1.0 D), serum 25-hydroxyvitamin D [25(OH)D] level (high performance liquid chromatography), and other key variables were extracted and analyzed. Three models were utilized to evaluate the dose response of vitamin D levels using stepwise logistic regression. Logistic regressions for sex subgroups and other covariates were also performed, and Forest plots were drawn. Results: Data were available from 6,814 children (49.5% girls; mean age: 14.9 +/- 1.85 years). The myopia and non-myopia differed in serum 25(OH)D level, gender, race, poverty income ratio (PIR), and body mass index (BMI). Serum 25(OH)D levels were negatively correlated with myopia [odds ratio (OR) =0.98, 95% confidence interval (CI): 0.77-0.99, P<0.05] regardless of sex. Although the relationship did not appear to be linear, there was a dose effect with higher serum 25(OH)D levels linked with lower rates of myopia. In addition, rates of myopia were increased in females compared with males (OR =1.12, 95% CI: 1.01-1.24, P=0.03), those with a high PIR (OR =1.08, 95% CI: 1.04-1.11, P<0.001), and those with high 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 leisuretime exercise (OR =0.94, 95% CI: 0.92-0.97, P=0.02) were associated with lower rates of myopia. Conclusions: These findings indicate that higher serum 25(OH)D levels and increased amounts of leisuretime exercise are associated with lower rates of myopia in this group of children and adolescents. Meanwhile, female gender, high PIR level, and high BMI were associated with greater rates of myopia. The findings indicated that children and adolescents needed leisure-time exercise to lower the risk of myopia.