25-hydroxy Vitamin D Status in Healthy Korean School Children and Adolescents: Striking Difference in Prevalence of Vitamin D Deficiency with School Grade and Season

Purpose: The aim of this study was to investigate the prevalence of vitamin D deficiency according to school grade and season in healthy Korean children and adolescents. Method: We screened for vitamin D deficiency using serum 25-hydroxyvitamin D (25-OHD) combined with anthropometric and laboratory findings. Findings: Vitamin D deficiency was present in 72.3% of study subjects and prevalence of vitamin D deficiency was higher in girls than in boys (76.6 vs 66.9%). During spring and winter, serum 25-OHD levels were found to be lower compared with other seasons. The prevalence of vitamin D deficiency was highest (87.4%) in high school students and followed by middle school (78.8%) and elementary school students (70.5%). The predictors for vitamin D deficiency were female, winter/spring seasons and high school students. Conclusion: Adequate outdoor activities and/or oral vitamin D supplements during winter and spring seasons should be necessary in female adolescents.