Methods: A nationwide cross-sectional survey was conducted in the first grade students from randomly selected 45 elementary schools. The participants of this survey were selected using a stratified two-stage cluster sampling design. The prevalence of atopic dermatitis (AD), allergic rhinitis (AR), and asthma was obtained through the Korean version of International Study of Asthma and Allergies in Childhood questionnaire. All the children were examined by a pediatrician to determine the presence of eczema in their neck and flexural areas of both arms. Serum 25-hydroxyvitamin D [25(OH)D] was measured by chemiluminescent microparticle immunoassay. For categorical analysis by 25(OH)D concentrations, we used cutoffs of <20 ng/mL (50 nmol/L), 20-29 ng/mL (50-70 nmol/L), and ≥ 30 ng/mL (70 nmol/L). Multivariable logistic regression analysis was applied, adjusting for gender, maternal education levels, allergic diseased of parents, family income and urbanization.
Result: The overall prevalence rates of vitamin D insufficiency (20 to 29 ng/mL) and deficiency (<20 ng/mL) were 64.1% and 18.4%. Vitamin D level was not associated with the symptom of AD, AR, or asthma in the last 12 months (P value = 0.071, 0.976, and 0.757, respectively). Vitamin D level was not related to the presence of treatment for AD, AR, or asthma in the last 12 months (P value = 0.256, 0.794, and 0.703, respectively). In addition, there was no significant association between vitamin D level and the presence of pediatrician-confirmed AD on the day of survey (P value = 0.195).
Conclusion: A high prevalence of vitamin D deficiency and insufficiency was found in Korean elementary schoolchildren, but vitamin D level was not associated with the recent symptoms of allergic diseases.
Keywords: vitamin D, atopic dermatitis, asthma, allergic rhinitis