How Vitamin D Levels of Children Changed During COVID-19 Pandemic: A Comparison of Pre-pandemic and Pandemic Periods

Objective: The synthesis of vitamin D is related to sun exposure, thus the restrictions during the Coronavirus disease-2019 (COVID-19) pandemic may have affected the levels of vitamin D in all age groups. The aim of this study was to evaluate vitamin D levels of healthy children and adolescents during the first year of the pandemic. Methods: The study group included healthy children and adolescents who were admitted for general check-ups and evaluated with 25(OH)D levels. Then, it was divided into two groups: Group 1 ???pre-pandemic???, and Group 2 ???pandemic???. Vitamin D levels were recorded from the hospital database and were compared according to age groups, gender, and the season, retrospectively. Results: The study group [mean age=90.29??59.45 median age=79 interquartile range (IQR): 102 months, male/female: 1409/1624] included 3033 children and adolescents (Group 1/Group 2 n=1864/1169). Although the mean 25(OH)D levels among preschool children did not differ between groups, the vitamin D levels of school-aged children and adolescents were significantly lower in the pandemic period than in the pre-pandemic period [Group 1 median=16.50 (IQR: 10.5) vs Group 2 median=15.9 (IQR: 11.3) in 6-12 age group (p=0.026); Group 1 median=13.30 (IQR: 10.2) vs Group 2 median=11.20 (IQR: 9.7) in 12-18 age group (p=0.003)]. Moreover, the 25(OH)D levels of adolescents showed seasonal variance with lower levels in winter, and unexpectedly, in summer. Conclusion: Pandemic-related restrictions have caused significant decreases in vitamin D levels of school-aged children and adolescents. We suggest that children and adolescents should be given vitamin D supplementation in order to maintain sufficient levels of vitamin D during the pandemic.