The Impact of COVID-19 Pandemic during 2020-2021 on the Vitamin D Serum Levels in the Paediatric Population in Warsaw, Poland

Background: The main source of vitamin D is skin synthesis, which depends on sunlight exposure. During the pandemic, COVID-19 children were obliged to home confinement, which potentially limiting sunlight exposure. The aim of this study was to evaluate whether home confinement led to decreased vitamin D serum levels in children in Warsaw, Poland. Methods: The study included 1472 children who were divided into two groups, based on the date of 25(OH)D level blood sampling: before and during the pandemic. Children under 1 year of age (infants) were analysed separately. Results: A statistically significant decrease in the average level of vitamin D was observed between groups of children over 1 year of age (35 ng/mL +/- 18 vs. 31 ng/mL +/- 14). In infants from both groups, the mean vitamin D levels were within the normal range (Group 1 inf 54 ng/mL +/- 21 vs. Group 2 inf 47 ng/mL +/- 15). The characteristic seasonal variability was observed before the pandemic, with maximal vitamin D levels in summer (40 ng/mL +/- 17) and minimal levels in winter (30 ng/mL +/- 14). During the pandemic, no seasonal variability was observed (summer 30 ng/mL +/- 11 vs. winter 30 ng/mL +/- 19). Conclusions: The COVID-19 pandemic restrictions led to a significant decrease in vitamin D serum levels in children.

Automated summary

Children experienced a significant decrease in vitamin D serum levels during the COVID-19 pandemic due to home confinement. The seasonal variability in vitamin D levels was no longer observed during the pandemic.