Evaluation of 25-hydroxyvitamin D (25(OH)D) levels before and during the COVID-19 pandemic: a cross-sectional study and trend analysis involving 86,772 samples

Abstract

Abstract Purpose The aim of this paper was to evaluate the change in 25-hidroxyvitamin D (25(OH)D) levels before and during the COVID-19 pandemic. Methods In this retrospective, cross-sectional and methodological study included 86,772 patients (18–75 years) samples who were admitted to the University Hospital for various reasons and whose 25(OH)D levels were measured in the biochemistry unit between 2019–2020 and 2020–2021 (before and during the COVID-19 outbreak). A time series analysis of monthly averages for 25(OH)D was performed. For the purpose of seasonal study, the mean levels of 25(OH)D are grouped by years. Data were modeled in terms of 25(OH)D levels using the MATLAB Curve Fitting Toolbox. Results There was no significant difference between the sexes according to 25(OH)D levels (p > .05). 25(OH)D levels were significantly higher in the summer months and lower in the winter months (p < .001). When comparing the spring months, 25(OH)D levels in 2020 were found to be significantly lower than in 2019 (p < .001); on the contrary, when examined based on the summer, autumn, and winter months, 25(OH)D levels increased in 2020 compared to 2019 (p < .001). In the estimates curve obtained with an error margin of 11% in the time series analysis, it was estimated that the 25(OH)D averages after the pandemic would be similar to those before the pandemic. Conclusion Restrictions, partial or complete closures, and curfews can significantly affect individuals' 25(OH)D levels during the COVID-19 outbreak. Evidence-based public health policies regarding vitamin D, especially during pandemic and closure periods, have critical importance.