Vitamin D Status and COVID-19: Some Implications

Abstract Background Vitamin D is essential for the maintenance of good health and its status is defined by the level of serum 25-hydroxyvitamin (25(OH)D). Negative correlations between mean levels of 25(OH)D per country and the number of COVID-19 confirmed cases per one million population, and COVID-19 mortality per one million population, were recently observed. The aim of this study was to identify levels of 25(OH)D below which, rates of COVID-19 confirmed cases, mortality and lethality, increase significantly.Methods A data table found in the literature, containing a list of twenty countries and their corresponding mean level of 25(OH)D was updated with COVID-19 latest numbers of confirmed cases and mortality rates. Cut points of 25(OH)D below which rates were significantly higher were found according to various statistical criteria: absolute difference of means, t-test p-values, between class variance, entropy. Thresholds of 25(OH)D below which there can be a significant rise of COVID-19 confirmed cases, mortality and lethality, were found performing a Gaussian kernel regression. Results All the criteria yielded 25(OH)D cut off points at 50 ± 10 nmol/L for Cases and Mortality variables and at 60 ± 10 nmol/L for Lethality variable. A Gaussian kernel regression showed a significant rise in the rates of COVID-19 confirmed cases, mortality and lethality, below 25(OH)D levels of 60 ± 6 nmol/L. Conclusion In this study, our method provided a reliable estimate (95 % confidence interval) of 25(OH)D levels, of 60 ± 6 nmol/L, in the range of vitamin D insufficiency, below which rates of COVID-19 confirmed cases per one million population, rates of COVID-19 mortality per one million population increased. We found that 25(OH)D levels below 50 ± 10 nmol/L, mainly in the range of vitamin D deficiency, associate with highest COVID-19 mortality rates. Therefore, we suggest that 25(OH)D concentrations should be above 60 ± 6 nmol/L to reduce morbidity and mortality during the COVID-19 pandemic.