Low serum vitamin D level and COVID-19 infection and outcomes, a multivariate meta-analysis

ABSTRACT

ObjectiveThis study aimed to determine whether serum vitamin D is independently associated with COVID-19 infection and outcomes in patients with COVID-19. MethodsWe identified relevant studies by searching the PubMed, Embase, and medRxiv databases from December 2019 to October 1, 2020. Odds ratios (ORs) were pooled using random-effects models. Only reports with multivariate adjusted results were included to avoid the impact of potential confounding factors. ResultsA total of six studies with 377,265 patients were identified. Overall, in the categorical analysis, a low serum vitamin D level was associated with an increased risk of COVID-19 infection (OR 1.47, 95% CI 1.09- 1.97, I2=81%), hospitalization (OR 1.83, 95% CI 1.22-2.74, I2=0%), but not in-hospital death (OR 2.73, 95% CI 0.27-27.61). Notably, when vitamin D level was analyzed as a continuous variable, each 5 ng/ml increase in vitamin D level was not associated with any increased risk of COVID-19 infection (OR 1.04, 95% CI 0.96-1.12, I2=74%) or in-hospital death (OR 1.02, 95% CI 0.93-1.12). ConclusionsLow serum vitamin D is associated with an increased risk of COVID-19 infection and hospitalization. In-hospital death showed a tendency to be increased in COVID-19 patients with low vitamin D levels. The ongoing clinical trials for evaluation of vitamin D supplementation will be key to the validation of this adjunctive treatment for COVID-19 patients.