The Impact of Vitamin D Deficiency on the Severity of Symptoms and Mortality Rate among Adult Patients with Covid-19: A Systematic Review and Meta-Analysis

INTRODUCTION: We aimed to study the prevalence of vitamin D deficiency (VDD) in patients with COVID-19 infection and evaluate the impact of vitamin D levels on the severity of symptoms and the case fatality rate. EVIDENCE ACQUISITION: A comprehensive literature search was performed up to December 20, 2020, using the following databases: MEDLINE, PubMed, EMBASE, SCOPUS, Web of Science, and preprint databases (BioRxiv and MedRxiv). Any individual observational study related to the prevalence and impact of vitamin D deficiency/insufficiency (VDD/VDI) on the severity of COVID-19 symptoms and mortality rates was included. No language restrictions were applied, and both published and non-published studies were included. EVIDENCE SYNTHESIS: Two of the authors independently performed the literature search and assessed the eligibility of studies. The quality of studies included was assessed using the Newcastle–Ottawa Scale. Data were analyzed using the Review Manager Software (version 5) and Comprehensive Meta-analysis Software (version 3). A total of 43 studies were included with a sample size of 254,963 patients with COVID-19. Pooled analysis showed a higher prevalence of VDD and VDI in patients with COVID-19 (59.0% and 40.1%, respectively). Moreover, a significant association was noticed between vitamin D levels and severity of symptoms (odds ratio [OR] = 3.38, 95% confidence interval [CI]: 1.94–5.87, P < 0.0001), as well as the case fatality rate (OR = 2.30, 95% CI: 1.47–3.59, P < 0.00001). CONCLUSIONS: VDD is highly prevalent in patients with COVID-19 infection. Lower vitamin D levels correlate with disease severity and poor prognosis although most of the data have been derived from moderate-quality observational studies.