Vitamin D supplementation and the outcomes of critically ill adult patients: a systematic review and meta-analysis of randomized controlled trials

This meta-analysis assessed the association between vitamin D supplementation and the outcomes of critically ill adult patients. A literature search was conducted using the PubMed, Web of Science, EBSCO, Cochrane Library, Ovid MEDLINE, and Embase databases until March 21, 2020. We only included randomized controlled trials (RCTs) comparing the efficacy of vitamin D supplementation with placebo in critically ill adult patients. The primary outcome was their 28-day mortality. Overall, 9 RCTs with 1867 patients were included. In the pooled analysis of the 9 RCTs, no significant difference was observed in 28-day mortality between the vitamin D supplementation and placebo groups (20.4% vs 21.7%, OR, 0.73; 95% CI, 0.46–1.15; I(2) = 51%). This result did not change as per the method of vitamin D supplementation (enteral route only: 19.9% vs 18.2%, OR, 1.19; 95% CI, 0.88–1.57; I(2) = 10%; intramuscular or intravenous injection route: 25.6% vs 40.8%, OR, 0.48; 95% CI, 0.21–1.06; I(2) = 19%) or daily dose (high dose: 20.9% vs 19.8%, OR, 0.83; 95% CI, 0.51–1.36; I(2) = 53%; low dose: 15.6% vs 21.3%, OR, 0.74; 95% CI, 0.32–1.68; I(2) = 0%). No significant difference was observed between the vitamin D supplementation and placebo groups regarding the length of ICU stay (standard mean difference [SMD], − 0.30; 95% CI, − 0.61 to 0.01; I(2) = 60%), length of hospital stay (SMD, − 0.17; 95% CI, − 041 to 0.08; I(2) = 65%), and duration of mechanical ventilation (SMD, − 0.41; 95% CI, − 081 to 0.00; I(2) = 72%). In conclusion, this meta-analysis suggested that the administration of vitamin D did not provide additional advantages over placebo for critically ill patients. However, additional studies are needed to confirm our findings.