Is the vitamin D status of patients with COVID-19 associated with reduced mortality? A systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational (cohort and case-control) studies
PubMed 36913680 · doi:10.20945/2359-3997000000588
What was done
A systematic review and meta-analysis of PubMed and Embase (searched through April 24, 2022) examined the relationship between admission serum vitamin D levels and COVID-19 mortality. Pooled risk ratios (RRs) with 95% confidence intervals (CIs) were calculated using fixed- or random-effects models across 21 studies (19 cohort, 2 case-control). Study risk of bias was assessed with the Newcastle-Ottawa Scale.
What was found
An association between vitamin D deficiency and COVID-19 mortality appeared in unadjusted studies (RR 1.51, 95% CI 1.28-1.74, I² 0.0%). However, no statistically significant association remained when analyzing studies using deficiency cutoffs < 10 or < 12 ng/mL (RR 1.60, 95% CI 0.93-2.27, I² 60.2%) or when restricting to studies that adjusted effect measures for confounding factors.
Why it matters
This review indicates that observed links between low vitamin D levels and COVID-19 mortality in observational literature are largely artifacts of confounding rather than an independent risk factor.
Limits
All 21 included studies were observational rather than randomized trials. Total participant count was not reported in the abstract. Moderate heterogeneity (I² 60.2%) was present in the cutoff-adjusted subgroup, and vitamin D deficiency thresholds varied across studies.
Cited by
- context Research during the COVID-19 pandemic demonstrated that people who were vitamin D deficient had higher mortality from COVID-19.