Severe vitamin D deficiency is not related to SARS-CoV-2 infection but may increase mortality risk in hospitalized adults: a retrospective case–control study in an Arab Gulf country

Single-center retrospective case-control study of hospitalized adults in Riyadh, Saudi Arabia (May–July 2020). 222 patients had measured 25(OH)D levels: 150 SARS-CoV-2 positive and 72 negative; children and pregnant women were excluded. Mean age 56.6 +/- 16.2 years; 135 men and 87 women. SARS-CoV-2 status determined by RT-PCR. Data included demographics, comorbidities (DM, hypertension, CVD, CHF, CKD), BMI, imaging, and laboratory tests. Vitamin D status defined as 25(OH)D < 50 nmol/L; severe deficiency < 12.5 nmol/L.

25(OH)D deficiency is highly prevalent (75%). After adjusting for age, sex, and BMI, SARS-CoV-2 positive patients had lower 25(OH)D than negative (35.8 +/- 1.5 vs 42.5 +/- 3.0 nmol/L; p=0.037). Age >60 years and pre-existing conditions predicted SARS-CoV-2 infection. For mortality, male sex (OR 3.3 (95% CI 1.2-9.2); p=0.02) and CKD (OR 3.5 (95% CI 1.4-8.7); p=0.008) were significant predictors; severe vitamin D deficiency (<12.5 nmol/L) showed elevated death risk but not significant after adjustment (OR 4.9 (95% CI 0.9-25.8); p=0.06). CKD remained an independent predictor of death (OR 3.5 (95% CI 1.4-8.7); p=0.008). Conclusion: In hospitalized adults, 25(OH)D deficiency is not linked to infection risk, but severe deficiency may be associated with higher mortality; randomized trials are needed to test whether correcting vitamin D status improves COVID-19 outcomes, especially in high-risk groups.

Limitations: Retrospective, single-center design; only 222/550 hospitalized patients had 25(OH)D measured, potentially introducing selection bias; observational design cannot establish causality; limited power to detect associations for severe vitamin D deficiency with mortality; results pertain to hospitalized adults with pre-existing conditions in Saudi Arabia and may not generalize.