Vitamin D status of Arab Gulf residents screened for SARS-CoV-2 and its association with COVID-19 infection: a multi-centre case–control study

Multi-center cross-sectional case-control study of 220 adults aged 30-60 years in Riyadh, Saudi Arabia; 138 RT-PCR-confirmed SARS-CoV-2 positive and 82 negative controls; asymptomatic to mild COVID-19; non-fasting blood samples; anthropometrics; measurements included glucose, lipids, inflammatory markers (CRP, IL-6), and serum 25(OH)D.

Serum 25(OH)D was significantly lower in SARS-CoV-2 positive vs negative after adjusting for age and BMI (52.8 ± 11.0 vs 64.5 ± 11.1 nmol/L; p = 0.009). Age >60 years (OR 6.2; 95% CI 2-18), type 2 diabetes (OR 6.4; 95% CI 3-14), and low HDL-cholesterol (OR 6.1; 95% CI 3-14) were significant infection risk factors after adjustment for age, sex and BMI. Conclusion: In Arab Gulf residents tested for SARS-CoV-2, lower vitamin D status was observed among positives, but older age, diabetes, and low HDL-cholesterol were the main risk factors for infection. Large population-based randomized trials are needed to determine whether vitamin D supplementation can protect against COVID-19.

Cross-sectional/case-control design limits causal inference; insufficient power for sex-stratified analyses; findings apply to none-to-mild COVID-19 and may not generalize to severe cases; vitamin D status may be affected by acute infection (negative acute phase reactant), potentially confounding associations.