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

OBJECTIVES: Vitamin D status in patients with COVID-19 is an on-going controversial issue. This study aims to determine differences in the serum 25(OH)D concentrations of Arab Gulf adult residents screened for SARS-CoV-2 and its association with risk of COVID-19 infection together with other comorbidities. METHODS: In this multi-center, case–control study, a total of 220 male and female adults presenting with none to mild symptoms were screened for COVID-19 (n = 138 RT-PCR-confirmed SARS-CoV-2 positive and 82 negative controls). Medical history was noted. Anthropometrics were measured and non-fasting blood samples were collected for the assessment of glucose, lipids, inflammatory markers and serum 25(OH)D concentrations. RESULTS: Serum 25(OH)D levels were significantly lower in the SARS-CoV-2 positive group compared to the negative group after adjustment for age and BMI (52.8 nmol/l ± 11.0 versus 64.5 nmol/l ± 11.1; p = 0.009). Being elderly (> 60 years) [Odds ratio 6 (95% Confidence Interval, CI 2–18; p = 0.001) as well as having type 2 diabetes (T2D) [OR 6 (95% CI 3–14); p < 0.001)] and low HDL cholesterol (HDL-c) [OR 6 (95% CI 3–14); p < 0.001)] were significant risk factors for COVID-19 infection independent of age, sex and obesity. CONCLUSIONS: Among Arab Gulf residents screened for SARS-CoV-2, serum 25(OH) D levels were observed to be lower in those who tested positive than negative individuals, but it was the presence of old age, diabetes mellitus and low-HDL-c that were significantly associated with risk of COVID-19 infection. Large population-based randomized controlled trials should be conducted to assess the protective effects of vitamin D supplementation against COVID-19. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12967-021-02838-x.