OBJECTIVE: Vitamin D (Vit. D) deficiency has been demonstrated to be a risk factor in the development of respiratory tract infection and inflammatory processes. However, the effect of Vit. D status on the outcome of coronavirus disease 2019 (COVID-19) infection remains uncertain. In this retrospective study, we aimed to determine the role of serum Vit. D level in the outcome of COVID-19 patients in terms of severity and mortality.

PATIENTS AND METHODS: We included in the study 452 adult patients (i.e., ≥18 years old) diagnosed with COVID-19 between March 2020 and December 2021 (before the availability of the COVID-19 vaccine). We reviewed patient charts to collect demographic, clinical, and laboratory data. We categorized serum Vit. D concentrations as follows: deficient (<20 ng/mL), insufficient (20-30 ng/mL), and sufficient (>30 ng/mL). We assessed disease severity in terms of hospitalization (requiring oxygen), intensive care unit (ICU) admission (requiring high-flow oxygen or ventilation), and mortality.

RESULTS: Serum Vit. D levels were available for 27.4% of the 452 studied adult COVID-19 patients (mean age=56.2±17.0 years; 57% male). However, we found no statistically significant differences in the rates of hospitalization requiring supplemental oxygen, ICU admission requiring high-flow oxygen or ventilation, mortality, or hypoxia based on vit. D status (p=0.658). COVID-19 severity was strongly linked to age, with higher average ages seen in hospitalized patients requiring oxygen, those admitted to the ICU, and those who died (p<0.001, p=0.013, and p<0.001, respectively); inflammatory markers were also significantly higher in these groups (p<0.001). Higher blood pressure was associated with hospitalization (p=0.017), ICU admission (p=0.003), and mortality (p<0.001). Dyslipidemia and pulmonary fibrosis were also linked to higher mortality. Although Hispanic patients accounted for 37.4% of the study population, they had a lower proportion of deaths compared to other ethnicities (7.4% vs. 42.7%; p<0.001).

CONCLUSIONS: The study included 452 adult patients diagnosed with COVID-19. We found no significant differences in hospitalization, ICU admission, mortality, or hypoxia based on Vit. D status. We identified age, inflammatory markers, and blood pressure as factors associated with COVID-19 severity and mortality. We suggest further research examining the impact of Vit. D levels, comorbidities, and ethnic disparities to help to understand the causes of COVID-19 severity and mortality.