The results of a recent study support a potential role for vitamin D as a risk factor for coronavirus disease 2019 (COVID-19), as suggested recently in studies from Italy and Spain. In addition, these data add clinical strength to basic information implicating vitamin D in the native, acquired immune response, according to the study.

One of the more recent potential risk factors of COVID-19 is vitamin D deficiency, which is an important modulator of innate and acquired immunity. Low levels are associated with bacterial and viral infections. Further, countries with lower mean levels of 25-hydroxyvitamin D have a higher COVID-19 mortality rate, according to the study authors.

Preliminary studies suggest that vitamin D supplementation may improve outcomes. Recent reports have shown markedly reduced levels of 25-hydroxyvitamin D among those hospitalized with COVID-19, whereas much of the data implicate vitamin D and COVID-19, according to the researchers.

The objective of this recent study was to compare levels of 25-hydroxyvitamin D with values that have been characterized in the healthier population of Armenia.

The researchers used blood samples for measurement of 25-hydroxyvitamin D from 330 consecutive hospitalized patients. The team also recorded age, gender, height, weight, occupation, chronic conditions, prior tuberculosis infection, smoking status, use of supplemental oxygen, intubation status, duration of hospitalization until discharge, or death.

Samples were collected over 5 weeks in the summer of 2020, with the most common comorbidities being hypertension, diabetes, smoking, and prior lung disease. Further, 52% required supplemental oxygen, whereas only 4.5% were intubated and 24 deaths. Mean 25-hydroxyvitamin D level was 13.4 ± 7.7 ng/mL, with 45% of patients under 12 ng/mL, according to the study authors.

The study authors noted positive relationships between age and the duration of hospitalization, age, and days of supplemental oxygen, body mass index (BMI) and days hospitalized, BMI with days on supplemental oxygen, and number of comorbidities with days on supplemental oxygen. Additionally, multivariate logistic regression identified age and duration of hospitalization and significant variables for death. There was no relationship between any of the demographic variables and intubation.

The researchers found no significant relationship between 25-hydroxyvitamin D and BMI, duration of stay, oxygen requirements, or death. Mean vitamin D of patients who passed away was mildly lower than that of those who survived, however, the difference was not significant.

A greater proportion of hospitalized patients had levels below 12 ng/mL in comparison to the national average. In comparing those with vitamin D levels below 12 ng/mL to those with vitamin D levels above 12 ng/mL, there was no difference in terms of mean age, BMI, duration of hospitalization, or days requiring supplemental oxygen, according to the study authors.

Future studies are important to conduct to determine whether intervention with vitamin D can be protective against COVID-19, as well as whether intervention with vitamin D can mitigate its severity.

Hutchings, N., Babalyan, V., Baghdasaryan, S. et al. Patients hospitalized with COVID-19 have low levels of 25-hydroxyvitamin D. Endocrine (2021).