Vitamin D Deficiency Increases Risk of Severe or Fatal COVID-19

Vitamin D is crucial to maintain bone health and facilitate immune system function. Early in the pandemic, health officials encouraged the public to take vitamin D supplements to boost immune response and potentially protect against COVID-19.

Now, studies are increasingly linking low vitamin D levels to an elevated risk of COVID-19 infection and death. One study, published today in PLOS ONE, is among the first to analyze vitamin D levels prior to COVID-19 infection.

Jointly led by Bar-Ilan University and Galilee Medical Center, the study looked for any correlation between pre-infection serum 25-hydroxyvitamin D (25(OH)D) level and COVID-19 severity and mortality. Investigators analyzed hospital records of individuals admitted to the Galilee Medical Center in Nahariya, Israel from April 7, 2020-February 4, 2021. Included subjects had a positive PCR COVID-19 test and 25(OH)D levels documented 14-730 days prior to their infection.

The investigators grouped patients by disease severity and level of 25(OH)D. Vitamin D levels were categorized as deficient, insufficient, adequate, or high-normal. They determined COVID-19 disease severity using multivariable regression analysis. Utilizing a cosinor model, the investigators isolated the influence of a sinusoidal pattern of seasonal 25(OH)D fluctuations.

Of the 1176 patients included in the study, 253 had a record of their 25(OH)D level before COVID-19 infection. Patients with a vitamin D deficiency, defined as < 20 ng/mL, were 14 times more likely to have severe or fatal COVID-19 disease than patients with 25(OH)D ≥ 40 ng/mL.

Overall, a low vitamin D status was present in 87.4% of patients with severe or critical COVID-19, but only 34.3% of patients with mild to moderate disease were vitamin D deficient. Mortality among patients with sufficient vitamin D was 2.3%, but 25.6% in vitamin D deficient patients.

"This study contributes to a continually evolving body of evidence suggesting that a patient's history of vitamin D deficiency is a predictive risk factor associated with poorer COVID-19 clinical disease course and mortality," said study co-author Michael Edelstein a professor at Bar-Ilan University. "It is still unclear why certain individuals suffer severe consequences of COVID-19 infection while others don’t. Our finding adds a new dimension to solving this puzzle."