Does vitamin D serum level affect prognosis of COVID-19 patients?

Since the beginning of the Coronavirus disease 2019 (COVID-19) pandemic there have been contradictions and speculations about the relationship between vitamin D and COVID-19. Given that there is an association between vitamin D deficiency and some diseases - including cancer, autoimmune disease and some infectious diseases - a higher incidence and mortality rate in the vitamin-D-deficient COVID-19 population was not a surprise; conversely, some research would argue this relationship. Considering these contradictions, this study aimed to determine the relationship between prognosis and vitamin D level in cases with COVID-19.

In this cross-sectional study, 329 confirmed cases of COVID-19 - who were admitted to Kamkar-ArabNia Hospital in Qom city, Iran from March-July 2020 - were categorized into three groups according to vitamin D serum levels (ng/ml): sufficient (>30), insufficient (20-30) and deficient (<20). Prognosis was determined across the groups.

There was a significant difference in hospital stay between patients with sufficient and insufficient vitamin D levels (P = 0.007). Adjusting vitamin D levels for confounding variables, linear regression underscored significant differences in the association between length of hospitalization and lower vitamin D levels, with a longer stay noted in insufficient groups (P = 0.002). However, there was no significant difference in the time interval to return to normal oxygen level (from SpO2 < 93%) or death rate between groups (P > 0.05).

There was a significant association between hospital stay and lower serum vitamin D levels. However, the relationship between vitamin D status and death rate or the time interval to return to normal oxygen levels was not significant.