The relationship between vitamin D and the severity of COVID-19 

This study of 204 patients, suggests that adequate (25(OH)D of >50 nmol/L) levels of vitamin D may play a role in inflammation and reduce the severity of COVID-19.

A total of 204 patients diagnosed with COVID-19 in Istanbul, Turkey with a median age of 59 years (range, 23-94 years) and 50.5% (n=103) female.

• Of the 204 total study subjects, 79.4% (n=162) were inpatients and 20.6% (n=42) were outpatients. 
• Vitamin D deficiency was found in 41.7% (n = 85) of cases and insufficiency in 46.0% (n = 94), while in 12.3% (n = 25) of cases normal vitamin D levels were found.
  
• The inpatient group had significantly lower levels of 25(OH)D and lymphocytes, but significantly higher ferritin, CRP and d-dimer levels than those in the outpatient group.
  
• The odds of having a serious clinical outcome (inpatient status) were increased for vitamin D insufficient patients by 5.604 times and for vitamin D deficient patients 38.095 times for each standard deviation decrease in serum 25(OH)D. 

• The observational design of the study cannot substantiate causality between serum vitamin D levels and severity of COVID-19 disease. 
• The group sizes and ages are not equal.  
• The clinical results of inpatients who were ultimately admitted to the intensive care unit were not available to the authors. 
• The data was not adjusted for patient comorbidities. 

Serum 25(OH)D levels in COVID-19 outpatients were significantly higher than in more severely ill COVID-19 inpatients. Regression analyses indicated that the odds of having a serious clinical outcome (inpatient status) increase when serum 25(OH)D levels decrease. 

• The study was a retrospective, observational study. 
• All patients had viral pneumonia, which was confirmed with chest computer tomography. 
• Blood samples were analyzed for all patients. 
• Cases were divided in two groups: mild (outpatients) or serious (inpatients) according to their clinical and laboratory data.  
• Vitamin D status of the patients was classified according to serum 25(OH)D level: 25(OH)D of < 25 nmol/L was considered deficient; 25(OH)D of 25–50 nmol/L was considered insufficient; and, 25(OH)D of >50 nmol/L was considered normal. 

Basaran N, Adas M, Gokden Y, Turgut N, Yildirmak T, Guntas G. The relationship between vitamin D and the severity of COVID-19. Bratisl Lek Listy. 2021;122(3):200-205. doi: 10.4149/BLL_2021_034. PMID: 33618529.  https://pubmed.ncbi.nlm.nih.gov/33618529/