Vitamin D deficiency is associated with COVID-19 positivity and severity of the disease

Among COVID‐19‐positive patients in Turkey in this retrospective cohort study, the group with vitamin D levels of >75 nmol/L had significantly lower D‐dimer and C‐reactive protein (CRP) levels (a marker of inflammation), number of affected lung segments and shorter hospital stays. No difference was found among the groups in terms of age and gender.

Two-thousand six-hundred patients >18 years and with a positive RT-PCR test for COVID-19 during the study period in Tokat, Turkey (39°52’ N latitude).

March 30, 2020 to November 1, 2020

• Vitamin D levels were below 75 nmol/L in 94.27% of COVID‐19‐positive patients (average age=46.32 ± 1.24 years and 56.54% women) while 93.07% of non‐COVID‐19 patients (average age=44.63 ± 1.30 years and 59.50% women) had vitamin D levels below 75 nmol/L.  
• Very severe vitamin D deficiency (<25 nmol/L) was considerably more common in COVID‐19 patients (44%) (average age=44.15 ± 1.89 years and 57.57% women) than in non‐COVID‐19 ones (31%) (average age=46.50 ± 2.21 years and 62.5% women). 
• Among COVID‐19‐positive patients, the group with vitamin D levels of >75 nmol/L had significantly lower D‐dimer and C‐reactive protein (CRP) levels, number of affected lung segments and shorter hospital stays.  
• No difference was found among the groups in terms of age and gender distribution. There were no significant differences among the four groups for white blood count, hemoglobin, platelet count, mean platelet volume, fasting glucose, urea, creatinine, alanine aminotransferase, aspartate aminotransferase, potassium, sodium and calcium levels, and neutrophil and lymphocyte counts. 

• Given the observational design of this study, it is unable to discern causal relationships. 
• Vitamin D deficiency could be due to various chronic conditions or behavioral factors, which themselves might be associated with a higher COVID‐19 risk.  
• In addition, the study covered data limited to the electronic database of Tokat State Hospital and may only be applicable to the Turkish population. 

In the present single‐centered retrospective cohort study, vitamin D deficiency was found to be associated with a higher COVID‐19 risk. The COVID‐19‐positive individuals with sufficient vitamin D levels had significantly lower blood levels of D‐dimer, inflammatory marker CRP, reduced frequencies of ground‐glass opacity appearance in chest CT scans and shorter hospital stays. The findings of the study indicated the need for randomized studies to determine whether the vitamin D level could affect COVID‐19 risk. 

• The design is a retrospective cohort study. 
• The study included 227 patients who had PCR positivity for COVID‐19 in the March 30–November 1, 2020 period and whose vitamin D levels were measured in the 6 months before the PCR test at Tokat State Hospital in Turkey. 
• For comparison, medical records of 1200 patients who had a hospital visit from November 1, 2019 to November 1, 2020 for complaints due to reasons not related to COVID‐19 were searched for vitamin D measurements. A total of 260 patients were identified. 
• COVID‐19 (n=227) and non‐COVID‐19 patients (n=260) were divided into four groups according to their vitamin D levels: 
  • Group I (0–25 nmol/L),  
  • Group II (25–50 nmol/L),  
  • Group III (50–75 nmol/L), and  
  • Group IV (vitamin D > 75 nmol/L).  
• Laboratory test results and the radiological findings were evaluated.  

Demir M, Demir F, Aygun H. Vitamin D deficiency is associated with COVID-19 positivity and severity of the disease. J Med Virol. 2021 May;93(5):2992-2999. doi: 10.1002/jmv.26832 https://pubmed.ncbi.nlm.nih.gov/33512007/