Associations of vitamin D levels and clinical parameters with COVID-19 infection, severity and mortality in hemodialysis patients: A cohort study.

Introduction: Vitamin D deficiency is prevalent among patients undergoing hemodialysis. This study aimed to investigate the associations between vitamin D levels and clinical parameters with the risk of COVID-19 infection, severity, and mortality in hemodialysis patients with end-stage kidney disease (ESKD).

Methods: This retrospective cohort study included 198 hemodialysis patients from a single center. Vitamin D deficiency was defined by the last measurement of 25-hydroxycholecalciferol less than 20 ng/mL. Vitamin D deficiency and vitamin D supplements were combined to categorize patients into three groups: deficiency, uncertain deficiency, and likely sufficient. COVID-19 infection status, severity, and outcomes were recorded. Statistical analyses were performed to assess the associations between vitamin D levels and COVID-19 severity and mortality.

Findings: Among the 198 patients, 73 patients (37%) were in the deficiency group, 29 patients (15%) had uncertain deficiency, and 96 patients (48%) were likely sufficient. The overall COVID-19 infection rate was 59%. The deficiency group had a similar infection rate (60.3%) compared to those with likely sufficient levels (54.2%). However, the severity and mortality rates of vitamin D deficiency group had a significantly higher rate than those with likely sufficient levels. Multivariate logistic regression analysis showed that vitamin D deficiency and uncertain deficiency group were significantly associated with an increased risk of COVID-19 severity (OR = 22.57, p = 0.01 and OR = 15.8, p = 0.03, respectively). Uncertain deficiency group was significantly associated with an increased risk of COVID-19 mortality (OR = 12.93, p = 0.04), while the deficiency group should similarly trend but did not reach statistical significance.

Discussion: Vitamin D deficiency is associated with an increased risk of COVID-19 severity in hemodialysis patients with ESKD. These findings suggest that monitoring and managing vitamin D levels may be important in reducing the risk of COVID-19 severity in this vulnerable population.