Prognostic significance of 25-hydroxivitamin D entirely explained by a higher comorbidity burden: experience from a South-Eastern European Dialysis Cohort.

Vitamin D deficiency is still a common problem particularly in the elderly and in individuals with various degrees of renal impairment. The present study aimed to evaluate the association between plasma concentrations of 25(OH)D and death in a large cohort of prevalent patients on hemodialysis (HD) from south-east Romania, a typical Balkan region. This is an observational prospective study that included a total of 570 patients on maintenance HD. Study patients were classified into three groups by baseline 25(OH)D levels: (1) sufficient 25(OH)D--i.e., >30 ng/mL; (2) insufficient 25(OH)D--i.e., between 10 and 29 ng/mL; and (3) deficient 25(OH)D--i.e., <10 ng/mL. During the follow-up period of 14 months, 68 patients (11.9%) died, the Kaplan-Meier analysis showing significant differences in all-cause mortality for chronic kidney disease patients in different 25(OH)D groups (P = 0.002). Unadjusted Cox regression analysis also showed significant differences in survival. The multivariate Cox regression model showed no significant differences in survival according to vitamin D levels. Hazard ratio for death in the "<10 ng/mL" group was 1.619 (P = 0.190) and in the "10-30 ng/mL" group was 0.837 (P = 0.609). In our dialysis population with a high comorbidity burden, low 25(OH)D concentration was not associated with mortality in the adjusted Cox model, suggesting that vitamin D deficiency could represent only a non-specific marker for a poor health status, with less impact on mortality.