Predictors of Vitamin D Status among Maintenance Hemodialysis Patients

Purpose:  Vitamin D deficiency has been associated with increased mortality in end-stage renal disease. Despite a high prevalence of hypovitaminosis D in the hemodialysis (HD) population, it remains unclear which patients are at increased risk. The objective of this study was to identify risk factors for vitamin D deficiency among maintenance HD patients.

Methods:  A cross-sectional study was conducted at Rubin Dialysis Centers in July 2009. Inclusion criteria were: age ≥ 18 years and availability of laboratory results to verify outcome status.  Vitamin D deficiency was defined as a serum 25-hydroxyvitmain D (25[OH]D) level < 30 ng/mL. Due to the high proportion (>10%) of patients with 25[OH]D concentrations < 30 ng/mL, log-Poisson regression was utilized to determine factors independently associated with vitamin D deficiency.

Results:  One hundred-sixteen patients (59% male, 84% white, 57% diabetic etiology) with a mean ± SD age = 63.3 ± 16.4 years, HD vintage = 3.3 ± 2.9 years and 25[OH]D = 32.3 ± 16.3 ng/mL were included in this analysis. Overall, 53% of patients (n = 62) were vitamin D deficient and 35% (n = 42) were receiving ergocalciferol supplementation (mean weekly dose = 41,071 ± 15,442  IU  and duration of therapy = 9.05 ± 6.14 months). In multivariate analyses, lack of current ergocalciferol use (prevalence ratio [PR] = 1.60; 95% CI 1.07 to 2.41; p = 0.0232), BMI ≥ 25 kg/m² (PR = 1.57; 95% CI 1.02 to 2.40; p = 0.0377) and  black race (PR = 1.59; 95% CI 1.21 to 2.11; p = 0.0011) were independently associated with vitamin D deficiency.

Conclusion:  Suboptimal vitamin D status is prevalent among HD patients. BMI and race appear to be important predictors of vitamin D deficiency. Furthermore, these data suggest supplementation with ergocalciferol is effective for normalization of 25[OH]D levels in the HD population.