Low 25-hydroxyvitamin D levels and mortality in non-dialysis-dependent CKD

Am J Kidney Dis. 2011 Oct;58(4):536-43. doi: 10.1053/j.ajkd.2011.04.028. Epub 2011 Aug 4.

Abstract

Background: Low 25-hydroxyvitamin D (25[OH]D) levels are common in patients with non-dialysis-dependent chronic kidney disease (CKD). The associations between low 25(OH)D levels and mortality in non-dialysis-dependent patients with CKD are unclear.

Study design: Retrospective cohort study.

Setting & participants: Patients with stages 3-4 CKD (estimated glomerular filtration rate, 15-59 mL/min/1.73 m(2); n = 12,673) who had 25(OH)D levels measured after the diagnosis of CKD in the Cleveland Clinic Health System.

Predictor: 25(OH)D levels categorized into 3 groups: <15, 15-29, and ≥30 ng/mL.

Outcomes: We examined factors associated with low 25(OH)D levels and associations between low 25(OH)D levels and all-cause mortality (ascertained using the Social Security Death Index and our electronic medical record) using logistic regression, Cox proportional hazard models, and Kaplan-Meier survival curves.

Measurements: 25(OH)D was measured using chemiluminescence immunoassay.

Results: Of 12,763 patients with CKD, 15% (n = 1,970) had 25(OH)D levels <15 ng/mL, whereas 45% (n = 5,749) had 25(OH)D levels of 15-29 ng/mL. Male sex, African American race, diabetes, coronary artery disease, and lower estimated glomerular filtration rate were associated significantly with 25(OH)D level <30 ng/mL. A graded increase in risk of 25(OH)D level <30 ng/mL was evident across increasing body mass index levels. Patients who had 25(OH)D levels measured in fall through spring had higher odds for 25(OH)D levels <30 ng/mL. After covariate adjustment, patients with CKD with 25(OH)D levels <15 ng/mL had a 33% increased risk of mortality (95% CI, 1.07-1.65). The group with 25(OH)D levels of 15-29 ng/mL did not show a significantly increased risk of mortality (HR, 1.03; 95% CI, 0.86-1.22) compared with patients with 25(OH)D levels ≥30 ng/mL.

Limitations: Single-center observational study, lack of data for albuminuria and other markers of bone and mineral disorders, and attrition bias.

Conclusions: 25(OH)D level <15 ng/mL was associated independently with all-cause mortality in non-dialysis-dependent patients with CKD.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • African Americans / statistics & numerical data
  • Aged
  • Aged, 80 and over
  • Body Mass Index
  • Cause of Death
  • Chi-Square Distribution
  • Chronic Disease
  • Comorbidity
  • Diabetic Nephropathies / blood
  • Diabetic Nephropathies / mortality
  • Female
  • Humans
  • Kaplan-Meier Estimate
  • Kidney Diseases / blood*
  • Kidney Diseases / mortality*
  • Male
  • Middle Aged
  • Prevalence
  • Proportional Hazards Models
  • Registries
  • Seasons
  • United States / epidemiology
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood
  • Vitamin D Deficiency / epidemiology*

Substances

  • Vitamin D
  • 25-hydroxyvitamin D