25-Hydroxyvitamin D deficiency and diabetes predict reduced BMD in patients with chronic kidney disease

In this study of 242 patients with renal failure, women, patients with diabetes, and patients on peritoneal dialysis had the highest risk of 25-hydroxyvitamin D deficiency. Levels correlated positively to BMD Z scores, and hip BMD was inversely related to prevalent fracture. Increasing 25-hydroxyvitamin D levels may benefit these patients.

25-Hydroxyvitamin D deficiency (<37 nM) is common in patients with chronic kidney disease (CKD) stage 5 (glomerular filtration rate < 15 ml/min/1.73 m(2) or on dialysis), but it is unclear if this deficiency is associated with bone disease and if supplementation is warranted.

Blood samples were collected on 242 patients with CKD stage 5 caused by type 1 diabetes (33%), type 2 diabetes (2%), and other causes (65%), who were about to undergo kidney or kidney pancreas transplantation. Prevalent spinal fracture was assessed by X-ray and BMD by DXA.

25-Hydroxyvitamin D deficiency was present in 28% of patients with diabetes versus 12% without (p < 0.0001). Patients on peritoneal dialysis (PD) had lower levels of 25-hydroxyvitamin D than patients on hemodialysis (HD; 49 +/- 26 versus 77 +/- 34 nM; p < 0.0001), and women had lower levels than men (51 +/- 25 versus 77 +/- 35 pM; p < 0.0001). BMD Z scores were within 1 SD of the mean at all sites, except in patients with diabetes (femoral neck Z score, -1.07 +/- 1.2; p < 0.0001) and patients who had undergone parathyroidectomy (lumbar spine Z score, 1.03 +/- 1.34, femoral neck Z score, 1.24 +/- 1.35; p < 0.001 and p < 0.0001, respectively). In multiple stepwise linear regression analysis, levels of 25-hydroxyvitamin D correlated positively and intact PTH (iPTH) correlated negatively to Z scores at the lumbar spine and wrist. Time on dialysis correlated positively to Z scores at the femoral neck and lumbar spine. Diabetes and serum alkaline phosphatase levels correlated negatively with Z scores at the femoral neck. Lower femoral neck BMD was associated with an increased prevalence of vertebral fracture and fragility fracture at any site (p = 0.03 and p < 0.03, respectively).

This study of patients with CKD stage 5 identifies women, patients with diabetes, and patients on PD as being at particular risk of 25-hydroxyvitamin D deficiency. We describe positive associations of 25-hydroxyvitamin D levels and BMD Z scores and an association between femoral neck BMD and fragility fracture at any site. Treatment to improve 25-hydroxyvitamin D levels may benefit these patients.