MO1011: The Effect of Vitamin D on Bone Mineral Density: A Real-Life Study in Long-Term Kidney Transplant Recipients Never Supplemented

Abstract

Abstract BACKGROUND AND AIMS Vitamin D insufficiency has been associated with decreased bone mineral density (BMD) in kidney transplant patients (KTRs). However, few data on BMD changes due to vitamin D supplementation in long-term KTRs are available. The purpose of our study is to ascertain the effect of 25-OH-vitamin D (25-OH-D) supplementation on the BMD over a follow-up period of up to 3 years in a real-life cohort of long-term KTRs never supplemented with 25-OH-D and not treated with active vitamin D, bisphosphonate and calciomimetics. METHOD Demographic, clinical and laboratory data were collected. Inclusion criteria were: (1) being a recipient of a kidney from a cadaveric or living donor, (2) age ≥ 18 years and (3) no therapy with inactive vitamin D sterols. Patients with parathyroidectomy and/or history of bone fractures were excluded. BMD was evaluated with standard DEXA, performed at baseline (before vitamin D supplementation) and at the end of the study period. BMD was assessed at lumbar vertebral bodies (LV) and right femoral neck (FN) by a single operator. Bone mineral content (BMC) was calculated in grams (g), bone area in centimetres squared (cm2), and BMD in g/cm2 (BMC divided by the area). According to WHO criteria, results were expressed as T-score [standard deviation (SD) relative to young healthy adults] and Z-score (SD relative to age-matched controls). Osteoporosis and osteopenia were defined as T-score ≤−2.5 SD and T-score <−1 and >−2.5 SD, respectively. According to plasma levels, 25-OH-D was supplemented as recommended for the general population. Linear mixed model analysis was implemented to test the impact of 25-OH-D use on Z-score, T-score and BMD changes (dependent variables) adjusted for sex, age, BMI and presence of diabetes. Z-score, T-score and BMD changes were defined as Z-score, T-score and BMD at follow-up, Z-score, T-score and BMD at study inception. RESULTS A total of 118 KTRs consecutive outpatients never supplemented with 25-OH-D, of whom 69 KTRs were untreated (KTRs-free) and 49 were treated (control group) with bisphosphonate (n = 13) and/or calcio-mimetics (n = 11) and/or active vitamin D (n = 29) were enrolled. Clinical and biochemical characteristics are shown in Table 1. At the basal DEXA, the percentage of osteopenia and osteoporosis was 39.0% and 21.2% at LV; 52.5% and 16.9% at FN, respectively. The mean study-period was 27.7 ± 3.4 months. Basal and follow-up Z-score, T-score and BMD at both measurement sites are reported in Table 2. In linear mixed model analysis, a positive interaction of 25-OH-D supplementation on T-score and Z-score changes at the lumbar vertebral bodies was found (P < .05). At the end of the study, no statistical differences in Z-score, T-score and BMD gains were observed. CONCLUSION Prolonged supplementation with 25-OH-D affects Z-score and T-score at LV in long-term KTRs never supplemented with active or inactive vitamin D.