Association between bone mineral density at different anatomical sites and both mortality and fracture risk in patients receiving renal replacement therapy: a longitudinal study

BACKGROUND: The clinical utility of bone mineral density (BMD) measurement by dual-energy X-ray absorptiometry (DXA) is debated in end-stage kidney disease (ESKD). We assessed the ability of BMD measured at different anatomical sites to predict mortality and fracture risk in patients requiring renal replacement therapy (RRT). METHODS: We reviewed all-cause mortality as well as incident hip and overall fracture risk in RRT patients who had BMD measured at the femoral neck, lumbar spine, arm, head, pelvis and total body as part of their routine follow-up between January 2004 and June 2012 at a single university centre. RESULTS: A total of 588 patients were included. The median follow-up was 6.5 years, the mean age was 59.6 years and 57.9% were males. Femoral neck BMD (FNBMD) (normal/high versus low) was negatively associated with mortality in univariate and multivariate analyses (P < .001 and P = .048, respectively). Other sites of BMD measurements were not associated with mortality. In multivariate analysis, FNBMD was negatively associated with hip and any fracture risk (P = .004 and P = .013, respectively). No significant interaction was found between FNBMD and gender or parathyroid hormone (PTH) (P = .112 and P = .794, respectively). CONCLUSIONS: BMD measured at the femoral neck is predictive of mortality in patients requiring RRT, regardless of modality. Low BMD might be a marker of global patient frailty rather than a direct causal factor in this setting. FNBMD is also a strong predictor of hip and any fracture risk in this population, regardless of bone turnover as assessed by PTH levels. FNBMD is thus an overall prognostic marker in patients requiring RRT.