Changes in bone mineral density in patients with non-dialysis dependent chronic kidney disease are associated with body composition.

Abstract

Chronic kidney disease (CKD) and low bone mineral density (BMD) are highly prevalent and can co-exist. Parameters of mineral metabolism are associated with BMD in CKD, but other contributing factors may contribute. The aim of this study was to assess changes in BMD and its determinants in patients with non-dialysis-dependent CKD (NDD-CKD). Body composition and biochemical profiles were assessed in a retrospective hospital-based cohort study of patients with NDD-CKD. BMD, lean soft tissue (LST), appendicular LST (ALST), and percentage fat mass were assessed by dual-energy X-ray absorptiometry (DXA). ALST index (ALSTI, ALST/height2) and load-capacity index (LCI, fat mass/LST) were calculated. Low BMD was defined as t-score ≤-1.0. Mean time between assessments was 2.8±1.3 years, 46 patients were included. A reduction in renal function was observed. Changes in body composition included reductions in ALST (p=0.031), ALSTI (p=0.021) and a trend for BMD (p=0.053); and an increase in percentage fat mass (p=0.044) and LCI (p=0.032). Females had a reduction in BMD (p=0.034), ALST (p=0.026), and ALSTI (p=0.037). Patients with low BMD at baseline had lower LST (p=0.013), ALST (p=0.023), and percentage fat mass (p=0.037) than those with normal BMD. Additionally, reductions in LST (p=0.041), ALST (p=0.006), and ALSTI (p=0.008) were observed in patients who had low BMD at baseline, while no significant changes in body composition were observed in those with normal BMD at baseline. The following body composition parameters at baseline were determinants of BMD status at follow-up: LST (OR:0.899, 95%CI:0.829-0.976, p=0.010), ALST (OR:0.825, 95%CI:0.704-0.967, p=0.017), and ALSTI (OR:0.586, 95%CI:0.354-0.968, p=0.037), independent of fat mass, and LCI. Detrimental body composition changes were observed without changes in body weight; these were more significant in females. Moreover, this is the first longitudinal study showing a protective effect of LST against BMD loss in patients with NDD-CKD.