#406 Association between skeletal muscle mass and bone mineral density in kidney transplant recipients: a retrospective cohort study

Abstract Background and Aims Kidney transplant recipients have a higher prevalence of osteoporosis and osteopenia compared to the general population. Sarcopenia, characterized by loss of skeletal muscle mass and strength, is also common in this population and is hypothesized to impact bone health. This study aimed to investigate the relationship between skeletal muscle mass index (SMI) and bone mineral density (BMD) in kidney transplant recipients, addressing sex-specific differences and other related factors. Method This retrospective observational cohort study included 371 kidney transplant recipients at least six months post-transplantation, followed at a single center for kidney transplant follow-up in Japan. BMD was measured at the femoral neck using dual-energy X-ray absorptiometry (DXA), while SMI was assessed using bioelectrical impedance analysis. Multivariate regression models were employed to analyze the independent association of SMI with BMD, adjusted for factors such as eGFRcysC and 25-hydroxy vitamin D (25(OH)D). Analyses were stratified by sex to account for biological differences. Results Of the 371 participants (65.4% male, median age 52 years), SMI was independently associated with BMD across both sexes. In multivariate analyses, eGFRcysC, 25(OH)D, and SMI were significant predictors of BMD. Additional sex-specific findings included hemoglobin as a significant factor in men, while age and serum albumin were influential in women. Neither dialysis history nor time since transplantation was significantly associated with BMD. Stratified comparisons by SMI and 25(OH)D levels highlighted their substantial impact on BMD. Conclusion Low SMI is independently associated with reduced BMD in kidney transplant recipients, underscoring the interplay between muscle and bone health. The findings suggest the importance of incorporating muscle mass evaluation into routine post-transplant care to better manage osteoporosis risk. Future prospective studies are warranted to explore whether interventions targeting skeletal muscle can improve BMD and reduce fracture risk in this population.