Clinical Significance of Incident Osteoporotic Fractures After Kidney Transplantation: A National Korean Cohort Study

Rationale & Objective: Recipients of kidney allografts are at risk of osteoporotic fractures (OF), but the association of OF with transplant patient outcomes remains uncertain due to common coexisting risks and complex medical conditions. This study sought to assess whether the overall incidences of OF among recipients of kidney allografts compared to that of patients receiving maintenance dialysis for kidney failure. Study Design: A national retrospective cohort study. Setting & Participants: 145,090 Korean patients newly diagnosed with kidney failure between 2009 and 2019. Exposure: Kidney transplantation versus dialysis resulting in OF, and OF increasing risk of death. Outcome: Incident OF overall and by site (hip, spine, forearm, and humerus); death. Analytical Approach: Comparison of patients receiving maintenance dialysis with recipients of kidney allografts matched by age, sex, year of new index date, duration of dialysis, and presence of hypertension and diabetes mellitus. Cause-specific Cox proportional hazards regression models estimated the association between modality of kidney replacement therapy and OF. Cox models incorporating OF as a time-updated covariate were used to estimate the association of OF and mortality. Results: A total of 11,413 pairs were matched. Over the entire study period, 541 (4.7%) OFs in allograft recipients and 657 (5.8%) in matched dialysis comparators occurred, respectively. After 5.5 years of follow-up evaluation, the risk of incident OF was lower in kidney transplant recipients compared with matched dialysis comparators (adjusted hazard ratio[AHR], 0.73 [95% CI, 0.64-0.84], P < 0.001). The differences in fracture rates were primarily driven by differences in hip fractures. Incident OF was associated with increased mortality risk (AHR, 2.18 [95% CI, 1.57-3.02], P < 0.001) and death-censored allograft failure (AHR, 1.42 [95% CI, 1.02-1.97], P = 0.040). Limitations: Use of claims data, and no data on bone mineral density or hyperparathyroidism; the definition of OF that was used encompassed traumatic fractures. Conclusions: Kidney allograft recipients have a lower rate of incident OF compared with dialysis patients, but when OF occurs it is associated with a higher rate of death and allograft loss.