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

Rationale & objective: Recipients of kidney allografts are at risk for osteoporotic fractures (OF), but their association with patient and allograft outcomes remains uncertain due to common coexisting risks and complex medical conditions. This study sought to assess if overall incidence of OF among recipients of kidney allografts compared to patients receiving maintenance dialysis for kidney failure.

Study design: A national retrospective cohort study.

Setting: & Participants: 145,090 Korean patients with newly diagnosed kidney failure between 2009 and 2019.

Exposure: Kidney transplantation vs dialysis for the outcome of OF. OF for the outcome of death.

Outcomes: Incident osteoporotic fractures, overall and by site (hip, spine, forearm, and humerus); death.

Analytical approach: Comparison of patients receiving maintenance dialysis to recipients of kidney allografts matched for 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, and the rates of incident OF in allograft recipients and the matched dialysis comparators were 5.2% and 5.6%, respectively. After 5.5 years of follow-up, the risk of incident OF was lower in KT recipients compared to matched dialysis comparators (adjusted hazard ratio[aHR] 0.73; 95% confidence interval [CI], 0.64-0.84; P<0.001). Differences in the rates of fracture were principally due to 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: No data on bone mineral density or hyperparathyroidism, and the definition of OFs used encompassed traumatic fractures. Use of claims data.

Conclusions: Kidney allograft recipients have a lower incidence of incident OF compared to dialysis patients, but when they occur OF was associated with a higher rate of death and allograft loss.