Background: Successful kidney transplantation (KT) has brought better survival and quality of life to patients with end-stage kidney disease (ESKD), although long-term immunosuppressive agent-related side effects such as osteoporosis remain unresolved. We aim to explore the incidence risk of de novo osteoporotic fractures after KT compared with matched dialysis patients.

Method: We constructed a nation-wide retrospective cohort consist of 141,674 ESKD patients from 2008 to 2020 using the National Health Insurance System database of Korea. After 1-year of wash out periods, patients younger than 18-year-old, having previous history of any kind of cancer, experiencing parathyroidectomy, re-transplantation, osteoporotic fracture, or taking osteoporosis-treating medication were excluded. Then, we extracted KT recipients and 1:1-matched dialysis patients according to the age, sex, era, and the presence of hypertension or diabetes. Osteoporotic fractures are defined as fractures associated with low bone mineral density including hip, spine, forearm, and humerus. We compared the de novo osteoporotic fracture incidence between the two groups.

Result: After exclusion of 26883 patients in wash-out periods, 483 children, 6953 having cancers, 336 experiencing parathyroidectomy, 8907 preexisting osteoporotic fractures, 3755 established osteoporosis medications, and 110 re-transplantations, we finally identified 12760 matched KT-dialysis pairs. Their average age was 51.0 ± (10.1) (standard deviation (SD)) years and 7951 (62.3%) were male. Patients with having hypertension and diabetes were 11800 (92.5%) and 4548 (35.6%), respectively. About 30.5% KT patients received their graft preemptively. New-onset osteoporotic fractures after inclusion occurred in 631 (4.9%) of dialysis patients and 588 (4.6%) of KT recipients, respectively. The most common fracture site was forearm in both groups. During overall 4.7 ± 3.1 years of follow up, KT recipients showed similar risk for the development of new-onset osteoporotic fracture compared with matched dialysis controls even after adjustment of matching variables, previous use of steroid or anti-depressants, vitamin D or its analog, calcium-based phosphate binders. In subgroup analysis, they showed a lower risk of hip fracture (adjusted hazard ratio 0.51, 95% CI 0.38-0.67, p <0.001), but similar risks of other types of osteoporotic fractures including spine, forearm, or humerus compared to dialysis controls.

Conclusion: In this study, overall new-onset osteoporotic fracture risk of KT recipients was not different from matched dialysis controls except a lower risk of hip fractures.