Estimated Number of Prevalent Kidney Transplant Recipients in Japan From 1964 to 2023

Dear Editors, Kidney transplantation is one of the primary modalities of kidney replacement therapy (KRT) for patients with kidney failure. Compared with dialysis, it offers multiple advantages, including improved survival, better quality of life, and reduced healthcare costs (1,2). Therefore, understanding the implementation of kidney transplantation is essential for appropriate healthcare resource allocation and policy planning in each region. In Western countries, kidney transplantation is highly prevalent, with approximately 30-50% of patients receiving KRT being transplant recipients (3,4). In contrast, in Japan, kidney transplantation remains a relatively limited treatment modality, primarily due to donor shortages and potential cultural factors (5)(6)(7).The Japan Society for Transplantation, in collaboration with the Japanese Society for Clinical Renal Transplantation, has long collected detailed data at the time of transplantation, providing accurate statistics on the number of transplants and donor types (5-7). However, longterm post-transplant follow-up is not always complete, leaving the number of kidney transplant recipients with functioning grafts (i.e., prevalent recipients) uncertain. This lack of information represents a significant limitation for evaluating the proportion of transplant recipients relative to patients on dialysis and for conducting international comparisons.To address this, we estimated temporal trends in the number of prevalent kidney transplant recipients in Japan using summary statistics published by the Japan Society for Transplantation (5)(6)(7). Furthermore, using data from the Japan Society for Dialysis Therapy Renal Data Registry (8), we calculated the proportion of prevalent kidney transplant recipients among all patients receiving KRT.The annual numbers of living-and deceased-donor kidney transplants performed from 1964 to 2023, obtained from the Japan Society for Transplantation records (5)(6)(7), are summarized in Supplementary Figure S1 and Table S1. The number of transplants was very low in the 1960s, Registry (8). Detailed numerical data are provided in Supplementary Tables S2 andS3.