Effects of the pretransplant obesity on kidney transplant outcomes in Korea: a nationwide cohort study

Background The prevalence of obesity is steadily increasing in patients with end-stage kidney disease. However, it is still debatable whether obesity affects outcomes after kidney transplantation. This study evaluated the relationship between pretransplant obesity, defined as a body mass index (BMI) >= 25 kg/m(2), and posttransplant outcomes in Korean kidney transplant recipients (KTRs). Methods We investigated prospective nationwide cohort data from the Korean Organ Transplantation Registry (KOTRY) from 2014 to 2021. KTRs were categorized into 4 groups based on pretransplant BMI: underweight (< 18.5), normal weight (18.5-22.9), overweight (23-24.9), and obesity (>= 25). Posttransplant outcomes, including death-censored allograft loss, cardiovascular events, and all-cause mortality, were compared using Kaplan-Meier curves with the log-rank test. Cox proportional hazard regression analysis was employed to assess associations between BMI and posttransplant outcomes. Results A total of 9,130 KTRs were finally analyzed. The mean age was 49.9 +/- 11.6 and 60.2% of KTRs were male. The prevalence of obesity in KTRs was 28.6% and continued to increase (24.8% in 2014 to 32.5% in 2021). Obese KTRs were characterized by male predominance, shorter dialysis vintage, and more diabetes as primary kidney disease. Kaplan-Meier curve showed a significant difference in death-censored allograft loss among BMI groups (P = 0.007). Obesity (BMI >= 25 kg/m(2)) was as an independent risk factor for death-censored allograft loss (adjusted hazard ratio 1.511, 95% confidence interval 1.063-2.148, P = 0.021), but not for cardiovascular events or mortality. Conclusions Our study evaluated BMI across a spectrum of categories, suggesting that obesity is an independent risk factor for graft survival in KTRs. Risk stratification using BMI and strategies to prevent obesity should be considered in the preparation for kidney transplantation.