Background. Metabolic syndrome (MetS) is prevalent in patients with end-stage kidney disease, and kidney transplantation is ex- pected to modify the metabolic status. However, whether changes in metabolic status at the time of transplantation affect recipient outcomes remains unclear. 

Methods. We analyzed 4187 recipients registered in a nationwide prospective cohort from 2014 to 2020. MetS was defined as the presence of three or more components of the metabolic syndrome. Patients were classified based on the pre- and post-transplant MetS status: MetS-free, MetS-developed, MetS-recovered and MetS-persistent. Study outcomes were occurrence of death-censored graft loss and a composite of cardiovascular events and death. 

Results. Among recipients without pre-transplant MetS, 19.6% (419/2135) developed post-transplant MetS, and MetS disappeared in 38.7% (794/2052) of the recipients with pre-transplant MetS. Among the four groups, the MetS-developed group showed the worst graft survival rate, and the MetS-persistent group had a poorer composite event-free survival rate. Compared with the MetS-free group, the MetS-developed group was associated with an increased risk of graft loss [adjusted hazard ratio (aHR) 2.35; 95% confidence interval (CI) 1.17–4.98] and the risk of graft loss increased with increasing numbers of dysfunctional MetS components. MetS-persistent was associated with increased risks of cardiovascular events and death (aHR 2.46; 95% CI 1.12–5.63), but changes in the number of dysfunctional MetS components was not. 

Conclusion. Kidney transplantation significantly alters the metabolic status. Newly developed MetS after transplantation was asso- ciated with an increased risk of graft loss, whereas persistent MetS exposure before and after transplantation was associated with increased risks cardiovascular events and patient survival.