Cardiovascular and Renal Outcomes Among Kidney Transplant Recipients With Metabolic Syndrome: A Systematic Review and Meta‐Analysis

BACKGROUND: Kidney transplant recipients (KTRs) are at elevated risk for metabolic syndrome (MS), primarily due to the side effects of immunosuppressive therapy. Emerging evidence suggests that MS may be associated with adverse outcomes such as cardiovascular disease (CVD), reduced graft function, and graft loss. This review aims to evaluate the association between MS and cardio-renal outcomes in KTRs, specifically its impact on the incidence of cardiovascular events, all-cause mortality, graft failure, and acute graft rejection. METHODS: We conducted a comprehensive search in MEDLINE, EMBASE, and CENTRAL databases from inception to August 2024. No language restrictions were applied. Two reviewers independently screened articles, extracted data, and assessed study quality. Meta-analyses were conducted using fixed-effect or random-effects models depending on heterogeneity. Effect estimates were reported as risk ratios (RRs) with 95% confidence intervals (CIs). RESULTS: Fifteen studies comprising a total of 8986 KTRs (3962 with MS and 5024 without MS) were included. Six studies reported major adverse cardiovascular events and all-cause mortality, nine studies reported graft failure, and seven studies reported acute graft rejection. KTRs with MS had higher risk for major adverse cardiovascular events (RR 2.12, 95% CI: 1.32 to 3.41, p = 0.002), all-cause mortality (RR 1.78, 95% CI: 1.21 to 2.62, p = 0.003), graft failure (RR 1.95, 95% CI 1.58 to 2.39, p < 0.00001) and acute graft rejection (RR 1.53, 95% CI 1.11 to 2.11, p = 0.009). CONCLUSION: KTRs with MS are at significantly increased risk of adverse cardiovascular and renal outcomes. Further large-scale prospective cohort studies using standardized definitions are needed to strengthen causal inference and guide clinical management in this population.