Effects of metabolic syndrome on kidney transplantation outcomes: a systematic review and meta-analysis.

Metabolic syndrome (MS) has been associated with proteinuria and reduced glomerular filtration rate. Immunosuppressive agents increase the incidence of traditional risk factors for cardiovascular disease (CVD) and have known effects on MS components after kidney transplantation. The purpose of this meta-analysis was to evaluate the impact of MS on relevant outcomes after kidney transplantation. MEDLINE, EMBASE, and Cochrane Library were searched up to November 7, 2015. Papers that compared patients with and without MS and assessed one of the following outcomes, graft loss, death by cardiovascular disease, and all-cause mortality, were included. Of 585 studies identified, five studies including 1269 patients were evaluated. MS was identified as a risk factor for graft loss [relative risk, 3.06; 95% confidence interval (CI), 2.17, 4.32; I² = 0%; P heterogeneity = 0.72] and death by CVD (relative risk, 3.53; 95% CI, 1.27, 9.85; I² = 0%; P heterogeneity = 0.40). Results on the association between MS and all-cause mortality were inconclusive (relative risk, 2.61; 95% CI, 0.70, 9.81; I² = 58%; P heterogeneity = 0.09). Graft loss and death by CVD were associated with the presence of MS after transplantation. Randomized clinical trials should be conducted to define whether interventions on each MS component would result in better outcomes after transplantation.