Gamma glutamyltransferase and metabolic syndrome risk: a systematic review and dose-response meta-analysis

We aimed to quantify and characterise in detail the nature of the dose-response relationship between baseline gamma glutamyltransferase (GGT) level and risk of incident metabolic syndrome (MetS) in the general population and determine the precise estimate of the magnitude of the association.We performed a systematic review and dose-response meta-analysis of published prospective cohort studies. Relevant studies were identified in a literature search of MEDLINE, EMBASE and Web of Science up to May 2014. A potential nonlinear relationship between GGT levels and MetS was examined using restricted cubic splines. Study-specific estimates were combined using random-effects models.Of the 323 studies reviewed, we included 10 prospective cohort studies with data on 67,905 participants comprising of 6595 incident MetS cases. In pooled analysis of seven studies with relevant data, baseline GGT level was statistically significantly positively associated with risk of MetS in a nonlinear fashion (p for nonlinearity = 0.003). Comparing individuals in the top vs. bottom thirds of baseline GGT levels, relative risk for MetS in pooled analysis of all 10 eligible studies was 1.88 (95% confidence interval: 1.49-2.38). Evidence was lacking of publication bias among the contributing studies.Baseline GGT level is positively and strongly associated with risk of the MetS in a nonlinear dose-response manner.