Combined Effect of Initial and Longitudinal Increases in γ-Glutamyltransferase on Incident Metabolic Syndrome: ARIRANG Study

PURPOSE Although γ-glutamyltransferase (GGT) is well known to be associated with metabolic syndrome (MS), prospective data on baseline and longitudinal changes in GGT levels and incident cases of MS are limited. We aimed to examine prospective associations between changes in GGT levels over time, as well as at baseline, and incident MS in Korean adults. MATERIALS AND METHODS A total of 2579 Korean adults free of MS were followed up for 2.6 years. Data were collected from 2005-2008 (baseline) and from 2008-2011 (follow-up). Serum GGT levels were determined by enzymatic methods. RESULTS During follow-up, 558 participants (21.6%) developed MS. A gradual increase in the incidence of MS was observed across GGT quartiles. After adjustment for confounding factors, the odds ratio and 95% confidence interval (CI) for new onset MS, comparing the highest to the lowest quartiles of baseline GGT, was 2.07 (95% CI: 1.52-2.80). The odds ratio for the highest GGT changes (>4 IU/L increase) in comparison to the lowest GGT changes (<-5 IU/L decrease) was 1.75 (95% CI: 1.32-2.33). Among participants with baseline GGT concentrations <the median, the odds ratio for incident MS, comparing participants with the highest GGT changes with the lowest GGT changes, was 1.52 (95% CI: 1.01-2.31). Among participants with baseline GGT concentration ≥the median, the corresponding odds ratio was 2.75 (95% CI: 1.84-4.10). CONCLUSION High initial GGT concentration and increases in GGT concentration over time should be considered independent predictors of and to have a combined effect on incident MS.