Persistent impaired glucose tolerance, insulin resistance, and β-cell dysfunction were independent predictors of type 2 diabetes

Background and Objective: To compare clinical profiles and risk of diabetes between subjects with transient (trIGT) and persistent (pIGT) impaired glucose tolerance in Taiwan. Study Design and Setting: In the pIGT group, IGT was diagnosed in two consecutive periods (1992-1994 and 1995-1996); in the trIGT group, the diagnosis was IGT at the baseline but normal glucose tolerance in the second period. The normal group was defined by fasting plasma glucose < 6.1 mmol/L and 2-hour post-load plasma glucose < 7.8 mmol/L in both periods. All three groups were considered eligible subjects for further follow up (1998-1999). Results: Among 298 nondiabetic subjects at baseline, there were 29 new cases of diabetes diagnosed according to 1999 WHO criteria in 1,614.3 person-years of follow-up (1.79%/year; 95% CI = 1.14-2.44%/year). Among subjects with normal, trIGT, or pIGT, the incidence rates were 0.73%/year (8/1,093.0; 95% CI = 0.22-1.24%/year), 2.57%/year (7/272.2; 95% CI = 0.67-4.47%/year), and 5.62%/year (14/249.1; 95% CI = 2.68-8.56%/year), respectively. Conclusion: The group with trIGT had abnormal glucose tolerance and β-cell dysfunction, which may represent an earlier stage than the group with pIGT in development of type 2 diabetes. Moreover, pIGT, insulin resistance, and β-cell dysfunction played independent roles in the deterioration from IGT to diabetes.