Abstract

Objective: To evaluate whether impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) are associated with increased risk of mortality and prevalent ischemic heart disease (IHD); to analyze if the increased risk of death is dependent on subsequent development of diabetes in Pima Indians.

Research Design and Methods: 2,993 Pima Indians aged 35 years and older were included. Prevalent IHD, defined by major ischemic ECG changes, was evaluated according to the following glucose/diabetes categories: normal glucose regulation (NGR), IFG and/or IGT, and diabetic groups by duration. During a median follow-up of 10.4 years, 780 subjects died from natural causes and 156 of these from IHD. Mortality was analyzed according to the same glucose/diabetes categories at baseline and then as time-dependent variables.

Results: Only subjects with diabetes ≥15 years of duration have a higher prevalence of IHD (odds ratio=1.9, 95% CI=1.4–2.5) relative to NGR. In baseline and time-dependent models, age-sex-adjusted death rates from natural causes and from IHD were similar among the nondiabetic groups. Among diabetic subjects, natural mortality was higher in those with ≥15 years diabetes duration (death rate ratio (DRR) relative to NGR=2.6, 95% CI=2.1–3.3). IHD mortality was higher in subjects with long diabetes duration (DRR for diabetes 10–15 yrs=3.8, 95% CI=1.5–9.5; DRR for diabetes ≥15 years=8.6, 95% CI=3.8–19.4) in the time-dependent model.

Conclusions: Natural and IHD mortality are not increased in Pima Indians with IFG and/or IGT. Only after the onset of diabetes do the rates of these events increase relative to NGR.