Plasma Glucose Regulation and Mortality in Pima Indians

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) and to analyze if the increased risk of death is dependent on subsequent development of diabetes in Pima Indians.

RESEARCH DESIGN AND METHODS—A total of 2,993 Pima Indians aged ≥35 years were included. Prevalent IHD, defined by major ischemic electrocardiogram 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 died 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- and 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 years = 3.8 [1.5–9.5]; DRR for diabetes ≥15 years = 8.6 [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.