Effects of isolated post-challenge hyperglycemia on mortality in American Indians: the Strong Heart Study

Abstract

Purpose: To assess the effects of isolated post-challenge hyperglycemia (IPH) on risk of cardiovascular disease (CVD), cancer, and all-cause mortality in American Indians using longitudinal data from the Strong Heart Study.

Methods: Of 4549 American Indian women and men aged 45 to 74 years participating in the Strong Heart Study, 4304 had fasting blood measurements or oral glucose tolerance test (OGTT) data to ascertain diabetes status. At baseline and follow-up, a personal interview was conducted, and physical examinations and laboratory tests were performed. Fasting blood samples were drawn for measurement of glucose, fibrinogen, insulin, lipids, lipoproteins, creatinine, and hemoglobin A1c (HbA1c). A 75-g OGTT was performed. Five diabetes categories were defined: (i) known diabetes, (ii) newly diagnosed diabetes (fasting glucose > or =126 mg/dL and no history of diabetes or diabetes medication; ADA-new diabetes), (iii) IPH, (iv) impaired fasting glucose (> or =110 - <126 mg/dL; IFG), and (v) normal fasting glucose (<110 mg/dL; NFG). Surveillance was initiated to determine CVD, cancer, and all-cause mortality over 9 years.

Results: IPH had a worse CVD risk factor profile than NFG, but IPH was associated with a better CVD risk factor profile than known diabetes or ADA-new diabetes. At follow-up, individuals with IFG had no increased risk for CVD or all-cause mortality, whereas those with ADA-new or known diabetes had significantly increased risk (RR = 1.70 and 1.40 for ADA-new diabetes, and RR = 2.87 and 2.19 for known diabetes, respectively). Those with IPH had nonsignificant elevations in risk for CVD (RR = 1.54) and all-cause (RR = 1.27) mortality. Cancer mortality was not increased in those with IFG, IPH, ADA-new diabetes, or known diabetes compared to those with NFG.

Conclusions: Among American Indians 45 to 74 years of age, IPH is associated with nonsignificant elevations in total and CVD mortality. The magnitude of mortality risk associated with IPH is intermediate between diabetes and IFG. Because those with IPH are at high risk for diabetes, American Indians with IPH should be targeted for diabetes prevention.