High-Normal HbA(1c) Is a Strong Predictor of Type 2 Diabetes in the General Population

OBJECTIVE: Glycosylated hemoglobin (HbA(1c)) recently has been recommended for the diagnosis of diabetes by the American Diabetes Association, but its value in the prediction of type 2 diabetes is poorly understood. In this study we evaluated how high-normal HbA(1c) levels predict type 2 diabetes. RESEARCH DESIGN AND METHODS: We measured HbA(1c) in 919 Caucasian subjects, aged 40–79 years, and recorded new cases of type 2 diabetes in the following 15 years. Diabetes was diagnosed with HbA(1c). RESULTS: Subjects were stratified according to baseline HbA(1c) (<5.0, 5.00–5.49 [reference], 5.50–5.99, and 6.00–6.49%). Sex- and age-adjusted hazard ratios (95% CI) for type 2 diabetes were 1.11 (0.30–4.41), 1.00, 3.79 (1.79–8.06), and 12.50 (5.51–28.34), respectively. Results did not change after adjusting for several putative confounding factors and were confirmed when models with updated variables were used. CONCLUSIONS: HbA(1c) is an independent risk factor for type 2 diabetes. Subjects with high-normal levels of HbA(1c) deserve particular attention because they have a strong risk of developing diabetes.