Predictive properties of impaired glucose tolerance for cardiovascular risk are not explained by the development of overt diabetes during follow-up

OBJECTIVE: To evaluate the relationship of impaired glucose tolerance (IGT) at baseline to coronary heart disease (CHD) incidence, and cardiovascular disease (CVD) and total mortality at follow-up, and to analyze whether the relationship is independent of the subsequent development of diabetes during follow-up. RESEARCH DESIGN AND METHODS: A baseline screening survey for diabetes was performed in 1987 using a 2-h 75-g oral glucose tolerance test. A total of 1234 men and 1386 women aged 45-64 years, who were free of diabetes at baseline, were followed up for 10 years. During the follow-up, 153 subjects had an incident CHD event, 224 died, and 100 deaths were due to cardiovascular causes. Multivariate adjusted (adjusted for age, sex, waist-to-hip ratio, systolic blood pressure, cholesterol, HDL cholesterol, and smoking) hazard ratio (HR) was estimated using Cox regression analysis. RESULTS: In subjects who had IGT at baseline and who did not progress to diabetes during the follow-up, the multivariate adjusted HR (95% CI) was 1.49 (0.95-2.34) for CHD incidence, 2.34 (1.42-3.85) for CVD mortality, and 1.65 (1.13-2.40) for all-cause mortality. CONCLUSIONS: Baseline IGT was an independent risk predictor for cardiovascular morbidity and mortality and for total mortality, which was not confounded by the subsequent development of overt diabetes.