Progression to clinically diagnosed and treated diabetes from impaired glucose tolerance and impaired fasting glycaemia.

AIMS: To evaluate the risk of diabetes in subjects with impaired fasting glycemia (IFG) as compared with impaired glucose tolerance (IGT) and normal glucose tolerance. METHODS: Men (1223) and women (1370) aged 45-64 years and free of diabetes at baseline were followed-up for 10 years, with 26 737 person years accumulated. The incident diabetic cases were identified through the national Drug Register and the Hospital Discharge Register. RESULTS: During the 10 years of follow-up, 53 (4.3%) men and 47 (3.4%) women developed diabetes. IFG alone defined 22 (15.5/1000 person years) diabetic cases, which was higher than for subjects with normal fasting glucose. Subjects with isolated IGT identified an additional 34 cases (155% more) which could not be defined by IFG alone. The area under the ROC curve was larger for 2-h glucose (0.77, 95% CI 0.72-0.82) than for fasting glucose (0.65, 0.58-0.71). The multivariate adjusted Cox hazard ratio was higher for isolated IGT (3.9, 95% CI 2.4-6.2) than for isolated IFG (2.3, 0.9-5.7) as compared with subjects with neither IFG nor IGT. CONCLUSION: Both IFG and IGT are risk predictors for diabetes, but IGT defines a much larger target population for prevention.