Objective: To determine the predictive risk factors for the development of type 2 diabetes mellitus (DM) or impaired glucose tolerance (IGT) in a normoglycemic population.
Research design and methods: This is a ten-year prospective study in a randomly selected urban population including 1835 subjects aged >=30 years living in Tunis, 1460 were normoglycemic according to 2 hours blood glucose WHO criteria, and 701 among them attended the follow-up assessment ten years later. Subjects with impaired glucose tolerance (IGT) were excluded. Subjects underwent a physical examination including weight/height, iliac circumference (IC) and blood pressure measurements. Fasting and 2-hour venous blood sampling, after a 75 g oral glucose load, were performed for the measurement of plasma glucose (G(0), G(2h)), insulin (I(0), I(2h)), total cholesterol (TC) and glycated hemoglobin (HbA(1c)) levels.
Results: Out of the 701 normoglycemic subjects in 1985, 77 developed diabetes and 130 impaired glucose tolerance after 10 years, giving a mean annual incidence rate of 1.1% for diabetes and 1.85% for IGT. Univariate analysis showed that risk factors for diabetes were age, BMI, IC, SBP, G(0) and total cholesterol in both sexes, I(0) and I(2h) in men only and DBP G(2h) and HbA(1c) in women only. Risk factors for IGT were BMI, IC and G(2h) in both sexes, I(2h) in men only and G(0) in women only. Multivariate analysis revealed that BMI, G(0) and G(2h) were independent risk factors for conversion to diabetes or IGT in both sexes, but HbA(1c) and IC were risk factors only in men.
Conclusion: Early screening and prevention of diabetes must focus on obese subjects, especially those with central fat distribution, and those with moderate increase in fasting and/or two-hour blood glucose levels within the normal range.