Aims: to examine the incidence rate of progression to Type 2 diabetes and baseline prognostic risk factors, focusing on hypertension and antihypertensive medication, in a cohort (n=207) with impaired glucose tolerance (IGT).
Methods: after 2 and 4.6 (1. 9-6.4) years new cases of diabetes were diagnosed by the oral glucose tolerance test (OGTT). Hypertension (BP 160/95 or antihypertensive medication) was included in multiple regression analyses to assess the effect of risk factors on the development of diabetes.
Results: diabetes developed in 32 subjects (19%), an incidence of 41/1000 (95% CI 28-57/1000) person-years. In univariate analyses, progression to diabetes was associated with a high (>9.0 mmol/l) 2-h OGTT value (P=0.008), a high fasting insulin (>12.0 mU/l) level (P=0.000), a high triglyceride (>/=1.3 mmol/l) level (P=0.028), a high BMI (>/=28.0 kg/m(2)) (P=0.013) and hypertension (P=0.003). The risk for the development of diabetes was not increased in hypertensive subjects without antihypertensive medication compared with normotensive subjects (OR 0.8, 95% CI 0.3-2. 6). However, it was increased in subjects with on medication, especially diuretics alone or in combination with other drugs. Hypertensive subjects on diuretics had higher levels of fasting insulin and triglycerides and higher BMIs at baseline than normotensive subjects. After adjustment for 2-h OGTT, fasting insulin, triglycerides and BMI, the OR for diabetes was 7.7 (95% CI 2.1-28.2) in hypertensive subjects using diuretics alone or in combination with other drugs and 2.6 (95% CI 1.0-6.7) in those using other drugs compared with normotensive subjects. The OR of diabetes corresponding to a one-unit increase in the 2-h OGTT concentration was 2.5 (95% CI 1.6-4.0) in the whole cohort.
Conclusions: the rate of progression from IGT to Type 2 diabetes in this population was similar to that seen in other studies among Caucasian populations. The use of antihypertensive medication, especially diuretics, and a high 2-h OGTT level were significant predictors of subsequent deterioration to diabetes.