Risk for diabetes and persistent impaired glucose tolerance among middle-aged Finns.

Among 183 middle-aged Finnish subjects with impaired glucose tolerance (IGT) defined according to the 1985 World Health Organization (WHO) criteria) who were retested on average 2.1 years after the first examination, diabetes developed in 14 (7.7%), persistent IGT in 54 (29.5%), and IGT was transient in 115 (62.8%). The odds ratio for diabetes was 4.4 (95% Confidence Interval (CI): 1.3-15.3) among subjects with a body mass index (BMI) of 30 kg/m2 or more, compared with those with a BMI of less than 30 kg/m2. The increase in BMI during the follow-up period was also an independent risk predictor for diabetes. The odds ratios of having persistent rather than transient IGT were 3.0 (95% CI: 1.2-7.8) and 4.3 (95% CI: 1.5-12.6), among subjects with fasting insulin levels of 8.1-12.9 mU/1 and 13.0 mU/1 or more, respectively, compared with subjects with a fasting insulin level of no more than 8.0 mU/1. the degree of glucose intolerance and the diagnosis of hypertension at the initial examination were predictive of persistent IGT. It is evident from the present data that fasting hyperinsulinaemia forms an essential basis of persistence of IGT and diabetes, and that obesity plays a precipitating role for the deterioration from IGT to diabetes. Efforts to prevented diabetes should be focused on ways to reduce insulin resistance and obesity.