Community screening for glucose intolerance in middle-aged Icelandic men. Deterioration to diabetes over a period of 71/2 years.

A number of 2203 middle-aged Icelandic men (aged 34-61 years) participated in a health survey in Reykjavik in 1967-68. Blood glucose in the fasting state and during an oral glucose tolerance test (OGTT) showed a unimodal distribution with a slight skewness towards higher values. A positive age gradient was established, which showed an increment of about 7 mg/dl per decade in capillary blood sugar values at 11/2 hours after a 50 g oral glucose load. The age gradient was mostly independent of age-related changes in body weight. A 71/2 year followup of the eligible participants (response rate 80%) showed an overall 1% incidence of metabolic deterioration to "overt diabetes" during this period. Those with positive screening tests (50 g OFTT) at baseline were at greater risk of developing diabetes, but the incidence of deterioration in this group was low, about 1% per year. The progression to diabetes was significantly related to body weight at baseline, suggesting that weight reduction might be beneficial in individuals showing impaired glucose tolerance at medical examination. This study, however, lends support to recent reports showing that mildly impaired glucose tolerance cannot be equated with early diabetes.