Development of diabetes in Japanese subjects with impaired glucose tolerance: a seven year follow-up study.

Five hundred and seven subjects with postprandial glycosuria underwent a 50g oral glucose tolerance test in an epidemiological survey of diabetes mellitus carried out in 1964-1965 in the town of Osaka, Japan. The oral glucose tolerance test was repeated 7 years late in 207 (40.8%) of the subjects. The results of the initial and the follow-up test were classified into three categories according to the new WHO criteria: normal, impaired glucose tolerance and diabetes. Most of the diabetic subjects (84.8%) remained unchanged between the initial and follow-up test. Of the subjects with impaired glucose tolerance at the time of the initial test, 38.5% showed diabetes in the follow-up test, while another 38.5% returned to normal. On the other hand, 13.5% of the normal subjects in the initial test developed impaired glucose tolerance or diabetes in the follow-up test. The rate of worsening to diabetes was related closely to the 2-h blood glucose value at the initial test. In addition, the rate of worsening was higher in males and obese subjects than in females and non-obese subjects. A multiple logistic analysis indicated that the fasting and 2-h glucose values were significantly predictive of worsening to diabetes.