Abstract
A total of 507 subjects who received oral glucose tolerance tests (OGTT) because of postprandial glycosuria in an epidemiologic survey, were called for retest 7 years later, and the 207 out of 419 subjects (excluding 88 deaths during this period) who responded to the retest are included in the present study. The rate of worsening to diabetes in those with impaired glucose tolerance, and the risk factors were examined.
1) The mean serum glucose' values in OGTT at the follow-up examination were elevated by about 10%, compared to those at the initial examination. The elevation of serum glucose values was much greater in obese subjects than in nonobese subjects.
2) Those with a 2-hour glucose value (2-h) between 110-199 mg/dl at the initial test tended to shift to the lower glucose category, 2-h<110 mg/dl, when they were not obese. On the other hand, there was an obvious trend to move to the higher glucose category, 2-h≥200 mg/gl, when associated with obesity.
3) Among those with a fasting glucose value (F)<140 mg/dl and a 2-hour glucose value <<200 mg/dl, the worsening rate to “diabetes” according to the new criteria recommended by WHO in 1980 (F≥140 mg/dl or 2-h≥200 mg/dl) was increased as the 2-hour level of the subjects at the initial test elevated. When these subjects were further broken down into three subgroups: normal, borderline and diabetic according to the criteria of Japan Diabetes Society, the corresponding worsening rates were 1.1%, 8.5% and 55.6%, respectively.
4) Multivariate discriminant function analysis indicated that three glucose determinations of OGTT, fasting, 1-hour and 2-hour values, sex and obesity were highly related to the worsening.
It was concluded that most “borderline” cases according to the conventional classification can be reclassified as normal for practical purposes. At the same time however, it should be pointed out that elevated serum glucose levels and obesity do represent important risk factors for worsening to diabetes.
