Classification of glucose intolerance in the aged based on hemoglobin A1

While the incidence of glucose intolerance increases with age, the diagnostic criteria of diabetes mellitus in the aged have been controversial. In this study, glucose intolerance in the aged was classified according to the changes in Hb A1 concentrations and plasma glucose levels at the time of 50 g oral glucose tolerance test. Ninety-six aged Japanese (60-90 years old, mean 72 years) were studied. Hb A1 was measured by Fast Hb Test System. The results suggested the existence of critical plasma glucose levels for the increment in Hb A1 in the aged, and the critical values were around 120 mg/100 ml at fasting, and around 240 mg/100 ml at 60 or 120 min after glucose load. Using these critical plasma glucose levels, glucose intolerance in the aged was classified into two groups, i.e., Group 1 with fasting plasma glucose below 120 mg/100 ml and both plasma glucose levels at 60 and 120 min below 240 mg/100 ml, and Group 2 with fasting plasma glucose above 120 mg/100 ml and both plasma glucose levels at 60 and 120 min above 240 mg/100 ml. The incidence of elevated Hb A1 in Group 1, 4.3%, was significantly lower than 94.1% in Group 2, and insulinogenic index at 30 min in Group 1, 0.74, was significantly higher than 0.07 in Group 2. In conclusion, it was proposed that subjects in Group 2 represent diabetes mellitus, while subjects in Group 1 might not be of pathological glucose intolerance in the aged.