The effect of age on glucose tolerance and plasma insulin level in hypertensive and normotensive subjects.

To elucidate the effect of aging and blood pressure on glucose tolerance, we examined the subjects who received 75g OGTT annually for 10 years. They were classified into 2 groups by blood pressure, and into 4 groups by age. The study group consisted of 34 cases (mean 62 years old), including 11 hypertensive (HT) and 23 normotensive (NT) control. All cases had their body weight fluctuate in less than 4 kgs. After blood pressure was measured, blood was drawn for determination of plasma glucose and insulin concentrations in each subject before 75g OGTT and 30, 60, 90, 120 minutes afterward. sigma BS and sigma IRI were defined as the sum of 5 points in BS and IRI, respectively. Insulinogenic index (I.I) was defined as deltaIRI/deltaBS in 30 min. sigma IRI/sigma BS and I.I of each year were calculated serially. They were compared between HT and NT group, and among 4 groups of age; 40s, 50s, 60s and 70s. sigma IRI/sigma BS was significantly decreased in both HT and NT groups (0.52 +/- 0.05 (mean +/- SE) to 0.29 +/- 0.04; p <0.0001 vs. 0.42 +/- 0.05 to 0.23 +/- 0.02; p < 0.0001, respectively). But significant difference between the 2 groups was not observed. No significant difference of sigma IRI/sigma BS among 4 groups of age was found. There were significant differences between I.I of the first year and that of several years, but they did not correlate linearly. These data indicate that the effect of age on the diminution of sigma IRI/sigma BS was significant for 10 years follow-up of the same subjects in both HT and NT groups. But there were no significant differences in classified groups by blood pressure and age.