[Insulin resistance in elderly patients with hypertension]

Insulin resistance and hyperinsulinemia have been linked to essential hypertension. Some epidemiological studies showed that the prevalence of hypertension, glucose intolerance, and diabetes mellitus increase with advancing age. Among normotensive subjects, insulin sensitivity was significantly lower in the elderly than in the young. A significant negative correlation was found between insulin sensitivity and age. During hyperinsulinemia, urinary sodium excretion and fractional excretion of sodium did not change in young normotensive subjects, but they decreased significantly in elderly normotensive subjects. Increases in plasma norepinephrine concentration and in plasma activity were observed in normotensive subjects of all ages. Among patients with essential hypertension insulin sensitivity did not differ between age groups. No age-related decrease in insulin sensitivity (as found in normotensives) was observed, and insulin sensitivity in patients with essential hypertension was low, even in those who were young. In both young and elderly hypertensive subjects, urinary sodium excretion and fractional excretion of sodium decreased, and plasma norepinephrine concentration and plasma renin activity increased significantly during hyperinsulinemia. These results indicate that 1) reduction in insulin sensitivity plays a role in age-related acceleration of hypertension and of glucose intolerance; 2) in patients with essential hypertension, selective insulin resistance with respect to glucose metabolism can be found even in those who are young; and 3) both sodium retention and pressor system activation via insulin might cause blood pressure to increase in patients with essential hypertension.