Sympathetic activity in borderline and established hypertension in the elderly

Although increased sympathetic outflow has been implicated in the induction of early essential hypertension, the increase in norepinephrine with advancing age could reflect a compensatory mechanism for a declining peripheral response to adrenergic stimuli or an age-related decrease in norepinephrine clearance. To evaluate the activity of the sympathetic system and of plasma renin in elderly patients with borderline and established essential hypertension, 31 borderline hypertensives aged less than 60 years (mean age 38 years), 30 established essential hypertensives aged less than 60 years (mean age 39 years), 15 borderline hypertensives aged greater than 60 years (mean age 66 years) and 15 essential hypertensives aged greater than 60 years (mean age 68 years) were studied at rest and after dynamic exercise. Blood pressure and the heart rate were automatically recorded and blood samples were collected for plasma renin activity and plasma epinephrine and norepinephrine assays. Plasma epinephrine levels showed no significant differences between the groups examined at rest. Nevertheless, young borderline hypertensives had higher plasma epinephrine levels than young essential hypertensives after stress, and elderly borderline hypertensives showed higher plasma epinephrine levels than the age-matched essential hypertensives in response to dynamic exercise. The plasma renin activity profile was similar among all the groups, but dynamic exercise induced a greater increase in borderline than in essential hypertensives. Moreover, the stress-induced increase in plasma norepinephrine levels was higher in essential than in borderline hypertensives. Our results show a greater epinephrine response to stress in elderly and young borderline hypertensives than in age-matched essential hypertensives.(ABSTRACT TRUNCATED AT 250 WORDS)