Age-related changes in autonomic control: the use of beta blockers in the treatment of hypertension.

Functional decrements in autonomic control and reflex activity in the elderly resemble the effects of beta-adrenoreceptor blockade. This arises partly from an age-related decrease in intrinsic beta-adrenoreceptor sensitivity and partly from effector changes associated with degenerative processes such as arteriosclerosis. In the elderly, compensatory adjustments in cardiovascular control result from both sympathetic and parasympathetic dysfunction. The characteristics of aging in autonomic nervous control are examined in relation to the treatment of essential hypertension by beta blockers in the elderly. Increased cardiac output with exercise depends more on increased intracardiac volume than on sympathetic modulation of heart rate in older people. Baroreceptor-dependent and renin blood pressure responses are diminished. The cold pressor response, which is found to be greater in the elderly than in young adults, is abolished by alpha and not beta blockers. Blood viscosity and blood platelets also increase in moderately cold conditions, and a beta blocker with vasodilator and antiplatelet activity may therefore be useful. Trigeminal cardiorespiratory reflex responses to facial cooling evoke a higher blood pressure but smaller bradycardia in old people. These constraints of autonomic nerve function on the use of beta blockers for treating hypertension are imposed on a background of altered drug pharmacokinetics and pharmacodynamics in the elderly.