INCREASED SYMPATHETIC AND DECREASED PARASYMPATHETIC CARDIAC INNERVATION IN PATIENTS WITH ALZHEIMERS-DISEASE

To assess whether Alzheimer's disease affects the sympathetic and parasympathetic influences on the heart rate, we used power spectrum analysis of heart rate variability derived from simple body-surface electrocardiography. We calculated the energy ratio of low- to high-frequency bands. This ratio was significantly higher in patients with Alzheimer's disease than in normal controls (upright posture, 0.41+/-0.21 vs 0.23+/-0.08). The parasympathetically mediated baroreceptor activity reflected by the energy ratio of medium- to low- and high-frequency bands was significantly depressed in patients with Alzheimer's disease (upright posture, 0.12+/-0.02 vs 0.07+/-0.03; supine posture, 0.11+/-0.02 vs 0.085+/-0.025). Compared with normal volunteer controls, patients with Alzheimer's disease manifested a relatively hypersympathetic, hypoparasympathetic state.