Increased Sympathetic and Decreased Parasympathetic Cardiac Innervation in Patients With Alzheimer's Disease

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Abstract
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.