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