Reduced Sympathetic Response to Head-Up Tilt in Subjects with Mild Cognitive Impairment or Mild Alzheimer's Dementia

Background: Hemodynamic control was compared in patients with mild cognitive impairment (MCI) or mild Alzheimer's dementia (AD) as well as in healthy elderly subjects. Methods: Noninvasive, continuous hemodynamic recordings were obtained from 14 patients and 48 controls during supine rest (tilt of 30 and 70°). Cardiac output, end-diastolic volume, total peripheral resistance, heart rate variability (HRV), systolic blood pressure variability (SBPV), and baroreceptor sensitivity were calculated. Results: At 70° tilt, the HRV indices differed significantly, with higher high-frequency (HF) variability as well as lower low-frequency (LF) variability and LF/HF ratios in the patients. The patients had significantly lower SBPV in the LF range at 30° tilt. Conclusions: The results indicate a poorer sympathetic response to orthostatic stress in MCI and mild AD