Blood pressure regulation in Alzheimer's disease.

Brain neurons which regulate blood pressure (BP), including the C-1 tonic vasomotor neurons, degenerate in Alzheimer's disease (AD). This study determines whether BP is decreased in AD. We reviewed records of three autopsy proven AD patients. Medical causes for decreased BP were investigated. Yearly averages for systolic (SBP), diastolic (DBP), mean arterial (AP) blood pressure and pulse pressure (PP) were calculated. BP in the year of diagnosis was compared to the sum of all BP in subsequent years. In addition, each yearly measurement through the course of AD was compared to its counterpart in the year of diagnosis. Three BP measurements were significantly decreased by from 6.9% to 15.9% in all patients when BP in the year of diagnosis was compared to the sum of each pressure in subsequent years. Sustained BP declines started in the third to fourth year after diagnosis of AD and continued for up to 9 years. The PP was decreased by 19.9% in one patient. There was a strong correlation between the number of C-1 neurons in these cases and their AP and SBP in the years after diagnosis. Hypothalamic phenylethanolamine N-methyltransferase activity was decreased by 63% in AD compared to control cases. Neurofibrillary tangles were found in the paraventricular nucleus of the hypothalamus in an AD case. We postulate that BP is altered in AD as neurons which regulate it degenerate.