Posture and brain function in dementia. A study with special reference to orthostatic hypotension

Sammanfattning: Orthostatic hypotension (OH) is believed to be an important cause of cerebral hypoperfusion, leading to chronic fatigue, blurred vision, unsteadiness, dizziness and sometimes syncope. It may also result in episodes of confusion, falls and fractures. The coupling between OH and organic dementia is not clear. Our findings in a large group of patients with Alzheimer's disease, vascular- and frontotemporal dementia has shown a higher prevalence of OH than is seen in healthy elderly people. To examine the blood pressure we used a standardized orthostatic test. The systolic blood pressure drop varied from 20 to about 100 mm Hg. In about 30% of the patients the blood pressure drop did not appear until after 5 minutes or later in the upright position. About 50% of the patients did not report or show any orthostatic symptoms despite marked blood pressure drops. Falls and multiple fractures were significantly higher in the orthostatic patients. The aim of the study was also to investigate whether postural challenge and OH alters the regional cerebral blood flow (rCBF). The results showed significant and consistent lower values in frontal areas during head-up tilt than during supine position. In autopsy verified Alzheimer-cases, additional white matter disease (wmd) was found in about 2/3 of the patients. A highly significant decrease of blood pressure was seen during the progression of dementia in the Alzheimer-patients, especially in those with wmd. The suggested cause of this regional white matter hypoperfusion is the interaction of non-occlusive small vessel sclerosis with recurrent episodes of low blood pressure. Our results also indicate, that in patients with orthostatic symptoms, the cerebral autoregulation seemed more vulnerable than in those without symptoms. Recognition of OH as well as low blood pressure is crucial, and as a risk factor it may not only be treatable but also preventable.