Blood pressure and dementia: A review

Hypertension is a well known risk factor for cerebrovascular events and, therefore, for vascular dementia, but the relationships of hypertension with senile dementia of Alzheimer's type (SDAT) are still debated. In cross-sectional studies, patients with cognitive impairment due to SDAT show blood pressure values lower than in normal controls or in subjects with other forms of dementia; this finding is explained by the atrophy of brain structures involved in central blood pressure regulation. However, longitudinal observations, revealed that high blood pressure values are independently related to the onset of SDAT, suggesting that hypertension may contribute to the development of degenerative dementias. Indeed, magnetic resonance imaging studies have shown, in old hypertensive subjects, atrophy of brain structures, which seems more evident when blood pressure is poorly controlled. Moreover, pathological studies show that, in patients with hypertension, the brain is characterized by higher density of senile plaques. An increased production or deposition of beta-amyloid substance and impairments in regional blood flow and/or in protective autoregulatory mechanisms, particularly significant in watershed areas of arterial supply, could explain the link between hypertension and SDAT. Recent therapeutical studies are in agreement with the above findings, showing that treatment with different classes of antihypertensive drugs may reduce the risk of incident dementia. New trials, specifically designed to assess the effects of therapy on cognition in elderly hypertensives, now in progress, will provide new insight on this issue, which represents a huge socioeconomic problem in industrialized countries.