Hypertension is a well known risk factor for cerebrovascular events and, th
erefore, for vascular dementia, but the relationships of hypertension with
senile dementia of Alzheimer's type (SDAT) are still debated. In cross-sect
ional studies, patients with cognitive impairment due to SDAT show blood pr
essure 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 observ
ations, revealed that high blood pressure values are independently related
to the onset of SDAT, suggesting that hypertension may contribute to the de
velopment of degenerative dementias. Indeed, magnetic resonance imaging stu
dies have shown, in old hypertensive subjects, atrophy of brain structures,
which seems more evident when blood pressure is poorly controlled. Moreove
r, pathological studies show that, in patients with hypertension, the brain
is characterized by higher density of senile plaques. An increased product
ion or deposition of beta-amyloid substance and impairments in regional blo
od flow and/or in protective autoregulatory mechanisms, particularly signif
icant 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 antihy
pertensive drugs may reduce the risk of incident dementia. New trials, spec
ifically designed to assess the effects of therapy on cognition in elderly
hypertensives, now in progress, will provide new insight on this issue, whi
ch represents a huge socioeconomic problem in industrialized countries.