Hypertension is a risk factor for stroke, ischemic white matter lesions, silent infarcts, general atherosclerosis, myocardial infarction and cardiovascular morbidity and mortality. This risk increases with increasing blood pressure also at blood pressure within the normal ranges, and a high percentage of these cardiovascular events occur in those with normal blood or mild hypertension. Several studies have reported that high blood pressure precedes Alzheimer's disease by decades, but blood pressure decreases the years before dementia onset and is lower in individuals with Alzheimer's disease than in controls. High blood pressure has also been related to the neuropathological manifestations of Alzheimer's disease. Hypertension often clusters with other vascular risk factors, including diabetes mellitus, obesity, and hypercholesterolemia. Also, these risk factors have been related to Alzheimer's disease. The exact mechanism behind these associations is not clear. Hypertension may cause cerebrovascular disease that may increase the likelihood that individuals with AD encephalopathy will express a dementia syndrome, but hypertension may also accelerate the AD process, subclinical AD may lead to increased blood pressure, and similar biological mechanisms may be involved in the pathogenesis of both disorders. Hypertension is a common disorder and often untreated. Even if hypertension only results in a moderately increased risk of AD, or overall dementia, better treatment of hypertension may have an immense effect on the total numbr of demented individuals.