Vascular aspects in Alzheimer's disease.

Alzheimer's disease is a primary degenerative dementia and is not considered to be of vascular origin. Furthermore, severe cerebrovascular diseases are generally exclusionary for the clinical diagnosis. During recent years both epidemiological and neuropathological studies have suggested an association between Alzheimer's disease and several vascular risk factors, such as hypertension, inheritance of the apolipoprotein E epsilon4 allele, coronary heart disease, diabetes mellitus, ischaemic white matter lesions and generalised atherosclerosis. These findings may reflect an overdiagnosis of Alzheimer's disease in individuals with silent cerebrovascular disease or that cerebrovascular disease may affects the clinical expression of Alzheimer's disease. Further possibilities include that Alzheimer's disease may increase the risk of vascular disease or that vascular disease may stimulate the Alzheimer's disease process. Similar mechanisms may also be involved in the pathogenesis of both disorders, such as disturbances in the renin-angiotensin system, apoptosis, and psychological stress.