[Approach to the dementia research].

Main causes of dementia in the elderly are vascular dementia and Alzheimer's dementia. Vascular dementia is related to both amounts and localization of lesions. Recently incidence of diffuse vascular leukoencephalopathy (Binswanger type, leukoaraiosis) and amyloid angiopathy are increasing. In Alzheimer's protein chemistry of amyloid (beta protein, A4 protein) revealed its precursor APP and its gene (chromosome 21), which produces protease inhibitor in the brain of Alzheimer and Down's brains. APP is considered as an membrane protein (receptor) and appears abundantly in the cerebral cortex. Immunohistochemical study showed that beta protein is observed also in normal aged brain. On the other hand, tau protein (main component of Alzheimer's neurofibrillary tangle, PHF) appeared as abnormal sprouting of neurites in Alzheimer's brain. The latter may related to dementia and neural death. In Alzheimer's dementia, several neurotransmitters, including acetylcholine, are reduced in the brain and related structural changes are observed. Recently olfactory bulb and mucosal changes are remarked as one of pathogenesis of this disease. Delayed neuronal death is a new phenomenon of nerve cell death of vascular origin and should be studied in human vascular dementia.