[Aging brains and the dementias].

Dementia has been defined generally as an acquired persistent impairment of intellectual function caused by organic brain diseases. The rapidly increasing incidence of dementias has been claimed on the basis of epidemic studies in Japan as well as in Western developed countries. These observations are justified by the facts that most dementias are found in people over the age of 65 years, and that the elderly population is increasing rapidly resulting in both absolute numbers and percentage of the population. In Japan, it is estimated that 1.5 million of demented persons are present. The purpose of this paper is to describe clinical manifestations and morphological alterations of aged and demented individuals, diagnostic process to differential diagnosis to provide knowledgeable approach to management, and adequate care of the demented individuals. In aged brain, there are a variety of morphological changes. Some of these are usually observed in aged brains; atrophy of the brains, loss of neurons, accumulations of lipofuscin. Others observed in pathologically aged brains, or accelerated aging brains are Alzheimer's neurofibrillary tangles, senile plaques, and granulovacuolar degeneration. Psychiatric manifestations associated with aging and dementing diseases are described. It should be realized that clinical manifestations of the demented reflect primarily the topography of the organic lesions in the brain, and functional alterations, and are influenced by psychological and socio-environmental factors.