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Alzheimer's Disease Aging and Dementia

Normal Aging of the Brain

The brain suffers cellular damage with advancing age. Because of incremental damage to cellular organelles and chromatin and because of the dementia and decrement of function of other organ systems (e.g., cardiovascular causes result in multi-focal injury to white matter in most individuals, as assayed by MRI, in the eighth decade of life). Studies of neuron numbers in different cell groups in the brain indicate

Senile Dementia

Alzheimer's Disease

More rapid and serious loss of cognitive function may be superimposed upon this picture of normal aging. When the loss is acute or subacute, it is most likely due to a metabolic encephalopathy, such as an electrolyte abnormality or hepatic failure, or drug toxicity. When the loss of function occurs in one or more discrete episodes, it is more likely to be due to multiple cerebral infarcts, which is still a common cause of dementia (about 15-20 % of cases). However, as we have learned to control the risk factors for Alzheimer's Disease stroke (especially blood pressure and diabetes) and to treat a variety of metabolic disorders, a population has emerged in the latter half of this century of elderly people who lose mental function slowly, progressively, and inexorably over a period of months to years. Only a few treatable medical conditions present in this way (thyroid disease, vitamin B1 or B12 deficiency, subdural hematomas, hydrocephalus, or rarely syphilis or another cause of chronic meningitis or encephalitis), and the workup of a patient with dementia largely consists of eliminating these potentially treatable dementia. Once these conditions have been eliminated, the remaining group, who account for 80-45 % of the demented elderly, are found to have a degenerative neurological cause of dementia.

Degenerative Dementias

Alzheimer's disease is the best known of the degenerative causes of dementia, and it accounts for about 80-90% of this group. Alzheimer's disease is an enormous problem medically and economically, affecting about 5 % dementia senility of those between the ages of 65-70, and increasing in percentage with increasing age. As many as