Alzheimer's Disease, progressive degenerative disease of the brain now considered a leading cause of dementia (among the old). First described by the German neuropathologist Alois Alzheimer in 1906, it affects an estimated 2.5 to 3 million persons in the U.S. The incidence of the disease increases with advancing age, but there is no evidence that it is caused by the aging process.
The average life expectancy of persons with the disease is between five and ten years, although many patients now survive 15 years or more due to improvements in care and medical treatment. The cause of this disease has not been discovered, although palliative therapy is available. The ability of doctors to diagnose Alzheimer's disease has improved over the last ten years, but this remains a process of elimination and final diagnosis can be confirmed only at autopsy.
At autopsy, Alzheimer's patients show nerve cell loss in the parts of the brain associated with cognitive functioning. The hallmark lesions of Alzheimer's disease include the formation of abnormal proteins known as neurofibrillary tangles and neuritic plaques. The nature of these abnormal proteins and the location of the gene for producing the precursor protein has been identified. Alzheimer's disease is also characterized by profound deficits in the brain's neurotransmitters, chemicals that transmit nerve impulses, particularly acetylcholine, which has been linked with memory function. The important scientific issue concerning Alzheimer's disease revolves around the question of why particular classes of nerve cells are vulnerable and subject to cell death. Many researchers are actively pursuing an answer to this question in studies examining the potential effects of genetic factors, toxins, infectious agents, metabolic abnormalities, and a combination of these factors. Recent findings indicate that a small percentage of Alzheimer's cases may be inherited.