Associated neuropathologic changes include loss of brain tissue cells (with a typical upward progression through memory centers such as the entorhinal cortex and the hippocampus) and collection of specific inclusions such as neurofibrillary ("tau") tangles and senile plaques. It is not yet certain whether these changes are primary (the cause of the disease) or secondary (the result of the disintegration of brain tissue), although the currently dominant hypothesis assigns cause to plaque. Whatever the mechanism, a strong epidemiological association has been shown between a diet high in fat and cholesterol and development and progress of the disease. In addition, animal feeding trials of high cholesterol and fat have demonstrated increased anatomical symptoms upon autopsied brains.
Alzheimer's disease is the most frequent reason for dementia in the elderly and affects almost half of all patients with dementia. There is no known definitive treatment, although there are drugs which reduce neurotransmitter degredation and delay memory loss associated with the disease. Non-steroidal anti-inflammatory drugs (including ibuprophen, acetominophen, and aspirin) seem to slow progress of the disease, according to clinical trials, but the mechanism is not understood.
The disease was thought to be uncommon, until the 1960s when it was realized that much of what had been regarded as the normal process of aging was actually the result of this disease. Alzheimer's is considered to be a major public health challenge since the average age of the industrialized world's population is increasing. Typically only 3% of persons aged 65 show signs of the disease while 50% of persons aged 85 have symptoms of Alzheimer's. However the proportion of persons with Alzheimer's begins to decrease after age 85 because of the increased mortality due to the disease, and relatively few people over the age of 100 have the disease.
There are ongoing tests of an Alzheimer's disease vaccine. Initial results in animals were promising. However when the first vaccines were used in humans, brain inflammation resulted and the trials were stopped. It is hoped that research will provide a better formulation and that in the future it can be of use in families with history of Alzheimer's Disease.
Unfortunately, a definitive diagnosis of Alzheimer's disease must await an autopsy, at present. However, many increasingly sophisticated diagnostic tests have been proposed (including: brain scans, behavioral tests and testing for genetic predisposition).
Psychological testing generally focuses on memory, attention, abstract thinking, the ability to name objects, and other cognitive functions. However, results of psychological tests do not easily distinguish between Alzheimers Disease and other types of dementia. Psychological testing can be helpful in establishing the presence of and severity of dementia. It can also be useful in distinguishing true dementia from temporary (and more treatable) cognitive impairment due to depression or psychosis, which has sometimes been termed pseudodementia.
See also: Familial Alzheimer disease