Alzheimer's Disease

Alzheimer's disease is a progressive, relentless loss of mental function, characterized by degeneration of brain tissue, including loss of nerve cells and the development of senile plaques and neurofibrillary tangles. The most common cause of dementia is Alzheimer's disease. In older people, it accounts for up to 65% of dementias. It is very rare among people younger than 60. It becomes more common with increasing age. It affects only about 1% of people aged 60 to 64, but up to 30% of those older than 85. What causes Alzheimer's disease is unknown, but genetic factors play a role: The disease seems to run in some families and is caused or influenced by several specific gene abnormalities. One abnormality affects apolipoprotein E (apo E) - the protein part of certain lipoproteins, which transport cholesterol through the bloodstream. There are three types of apo E (e2, e3, and e4). People with the e4 type develop Alzheimer's disease more commonly and at an earlier age than other people. In contrast, people with the e2 type seem to be protected against Alzheimer's disease. People with the e3 type are neither protected nor more likely to develop the disease. (These associations have been studied primarily in whites and may not apply to other races.) Genetic testing for apo E type cannot determine whether a person will develop Alzheimer's disease. Therefore, this testing is not routinely recommended.
In Alzheimer's disease, parts of the brain degenerate, destroying nerve cells and reducing the responsiveness of the remaining ones to many of the chemical messengers that transmit signals in the brain (neurotransmitters). Abnormalities in brain tissue consist of senile or neuritic plaques (clumps of dead nerve cells containing an abnormal, insoluble protein called amyloid) and neurofibrillary tangles (twisted strands of insoluble proteins in the nerve cell). Such abnormalities develop to some degree in all people as they age but are much more numerous in people with Alzheimer's disease.

Symptoms
Dementia resulting from Alzheimer's disease usually begins subtly. People whose disease develops while they are still employed may not perform as well in their jobs. In those who are retired and not very active, the changes may not be as noticeable. The first sign may be forgetting recent events, although sometimes the disease begins with depression, fears, anxiety, decreased emotion, or other personality changes. In the early stages, judgment and abstract thinking may be impaired. Speech patterns may change slightly; the person may use simpler words, use words incorrectly, or be unable to find the appropriate word. An inability to interpret visual cues may make driving a car difficult. People with Alzheimer's disease may be able to function socially but may behave unusually. For example, they may forget the name of a recent visitor, and their emotions may change unpredictably and rapidly. They may get lost on their way to the store. As Alzheimer's disease progresses, people have trouble remembering events in the past. They may require help with eating, dressing, bathing, or going to the toilet. Wandering, agitation, irritability, hostility, and physical aggression are common. All sense of time and place is lost: People with Alzheimer's disease may even get lost on their way to the bathroom at home. Their increasing confusion puts them at risk of falling. Psychoses, with hallucinations, delusions, and paranoia, develop at some point in about half of people with Alzheimer's disease.
Eventually, people with Alzheimer's disease cannot walk or take care of their personal needs. They may be incontinent and unable to swallow, eat, or speak. These changes put them at risk of undernutrition, pneumonia, and bedsores (pressure sores). Memory is completely lost. Because these people become totally dependent on others, a nursing home may become necessary.
Ultimately, coma and death, often due to infections, result. Progression is unpredictable. The expected survival from the time the disorder is diagnosed ranges from 2 to 10 years, but usually 3 to 5 years. On average, people with Alzheimer's disease who can no longer walk live no more than 6 months.

Diagnosis
Doctors suspect Alzheimer's disease as the most likely cause of dementia in older people whose memory gradually deteriorates. Although a diagnosis based on examination of the person can be correct most of the time, the diagnosis of Alzheimer's disease is proved only by microscopic examination of brain tissue obtained during an autopsy. When brain tissue is examined, the characteristic loss of nerve cells, neurofibrillary tangles, and senile plaques containing amyloid can be seen throughout the brain but particularly in the area of the temporal lobe that is involved in the formation of new memories. Analysis of spinal fluid and positron emission tomography (PET) have been suggested as ways to diagnose Alzheimer's disease during life, but these procedures are not yet reliable in predicting who will develop Alzheimer's disease or in identifying people who already have it.

Treatment
General measures for treatment of Alzheimer's disease are the same as for all dementias.
The use of certain drugs (such as nonsteroidal anti-inflammatory drugs [NSAIDs]) to prevent and slow the progression of Alzheimer's disease is under study. Estrogen and vitamin E may help prevent and slow progression of the disease, although study results are inconsistent. Before any of these substances are taken, their risks and benefits should be discussed with a
doctor.
Donepezil, rivastigmine, tacrine, and galantamine increase the levels of the chemical messenger (neurotransmitter) acetylcholine, which may be low in many forms of dementia. These drugs may improve cognitive function temporarily, but they do not slow the progression of the disease. About half of the people who have Alzheimer's disease benefit from these drugs. For these people, the drugs effectively turn the clock back 6 to 9 months. These drugs are most effective in people with mild to moderate disease. Because the drugs are expensive and may have side effects, they should not be continued in people who do not benefit from them. The most common side effects include nausea, vomiting, weight loss, and abdominal pain or cramps. Side effects are usually mild and relatively uncommon with donepezil and galantamine.
An extract of ginkgo biloba (called EGb) has been claimed to have effects similar to those of the drugs described above. However, further study of this medicinal herb is needed.
(Merck)