Alzheimer's disease is a brain disease that causes increasing loss of memory and other mental abilities. The disease attacks few people before age 60, but it occurs in about 20 per cent of people who live to age 85. The disease is named after the German psychiatrist and neuropathologist Alois Alzheimer, who first described its effects on brain cells in 1907.
Symptoms.
In the early stages of Alzheimer's disease, people forget very recent events but can clearly recall events that took place many years earlier. Later in the illness, people can no longer remember events of the distant past, and they may not be able to recognize friends and family members. Judgment and ability to reason also decline as the disease progresses. Fatigue and anxiety worsen the mental disabilities and make it more difficult to cope with ordinary life.
Eventually, patients cannot care for themselves, and most become bedridden. In their weakened condition, patients are vulnerable to pneumonia and other infectious diseases. Most patients die from such diseases 8 to 10 years after developing Alzheimer's disease.
Cause.
Alzheimer's disease results from the gradual destruction of brain cells. The cause of this destruction is not fully understood, and there is no known cure. Brain tissue from affected people shows a slight excess of aluminium. But most experts regard this excess as a result rather than as a cause of brain cell death.
Genetic factors play an important role in the development of Alzheimer's disease in most cases. Scientists have identified several genetic mechanisms that lead to the disease. One of these involves a mutation (random change) in a gene located on a pair of chromosomes known as chromosome 21. This gene carries the chemical instructions for producing amyloid precursor protein, a protein found in most body tissues, including the brain. A small portion of this protein forms amyloid, a waxy substance present in great excess in affected brain cells of Alzheimer's patients. Scientists believe that the gene mutation interferes with normal processing of amyloid precursor protein, causing excessive amyloid to form. This mutation is rare. It affects only about 3 per cent of Alzheimer's patients, most of them between the ages of 40 and 60.
Similarly, a mutation in a gene on chromosome 14 also can result in Alzheimer's disease. This gene mutation is associated with most cases of the disease that begin before age 65, and about 8 per cent of all cases.
Most cases of Alzheimer's disease that begin after age 65--and probably the majority of all cases--are associated with a gene on chromosome 19. This gene controls production of one of three forms of a protein called apolipoprotein E (ApoE). A person inherits two genes for ApoE production, one from each parent. Each gene produces one of the three types of ApoE. A person's ApoE type strongly predicts whether the individual will develop Alzheimer's disease. However, ApoE type does not directly cause the disease. Scientists do not know why ApoE type is related to increased risk.
Researchers believe that other genetic factors also may trigger Alzheimer's disease. For example, evidence suggests that mutations of genes located on chromosomes other than chromosomes 14 and 21 may lead to the disease.
Treatment.
Proper care, including good nutrition and hygiene, can help preserve the comfort and dignity of Alzheimer's patients. The drugs tacrine and donepezil may slightly slow the progress of the disease.
The Alzheimer Association offers support and information to patients and their family members. The organization has offices in most large cities.
