What is Alzheimer's disease?

Alzheimer's disease (AD) is a progressive disease of the brain that is characterized by impairment of memory and a disturbance in at least one other thinking function (for example, language or perception of reality). Many scientists believe that AD results from an increase in the production or accumulation of a specific protein (beta-amyloid protein) that leads to nerve cell death. Loss of nerve cells in strategic brain areas, in turn, causes deficits in the neurotransmitters, which are the brain's chemical messengers.

Alzheimer's disease is not a normal part of aging and is not something that inevitably happens in later life. Rather, it is one of the dementing disorders, which are a group of brain diseases that result in the loss of mental and physical functions.

Who develops Alzheimer's disease?

The main risk factor for AD is increased age. As the population ages, the frequency of AD continues to increase. 10 % of people over age 65 and 50 % of those over 85 have AD. The number of individuals with AD is expected to be 14 million by the year 2050. In 1998, the annual cost for the care of patients with AD in the United States was approximately $40,000 per patient.

There are also genetic risk factors for AD. The presence of several family members with AD has suggested that, in some cases, heredity may influence the development of AD. A genetic basis has been identified through the discovery of mutations in several genes that cause AD in a small subgroup of families in which the disease has frequently occurred at relatively early ages (beginning before age 50). Some evidence points to chromosome 19 as implicated in certain other families in which the disease has frequently developed at later ages.

Studies of aging and dementia (general mental deterioration) in the general population have identified three groups of subjects; persons who are not demented, those who are demented, and individuals who cannot be classified because they have a cognitive (thinking, memory) impairment, but do not meet the criteria for dementia.