Alzheimer’s disease (AD) is an irreversible, progressive brain disorder that occurs gradually and results in memory loss, behavior and personality changes, and a decline in thinking abilities. These losses are related to the death of brain cells and the breakdown of the connections between them. The course of this disease varies from person to person, as does the rate of decline. On average, AD patients live for 8 to 10 years after they are diagnosed, though the disease can last for up to 20 years.
AD advances by stages, from early, mild forgetfulness to a severe loss of mental function. This loss is called dementia. In most people with AD, symptoms first appear after age 60. The earliest symptoms often include loss of recent memory, faulty judgment, and changes in personality. Often, people in the initial stages of AD think less clearly and forget the names of familiar people and common objects. Later in the disease, they may forget how to do simple tasks, such as washing their hands. Eventually, people with AD lose all reasoning ability and become dependent on other people for their everyday care. Finally, the disease becomes so debilitating that patients are bedridden and likely to develop other illnesses and infections. Most commonly, people with AD die from pneumonia.
Although the risk of developing AD increases with age, AD and dementia symptoms are not a part of normal aging. AD and other dementing disorders are caused by diseases that affect the brain. In the absence of disease, the human brain often can function well into the tenth decade of life.
National Institutes of Health
National Institute on Aging
1999 PROGRESS REPORT ON ALZHEIMER’S DISEAS