Alzheimer's disease (AD) is the most common cause of dementia in older people.
Dementia is a brain disorder that makes it hard for a person to carry out normal daily
activities. Symptoms of dementia include changes in memory, personality, and behavior.
There are other conditions besides AD that can cause dementia. For example, small
strokes or changes in the brain's blood supply can cause multi-infarct or vascular
dementia. Some causes of dementia are reversible, such as drug reactions, dehydration, and thyroid problems.
AD affects the parts of the brain that control thought, memory, and language. It is a
slow disease that starts with mild memory problems and leads to severe brain damage.
People with AD lose their abilities at different rates. AD can last from 3 to 20 years or
more after the onset of symptoms. It is not yet clear what causes AD and there is no known
An estimated 4 million people in the U.S. suffer from AD. The disease usually begins
after age 60, and the risk of AD goes up with age. However, some cases of AD occur in
younger people. About one in ten persons over 65 have AD, and nearly half of those age 85
and older may have the disease. But AD is not a normal part of aging.
AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer noticed
changes in the brain tissue of a woman who had died of an unusual mental illness. He found
abnormal clumps (now called neuritic plaques) and tangled bundles of fibers (now called
neurofibrillary tangles). Today, these plaques and tangles in the brain are considered
hallmarks of AD.
Scientists have found other changes in the brains of people with AD. There is a loss of
nerve cells in areas of the brain that are vital to memory and other mental abilities.
There also are lower levels of chemicals in the brain that carry complex messages back and
forth among nerve cells. AD may disrupt normal thinking and memory by blocking these
messages in the brain.
Causes of Alzheimer's Disease
Symptoms of Alzheimer's Disease
Diagnosis of Alzheimer's Disease
Treatments for Alzheimer's Disease
Alzheimer's Disease Research
Prevention of Alzheimer's Disease