Alzheimer’s disease (AD) is an irreversible, progressive brain disease that slowly destroys memory and thinking skills and, eventually, the ability to carry out the simplest tasks of daily living. In most people with AD, symptoms first appear after age 60.
AD is the most common cause of dementia among older people, but it is not a normal part of aging. Dementia refers to a decline in cognitive function that interferes with daily life and activities. AD starts in a region of the brain that affects recent memory, then gradually spreads to other parts of the brain. Although treatment can slow the progression of AD and help manage its symptoms in some people, currently there is no cure for this devastating disease.
AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer described changes in the brain tissue of a woman who had died of an unusual mental illness. He found abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles).
Today, these plaques and tangles in the brain are considered hallmarks of AD. The third main feature of AD is the gradual loss of connections between nerve cells (neurons) in the brain. This loss leads to diminished cell function and cell death.
We don’t know what starts the AD process, but we do know that damage to the brain begins as many as 10 to 20 years before any obvious signs of forgetfulness appear.
As nerve cells die throughout the brain, affected regions begin to shrink. By the final stage of AD, damage is widespread, and brain tissue has shrunk significantly.
This 4-minute captioned video shows the intricate mechanisms involved in the progression of Alzheimer's disease in the brain.
According to recent estimates, as many as 2.4 million to 5.1 million Americans have AD. Unless the disease can be effectively treated or prevented, the number of people with AD will increase significantly if current population trends continue. That’s because the risk of AD increases with age, and the U.S. population is aging. The number of people age 65 and older is expected to grow from 39 million in 2008 to 72 million in 2030, and the number of people with AD doubles for every 5-year interval beyond age 65.
In the years to come, AD is expected to pose physical and emotional challenges for more and more families and other caregivers, in addition to those with the disease. The growing number of people with AD and the costs associated with the disease also will put a heavy economic burden on society.
AD is a slow disease that starts with mild memory problems and ends with severe brain damage. The time from diagnosis to death varies—as little as 3 or 4 years if the person is older than 80 when diagnosed to as long as 10 or more years if the person is younger. Other factors that affect how long a person will live with AD include the person’s sex, the presence of other health problems, and the severity of cognitive problems at diagnosis.
Dementia is a general term that refers to a decline in cognitive function so extensive that it interferes with daily life and activities. This loss in the ability to think, remember, and reason is not a disease itself, but a group of symptoms that often accompanies a disease or condition.
Many conditions and diseases cause dementia. Two of the most common causes of dementia in older people are AD and vascular dementia, which is caused by a series of strokes or changes in the brain’s blood supply.
Other conditions that cause memory loss or dementia include:
medication side effects chronic alcoholism certain tumors and infections in the brain blood clots in the brain vitamin B12 deficiency dehydration high fever some thyroid, kidney, or liver disordersMany of these conditions are temporary and reversible, but they can be serious and should be treated by a doctor as soon as possible.
Emotional problems, such as stress, anxiety, or depression, can make a person more forgetful and can be mistaken for dementia. Someone may feel sad, lonely, worried, or bored when facing retirement or coping with the death of a spouse, relative, or friend. Adapting to these changes leaves some people feeling confused or forgetful. Supportive friends and family or professional help from a doctor or counselor can help older adults adjust to big changes.Mild cognitive impairment (MCI) is a condition in which a person has memory problems greater than those expected for his or her age. However, people with MCI do not have the personality changes or cognitive problems that characterize AD.
MCI has several types. The type most associated with memory loss is called amnestic MCI. People with this condition have more memory problems than normal for their age, but their symptoms are not as severe as those of people with AD. More people with MCI go on to develop AD than those without MCI within a certain timeframe. However, not everyone who has MCI develops AD. Studies are underway to learn why some people with MCI progress to AD and others do not.Other questions? Call the ADEAR Center at 1-800-438-4380 or e-mail our information specialists.
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