The Facts about Alzheimer's Disease

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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 cure.

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.

What causes Alzheimer's disease?

Scientists do not yet fully understand what causes AD. There probably is not one single cause, but several factors that affect each person differently. Age is the most important known risk factor for AD. The number of people with the disease doubles every 5 years beyond age 65.

Family history is another risk factor. Scientists believe that genetics may play a role in many AD cases. For example, familial AD, a rare form of AD that usually occurs between the ages of 30 and 60, can be inherited. However, in the more common form of AD that occurs later in life, no obvious family pattern is seen.

Scientists still need to learn a lot more about what causes AD. In addition to genetics, they are studying education, diet, environment, and infections to learn what role they might play in the development of this disease.

What are the symptoms of Alzheimer's disease?

AD begins slowly. At first, the only symptom may be memory problems. People with AD may have trouble remembering recent events, activities, or the names of familiar people or things. They may ask the same question over and over again. Simple math problems may become hard to solve. Such difficulties begin to interfere with jobs or other activities.

As the disease gets worse, people with AD may:

Forget something that just happened even though they can remember events from many years ago.
Become disoriented and get lost in once familiar places.
Become passive and lose their initiative.
Forget how to do simple tasks, like brushing their teeth or combing their hair.
Not be able to think clearly.
Have trouble talking, understanding, reading, and writing.
Stop bathing regularly or eating regular meals.
Have sudden, unpredictable mood changes.
Become suspicious and paranoid about other people's intentions and behavior.
Become confused, anxious or aggressive. Some may become violent or angry, while others may be docile or helpless.
Wander away from home.

Eventually, persons with AD need total care.

The behavioral problems in AD are not something the person can control. They result from the brain damage that worsens over time.

How is Alzheimer's disease diagnosed?

An early, accurate diagnosis of AD helps persons with AD and their families plan for the future. It gives them time to discuss care options while the patient can still take part in making decisions. Early diagnosis also offers the best chance to treat the symptoms of the disease.

Today, the only definite way to diagnose AD is to find out whether there are plaques and tangles in brain tissue. To look at brain tissue, doctors must wait until they do an autopsy, which is an exam of the body done after a person dies. Therefore, doctors must make a diagnosis of "possible" or "probable" AD. Finding new and better ways to diagnose early AD is one area of current research.

At specialized centers, doctors can diagnose AD correctly up to 90 percent of the time. Doctors use several tools to diagnose probable AD:

A complete medical history that includes information about the person's general health, past medical problems, and any difficulties the person has carrying out daily activities. The doctor may want to speak with the person's family and friends to get more information.
Tests of blood, urine, or spinal fluid to look for other possible causes of the symptoms.
Tests of memory, problem solving, attention, counting, and language.
Brain scans that allow the doctor to look at a picture of the brain to see if anything does not look normal. Types of brain scans include computerized tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans.
Information from the medical history and from test results helps the doctor rule out other possible causes of the person's symptoms. For example, thyroid problems, drug reactions, depression, brain tumors, and blood vessel disease in the brain can cause AD-like symptoms. Some of these other conditions can be treated successfully.
Recently, scientists have focused on a type of memory change called mild cognitive impairment (MCI). MCI is different from both AD and normal age-related memory change. People with MCI have ongoing memory problems but do not have other losses like confusion, attention problems, and difficulty with language. Researchers are studying MCI to learn whether early diagnosis and treatment might prevent or slow further memory loss, including the development of AD.