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Other Names:
Senile dementia Alzheimer's type, SDAT, AD
Alzheimer's Disease

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Alzheimer's Disease Defined

Dementia is a brain disorder that seriously affects a person's ability to carry out daily activities. Alzheimer's disease is the most common form of dementia among older people. It involves the parts of the brain that control thought, memory, and language. Every day scientists learn more, but right now the causes of Alzheimer's disease are still unknown, and there is no cure.

Scientists think that up to 4 million Americans suffer from Alzheimer's disease. The disease usually begins after age 60, and risk goes up with age. While younger people also may get Alzheimer's disease, it is much less common.

About 3 percent of men and women ages 65 to 74 have Alzheimer's disease, and nearly half of those age 85 and older may have the disease. It is important to note, however, that Alzheimer's disease is not a normal part of aging.

Alzheimer's disease 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 and tangled bundles of fibers. The clumps are now called amyloid plaques and the tangles are called neurofibrillary tangles. Today, these plaques and tangles in the brain are considered hallmarks of Alzheimer's disease.

Scientists also have found other brain changes in people with Alzheimer's disease. 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 between nerve cells.

Alzheimer's disease may disrupt normal thinking and memory by blocking these messages between nerve cells.

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Causes and Risk Factors

Scientists do not yet fully understand what causes Alzheimer's disease. There probably is not one single cause, but several factors that affect each person differently. Age is the most important known risk factor for Alzheimer's disease. 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 Alzheimer's disease cases. For example, familial Alzheimer's disease, a rare form of Alzheimer's disease that occurs between the ages of 30 and 60, can be inherited. However, in the more common form of Alzheimer's disease, which occurs later in life, no obvious family pattern is seen. One risk factor for this type of Alzheimer's disease is a protein called apolipoprotein E, or apoE.

Everyone has apoE, which helps carry cholesterol in the blood. The apoE gene has three forms. One form seems to protect a person from Alzheimer's disease, and another form seems to make a person more likely to develop the disease. Other genes that increase the risk of Alzheimer's disease or that protect against Alzheimer's disease probably remain to be discovered.

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

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Symptoms and Diagnosis

Alzheimer's disease begins slowly. At first, the only symptom may be mild forgetfulness. People with Alzheimer's disease may have trouble remembering recent events, activities, or the names of familiar people or things. Simple math problems may become hard to solve. Such difficulties may be a bother, but usually they are not serious enough to cause alarm.

However, as the disease goes on, symptoms are more easily noticed and become serious enough to cause people with Alzheimer's disease or their family members to seek medical help. For example, people in the later stages of Alzheimer's disease may forget how to do simple tasks, like brushing their teeth or combing their hair. They can no longer think clearly.

They begin to have problems speaking, understanding, reading, or writing. Later on, people with Alzheimer's disease may become anxious or aggressive, or wander away from home. Eventually, patients need total care.

An early, accurate diagnosis of Alzheimer's disease helps patients 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 Alzheimer's disease 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 examination of the body done after a person dies.

Therefore, doctors must make a diagnosis of "possible" or "probable" Alzheimer's disease. At specialized centers, doctors can diagnose Alzheimer's disease correctly up to 90 percent of the time. Doctors use several tools to diagnose "probable" Alzheimer's disease:

  • A complete medical history includes information about the person's general health, past medical problems, and any difficulties the person has carrying out daily activities.
  • Medical tests - such as tests of blood, urine, or spinal fluid - help the doctor find other possible diseases causing the symptoms.
  • Neuropsychological tests measure memory, problem solving, attention, counting, and language.
  • Brain scans allow the doctor to look at a picture of the brain to see if anything does not look normal.
Information from the medical history and test results help 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 Alzheimer's disease-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, or MCI. MCI is different from both Alzheimer's disease 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.

Scientists funded by the National Institute on Aging are conducting the Memory Impairment Study to learn whether early diagnosis and treatment of MCI might prevent or slow further memory loss, including the development of Alzheimer's.

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Treatments and Research

Alzheimer's disease is a slowly developing disease, starting with mild memory problems and ending with severe brain damage. The course the disease takes and how fast changes occur vary from person to person. On average, Alzheimer's disease patients live from 8 to 10 years after they are diagnosed, though the disease can last for as many as 20 years.

No treatment can stop Alzheimer's disease. However, for some people in the early and middle stages of the disease, the drugs Cognex®, Aricept®, Exelon® or Reminyl® may help prevent some symptoms from becoming worse for a limited time. Memantine, also known by its brand name Namenda®, is approved for use in moderate to severe forms of the disease.

Also, some medicines may help control behavioral symptoms of Alzheimer's disease such as sleeplessness, agitation, wandering, anxiety, psychosis, and depression. Treating these symptoms often makes patients more comfortable and makes their care easier for caregivers.

Developing new treatments for Alzheimer's disease is an active area of research. Scientists are testing a number of drugs to see if they prevent Alzheimer's disease, slow the disease, or help reduce behavioral symptoms.

There is evidence that inflammation in the brain may contribute to Alzheimer's disease and that drugs to cut down on inflammation may help. One recent study showed that two non-steroidal anti-inflammatory drugs -- rofecoxib and naproxen -- did not slow the progression of Alzheimer's disease in people already diagnosed.

Scientists believe, however, that anti-inflammatory drugs may still prove effective in preventing Alzheimer's disease in people who are at risk, but who do not yet have symptoms of Alzheimer's. A clinical prevention trial is now under way. A clinical trial is a research study on people to find out whether a new drug or treatment is both safe and effective.

Research has shown that vitamin E slows the progress of some consequences of Alzheimer's disease by about 7 months. Scientists now are studying vitamin E to learn whether it can prevent or delay Alzheimer's disease in patients with mild cognitive impairment, or MCI.

Medicines already used to help reduce the risk of heart disease may help lower the chances of developing Alzheimer's disease or may slow its progression. Clinical trials of drugs known as statins have begun to see if they might help slow down the progression of Alzheimer's disease.

Studies have shown that people with Alzheimer's often have higher levels of an amino acid called homocysteine in their blood. Folic acid and vitamins B6 and B12 can reduce levels of homocysteine in the blood, and scientists are conducting studies to see whether these substances can also slow rates of mental decline.

Research also is under way to see if estrogen reduces the risk of Alzheimer's disease or slows the disease. One study showed that estrogen does not slow the progression of already diagnosed disease, but more research is needed to find out if estrogen may play another role. For example, scientists now are trying to find out whether estrogen can prevent Alzheimer's disease in women with a family history of the disease.

Estrogen and progesterone combination therapy is not recommended for prevention of cognitive decline or dementia. In one large national study of women 65 and older, Prempro, a specific form of combination hormone therapy, was found to double the risk of dementia in women on combination therapy when compared to those not taking the medication.

Recent research suggests that ginkgo biloba, an extract made from the leaves of the ginkgo tree, may be of some help in treating Alzheimer's disease symptoms. There is no evidence that ginkgo will cure or prevent Alzheimer's disease. Scientists now are trying to find out whether ginkgo biloba can delay or prevent dementia in older people.

People with Alzheimer's disease and those with mild cognitive impairment who want to help scientists test new treatments may be able to take part in research studies, otherwise known as clinical trials. These research studies are done on people to find out whether a new drug or treatment is both safe and effective.

New therapies are tested on people only after laboratory and animal studies show promising results. The Food and Drug Administration sets strict rules to make sure that people who agree to be in the studies are treated as safely as possible.

The U.S. National Institutes of Health, through its National Library of Medicine and other Institutes, maintains a database of clinical trials at Click here to see a list of the current clinical trials on Alzheimer's disease. A separate window will open. Click the "x" in the upper right hand corner of the "Clnical Trials" window to return here.

The National Institute on Aging's Alzheimer's Disease Education and Referral Center, or ADEAR Center, is another reliable source of information about Alzheimer's disease. Contact them at 1-800-438-4380 or visit the ADEAR Center web site at

Scientists have come a long way in their understanding of Alzheimer's disease. Findings from years of research have begun to clarify differences between normal age-related memory changes, mild cognitive impairment, and Alzheimer's disease. Scientists also have made great progress in defining the changes that take place in the Alzheimer's disease brain, which allows them to pinpoint possible targets for treatment.

These advances are the foundation of the National Institutes of Health's Alzheimer's Disease Prevention Initiative, which is designed to

  • understand why Alzheimer's disease occurs and who is at greatest risk of developing it.
  • improve the accuracy of diagnosis and the ability to identify those at risk.
  • discover, develop, and test new treatments.
  • discover treatments for behavioral problems in patients with Alzheimer's disease.

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Alzheimer's Disease