contributed by the Alzheimer's Disease Education and Referral Center

Alzheimer's Disease Fact Sheet

Introduction

Alzheimer's disease (AD) is the most common cause of dementia in older people. A dementia is a medical condition that disrupts the way the brain works. AD affects the parts of the brain that control thought, memory, and language. Every day, scientists learn more about AD, but right now the cause of the disease still is unknown, and there is no cure. An estimated 4 million people in the United States suffer from AD. The disease usually begins after age 65, and risk of AD goes up with age. While younger people also may have AD, it is much less common. About 3 percent of men and women ages 65 to 74 have AD, and nearly half of those age 85 and older may have the disease. It is important to note, however, that 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 senile or 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 also 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 between billions of nerve cells. AD may disrupt normal thinking and memory by blocking these messages between nerve cells.

Symptoms

AD begins slowly. At first, the only symptom may be mild forgetfulness. People with AD may have trouble remembering recent events, activities, or the names of familiar people or things. Simple math problems may become hard for these people 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 AD or their family members to seek medical help. For example, people with AD may forget how to do simple tasks, like brushing their teeth or combing their hair. They can no longer think clearly; and they begin to have problems speaking, understanding, reading, or writing. Later on, people with AD may become anxious or aggressive, or wander away from home. Eventually, patients may need total care.

Diagnosis

Doctors at specialized centers can diagnose probable AD correctly 80 to 90 percent of the time. They can find out whether there are plaques and tangles in the brain only by looking at a piece of brain tissue under a microscope. It can be painful and risky to remove brain tissue while a person is alive. Doctors cannot look at the tissue until they do an autopsy, which is an examination of the body done after a person dies.

Doctors may say that a person has "probable" AD. They will make this diagnosis by finding out more about the person's symptoms. The following is some of the information the doctor may need to make a diagnosis:

• A Complete Medical History

  The doctor may ask about the person's general health and past medical problems. He or she will want to know about any problems the person has carrying out daily activities. The doctor may want to speak with the person's family or friends to get more information.

• Basic Medical Tests

  Tests of blood and urine may be done to help the doctor eliminate other possible diseases. In some cases, testing a small amount of spinal fluid also may help. In addition, scientists are busy trying to develop a test to diagnose AD that will be easy and accurate.

• Neuropsychological Tests

  These are tests of memory, problem solving, attention, counting, and language. They will help the doctor pinpoint specific problems the person has.

• Brain Scans

  The doctor may want to do a special test, called a brain scan, to take a picture of the brain. There are several types of brain scans, including a computerized tomography (CT) scan, a magnetic resonance imaging (MRI) scan, or a positron emission tomography (PET) scan. By looking at a picture of the brain, the doctor will be able to tell if anything does not look normal. Information from the medical history and any test results help the doctor rule out other possible causes of the person's symptoms. For example, thyroid gland 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.
  
  

Research

Scientists at research centers across the country are trying to learn what causes AD and how to prevent it. They also are studying how memory loss happens. They are looking for better ways to diagnose and treat AD, to improve the abilities of people with the disease, and to support caregivers.

The major risk factors for AD are age and family history. Other possible risk factors include a serious head injury and lower levels of education. Scientists also are studying additional factors to see if they may cause the disease. Some of these factors include:

• Genetic (Inherited) Factors

  Scientists believe that genetic factors may be involved in more than half of the cases of AD. For example, a protein called apolipoprotein E (ApoE) may be important. Everyone has ApoE, which helps carry cholesterol in the blood. However, the function of ApoE in the brain is less understood. The ApoE gene has three forms. One form seems to protect a person from AD, and another form seems to make a person more likely to develop the disease. Scientists still need to learn a lot more about ApoE and its role in AD.

• Environmental Factors

  Scientists have found aluminum, zinc, and other metals in the brain tissue of people with AD. They are studying these metals to see if they cause AD or if they build up in the brain as a result of the disease.

• Viruses

  Some scientists think that a virus may cause AD. They are studying viruses that might cause the changes seen in the brain tissue of people with AD.

AD probably is not caused by any one factor. It is more likely to be several factors that act differently in each person. For example, genetic factors alone may not be enough to cause the disease. Other risk factors may combine with a person's genetic makeup to increase his or her chance of developing the disease.

Scientists also are trying to develop a test that can detect or predict AD. If the onset of the disease could be delayed for even a short time, the number of people with the disease would drop. Delaying AD also would make the quality of life better for older people and lead to savings in health care costs.

Other research is aimed at helping both patients and caregivers cope with the patients' loss of abilities and the stress this causes. For example, researchers are studying ways to manage problem behaviors in patients, such as wandering and agitation. Still other scientists are evaluating services and programs for patients and caregivers, including respite care. Respite care covers a variety of situations in which someone else cares for the patient for a period of time, giving family caregivers temporary relief.

The National Institute on Aging, the Federal Government's lead agency for AD research, funds Alzheimer's Disease Centers located throughout the United States. The centers carry out a wide range of research, including studies on the causes, diagnosis, treatment, and management of AD.