Alzheimer's disease (AD) is the most common form of dementia (a brain disorder that seriously affects a person's ability to carry out daily activities) 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 AD are still unknown, and there is no cure.
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 amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles). Today, these plaques and tangles in the brain are considered hallmarks of AD.
How many Americans have AD?
Scientists think that up to 4 million Americans suffer from AD. The disease usually begins after age 60, and risk goes up with age. While younger people also may get 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.
How long can a person live with AD?
AD is a slow 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, AD patients live from 8 to 10 years after they are diagnosed, though the disease can last for as many as 20 years.
What is Dementia?
The term "dementia" describes a group of symptoms that are caused by changes in brain function. Dementia symptoms may include asking the same questions repeatedly; becoming lost in familiar places; being unable to follow directions; getting disoriented about time, people, and places; and neglecting personal safety, hygiene, and nutrition. People with dementia lose their abilities at different rates.
Dementia is caused by many conditions. Some conditions that cause dementia can be reversed, and others cannot. The two most common forms of dementia in older people are Alzheimer's disease and multi-infarct dementia (sometimes called vascular dementia). These types of dementia are irreversible, which means they cannot be cured.
Reversible conditions with symptoms of dementia can be caused by a high fever, dehydration, vitamin deficiency and poor nutrition, bad reactions to medicines, problems with the thyroid gland, or a minor head injury. Medical conditions like these can be serious and should be treated by a doctor as soon as possible.
Sometimes older people have emotional problems that can be mistaken for dementia. Feeling sad, lonely, worried, or bored may be more common for older people facing retirement or coping with the death of a spouse, relative, or friend. Adapting to these changes leaves some people feeling confused or forgetful. Emotional problems can be eased by supportive friends and family, or by professional help from a doctor or counselor.
What is Multi-Infarct Dementia (MID)?
In multi-infarct dementia, a series of small strokes or changes in the brain's blood supply may result in the death of brain tissue. The location in the brain where the small strokes occur determines the seriousness of the problem and the symptoms that arise. Symptoms that begin suddenly may be a sign of this kind of dementia. People with multi-infarct dementia are likely to show signs of improvement or remain stable for long periods of time, then quickly develop new symptoms if more strokes occur. In many people with multi-infarct dementia, high blood pressure is to blame. One of the most important reasons for controlling high blood pressure is to prevent strokes.
What is Mild Cognitive Impairment (MCI)?
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. Scientists funded by the National Institute on Aging (NIA) 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 AD.
What Causes AD?
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, which occurs later in life, no obvious family pattern is seen. One risk factor for this type of AD is a protein called apolipoprotein E (apoE).
Everyone has apoE, which helps carry cholesterol in the blood. The apoE gene has three forms. One seems to protect a person from AD, and another seems to make a person more likely to develop the disease. Other genes that increase the risk of AD or that protect against AD probably remain to be discovered.
Scientists still need to learn a lot more about what causes AD. 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.
What are the Symptoms of AD?
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 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 in the later stages of AD 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 AD may become anxious or aggressive, or wander away from home. Eventually, patients need total care.
Many different medical conditions may cause symptoms that seem like Alzheimer's disease, but are not. Some of these medical conditions may be treatable. Reversible conditions can be caused by a high fever, dehydration, vitamin deficiency and poor nutrition, bad reactions to medicines, problems with the thyroid gland, or a minor head injury. Medical conditions like these can be serious and should be treated by a doctor as soon as possible.
How is AD Diagnosed?
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 examination of the body done after a person dies. Therefore, doctors must make a diagnosis of "possible" or "probable" AD.
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 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 AD-like symptoms. Some of these other conditions can be treated successfully.
Why is early diagnosis important?
An early, accurate diagnosis of AD 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.
What drugs are currently available to treat AD?
No treatment can stop AD. However, for some people in the early and middle stages of the disease, the drugs tacrine (Cognex), donepezil (Aricept), rivastigmine (Exelon), or galantamine (Reminyl) may help prevent some symptoms from becoming worse for a limited time. Also, some medicines may help control behavioral symptoms of AD such as sleeplessness, agitation, wandering, anxiety, and depression. Treating these symptoms often makes patients more comfortable and makes their care easier for caregivers.
The fifth approved medication, known as Namenda® (memantine), is an N-methyl D-aspartate (NMDA) antagonist. It is prescribed for the treatment of moderate to severe AD. Studies have shown that the main effect of Namenda® is to delay progression of some of the symptoms of moderate to severe AD. The medication may allow patients to maintain certain daily functions a little longer. For example, Namenda® may help a patient in the later stages of AD maintain his or her ability to go to the bathroom independently for several more months, a benefit for both patients and caregivers.
What potential new treatments are being researched?
Developing new treatments for AD is an active area of research. Scientists are testing a number of drugs to see if they prevent AD, slow the disease, or help reduce behavioral symptoms.
Scientists are testing two different types of nonsteroidal anti-inflammatory drugs (NSAIDs) to find out if they slow the disease. There is evidence that inflammation in the brain may contribute to AD damage. Scientists believe that anti-inflammatory drugs such as NSAIDs might help slow the progression of AD. Rofecoxib (Vioxx) and naproxen (Aleve) are two NSAIDs currently being studied.
Research has shown that vitamin E slows the progress of some consequences of AD by about 7 months. Scientists now are studying vitamin E to learn whether it can prevent or delay AD in patients with mild cognitive impairment (MCI). Recent research suggests that ginkgo biloba, an extract made from the leaves of the ginkgo tree, may be of some help in treating AD symptoms. There is no evidence that ginkgo will cure or prevent AD. Scientists now are trying to find out whether ginkgo biloba can delay or prevent dementia in older people.
Research also has been conducted to see if estrogen reduces the risk of AD or slows the disease. One study showed that estrogen does not slow the progression of already diagnosed disease. Furthermore, a study on combination hormone therapy (estrogen and progestin) showed that older women (over 65) participating in the study had twice the rate of dementia, including Alzheimer's disease (AD), compared with women who did not take the medication. For more information on the latest findings on hormone therapy and dementia, see:
Researchers are also studying substances already used to reduce cardiovascular risk factors, such as statin drugs and folic acid, B6 and B12 vitamins, to determine whether they may also reduce AD risk.
People with AD and those with mild cognitive impairment (MCI) who want to help scientists test possible treatments may be able to take part in clinical trials. Clinical trials are studies to find out whether a new treatment is both safe and effective. For more information, go to the AD Clinical Trials Database.
What are Clinical Trials?
Clinical trials are studies to find out whether a new treatment is both safe and effective. People with AD and those with MCI who want to help scientists test possible treatments may be able to take part in clinical trials. Healthy people also can help scientists learn more about the brain and AD. The NIA and the Food and Drug Administration (FDA) are working together to maintain the AD Clinical Trials Database, which lists AD clinical trials sponsored by the Federal government and private companies.
Many of these studies are being done at NIA-supported Alzheimer's Disease Centers located throughout the United States. These centers carry out a wide range of research, including studies of the causes, diagnosis, treatment, and management of AD.
The NIA also supports the Alzheimer's Disease Cooperative Study (ADCS), a consortium of researchers at 109 sites in the U.S. and Canada conducting large-scale clinical trials of new approaches to treating and preventing AD. The ADCS is based at the University of California, San Diego.