What is Alzheimer's Disease?
The information on this page comes from the U.S. Department of Health and Human Services and the National Institute on Aging.
Alzheimer’s disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills. It eventually prevents even the simplest tasks. In most people with Alzheimer’s, symptoms first appear after age 65. Estimates vary, but experts suggest that as many as 5 million Americans age 65 and older may have Alzheimer’s disease.
Alzheimer’s disease is the most common cause of dementia among older people. Dementia is the loss of cognitive functioning—thinking, remembering, and reasoning—and behavioral abilities. It interferes with a person’s daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’s functioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living.
Common behavioral symptoms of Alzheimer’s include sleeplessness, agitation, wandering, anxiety, anger, and depression. Scientists are learning why these symptoms occur and are studying new treatments—drug and non-drug—to manage them. Treating behavioral symptoms often makes people with Alzheimer’s more comfortable and makes their care easier for caregivers.
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Alzheimer’s disease is named after Dr. Alois Alzheimer. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. Her symptoms included memory loss, language problems, and unpredictable behavior. After she died, he examined her brain and found many abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles). Plaques and tangles in the brain are two of the main features of Alzheimer’s disease. The third is the loss of connections between nerve cells (neurons) in the brain.
Memory problems are typically one of the first warning signs of cognitive loss, possibly due to the development of Alzheimer’s disease. Some people with memory problems have a condition called amnestic mild cognitive impairment (MCI). People with this condition have more memory problems than normal for people their age, but their symptoms are not as severe as those seen in people with Alzheimer’s disease. Other recent studies have found links between some movement difficulties and MCI. Researchers also have seen links between MCI and some problems with the sense of smell. The ability of people with MCI to perform normal daily activities is not significantly impaired. However, more older people with MCI, compared with those without MCI, go on to develop Alzheimer’s.
A decline in other aspects of cognition, such as word-finding, vision/spatial issues, and impaired reasoning or judgment, may also signal the very early stages of Alzheimer’s disease. Scientists are looking to see whether brain imaging and biomarker studies, for example, of people with MCI and those with a family history of Alzheimer’s, can detect early changes in the brain like those seen in Alzheimer’s. Initial studies indicate that early detection using biomarkers and imaging may be possible, but findings will need to be confirmed by other studies before these techniques can be used to help with diagnosis in everyday medical practice.
As Alzheimer’s disease progresses, memory loss worsens, and changes in other cognitive abilities are evident. Problems can include, for example,getting lost, trouble handling money and paying bills (PDF, 159K), repeating questions, taking longer to complete normal daily tasks, using poor judgment, and having some mood and personality changes. People often are diagnosed in this stage.
In this stage, damage occurs in areas of the brain that control language, reasoning, sensory processing, and conscious thought. Memory loss and confusion grow worse, and people begin to have problems recognizing family and friends. They may be unable to learn new things, carry out tasks that involve multiple steps (such as getting dressed), or cope with new situations. They may have hallucinations, delusions, and paranoia, and may behave impulsively.
By the final stage, plaques and tangles have spread throughout the brain, and brain tissue has shrunk significantly. People with severe Alzheimer’s cannot communicate and are completely dependent on others for their care. Near the end, the person may be in bed most or all of the time as the body shuts down.
Scientists don’t yet fully understand what causes Alzheimer’s disease, but it has become increasingly clear that it develops because of a complex series of events that take place in the brain over a long period of time. It is likely that the causes include some mix of genetic, environmental, and lifestyle factors. Because people differ in their genetic make-up and lifestyle, the importance of any one of these factors in increasing or decreasing the risk of developing Alzheimer’s may differ from person to person.
Early-onset Alzheimer’s is a rare form of the disease. It occurs in people age 30 to 60 and represents less than 5 percent of all people who have Alzheimer’s disease. Most cases of early-onset Alzheimer’s are familial Alzheimer’s disease, caused by changes in one of three known genes inherited from a parent. For more information, see NIA's Early-Onset Alzheimer's Disease: A Resource List.
Most people with Alzheimer’s disease have “late-onset” Alzheimer’s, which usually develops after age 60. Many studies have linked the apolipoprotein E (APOE) gene to late-onset Alzheimer’s. This gene has several forms. One of them, APOE ε4, seems to increase a person’s risk of getting the disease. However, carrying the APOE ε4 form of the gene does not necessarily mean that a person will develop Alzheimer’s disease, and people carrying no APOE ε4 can also develop the disease.
Research also suggests that a host of factors beyond basic genetics may play a role in the development and course of Alzheimer’s disease. There is a great deal of interest, for example, in associations between cognitive decline and vascular and metabolic conditions such as heart disease, stroke, high blood pressure, diabetes, and obesity. Understanding these relationships and testing them in clinical trials will help us understand whether reducing risk factors for these conditions may help with Alzheimer’s as well.
Further, a nutritious diet, physical activity (PDF, 871K), social engagement, and mentally stimulating pursuits can all help people stay healthy as they age. New research suggests the possibility that these and other factors also might help to reduce the risk of cognitive decline and Alzheimer’s disease. Clinical trials of specific interventions are underway to test some of these possibilities.
Alzheimer’s disease can be definitively diagnosed only after death, by linking clinical measures with an examination of brain tissue and pathology in an autopsy. But doctors now have several methods and tools to help them determine fairly accurately whether a person who is having memory problems has “possible Alzheimer’s dementia” (dementia may be due to another cause) or “probable Alzheimer’s dementia” (no other cause for dementia can be found).
To diagnose Alzheimer’s, doctors may:
- Ask questions about overall health, past medical problems, ability to carry out daily activities, and changes in behavior and personality
- Conduct tests of memory, problem solving, attention, counting, and language
- Carry out standard medical tests, such as blood and urine tests, to identify other possible causes of the problem
- Perform brain scans, such as computed tomography (CT) or magnetic resonance imaging (MRI), to distinguish Alzheimer’s from other possible causes for symptoms, like stroke or tumor
- These tests may be repeated to give doctors information about how the person’s memory is changing over time.
Early, accurate diagnosis is beneficial for several reasons. It can tell people whether their symptoms are from Alzheimer’s or another cause, such as stroke, tumor, Parkinson’s disease, sleep disturbances, side effects of medications, or other conditions that may be treatable and possibly reversible.
In addition, an early diagnosis can provide greater opportunities for people to get involved in clinical trials. In a typical clinical trial, scientists test a drug or treatment to see if that intervention is effective and for whom it would work best.
Alzheimer’s disease is complex, and it is unlikely that any one intervention will be found to delay, prevent, or cure it. That’s why current approaches in treatment and research focus on several different aspects, including helping people maintain mental function, managing behavioral symptoms, and slowing or delaying the symptoms of disease.
Four medications are approved by the U.S. Food and Drug Administration to treat Alzheimer’s. Donepezil (Aricept®), rivastigmine (Exelon®), and galantamine (Razadyne®) are used to treat mild to moderate Alzheimer’s (donepezil can be used for severe Alzheimer’s as well). Memantine (Namenda®) is used to treat moderate to severe Alzheimer’s. These drugs work by regulating neurotransmitters (the chemicals that transmit messages between neurons). They may help maintain thinking, memory, and speaking skills, and help with certain behavioral problems. However, these drugs don’t change the underlying disease process, are effective for some but not all people, and may help only for a limited time.
Additionally, it's important not to overlook the challenges of caring for another population of Alzheimer's and dementia sufferers, people diagnosed with intellectual and developmental disabilities prior to the onset of any form of dementia. The National Task Group on Intellectual Disabilities and Dementia Practices (NTG) describes itself as, "a coalition of individuals and organizations working toward ensuring that the needs and interests of adults with intellectual and developmental disabilities who are affected by Alzheimer’s disease and related dementias – as well as their families and friends – are taken into account as part of the National Plan to Address Alzheimer’s Disease." Read more about NTG on the American Academy of Developmental Medicine and Dentistry's website.
Becoming well-informed about the disease is one important long-term strategy. Programs that teach families about the various stages of Alzheimer’s and about flexible and practical strategies for dealing with difficult caregiving situations provide vital help to those who care for people with Alzheimer’s.
Developing good coping skills and a strong support network of family and friends also are important ways that caregivers can help themselves handle the stresses of caring for a loved one with Alzheimer’s disease. For example, staying physically active provides physical and emotional benefits.
Some Alzheimer’s caregivers have found that participating in a support group is a critical lifeline. These support groups allow caregivers to find respite, express concerns, share experiences, get tips, and receive emotional comfort. Many organizations, such as those listed in the “For More Information” section, sponsor in-person and online support groups across the country. There are a growing number of groups for people in the early stage of Alzheimer’s and their families. Support networks can be especially valuable when caregivers face the difficult decision of whether and when to place a loved one in a nursing home or assisted living facility. For more information about at-home caregiving, see Caring for a Person with Alzheimer’s Disease: Your Easy-to-Use Guide from the National Institute on Aging.
To learn about support groups, services, research centers, research studies, and publications about Alzheimer’s disease, contact the following resources:
Alzheimer’s Disease Education and Referral (ADEAR) Center
P.O. Box 8250
Silver Spring, MD 20907-8250
225 North Michigan Avenue, Floor 17
Chicago, IL 60601-7633
Alzheimer’s Foundation of America
322 Eighth Avenue, 7th Floor
New York, NY 10001
Family Caregiver Alliance
785 Market Street, Suite 750
San Francisco, CA 94103
Syndicated Content Details
Source URL: http://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-fact-sheet
Source Agency: National Institute on Aging (NIA)
Capture Date: 2014-07-16