Diseases & Conditions

Alzheimer's Disease

Overview, Causes, & Risk Factors

Alzheimer's disease is a common, progressive, degenerative disease of the brain. It is characterized by loss of memory and other cognitive functions. Among people aged 65 or older, it is the most common cause of dementia. Dementia is a group of symptoms marked by the gradual loss of mental function.

What is going on in the body?

People who have Alzheimer's disease have abnormal deposits of a protein called beta-amyloid. Abnormal structures called plaque are formed from a combination of destroyed nerve cells and the beta-amyloid. Tangles of nerve fibers are formed from abnormal nerve cells along with a type of protein called TAU. As the tangles and plaque develop, nerve cell connections are reduced. The elimination of nerve cell connections causes damage to certain pathways in the brain. These pathways are essential for thinking, learning, and memory.

People who have Alzheimer's disease have smaller brains than the normal population. They also have lower amounts of a neurotransmitter called acetylcholine. This chemical is essential for memory and thinking.

What are the causes and risks of the disease?

The cause of Alzheimer's disease is unknown. Factors that may increase the risk of developing Alzheimer's disease include the following:

  • genetics. Scientists have found links between the disease and certain chromosomes, including chromosomes 10, 14, 19, and 21. Individuals with Down syndrome, an abnormality of the 21st chromosome, have a significantly higher risk of developing Alzheimer's disease.
  • age. Most people with Alzheimer's disease are older than age 65, although it is sometimes seen in individuals in their 30s, 40s, and 50s. Alzheimer's disease is seen in 1 out of 4 people over the age of 85.
  • educational level or cognitive activities, which are tasks that involve active learning in the brain. Several research studies have shown that Alzheimer's disease is less likely to develop in individuals who have reached higher educational levels or have jobs that are more intellectually stimulating. Cognitive activities such as reading are associated with a later onset of Alzheimer's disease.
  • estrogen. There is some research suggesting a possible link between the hormone estrogen and Alzheimer's disease in women. Menopause, the stage of life when a woman stops having periods and her body makes little estrogen, is associated with an increase in the onset of Alzheimer's disease.
  • head injuries. A recent study of US armed forces veterans showed that a head injury early in life is associated with a higher risk of Alzheimer's disease and other forms of dementia as the veterans aged. Furthermore, the risk of Alzheimer's disease increased with the severity of the head injury in early life.
  • environmental toxins, such as aluminum and mercury. There has been conflicting research about the accumulation of heavy metals in the brains of individuals with Alzheimer's disease.
  • chemical deficiencies. People with Alzheimer's disease have a lower than normal level of acetylcholine in their brains.
  • autoimmune disorder, which is a condition in which the body attacks its own cells. Some researchers have found antibrain antibodies in the brains of people with Alzheimer's disease.

  • Symptoms & Signs

    What are the signs and symptoms of the disease?

    Symptoms include:

  • memory loss that affects the person's skills. Short-term memory, or memory of recent events, is particularly affected in individuals who have Alzheimer's disease.
  • difficulty doing familiar activities
  • misplacing belongings
  • poor or decreased judgment
  • language deterioration, with difficulty finding the right words
  • disorientation to time and place
  • changes in mood, including depression
  • hallucinations
  • delusions
  • personality changes, including agitation and irritability
  • impaired ability to orient the body to the surrounding space
  • a loss of interest in activities that were previously pleasurable
  • loss of bowel and bladder control
  • Sometimes individuals will wander. They can have problems doing complex tasks such as cooking or keeping track of a checkbook.

    Diagnosis & Tests

    How is the disease diagnosed?

    The diagnosis of Alzheimer's disease is based on a history of increasing memory loss and other cognitive impairments. Changes in behavior, personality, and judgment may also be clues to the disease.

    Since there is no definitive test for Alzheimer's disease, it is important to rule out other conditions or diseases that may cause the symptoms. These include the following:

  • multiple strokes
  • Parkinson's disease, a degenerative nerve disorder that causes tremors and mental decline
  • normal pressure hydrocephalus, which is excessive fluid around the brain
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  • hypothyroidism, or low levels of thyroid hormone
  • alcoholism and drug abuse
  • infectious diseases that cause brain degeneration, such as Creutzfeldt-Jakob disease, viral infections, or fungal infections
  • poisoning with carbon monoxide or methyl alcohol
  • depression
  • medication side effects or drug interactions
  • brain tumors
  • The clinical diagnosis of Alzheimer's can be made with an accuracy up to 90% based on these symptoms and the results of a collection of tests.

    Prevention & Expectations

    What can be done to prevent the disease?

    Although there are no proven methods to prevent Alzheimer's disease, recent research findings provide some options that may slow the onset of the disease or the progression of symptoms. These findings, which need further study, include:

  • low doses of aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), which may work by making blood cells and vessels less sticky and improving blood flow
  • actively engaging in cognitive activities such as reading, which may increase the nerve connections in the brain and delay the onset of the disease
  • taking antioxidants such as Vitamin E and selignine. In the Alzheimer's Disease Cooperative Study, a dose of 1,000 IU of vitamin E and 5 mg of selignine twice daily delayed nursing home placement, loss of the ability to perform self care, and severe dementia.
  • hormone replacement therapy for menopausal women, which may delay the onset of symptoms of Alzheimer's disease. The relationship between the hormone estrogen and Alzheimer's disease still needs further investigation.
  • avoiding head injuries. A person should wear a seatbelt at all times when riding in a motor vehicle. Sports safety guidelines for children, adolescents, and adults can be helpful in avoiding other head injuries.
  • What are the long-term effects of the disease?

    There is no cure for Alzheimer's disease. The disease is progressive. The symptoms get worse as the disease progresses. From the time the disease is recognized until the person dies is generally about 6 to 8 years, although it can range from less than 2 years to over 20 years.

    What are the risks to others?

    Alzheimer's disease is not contagious and poses no risk to others.

    Treatment & Monitoring

    What are the treatments for the disease?

    The 3 medications currently approved by the Food and Drug Administration for treatment of Alzheimer's disease are donepezil, tacrine, and rivastigmine. These medications are designed to improve memory by increasing the amount of acetylcholine in the body.

    Other medications, such as risperidone or quetiapine, may also be used to help behavioral problems such as hallucinations, delusions, or agitation. Some individuals with Alzheimer's disease may also need medications for depression, anxiety, or insomnia.

    Other treatments include support and education for those caring for people with Alzheimer's. Individual and family counseling can be beneficial. Support groups have also been found to assist caregivers. As the disease progresses, many families are unable to care for the person with Alzheimer's disease at home, and placement in a special facility is needed.

    What are the side effects of the treatments?

    Medications used to treat Alzheimer's disease can damage the liver, so periodic liver function tests are needed. Other side effects may include nausea, diarrhea, insomnia, vomiting, fatigue, or muscle cramps.

    What happens after treatment for the disease?

    Alzheimer's disease is a degenerative disease without a cure. Treatment is lifelong. Because the course of Alzheimer's disease is unpredictable, individuals with the disease should make plans for end-of-life care while they are still able to participate in the decision-making.

    Difficult issues that family members may face include the following:

  • promoting independence while making sure the individual is safe
  • removing driving privileges
  • finding supportive care among family, in an assisted living facility or nursing home
  • making business decisions
  • determining executors of written wills and making sure advanced directives are in the individual's patient file at his or her doctor's office
  • How is the disease monitored?

    Individuals with Alzheimer's disease will have periodic visits to the healthcare provider for evaluation and treatment. Periodic liver function tests may be ordered if the person is taking one of the medications that can cause liver damage. Any new or worsening symptoms should be reported to the provider.


    Author:Tamara Miller, MD
    Date Written:
    Editor:Ballenberg, Sally, BS
    Edit Date:01/31/01
    Reviewer:Barbara Mallari, RN, BSN, PHN
    Date Reviewed:07/15/01