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You are here : 3-RX.com > Medical Encyclopedia > Diseases and Conditions > Alzheimer's Disease
      Category : Health Centers > Brain and Nervous System

Alzheimer's Disease

Alternate Names : Organic Brain Syndrome

Overview, Causes, & Risk Factors | Symptoms & Signs | Diagnosis & Tests | Prevention & Expectations | Treatment & Monitoring

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.


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    Alzheimer's Disease: Symptoms & Signs

    Author: Tamara Miller, MD
    Reviewer: Barbara Mallari, RN, BSN, PHN
    Date Reviewed: 07/15/01

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