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Causes and Risk Factors of Alzheimer's Disease

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Researchers don't know exactly what causes Alzheimer's disease, but it probably results from a complex set of factors.

The Brain and Alzheimer's Disease

There are certain abnormalities found in the brains of people with Alzheimer's disease, but experts don't know whether these cause the disease or are a result of the disease. Abnormalities found in the brains of people with Alzheimer's disease include:

  • Neurofibrillary tangles, twisted structures formed from part of the nerve
  • Beta amyloid, a sticky substance that clumps to form structures called plaques

Plaques and tangles damage the healthy brain cells that surround them, causing the brain to waste away and shrink. 

Another characteristic of Alzheimer's disease is that brain cells produce reduced amounts of chemicals, known as neurotransmitters, that are required for communication between nerves. These chemicals include acetylcholine, serotonin, and norepinephrine.

Risk Factors for Alzheimer's Disease

Factors that may increase the risk for Alzheimer's disease include:

  • Age. The risk of developing Alzheimer's disease increases with age. According to the Alzheimer's Association, 10% of all people over age 65 have Alzheimer's disease, and as many as 50% of people over age 85 have it.
  • Gender. Alzheimer's disease affects women more frequently than men.
  • Family history. Fewer than 1% of people with Alzheimer's disease inherited the condition.
  • Down syndrome. People with Down syndrome often develop Alzheimer's disease in their 30s and 40s, although the exact reason is not known.
  • Head injury. Some studies have shown a link between Alzheimer's disease and a significant head injury.
  • Environmental toxins. Some researchers suspect that increased exposure to certain substances such as aluminum may make a person more susceptible to Alzheimer's disease.
  • Low education level. Although the reason is not clearly understood, some studies have shown that low education levels can be related to an increased risk for Alzheimer's disease.
  • Other factors. Research also suggests that high cholesterol levels and high blood pressure -- factors linked to heart disease and stroke -- may also increase the risk for developing Alzheimer's.


WebMD Medical Reference

Reviewed by Neil Lava, MD on June 28, 2014
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