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Conditions InDepth: Alzheimer's Disease

Alzheimer’s disease is a chronic, slowly progressive, gradual in onset, irreversible condition that destroys brain nerve cells and other structures in the central nervous system. People with Alzheimer’s disease slowly develop dementia —a loss of memory and intellectual and social skills that result in confusion, disorientation, and the inability to think, reason, and understand. The decline in cognition and memory results in activities of daily living to performed with increasing difficulty.

People with Alzheimer’s disease (and other dementias) have symptoms that can change from day to day, usually getting worse but occasionally seeming to get better. However, people with Alzheimer’s disease do get worse over time, especially regarding memory loss (which is the most common initial symptom).

Common symptoms include:

  • Difficulty with short term memory (often with maintenance of long term memories)
  • Forgetting recent events and conversations
  • Impaired orientation
  • Misplacing items
  • Poor judgment and insight
  • Loss of interest in hobbies
  • Difficulty with cooking, dressing, shopping, finances
  • Changes in behavior and mood
  • Depression
  • Anxiety
  • Irritability

Scientists know that Alzheimer’s disease is caused by damage to brain nerve cells, as well as a loss of certain chemicals that facilitate communication between nerve cells. What is still not clearly understood is why this damage occurs.

Areas of the Brain Affected by Alzheimer's Disease
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Brain autopsies of Alzheimer's patients show two characteristic brain abnormalities:

  • Neurofibrillary tangles—These are found inside nerve cells in the hippocampus and temporal and frontal lobes of the brain. A type of protein called tau is found within these tangles.
  • Neuritic plaques—Located outside the nerve cells, the plaques are surrounded by dying neurons (nerve cells) and contain a sticky protein called beta amyloid. The presence of the plaque seems to be linked to reduction of an important chemical called acetylcholine. Acetylcholine helps neurons relay messages in the brain and is essential for memory and learning.

It has been estimated that over 4 million Americans have Alzheimer’s disease and the total healthcare costs are estimated to be over $100 billion in the United States alone. The number of patients with Alzheimer’s disease is expected to triple during the next 20 years as the baby boomer generation ages with an associated rise in the economic burden. In most cases, Alzheimer’s disease develops in people over the age of 65. Although, there is a rare, early-onset form of the disease that may strike people as young as 30. Nearly all people who have Down syndrome develop Alzheimer's disease if they live into their forties.

What are the risk factors for Alzheimer’s disease?What are the symptoms of Alzheimer’s disease?How is Alzheimer’s disease diagnosed?What are the treatments for Alzheimer’s disease?Are there screening tests for Alzheimer’s disease?How can I reduce my risk of Alzheimer’s disease?What questions should I ask my doctor?What is it like to live with Alzheimer's disease?Where can I get more information about Alzheimer’s disease?

Revision Information

  • Reviewer: Rimas Lukas, MD
  • Review Date: 09/2014 -
  • Update Date: 09/17/2014 -
  • Alzheimer's disease. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated July 11, 2012. Accessed August 22, 2012.

  • Alzheimer's disease medications fact sheet. National Institute on Aging website. Available at: http://www.nia.nih.gov/Alzheimers/Publications/medicationsfs.htm . Updated July 2010. Accessed August 22, 2012.

  • What is Alzheimer's? Alzheimer’s Association website. Available at: http://www.alz.org/alzheimers%5Fdisease%5Fwhat%5Fis%5Falzheimers.asp . Accessed August 22, 2012.