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 activities to performed with increasing difficulty.

People with Alzheimer’s disease (and other dementias) can have symptoms that change significantly 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, 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, and 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

© 2008 Nucleus Medical Art, Inc.

Brain autopsies of Alzheimer's patients always show two characteristic brain abnormalities:

Neurofibrillary Tangles (twisted nerve cell fibers)—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. It is believed that beta amyloid may cause narrowing of blood vessels in the brain, which in turn cuts off the blood supply and kills nerve cells. The presence of the neuritic plaques 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 US alone. The number of Alzheimer’s disease patients 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 healthcare provider?
What is it like to live with Alzheimer's disease?
Where can I get more information about Alzheimer’s disease?


Alzheimer’s Association website. Available at: .

Last reviewed April 2007 by Roshni N. Patel, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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