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Alzheimer's disease | Dementia with Lewy bodies | Vascular dementia | Other causes
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Causes of dementia

There are more than 60 disorders that can cause dementia. Most of these conditions slowly get worse.
 
 
 
 
 
Source:
Bird TR.
Memory loss and dementia.
In: Braunwald E, Hauser SL, Fauci AS, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw Hill, New York, U.S.A.; 2001.
 
 
 
 
 
 1 Here are some of the most common problems that can cause dementia.

Alzheimer's disease
This is the most common cause of dementia. More than half of the people with dementia have Alzheimer's.
 
 
 
 
 
Source:
Katzman R.
Alzheimer's disease.
New England Journal of Medicine. 1986; 314: 964-973.
 
 
 
 
 
 2

In Alzheimer's disease, several changes happen in the brain that stop it from working properly.

  • Small lumps form in the brain. Doctors call these amyloid plaques. They're made of protein and bits of dead cells. The lumps grow in the parts of the brain used for memory and thinking.
     
     
     
     
     
    Source:
    National Institute of Aging
    Progress report on Alzheimer's disease - taking the next steps
    National Institutes of Health, 2000
     
     
     
     
     
     3 They can stop messages from passing between brain cells.
  • Bundles of twisted threads form inside brain cells. Doctors call these neurofibrillary tangles. These also stop brain cells from talking to each other, and they can cause cells to die.
     
     
     
     
     
    Source:
    National Institute of Aging
    Progress report on Alzheimer's disease - taking the next steps
    National Institutes of Health, 2000
     
     
     
     
     
     3
     
     
     
     
     
    Source:
    Whitehouse PJ.
    Genesis of Alzheimer's disease.
    Neurology. 1997; 48 (supplement 7): S2-S7.
     
     
     
     
     
     4
  • Holes or gaps appear where brain cells have died.
  • The brain does not have enough chemical messengers (neurotransmitters).
When Alzheimer's disease starts, it damages cells in the parts of the brain that store memories. This can cause problems with short-term memory. So, when someone gets Alzheimer's, they may forget what they did two days ago.

Over time, the disease damages the parts of the brain that control language and thinking. People with Alzheimer's may forget words or have trouble understanding what others are saying.

Eventually, many areas of the brain get damaged and stop working properly.

Dementia with Lewy bodies
This is the second most common cause of dementia. Up to a quarter of people with dementia have Lewy body dementia.
 
 
 
 
 
Source:
Lewy Body Dementia Association Inc.
What is Lewy Body Dementia?
Available at: http://www.lewybodydementia.org/lbdinfo.php. (accessed on 7 October 2008).
 
 
 
 
 
 5

In this type of dementia, you get small, round clusters of proteins inside your brain cells. These are called Lewy bodies. They stop important chemicals in the brain from working normally. But we don't know why these clusters appear.

Lewy bodies are also found in people with Parkinson's disease. People with this condition find it difficult to move. They get stiff muscles and shuffle when they walk. They also lose facial expressions as the muscles in their face become stiff. You can also get these symptoms if you have dementia with Lewy bodies.

This type of dementia can also cause the small lumps in the brain that people with Alzheimer's get. Doctors call these amyloid plaques. They're made of protein and bits of dead cells. The lumps grow in the parts of the brain used for memory and thinking.
 
 
 
 
 
Source:
National Institute of Aging
Progress report on Alzheimer's disease - taking the next steps
National Institutes of Health, 2000
 
 
 
 
 
 3 They may stop messages from passing between brain cells.

People with dementia from Lewy bodies get the usual brain problems, such as memory loss and confusion, which happen with other types of dementia. But they might also see things that aren't there (have halucinations) and have problems keeping their balance.

Vascular dementia
Dementia can also happen when blood vessels near the brain get damaged. If these vessels are blocked or burst, the brain doesn't get enough blood (this is what happens if you have a
 
 
 
 
 
stroke
You have a stroke when the blood supply to a part of your brain is cut off. This damages your brain and can cause symptoms like weakness or numbness on one side of your body. You may also find it hard to speak if you've had a stroke.
 
 
 
 
 
 stroke). This can cause some of cells in the brain to die, and this can lead to dementia. Between 1 in 10 and 2 in 10 people with dementia have vascular dementia.
 
 
 
 
 
Source:
Katzman R.
Alzheimer's disease.
New England Journal of Medicine. 1986; 314: 964-973.
 
 
 
 
 
 2

Vascular dementia can happen suddenly if you have a stroke. Or it can come on gradually if you have a series of little strokes (this is called multi-infarct dementia). If you have a stroke, some symptoms can clear up with treatment. But they may gradually get worse.

Other causes
Lots of other things can also lead to the personality changes and problems with memory, thinking and behaviour seen in dementia. These include:
 
 
 
 
 
Source:
Bird TR.
Memory loss and dementia.
In: Braunwald E, Hauser SL, Fauci AS, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw Hill, New York, U.S.A.; 2001.
 
 
 
 
 
 1

  • Infections, such as
     
     
     
     
     
    HIV
    HIV stands for human immunodeficiency virus. It's the virus that causes AIDS. It makes you sick by damaging cells called CD4 cells. Your body needs these cells to fight infections. You can get HIV by sharing needles for injecting drugs ,or by having sex without a condom with someone who already has the virus.
     
     
     
     
     
     HIV
  • Alcohol abuse
  • A head injury
  • A brain tumor
  •  
     
     
     
     
    depression
    Depression is a mental illness in which your mood is low and you feel sad much of the time. It can range from a mild illness through to a severe one in which you lose interest in life and may be suicidal.
     
     
     
     
     
     Depression
  • Other mental health problems, such as
     
     
     
     
     
    schizophrenia
    Schizophrenia is a mental illness that causes delusions and hallucinations.
     
     
     
     
     
     schizophrenia
  • Other diseases that affect cells in your brain, such as
     
     
     
     
     
    Huntington's disease
    This disease of the brain causes uncontrolled movements, emotional problems, and problems with walking, talking and thinking. It is inherited (passed on in your genes). Symptoms don't usually start before people are in their 40s or 50s. There is no treatment.
     
     
     
     
     
     Huntington's disease,
     
     
     
     
     
    motor neuron disease
    Motor neuron disease (MND for short) is the name given to a group of diseases that affect the nerve cells (neurons) that control muscles. People with these diseases can have trouble moving around, speaking, breathing and swallowing normally. Symptoms gradually get worse as a person's muscles weaken.
     
     
     
     
     
     motor neuron disease or
     
     
     
     
     
    multiple sclerosis
    Multiple sclerosis, or MS for short, is a disease that involves damage to the walls of nerves. No one knows for sure what causes it. If you have multiple sclerosis, you may lose feeling in certain parts of your body. You may also have trouble with your vision or controlling your movements.
     
     
     
     
     
     multiple sclerosis.

Sources for the information on this page:
  1. Bird TR.Memory loss and dementia.In: Braunwald E, Hauser SL, Fauci AS, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw Hill, New York, U.S.A.; 2001.
  2. Katzman R.Alzheimer's disease.New England Journal of Medicine. 1986; 314: 964-973.
  3. National Institute of AgingProgress report on Alzheimer's disease - taking the next stepsNational Institutes of Health, 2000
  4. Whitehouse PJ.Genesis of Alzheimer's disease.Neurology. 1997; 48 (supplement 7): S2-S7.
  5. Lewy Body Dementia Association Inc.What is Lewy Body Dementia?Available at: http://www.lewybodydementia.org/lbdinfo.php. (accessed on 7 October 2008).
This information was last updated on Mar 05, 2009
BMJ Group
This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment.
© BMJ Publishing Group Limited 2009. All rights reserved.
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