Lewy body dementia is the second most common type of dementia after Alzheimer's disease. Protein deposits called Lewy bodies develop in nerve cells in the brain. The protein deposits affect brain regions involved in thinking, memory and movement. This condition is also known as dementia with Lewy bodies.

Lewy body dementia causes a decline in mental abilities that gradually gets worse over time. People with Lewy body dementia might see things that aren't there. This is known as visual hallucinations. They also may have changes in alertness and attention.

People with Lewy body dementia might experience Parkinson's disease symptoms. These symptoms may include rigid muscles, slow movement, trouble walking and tremors.


Lewy body dementia symptoms can include:

  • Visual hallucinations. Seeing things that aren't there, known as hallucinations, might be one of the first symptoms of Lewy body dementia. This symptom often occurs regularly. People with Lewy body dementia might see shapes, animals or people that aren't there. Hallucinations involving sounds, smells or touch are possible.
  • Movement disorders. Signs of Parkinson's disease, known as parkinsonian signs, may occur. These symptoms include slowed movement, rigid muscles, tremor or a shuffling walk. This can cause the person to fall.
  • Poor regulation of body functions. The part of the nervous system that controls automatic functions is called the autonomic nervous system. Lewy body dementia can affect how well the autonomic nervous system controls blood pressure, heart rate, sweating and digestion. This can result in sudden drops in blood pressure upon standing, dizziness, falls, loss of bladder control and bowel issues such as constipation.
  • Cognitive problems. People with Lewy body dementia might have thinking problems similar to those of Alzheimer's disease. They may include confusion, poor attention, visual-spatial problems and memory loss.
  • Trouble with sleep. People with Lewy body dementia can have rapid eye movement (REM) sleep behavior disorder. This disorder causes people to physically act out their dreams while asleep. People with REM sleep behavior disorder may punch, kick, yell or scream while sleeping.
  • Varying attention. Episodes of drowsiness, long periods of staring into space, long naps during the day or disorganized speech are possible.
  • Depression. People with Lewy body dementia might develop depression.
  • Apathy. Loss of motivation may occur.


Lewy body dementia is characterized by the buildup of proteins into masses known as Lewy bodies. This protein also is associated with Parkinson's disease. People who have Lewy bodies in their brains also have the plaques and tangles associated with Alzheimer's disease.

Risk factors

A few factors seem to increase the risk of developing Lewy body dementia, including:

  • Age. People older than 60 are at greater risk.
  • Sex. Lewy body dementia affects more men than women.
  • Family history. Those who have a family member with Lewy body dementia or Parkinson's disease are at greater risk.


Lewy body dementia is progressive. This means it gradually gets worse over time. As symptoms get worse, Lewy body dementia can lead to:

  • Severe dementia.
  • Aggressive behavior.
  • Depression.
  • Increased risk of falling and injury.
  • Worsening of parkinsonian symptoms, such as tremors.
  • Death, on average about 7 to 8 years after symptoms start.