Parkinson's Disease Dementia

Parkinson's Disease Dementia

Parkinson's disease dementia is an impairment in thinking and reasoning that eventually affects many people with Parkinson's disease.

About Parkinson's disease dementia

The brain changes caused by Parkinson's disease begin in a region that plays a key role in movement. As Parkinson's brain changes gradually spread, they often begin to affect mental functions, including memory and the ability to pay attention, make sound judgments and plan the steps needed to complete a task.

The key brain changes linked to Parkinson's disease and Parkinson's disease dementia are abnormal microscopic deposits composed chiefly of alpha-synuclein, a protein that's found widely in the brain but whose normal function isn't yet known. The deposits are called "Lewy bodies".

Lewy bodies are also found in several other brain disorders, including dementia with Lewy bodies. Evidence suggests that dementia with Lewy bodies, Parkinson's disease and Parkinson's disease dementia may be linked to the same underlying abnormalities in brain processing of alpha-synuclein.

Another complicating factor is that many people with both dementia with Lewy bodies and Parkinson's disease dementia also have plaques and tangles— hallmark brain changes linked to Alzheimer's disease.

Parkinson's disease is a fairly common neurological disorder in older adults, estimated to affect nearly 2 percent of those older than age 65. The Parkinson's Foundation estimates that 1 million Americans have Parkinson's disease. It is estimated that 50 to 80 percent of those with Parkinson's disease eventually experience Parkinson's disease dementia. 

What percentage of people with Parkinson's develop dementia?

An estimated 50 to 80 percent of those with Parkinson's eventually experience dementia as their disease progresses. The average time from onset of Parkinson's to developing dementia is about 10 years.

Parkinson's disease dementia is a decline in thinking and reasoning that develops in someone diagnosed with Parkinson's disease at least a year earlier. Common symptoms include:

  • Changes in memory, concentration and judgment
  • Trouble interpreting visual information
  • Muffled speech
  • Visual hallucinations
  • Delusions, especially paranoid ideas
  • Depression
  • Irritability and anxiety
  • Sleep disturbances, including excessive daytime drowsiness and rapid eye movement (REM) sleep disorder

Please call the Memory & Aging Center for more information on our current Parkinson's study.