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 (DLB). 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 National Parkinson 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. Sign up for our enews to receive updates about Alzheimers and dementia care and research.

Learn more: Dementia with Lewy Bodies, Mixed 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:

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As with other types of dementia there is no single test or any combination of tests that conclusively determines that a person has Parkinson's disease dementia.

Many experts now believe that Parkinson's disease dementia and dementia with Lewy bodies are two different expressions of the same underlying problems with brain processing of the protein alpha-synuclein. But most experts recommend continuing to diagnose dementia with Lewy bodies and Parkinson's dementia as separate disorders.

Guidelines for diagnosing Parkinson's disease dementia and dementia with Lewy bodies are:

Brain Imaging

Since individuals with Parkinson's are at high risk for dementia as their disease progresses, doctors monitor those with Parkinson's closely for signs of thinking changes. When someone with Parkinson's develops thinking changes, doctors often order magnetic resonance imaging (MRI) of the brain to rule out tumors, structural changes and evidence for vascular disease.

Certain factors at the time of Parkinson's diagnosis may increase future dementia risk, including older age, greater severity of motor symptoms, and having mild cognitive impairment (MCI).

Additional risk factors may include:

There are no treatments to slow or stop the brain cell damage caused by Parkinson's disease dementia. Current strategies focus on helping symptoms.

If your treatment plan includes medications, it's important to work closely with your physician to identify the drugs that work best for you and the most effective doses. Treatment considerations involving medications include the following issues:

Find a clinical trial

More than 100 research studies pertaining to Alzheimer's and other dementias are underway. Alzheimer's Association TrialMatch lets you search these trials quickly and easily. Find a trial.

Like other types of dementia that destroy brain cells, Parkinson's disease and Parkinson's disease dementia get worse over time and speed of progression can vary.

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Parkinson's Disease Dementia | Signs, Symptoms, & Diagnosis