Parkinson’s disease dementia refers to the symptoms of Parkinson’s that impair thought processes, mental function, and memory.

Parkinson’s disease (PD) is a progressive disease of the nervous system that can affect a person’s mobility and their ability to perform daily activities.

The Parkinson’s Foundation estimates that over one million people in the U.S. will be living with PD by 2020, and that around 60,000 people per year receive a diagnosis. The Foundation also proposes that at least 10 million people worldwide currently have PD.

The disease damages the nerve cells responsible for producing dopamine in the substantia nigra, an area of the brain. Dopamine is a chemical in the brain that has several functions, including assisting in the coordinated movement of muscles.

Without this neurotransmitter, a person finds initiating movements and moving in a coordinated fashion difficult.

PD can affect physical movements, but it can also impact their thought processes, mental function, and memory. The result can be a condition called Parkinson’s disease dementia.

In this article, we look at the symptoms, causes, and management of PD dementia.

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Symptoms that individuals with Parkinson’s disease dementia experience may include:

  • anxiety and irritability
  • delusions
  • depression
  • difficulty sleeping well
  • slurred speech and issues speaking clearly
  • difficulty absorbing and interpreting visual information
  • excessive daytime sleepiness and rapid eye movements (REM)
  • memory changes
  • paranoia
  • visual hallucinations

Comparison with other dementias

Dementia is the result of physical changes in the brain that can lead to memory loss and an inability to think clearly.

Several types of dementia exist, including:

  • Alzheimer’s disease: According to the Alzheimer’s Association, Alzheimer’s disease is the most common type of dementia, affecting between 60 and 80 percent of all people with dementia. Symptoms include depression, affected communication, confusion, difficulty walking, and trouble swallowing.
  • Creutzfeldt-Jakob disease: Creutzfeldt-Jakob disease (CJD) represents a number of diseases, which can include “mad cow disease.” A person with CJD may experience rapid memory, behavior, and movement changes.
  • Dementia with Lewy bodies: This condition causes deposits of alpha-synuclein in a person’s brain. The symptoms can be similar to those of Alzheimer’s disease. People who have dementia with Lewy bodies may also experience sleep disturbances and visual hallucinations. They might have an unsteady walking pattern.
  • Frontotemporal dementia: Frontotemporal dementia often affects people at a younger age and does not cause any defined changes in the brain. However, it alters personality, behavior, and movement.
  • Huntington’s disease: This genetic disorder occurs due to an anomaly on chromosome 4 that leads to mood changes, abnormal movements, and depression.
  • Mixed dementia: Mixed dementia occurs when a person has dementia due to more than one cause, such as Lewy body dementia with vascular dementia or Alzheimer’s disease.
  • Normal pressure hydrocephalus: Fluid pressure buildup in the brain can cause this condition. It affects a person’s memory, movement, and their ability to control urination.
  • Vascular dementia: Also known as post-stroke dementia, this condition occurs after a person experiences a stroke, which is bleeding or vessel blockage in the brain. This dementia type impairs a person’s thinking and physical movements.
  • Wernicke-Korsakoff syndrome: This condition occurs due to a long-term deficiency of vitamin B1 or thiamine. It is most common in those who abuse alcohol. The chief symptom is severely impaired memory.

PD dementia has different symptoms to other types.

Alzheimer’s dementia, for example, impairs memory and language. PD dementiam on the other hand, affects problem-solving, the speed at which thoughts occur, memory, and mood, alongside other important cognitive functions.

Dementia with Lewy bodies and Parkinson’s disease dementia are similar in that the Lewy Bodies might be present in both forms.

However, whether the disease causes Lewy bodies or if Lewy bodies cause the disease symptoms is unclear. Researchers also believe that the way the Lewy bodies form in Parkinson’s disease dementia is different from those in Lewy body dementia.

PD is idiopathic, meaning that a doctor does not know why a person has the condition. However, according to Johns Hopkins Medicine, early-onset Parkinson’s disease has links to genetic inheritance from a parent.

Researchers have identified several risk factors that may make a person with Parkinson’s disease more likely to experience dementia.

These risk factors include:

  • advanced age at time of diagnosis
  • experiencing excessive daytime sleepiness
  • hallucinations before the onset of other dementia symptoms
  • having a specific Parkinson’s symptom that causes a person to have difficulty starting to take a step or to halt mid-step while walking
  • a history of mild thought impairment
  • more severe movement impairment symptoms than most people with Parkinson’s disease

However, researchers do not know why some people with Parkinson’s disease develop cognitive difficulties as well as movement problems.


According to the Alzheimer’s Association, around 50 to 80 percent of people with PD will develop dementia.

The average progression of time from diagnosis to the development of dementia is 10 years.

PD dementia can reduce a person’s ability to live independently. Advanced stages can affect communication, the ability to understand spoken language, memory, and concentration.

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A person who develops PD dementia will often already have a diagnosis of Parkinson’s.

A person will most often receive a diagnosis of PD before any dementia symptoms start. They are more likely to develop mobility problems before any disruption to thought processes.

If a person presents with these symptoms, a doctor should monitor them for both movement issues and cognitive changes.

An individual with a PD diagnosis should notify their doctor if they experience any of the following symptoms:

  • depression
  • difficulty thinking clearly
  • hallucinations
  • memory loss
  • sleep disturbances

Some of these symptoms might be side effects of PD medications, but a person experiencing any of these should notify their doctor to rule out possible dementia.

Diagnosing dementia can be difficult, as no single test can definitively identify the presence or type of dementia.

The first step a doctor should take is to consider overall health. They can also note any changes to general state of health, movement, and behavior over time. Family members or caregivers will sometimes have to provide this information, as the person with PD may not recall or be aware of all changes.

If a person with PD starts to experience dementia symptoms 1 year or more after their diagnosis, a doctor may diagnose the condition as PD dementia.

At this point, a doctor will also recommend imaging studies, such as an MRI scan. This can help identify any brain changes that could be causing the symptoms.

Examples would be a brain tumor or restricted blood flow to the brain. The scan might not necessarily confirm that a diagnosis of PD dementia, but it would rule out other possible causes.

No cure exists for PD dementia. Instead, treatments focus on reducing the symptoms of dementia and maintaining quality of life.

A doctor may prescribe certain medications, including:

  • Antidepressants: Doctors most often prescribe selective serotonin reuptake inhibitors (SSRIs) to reduce depression symptoms, such as Prozac, Celexa, Lexapro, or Zoloft.
  • Cholinesterase inhibitors: These medications help reduce the effects of cognitive decline in people with dementia.
  • Clonazepam: This medication can help to enhance sleep quality.
  • L-dopa: This medicine may reduce the movement issues that PD can cause but might make confusion and dementia symptoms worse.

Doctors may also prescribe antipsychotic drugs but must do so with caution, as they may reduce psychotic episodes but have the adverse effect of increasing symptoms of Parkinson’s.

These drugs may also cause increased confusion and changes in consciousness.

In 2016, the United States Food and Drug Administration (FDA) approved pimavanserin, or Nuplazid, an antipsychotic drug. Research has demonstrated that his drug can effectively treat hallucinations, without causing the side effects of some other antipsychotic medications.

Doctors may prescribe a combination of these medications for the safest and most effective results. Discuss both benefits and side effects when considering treatments.

People with Parkinson’s may also benefit from physical, occupational, and speech therapy to enhance movement and communication abilities.

Doctors do not currently know how to prevent Parkinson’s disease. While some people may have a genetic predisposition toward the disease, researchers have not identified a specific gene.

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PD dementia increases the mortality of people with Parkinson’s.

The life expectancy of people with PD dementia is different than those with without dementia symptoms.

A 2017 study published in JAMA Neurology suggests that while PD without dementia only moderately increased mortality in comparison with the general population.

The mortality rate of people with PD dementia, however, greatly increased.

While dementia does impact on survival rate, many medications, treatments, and support systems are available to a person who has Parkinson’s disease.


How do I recognize the first signs of PD in a friend or relative?


No single universal sign of Parkinson’s disease occurs in everyone.

However, changes in handwriting, voice, tremors of the hands at rest, lack of facial expression, or even constipation can represent early warning signs.

Timothy J. Legg, PhD, CRNP Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.