Parkinson’s Disease Dementia: Causes, Symptoms, And Prospects

5 Dec

MNT Knowledge Center

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


The disease causes damage to the nerve cells that are responsible for producing dopamine, a chemical in the brain that helps with the transmission of electrical impulses to the muscles. Without these impulses, a person has difficulty moving in a coordinated fashion.

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

Contents of this article:

  1. What is Parkinson’s disease dementia?
  2. Causes and risk factors
  3. Diagnosing Parkinson’s disease dementia
  4. Treatment and prevention


What is Parkinson’s disease dementia?

Parkinson’s disease dementia is caused when deposits of a compound, known as alpha-synuclein, build up in the brain. These protein deposits are called Lewy bodies.

[man in wheelchair]
Parkinson’s dementia affects the mind as well as the body.

Symptoms associated with Parkinson’s disease dementia include:

  • Anxiety and irritability
  • Delusions
  • Depression
  • Difficulty sleeping well
  • Difficulty speaking clearly
  • Difficulty taking in what is seen and interpreting it
  • Excessive daytime sleepiness and rapid eye movements
  • Memory changes
  • Paranoia
  • Visual hallucinations

How does Parkinson’s disease dementia compare with other dementia types?

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.

  • 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 with dementia with Lewy bodies may also experience sleep disturbances and visual hallucinations, and they may have an unsteady walking pattern.
  • Frontotemporal dementia: Frontotemporal dementia often affects people at a younger age, but it doesn’t have any defined brain changes. However, it causes changes in personality, behavior, and movement.
  • Huntington’s disease: This genetic disorder is due to a gene defect 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 affects a person’s thinking and their 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.

Dementia with Lewy bodies and Parkinson’s disease dementia are similar in that they both cause Lewy bodies to form. However, the way the Lewy bodies form in Parkinson’s disease dementia appears different to those formed in Lewy body dementia.


Causes and risk factors

Most causes of Parkinson’s disease are idiopathic. This means that a doctor does not know why a person has the condition. However, according to Johns Hopkins Medicine, early-onset Parkinson’s disease is most commonly attributed to genetic defects, possibly those inherited from a parent.

Parkinson's and genetics jigsaw puzzle pieces.
Early-onset Parkinson’s disease could be linked to genetic defects passed on 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
  • Experiencing hallucinations before other dementia symptoms occurred
  • Having a specific Parkinson’s symptom, which causes a person to have difficulty starting to take a step or who may halt mid-step when walking
  • 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 the nerve damage that affects thinking as well as movement problems.

How does Parkinson’s disease progress over time?

According to the Alzheimer’s Association, an estimated 50 to 80 percent of people with Parkinson’s disease will experience Parkinson’s disease dementia. The average progression of time from diagnosis of Parkinson’s disease to Parkinson’s disease dementia is 10 years.

Parkinson’s disease dementia can affect a person’s ability to live by themselves. This is because advanced stages can affect communication, ability to understand spoken language, memory, and difficulty paying attention.


Diagnosing Parkinson’s disease dementia

A person will most often be diagnosed with Parkinson’s disease before any dementia symptoms start. This is because a person is more likely to develop mobility problems before any changes in thinking patterns occur.

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

An individual 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 can be side effects of medications taken for Parkinson’s disease, but if a person experiences any of them, they should notify their doctor so they can rule out possible dementia causes.

Doctors can have difficulty diagnosing dementia because there isn’t one test that can definitively say a person has dementia or a specific dementia type.

The first step a doctor can take is to consider the person’s overall health. They can also note any changes to health, movement, and behavior over time. Sometimes family members or caregivers will have to provide this information, as the person may not recall or be aware of all changes.

If a person with Parkinson’s disease starts to experience dementia symptoms 1 year or longer after their diagnosis, a doctor may diagnose the condition as Parkinson’s disease dementia.

At this point, a doctor will also recommend imaging studies, such as a magnetic resonance imaging (MRI) scan, which can 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 wouldn’t necessarily confirm that a person has Parkinson’s disease dementia, but it would rule out other possible causes.


Treatment and prevention

No cure exists for Parkinson’s dementia. Instead, treatments are focused on reducing symptoms associated with dementia. This can include medications.

[older lady with nurse]
Medications and other kinds of therapy can help people to cope with Parkinson’s dementia.

Examples of treatment medications include:

  • Antidepressants: Doctors most often prescribe selective serotonin reuptake inhibitors (SSRIs) like Prozac, Celexa, Lexapro, or Zoloft to reduce depression.
  • Cholinesterase inhibitors: These medications are intended to reduce the effects of thought decline in those with dementia.
  • Clonazepam: This medication can help to enhance sleep quality.
  • L-dopa: This medicine may reduce Parkinson’s disease-affected movement but can worsen confusion and dementia symptoms.

Doctors may also prescribe antipsychotic drugs but must do so with caution. This is because the side effects may reduce psychotic episodes but increase Parkinson’s symptoms. These drugs may also cause increased confusion and changes in consciousness.

The United States Food and Drug Administration (FDA) have recently approved a new antipsychotic drug, known as pimavanserin, or Nuplazid. This drug has been shown to effectively treat hallucinations, without causing the side effects of some other antipsychotic medications.

Doctors may prescribe a combination of these medications as a means to reduce symptoms. It is important to 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.

Preventing Parkinson’s dementia

Currently, doctors do not 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.

It is difficult to recommend reproduction changes or genetic tests, as most people are not affected by Parkinson’s until later in life. This may mean that a person will not know they are affected until their sons or daughters have already had children.


The life expectancy of people with Parkinson’s disease dementia is different to those with Parkinson’s disease. According to the Parkinson’s Disease Foundation, 79.1 percent of people with Parkinson’s disease dementia died in a 6-year period, while 64 percent died with Parkinson’s alone.

While dementia does affect a person’s survival rate, there are many medications, treatments, and support available to a person who has Parkinson’s disease. Researchers are working on new medications and treatments. This may eventually lead to a cure.

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