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PD Dementia: An Important Conversation

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Many people with Parkinson’s disease (PD) experience some degree of cognitive change, such as slowness of memory, changes in thinking, trouble focusing or difficulty finding words. Dementia is a permanent cognitive change that interferes with daily activities and quality of life. Identifying thinking changes early and discussing them with your doctor are the first steps in treating or ruling out PD-related dementia.

This article is based on a Parkinson’s Foundation Expert Briefing Let’s Talk About Dementia presented by Dr. James Leverenz, Director, Lou Ruvo Center for Brain Health at Cleveland Clinic, a Parkinson’s Foundation Center of Excellence.

Slowed movement, tremor and stiffness are some of the visible movement signs of Parkinson's disease. Though not visible, the impact of non-movement symptoms can be even more challenging for people with PD and their loved ones — this includes issues with thinking and memory. While PD-related cognitive change can be mild, between 60 to 80% of people living with PD for 15 years or more can experience disease-related dementia. Awareness of thinking changes can ensure early treatment.

Lewy Body Dementias

In Parkinson’s, the protein alpha-synuclein misfolds and forms clusters in the brain called Lewy bodies. These sticky clusters upset normal brain function. Lewy bodies are strongly linked to PD and dementia.

Nearly 1.5 million Americans are impacted by Lewy body dementias, including those living with:

  • Parkinson’s disease dementia (PDD): diagnosed when significant cognitive decline occurs in someone living with Parkinson’s movement symptoms for a year or more (usually several years).
  • Dementia with Lewy bodies (DLB): diagnosed when cognitive decline occurs before or at the same time as motor symptoms.

Almost 50% of people with Alzheimer's disease also have some Lewy body brain abnormalities. These are frequently seen in both people who live with sporadic and familial forms of Alzheimer's. When these changes go beyond a part of the brain called the amygdala, people often have some of the same symptoms as people living with dementia with Lewy bodies , frequently developing Parkinson's-like motor symptoms. This is known as the Lewy body variant of Alzheimer disease.

Some researchers theorize that Alzheimer's disease may drive clumping of Lewy bodies. New therapies designed to slow Alzheimer's progression could also hold possibility to slow Lewy body development — another reason for the importance of an early and correct diagnosis, and early treatment.

Dementia Signs and Symptoms

In addition to memory, thinking and behavior changes, other symptoms include:

Despite many shared symptoms across Lewy body dementia diseases, people often store and recall information differently, depending on which cognitive disorder they are living with.

Adding and retaining new memories is often difficult for people living with Alzheimer's disease. It may be challenging for someone with Alzheimer's to remember a question or conversation just minutes after, or they may have forgotten events from the previous day. Encoding new information can be an issue. However, if a person experiencing PD thinking changes struggles retrieving a memory, they can often pull it up with a clue or a reminder.

This means people with PD dementia can store memories. Rather than primary encoding difficulty, they often experience retrieval challenges — an executive dysfunction similar to difficulty multitasking or staying on track during conversations.

People with Alzheimer’s disease tend to have less awareness that they are hallucinating. A person with PD dementia or dementia with Lewy bodies can more often recognize that they are experiencing hallucinations. It’s important for the care provider to ask the person experiencing changes “Do you see things?” People with PD-related dementia will often acknowledge that they do see things, are aware the hallucinations are not real and are not bothered by what they see.

Diagnosing Lewy Body Dementias

Ensuring the person living with thinking changes receives the correct diagnosis is important. When diagnosing dementia, a doctor, neurologist or other healthcare expert will look for the ability to retrieve retained memories, early executive dysfunction or multitasking difficulties.

A review of symptoms, medications, medical history and more are also key to an accurate diagnosis. Your doctor will also rule out other medical illnesses — urinary tract infections or pneumonia can be related to sudden confusion and agitation.

Work with your doctor to identify any medications that might impact symptoms. Some medicines can cause or worsen confusion and hallucinations, including:

  • Certain dopamine-boosting medications that ease movement at lower doses but may worsen thinking problems at higher doses
  • Old antipsychotics, such as haloperidol, and anticholinergic (acetylcholine-blocking)
  • Medications, such as trihexyphenydil, sometimes used to treat tremor


Medications used in Alzheimer’s disease have benefits in PD dementia, including rivastigmine, donepezil and galantamine. Selective serotonin reuptake inhibitors (SSRIs), used for depression, may also be beneficial.

For people with Parkinson’s experiencing rapid eye movement (REM) sleep behavior disorder, your doctor might recommend the over-the-counter sleep aid melatonin. Clonazepam is frequently used if melatonin is not effective, although it can cause confusion, daytime sleepiness and other side effects.

Cognitive remediation, provided by a neuropsychologist or speech-language pathologist, focuses on strengthening cognition.

Behavior management modifies activities and environments to improve abilities and independence. It includes creating a daily routine, decluttering living spaces, increasing lighting and using assistive tools to reduce confusion.

Exercise, physical activity and social connection can also benefit cognitive health.

On the Horizon

Research is currently underway to better understand dementia and discover disease-specific therapies. Diagnosing and treating the earliest stages of thinking change can ensure early lifestyle adjustments and the best chance for responsive therapy.

Understanding the biological differences behind the development and onset of all Lewy body dementias will be essential to future disease-specific therapies.

Scientists are currently working to standardize testing of blood and body fluids to reveal amassed Lewy body alpha-synuclein. This could serve as an early detection tool for neurodegenerative disorders related to the protein, such as PD.

Biomarkers for the Lewy Body Dementias, a National Institutes of Health-funded study, recently awarded more than $10 million to the Cleveland Clinic to expand the national Dementia with Lewy Bodies Consortium. A collaboration with several Parkinson’s Foundation Centers of Excellence and others, the coalition accelerates research to improve diagnosis and treatment of dementia with Lewy bodies, including Parkinson’s disease dementia.

People who experience rapid eye movement (REM) sleep behavior disorder (RBD) are at risk for developing Lewy body dementias. This risk factor might be another potential early diagnosis clue or cue to begin preventative future preventative therapies as they become available.

Learn More

The Parkinson’s Foundation believes in empowering the Parkinson’s community through education. Learn more about PD and dementia by calling our free Helpline at 1-800-4PD-INFO (1-800-473-4636) or visiting Parkinson’s Foundation resources below.

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