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Gut-Brain Connection

Answering Dementia & Parkinson’s Questions

By The Parkinson’s Foundation

When most people think of Parkinson’s disease (PD), they think of a tremor. While movement symptoms are more noticeable, such as stiffness and trouble with balance, there are also cognitive changes (noticeable changes in memory and thinking) that accompany the disease.

As Parkinson’s progresses, people living with PD can develop more significant or severe memory and thinking problems, sometimes called dementia. It’s important to note that dementia or significant cognitive decline can also seriously impact care partners and is associated with care partner stress. To best care for those living with the disease, care partners of people with Parkinson’s-related dementia must also prioritize themselves.

What are the types of Parkinson’s-related dementia?

Changes in the structure and chemistry of the brain can cause memory and thinking problems in Parkinson’s. A protein that is central to Parkinson’s, forms sticky clumps called Lewy bodies, can disrupt normal brain functioning and lead to dementia. Because of this, the term ‘Lewy body dementia’ may sometimes be used. There are two types of PD-related dementia:

  • Parkinson’s disease dementia – diagnosed when a person living with PD experiences significant cognitive decline after a year or more of movement symptoms (typically after many years of these symptoms).
  • Lewy Body Dementia – diagnosed when cognitive decline is the earliest symptom, or when cognitive decline and movement symptoms begin and progress together. Recently, this dementia is associated with Robin Williams, whose passing brought much needed attention to the importance of mental health and neurodegenerative diseases.
What are the symptoms of Parkinson’s disease dementia?

Symptoms can be wide-ranging and associated with mood, sleep and medications. Common symptoms can include:

  • Memory changes and confusion: signs range from forgetting how to do simple tasks, such as making coffee, to difficulty concentrating, learning,  remembering or problem-solving.
  • Becoming agitated, irritable, or even aggressive.
  • Experiencing hallucinations and delusions.
  • Difficulty communicating, including problems naming objects or misnaming them, and difficulty with speech.
Is there a test to diagnose PD dementia?

There is no single diagnostic test for PD dementia. A doctor makes the diagnosis. If you or someone you spend time with notices cognitive changes, it is important to discuss them with your care team. If you don’t have a care team in place, find a specialist or physician familiar with dementia or geriatric medicine. Call the Parkinson's Foundation Helpline 1-800-4PD-INFO (1-800-473-4636) for a referral.

How many people with Parkinson’s develop dementia?

According to recent research, up to 70 percent of people with Parkinson’s will develop dementia as a part of the disease progression.

Can a person have Parkinson’s disease dementia and Alzheimer’s disease?

While rare, it is possible for a person with PD to be diagnosed with Parkinson’s disease dementia and Alzheimer’s disease. A neurologist who treats Parkinson’s with a neuropsychologist, geriatrician or a geriatric psychiatrist can help diagnose Alzheimer’s disease.

Can you share tips for communicating with someone with Parkinson’s disease dementia?
  • If the person is stuck on an idea, try agreeing with them, then changing the subject.
  • Speak slowly and at eye level. Communicate in simple sentences.
  • If they are experiencing a hallucination or delusion, stay calm and be patient. Acknowledging what the person is seeing, even if you do not see it, can reduce stress.
  • View all tips at


The Parkinson’s Foundation is here to help. Learn more about cognitive changes and Parkinson’s in the educational book, Cognition: A Mind Guide to Parkinson’s Disease. Have Parkinson’s questions? Contact the Parkinson’s Foundation Helpline at 1-800-4PD-INFO (1-800-473-4636).




"I like that IMCC focuses on dementia-related problems and provides a focal point for families to network and socially interact in coping with dementia. It provides a community that helps us in our struggle."