Parkinson’s Disease, Dementia, and Lewy Body Dementia: Understanding the Differences
As someone who has spent more than 17 years advocating for individuals and families affected by Alzheimer’s disease and other forms of dementia, I recently found myself asking a question that surprised me:
"Is Parkinson’s disease a form of dementia?"
It seemed like a simple question, but the answer was more complex than I expected. In fact, it highlighted just how confusing the relationship between Parkinson’s disease and dementia can be, even for those of us who have been immersed in this world for years.
If I was confused, I know I’m not alone.
That’s why I wanted to share what I learned in hopes of helping others better understand the differences between Parkinson’s disease, Parkinson’s Disease Dementia, and Dementia with Lewy Bodies.
First, What Is Dementia?
One of the biggest misconceptions is that dementia and Alzheimer’s disease are the same thing.
They are not.
Dementia is an umbrella term used to describe a group of symptoms that affect memory, thinking, reasoning, communication, and the ability to perform everyday activities.
Alzheimer’s disease is the most common cause of dementia, but there are many other forms, including:
Alzheimer’s Disease
Vascular Dementia
Lewy Body Dementia
Frontotemporal Dementia
Parkinson’s Disease Dementia
Mixed Dementia
Understanding this distinction is important because different types of dementia can present with different symptoms, progress differently, and require different approaches to care and treatment.
What Is Parkinson’s Disease?
Parkinson’s disease is primarily a neurological movement disorder.
It occurs when nerve cells in the brain that produce dopamine begin to deteriorate. Dopamine is a chemical messenger that helps control movement and coordination.
Common symptoms include:
Tremors
Muscle stiffness
Slowed movement
Balance difficulties
Changes in walking patterns
Softened speech
When most people think of Parkinson’s disease, these physical symptoms are what come to mind. What many people don't realize is that Parkinson’s can also affect thinking and cognition over time.
Does Parkinson’s Cause Dementia?
The answer is sometimes. Not everyone diagnosed with Parkinson’s disease will develop dementia. However, some individuals who live with Parkinson’s for many years may eventually experience significant cognitive changes.
When dementia develops after a person has already been living with Parkinson’s disease, it is called:
Parkinson’s Disease Dementia (PDD)
Symptoms may include:
Memory challenges
Difficulty concentrating
Problems with planning and decision-making
Reduced attention span
Visual-spatial difficulties
Hallucinations in some cases
The key distinction is that the movement symptoms of Parkinson’s were present first, often for years, before the cognitive symptoms appeared.
Where Does Lewy Body Dementia Fit In?
This is where things become especially confusing. Both Parkinson’s Disease Dementia and Dementia with Lewy Bodies involve abnormal protein deposits in the brain called Lewy bodies.
These protein deposits disrupt normal brain function and can affect movement, thinking, behavior, sleep, and emotions. Because the underlying disease process is so similar, both conditions fall under the broader category of:
Lewy Body Dementias
The difference between them largely comes down to timing.
Dementia with Lewy Bodies (DLB)
In Dementia with Lewy Bodies, cognitive symptoms appear first or around the same time as movement symptoms.
Individuals may experience:
Changes in thinking and reasoning
Fluctuations in alertness and attention
Visual hallucinations
Sleep disturbances
Parkinson-like movement symptoms
Parkinson’s Disease Dementia (PDD)
In Parkinson’s Disease Dementia, the person has already been diagnosed with Parkinson’s disease and lived with movement symptoms for more than a year before dementia symptoms develop.
Neurologists often use what is known as the "one-year rule."
Dementia symptoms first or within one year of movement symptoms = Dementia with Lewy Bodies
Dementia symptoms develop after more than one year of Parkinson’s symptoms = Parkinson’s Disease Dementia
While this may seem like a technical distinction, it helps physicians diagnose, treat, and manage these conditions appropriately.
Why This Matters
For families navigating a diagnosis, understanding these differences can be incredibly important.
Too often, people hear the word "dementia" and automatically think Alzheimer's disease. While Alzheimer's is the most recognized form, it is only one piece of a much larger picture.
Different forms of dementia can present differently:
Some affect memory first.
Some affect movement first.
Some involve hallucinations early in the disease process.
Some cause significant personality or behavioral changes.
Greater awareness leads to earlier recognition, better support, and more informed conversations with healthcare providers.
A Personal Reflection
Even after years of advocacy, fundraising, education efforts, and supporting families impacted by Alzheimer's disease and other dementias, there is always more to learn. I just needed to dig into this topic more to get a better understanding and thought it was important to share my findings.
That realization is exactly why education remains one of the core pillars of LMJ’s Lost Souls – Alzheimer’s Fund. The more we understand the various forms of dementia, the better equipped we are to support those living with these diseases and the loved ones who care for them.
At LMJ’s Lost Souls, we believe every conversation about brain health matters. If this article helped clarify the differences between Parkinson’s disease, Parkinson’s Disease Dementia, and Dementia with Lewy Bodies, please consider sharing it. You never know who may be searching for answers to the very same question.
LMJ’s Lost Souls – Alzheimer’s Fund is dedicated to raising awareness, advancing education, supporting research, and providing resources for individuals and families impacted by Alzheimer’s disease and other forms of dementia.
Together, we remember. Together, we learn. Together, we make a difference.