What is: Parkinson’s Disease Dementia?

Parkinson’s disease is a disorder in the central nervous system. The central nervous system (CNS) processes information and sends motor signals through the body in response. Thus, Parkinson’s disease often affects motor functions, resulting in involuntary movements, such as tremors and loss of balance. 

Parkinson’s disease dementia (PDD) is diagnosed when people living with or exhibiting symptoms of Parkinson’s disease begin to express symptoms of dementia. The development of PDD starts in a part of the brain that is key to physical movement. As the disease progresses, some people begin to experience a decline in cognitive function, in addition to struggling to remember things and pay attention. 

The development of Parkinson’s disease is attributed, in part, to decreased dopamine in the brain. Dopamine is both a hormone and a neurotransmitter, and, among other things, it is responsible for muscle movement, coordination and mood regulation. Neurons in the brain’s basal ganglia produce dopamine, but when they are damaged or die, the production of dopamine decreases significantly. The exact cause of death of these neurons remains unknown, but scientists have established a connection between decreased dopamine function and correlated symptoms of Parkinson’s disease, such as mood instability. 

There is also a large genetic factor in the development of Parkinson’s disease. Those with a family history of Parkinson’s disease, as well as biological males (over females), have a higher probability of developing Parkinson’s disease. This is especially true for early onset Parkinson’s disease.

Parkinson’s-related dementia differs from Alzheimer’s disease, the most common form of dementia, in a number of ways. Not only are the root causes different, the associated symptoms also vary. Alzheimer’s disease tends to affect the ability to process both semantics (i.e. meaning) and pragmatics (i.e. meaning in context) of language, while PDD affects both the processing of pragmatics and speech production. Similar to other forms of dementia, PDD also affects mood, reasoning skills, and speed of thinking in addition to memory. Further, people suffering from PDD may also experience hallucinations and delusions, which are not typically associated with Alzheimer’s disease.


“Parkinson’s Disease and Dementia.” Johns Hopkins Medicine, August 8, 2021. https://www.hopkinsmedicine.org/health/conditions-and-diseases/parkinsons-disease/parkinsons-disease-and-dementia.

“Parkinson’s Disease.” Alzheimer’s Disease and Dementia, n.d. https://www.alz.org/alzheimers-dementia/what-is-dementia/types-of-dementia/parkinson-s-disease-dementia.

“Parkinson’s Disease: Causes, Symptoms, and Treatments.” National Institute on Aging. U.S. Department of Health and Human Services, n.d. https://www.nia.nih.gov/health/parkinsons-disease.

Team, Editorial, and Lynn Marie Witt Moderator. “Alzheimer’s and Parkinson’s Disease-Related Dementia.” AlzheimersDisease.net, n.d. https://alzheimersdisease.net/answers/parkinsons-dementia-differences.