An estimated 50 to 80 percent of individuals with Parkinson’s Disease (PD) eventually develop dementia as their disease progresses. The average time from onset of Parkinson’s to developing dementia is about 10 years.
The key brain changes linked to PD and Parkinson’s disease dementia (PDD) are deposits of alpha-synuclein. These abnormal deposits are called “Lewy Bodies;” dementia with Lewy bodies, Parkinson’s disease and Parkinson’s disease dementia PDD may be linked to the same underlying abnormalities in brain processing of alpha-synuclein. To complicate matters further, many person’s with PDD also have plaques and tangles, brain changes linked to Alzheimer’s disease.
The brain changes caused by PD begin in the basal ganglia, a region that plays a key role in movement (i.e., substantia nigra’s dopaminergic cells). As PD gradually spreads through the brain, it may affect mental functions such as memory, the ability to pay attention, make sound judgments and plan the steps needed to complete tasks.
PDD is characterized by decline in cognition that develops in someone diagnosed with Parkinson’s disease at least a year earlier. Common symptoms of PDD are:
- Changes in memory, concentration and judgment
- Trouble interpreting visual information
- Muffled speech
- Visual hallucinations
- Delusions, especially paranoid ideas
- Irritability and anxiety
- Sleep disturbances, including excessive daytime drowsiness and rapid eye movement (REM) sleep disorder
PD often has co-occurring changes in mood, such as depression or apathy. Anxiety is also very common in PD. Some treatments used in PD an affect an individual’s personality, increasing desire to engage in pleasurable activities (e.g., sex, gambling, spending money). Such personality changes should be reported to prescribing physician right away.
PD’s drastic changes in overall functioning (movement, sleep, bowel and urinary difficulties, sexuality) understandably cause significant psychological adjustment issues that respond well to counseling and support groups.