Parkinson’s Disease

Parkinson’s disease dementia is a cognitive decline that occurs in some individuals at least one year after being diagnosed with Parkinson’s disease. Here is important information regarding Parkinson’s disease dementia:


Parkinson’s disease dementia involves a decline in thinking and reasoning skills that develops in individuals living with Parkinson’s disease. The brain changes associated with Parkinson’s disease initially occur in a region responsible for movement, resulting in early symptoms such as tremors, muscle stiffness, shuffling gait, and difficulty initiating movement. As the brain changes progress, individuals may experience cognitive impairments, including memory difficulties, attention problems, impaired judgment, and difficulties planning tasks.

The key brain changes in Parkinson’s disease and Parkinson’s disease dementia involve abnormal deposits called Lewy bodies. These deposits primarily consist of a protein called alpha-synuclein, which is found throughout the brain but whose exact function is not fully understood. Lewy bodies are also found in other types of dementia, such as dementia with Lewy bodies (DLB). Evidence suggests that DLB, Parkinson’s disease, and Parkinson’s disease dementia may share similar underlying abnormalities related to the processing of alpha-synuclein in the brain. Additionally, many individuals with both Parkinson’s disease dementia and DLB also exhibit hallmark brain changes associated with Alzheimer’s disease, known as plaques and tangles. When multiple types of dementia are present in the brain, it is referred to as mixed dementia.


Parkinson’s disease is a relatively common neurological disorder in older adults, affecting nearly 2% of individuals over the age of 65. It is estimated that almost one million Americans are living with Parkinson’s disease, with projections indicating that this number will rise to 1.2 million by 2030.

Causes and Risk Factors

Studies have shown that, on average, it takes approximately ten years from the onset of Parkinson’s disease to the development of dementia. About three-quarters of individuals who have been living with Parkinson’s disease for more than ten years will eventually develop dementia. Before the onset of dementia, individuals may experience milder cognitive changes referred to as mild cognitive impairment (MCI). The occurrence and timing of cognitive changes can vary from person to person.

Certain factors at the time of Parkinson’s disease diagnosis can increase the risk of future dementia, including advanced age, greater severity of motor symptoms, and the presence of mild cognitive impairment. Additional risk factors may include the presence of hallucinations, excessive daytime sleepiness, and a pattern of Parkinson’s symptoms called postural instability and gait disturbance (PIGD), characterized by freezing during movement, difficulty initiating movement, shuffling gait, balance problems, and falls.


There is no single test or combination of tests that can definitively diagnose Parkinson’s disease dementia. The diagnostic guidelines for Parkinson’s disease dementia and DLB state that the diagnosis is Parkinson’s disease dementia when dementia occurs at least one year after the onset of Parkinson’s disease symptoms, which may include motor changes like tremors. DLB is diagnosed when dementia occurs before, at the same time as, or within one year of Parkinson’s disease symptoms, with motor symptoms not always present in DLB cases.

Outcomes and Treatment

Both Parkinson’s disease and Parkinson’s disease dementia lead to the damage and destruction of brain cells, resulting in the progression of both disorders over time. However, the speed of progression can vary significantly from person to person.

Currently, there are no treatments available to halt or slow down the brain cell damage caused by Parkinson’s disease dementia. Treatment strategies primarily focus on managing symptoms. Cholinesterase inhibitors, commonly used in Alzheimer’s disease treatment, may help alleviate symptoms of Parkinson’s disease dementia, including visual hallucinations, sleep disturbances, and cognitive changes. Carbidopa-levodopa, a medication for Parkinson’s movement symptoms, may be prescribed, although it can sometimes worsen hallucinations and confusion in individuals with Parkinson’s dementia or DLB. Deep brain stimulation is currently not recommended for Parkinson’s disease dementia, as further studies are needed to confirm its effectiveness. Selective serotonin reuptake inhibitors (SSRIs) can be used to treat depression, which is common in both DLB and Parkinson’s disease dementia. Clonazepam and melatonin may be prescribed to manage REM sleep disorder. It is important to avoid antipsychotic drugs for behavioral symptoms, as they can worsen Parkinson’s symptoms and lead to serious complications.