Definition and Overview

Dementia associated with Parkinson’s disease (DAPD) refers to impaired mental functions that commonly affect patients with dementia. This condition progresses over time. However, the speed at which it develops varies in every case.

Parkinson’s disease is a common neurological disorder that affects the elderly. It is the second most common neurodegenerative illness after Alzheimer’s disease. Parkinson’s disease is estimated to affect up to 2% of elderly individuals beyond the age of 65. Its main symptoms affect the patient’s physical movements. These include tremors, stiffness, and loss of balance and coordination.

Up to 80% of Parkinson’s disease patients also experience some form of mental impairment. If these symptoms affect the patient’s ability to perform everyday tasks, they are also diagnosed with dementia. This problem affects up to 40% of Parkinson’s sufferers. It is more common among patients with severe or advanced Parkinson’s disease. Its symptoms usually develop between 10 and 15 years after a patient is first diagnosed.

Causes of Condition

Parkinson’s disease can cause some changes to occur in the brain. These changes, in turn, cause dementia. When a person suffers from dementia, his or her mental functions become impaired.

One of the main brain changes that lead to dementia is the presence of alpha-synuclein. This protein is found in the brain and is also called Lewy bodies. It is also linked to other brain disorders. The symptoms of dementia are believed to be due to the brain’s abnormal processing of this protein.

Patients with Parkinson’s disease usually also have tangles and plaques in their brain. These are also commonly found in patients with Alzheimer’s.

Dementia is more likely to develop when patients are older (around 70 years old) when they are first diagnosed with Parkinson’s disease. On the other hand, patients who are diagnosed before age 50 are less likely to develop dementia.

Key Symptoms

Dementia can affect memory, ability to pay attention, and decision-making skills. It can also affect reasoning, planning, and problem-solving skills. It can also cause apathy and psychosis.

Due to this, patients may suffer from delusions, hallucinations, and muffled speech. Irritability, anxiety, and depression are also common symptoms. Other common complaints are sleeping problems, such as REM disorder and excessive drowsiness.

These symptoms usually occur together with the common symptoms of Parkinson’s disease. These include tremors, impaired physical movements, and decreased facial expression. Other symptoms include a decreased sense of smell, malaise, weakness, and sexual dysfunction.

Moreover, dementia is closely associated with postural instability and gait disturbance (PIGT). This causes patients to shuffle when walking and to freeze in mid-step.

Who to See and Types of Treatments Available

The condition is treated by neurologists. These are doctors who focus on treating conditions that affect the nervous system.

Patients diagnosed with Parkinson’s disease face a higher risk of developing dementia. This is why they are closely monitored for signs of dementia as their condition worsens. When some signs and changes occur, patients are advised to undergo magnetic resonance imaging (MRI) scans. MRI scans can rule out brain tumours and other structural changes in the brain that may be causing the symptoms. If no other cause is found, the patient is diagnosed with dementia. Positron emission tomography (PET) scans may also be performed. This test can detect abnormal protein deposits in the brain.

There is no treatment that can stop or slow down brain changes that lead to dementia. Available treatment focuses on providing symptoms relief. Treatment options include:

  • Cholinesterase inhibitor drugs - These drugs are used to treat thinking and reasoning symptoms. They can boost the levels of a chemical messenger in the brain to help improve the patient’s memory and ability to make sound judgments. However, the drugs can cause some side effects, including nausea and diarrhoea.

  • Memantine - This medication regulates the activity of glutamate in the brain. This is a brain chemical that plays a key role in learning and memory.

  • Antipsychotic drugs - These help treat behavioural changes that occur due to dementia.

  • Levodopa - This drug helps treat movement symptoms caused by Parkinson’s.

  • Antidepressants - Doctors often prescribe SSRIs or selective serotonin reuptake inhibitors for patients showing signs of depression.

  • Clonazepam - These are used to treat sleeping disorders.

Patients with DAPD may also need occupational therapy. This treatment helps them cope with their condition and make their surroundings safer for them. Such therapy helps prevent accidents, such as falls.

As part of this treatment, patients’ tasks and environments are changed and simplified. Tasks are made simpler by breaking them down into smaller, easier steps. Patients with dementia are also given normal routines and structures that are easy for them to follow. These make everyday tasks more manageable.

Alternative therapies may also be considered. These include music, art, aroma, and massage therapies. Listening to calming music or creating art can help patients relax. These activities can help reduce their symptoms, such as anxiety and irritability.

Patients are also encouraged to seek support. They can do so by joining a support group and undergoing family counselling. These activities help prepare the patient and their family members for when their condition gets worse. It is also important for the patient to find someone they can trust to help them make decisions.

In addition, patients are encouraged to exercise. This helps improve their physical strength and cardiovascular health. Some studies show that continuous physical activity can help slow the progress of DAPD. It can also help prevent the onset of depression.

As the disease progresses, the patient may require a full-time caregiver.


  • Emre M. “Dementia associated with Parkinson’s disease.” Lancet Neurol. 2003 Apr;2(4): 229-37.

  • Aarsland D, Kurz MW. “The epidemiology of dementia associated with Parkinson’s disease.” Brain Pathol. 2010 May; 20(3):633-9.

Share This Information: