Dementia and Parkinson’s: ask the expert

The symptoms of dementia can include problems with memory, concentration and planning. In this blog we explore the relationship between dementia and Parkinson’s, and how research is looking to help.

Annie Amjad
Jul 9, 2018 · 8 min read

We’re joined by Gemma Jolly, Knowledge Manager at the Alzheimer’s Society.

What is dementia?

The word ‘dementia’ describes a set of symptoms that may include memory loss and difficulties with thinking, problem-solving or language. These changes are often small to start with, but for someone with dementia they have become severe enough to affect daily life. A person with dementia may also experience changes in their mood or behaviour.

Dementia is caused when the brain is damaged by diseases, such as Alzheimer’s or a series of strokes. Alzheimer’s is the most common cause of dementia, but not the only one.

The specific symptoms that someone with dementia experiences will depend on the parts of the brain that are damaged and the condition that is causing the dementia.

What is the connection between Parkinson’s and dementia?

Parkinson’s, Parkinson’s dementia and dementia with Lewy bodies are a group of conditions which all have the same underlying cause — Lewy bodies.

Lewy bodies are small deposits of protein (mainly alpha-synuclein) which are found within nerve cells in the brain at autopsy. For this reason, conditions where Lewy bodies form are also called ‘alpha-synucleinopathies’.

Exactly what effect Lewy bodies have is not clear, but they are linked to:

  • low levels of neurotransmitters (chemical messengers) in the brain — especially acetylcholine and dopamine
  • death of nerve cells — scans show loss of brain tissue in people with dementia with Lewy bodies or Parkinson’s dementia.

Where Lewy bodies are found in the brain seems to influence symptoms. In broad terms:

  • Lewy bodies in the brainstem (and low levels of dopamine) are linked to problems with movement. These are seen especially in Parkinson’s and Parkinson’s dementia.
  • Lewy bodies in the cerebral cortex (and low levels of acetylcholine) are linked to cognitive symptoms. These are most obvious in dementia with Lewy bodies and Parkinson’s dementia.

The main Lewy body conditions all share a group of symptoms — these include:

  • cognitive impairment — at worst, dementia
  • mood disorders — anxiety and depression
  • psychosis — hallucinations and delusions
  • motor disorders — e.g. muscle stiffness, slow movement
  • sleep disturbance

The Lewy body conditions differ in how common and severe these symptoms are — for example, dementia with Lewy bodies does not always have motor symptoms. The conditions also differ in the order in which symptoms occur — motor symptoms come before cognitive symptoms in Parkinson’s dementia. In dementia with Lewy bodies, motor symptoms appear after (or with) cognitive symptoms.

Lewy body dementias are less common than Alzheimer’s, mixed or vascular dementia — dementia with Lewy bodies represents four percent of all recorded dementia diagnoses (but this is an underestimate, it’s probably more like 10–15 percent) and Parkinson’s dementia is just two percent of dementia cases.

Why are people with Parkinson’s at a higher than average risk of developing dementia?

We still don’t fully understand why some people with Parkinson’s get dementia. It isn’t entirely possible to predict who it will affect, but there are factors that put certain groups of people at more risk.

Not everyone with Parkinson’s will develop dementia, but having Parkinson’s does significantly increase — by about six times — someone’s risk of developing dementia. If you follow a group of people with Parkinson’s over time, about half will have dementia by 8–10 years after their diagnosis of Parkinson’s, rising to 80% by 20 years.

If someone has been diagnosed with Parkinson’s later in life, has had Parkinson’s for a long time, experiences hallucinations and delusions early on in their Parkinson’s, has more severe motor symptoms or has a family member with dementia, this can increase their risk of developing dementia.

Recent research found that an MRI test may be able to predict which people with Parkinson’s will go on to develop dementia. The team identified a specific brain region that is damaged before any thinking and memory symptoms appear.

The researchers found that people with Parkinson’s with cognitive symptoms had lost more brain tissue in a structure in the brain called the nucleus basalis of Meynert, compared to those without cognitive symptoms.

The researchers compared people with Parkinson’s who had cognitive symptoms to people with Parkinson’s who did not. They also followed people for three years, comparing people who developed cognitive symptoms to those that didn’t.

Their findings suggest that damage of the nucleus basalis of Meynert predicts the development of cognitive symptoms, and might be useful to identify people at higher risk of dementia.

Is there anything people with Parkinson’s can do to reduce their risk of developing dementia?

This is a complicated question. We don’t fully understand why some people with Parkinson’s develop dementia and others do not. It’s further complicated because we don’t know what causes Parkinson’s.

A risk factor is anything that increases a person’s risk of developing a condition. For dementia there are a mixture of factors — some that can be avoided and others that are impossible to control. However, having any of the risk factors does not mean a person will necessarily develop dementia in the future. Likewise, avoiding risk factors does not guarantee that a person will stay healthy, but it does make this more likely.

In the case of Parkinson’s dementia many of the identified risk factors can’t be changed, for example, age. However, lifestyle factors including smoking and hypertension may increase a person’s risk of developing Parkinson’s dementia.

In general there are things which may reduce a person’s risk of dementia including eating healthily, not smoking, keeping your mind active and staying physically active.

What are the current treatment approaches to Parkinson’s dementia?

There is no cure for Parkinson’s dementia, although there is ongoing research into this area. As with other forms of dementia, non-drug approaches are important to helping a person live well with their condition such as Cognitive Stimulation Therapy, adapting the environment, providing opportunities for engagement or arts based therapy.

There is usually a need for a range of professionals to be involved in supporting the person, due to the variety of symptoms they experience. Treatment should look at which symptoms the person (and those supporting them) finds the most troubling, and should look at non-drug approaches in the first instance.

Someone with Parkinson’s dementia is likely to be already taking a drug such as levodopa for motor symptoms — such drugs work much better in Parkinson’s and Parkinson’s dementia than they do in dementia with Lewy bodies. However, levodopa lowers levels of a chemical messenger in the brain, called acetylcholine, and so can make attention or hallucinations worse. This is a problem with medication for both Parkinson’s dementia and dementia with Lewy bodies — drugs for motor symptoms tend to worsen cognition or hallucinations, and vice versa. So a balance has to be struck for that person, usually by trying out different drugs and combinations.

There is good evidence that the acetylcholinesterase inhibitors reduce hallucinations (and possibly improve cognition) in people living with Parkinson’s dementia. Rivastigmine is licensed and approved by NICE for distressing hallucinations, but donepezil and galantamine may work just as well.

The use of antipsychotics is problematic and if they are used it should be after other approaches have been tried and they should be regularly and carefully monitored.

Are there any promising new potential treatments being developed?

There are new treatments being developed that aim to relieve the thinking and memory symptoms of Parkinson’s dementia. At the end of last year the pharmaceutical company Eli Lilly launched a clinical trial of a drug designed to boost certain chemical messages in the brain. It aims to enhance the function of a particular type of dopamine receptor. The main effect they’re looking for is an improvement in people’s scores in tests of sustained attention to cognitive tasks.

It would be better to slow or stop the progression of Parkinson’s altogether, which could prevent people from going on to get Parkinson’s dementia. There are a number of new treatments that are aiming to target an important part of the underlying biology, removing clumps of alpha-synuclein from the brain.

What are the remaining research questions?

The relationship between Parkinson’s, Parkinson’s dementia and dementia with Lewy bodies is still not completely clear. To make matters even more complex, research looking at changes in the brains of people who have had Parkinson’s dementia reveals that most have some aspects of the biological changes seen in Alzheimer’s too. What causes this to happen? Does this contribute to the symptoms that people experience? And will we need to treat these changes as well as the alpha-synuclein clumps? These are just a few questions that need answers if we are to be successful in finding treatments that can prevent people from developing Parkinson’s dementia.

This blog is not meant as health advice. You should always consult a qualified health professional or specialist before making any changes to treatment or lifestyle.

Huge thanks to Gemma Jolly. For more information about dementia, visit the Alzheimer’s Society website, or follow the Alzheimer’s Society on twitter.

Parkinson’s UK

Get the latest research news, discover more about…

Annie Amjad

Written by

Research Involvement @ParkinsonsUK

Parkinson’s UK

Get the latest research news, discover more about Parkinson’s and read about how others are getting involved. For information and support, visit

Annie Amjad

Written by

Research Involvement @ParkinsonsUK

Parkinson’s UK

Get the latest research news, discover more about Parkinson’s and read about how others are getting involved. For information and support, visit

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