How does Parkinson’s disease cause dementia?

Parkinson’s disease is a progressive, neurodegenerative condition currently affecting around 153,000 people in the UK. 

Parkinson’s and dementia 

Parkinson’s disease is often thought of as a condition that affects movement. However some people experience other symptoms such as nerve pain, insomnia, and problems with their memory.  

People with Parkinson’s are up to six times more likely to develop dementia compared to the general population. This is called Parkinson’s disease dementia.  

Dementia is a word used to describe a set of symptoms that can include problems with memory, thinking and communication that get worse over time. There are different types of dementia which are caused by different underlying diseases.  

Up to 70% of people with Parkinson’s disease will go on to develop dementia, as the damage caused by Parkinson’s spreads throughout the brain. 

 

 

This area of the brain produces a chemical messenger called dopamine, the release of which allows messages to be sent between our brain and our muscles. People with Parkinson’s have damage to the nerve cells in the substantia nigra and therefore cannot produce enough dopamine. This results in a lack of control over motor functions, leading to uncontrollable movements and coordination difficulties.

Alpha-synuclein is a protein found in healthy brains contributing to normal brain function. It provides structural support for our brain cells, helps them to communicate with each other, and regulates the release of dopamine.

In a brain affected by Parkinson’s disease, alpha-synuclein protein behaves abnormally and forms clumps called ‘Lewy bodies’. These clumps form inside nerve cells that control our thinking, memory and body movement. They affect the way that the nerve cells communicate and lead to dementia symptoms.

These clumps are also a key feature of another types of dementia called dementia with Lewy bodies (often called DLB) which affects about 100,000 people in the UK.

Although they can affect people in very similar ways, PDD and DLB are not thought of as the same condition. While there is no definitive test for PDD or DLB the diagnosis someone receives will depend on the order in which their symptoms first developed:

• If someone’s movement is affected a year or more before memory problems appear, a diagnosis of PDD is more likely.
• If memory and dementia symptoms develop before (or at the same time) as movement problems, a diagnosis of DLB is more likely.

It’s not always easy to be sure which condition a person may have. For this reason, even though they are different conditions, PDD and DLB are grouped under the term ‘Lewy body dementia’.

 

 

You can read more about dementia with Lewy bodies here.

Symptoms of Parkinson’s disease dementia

As with all types of dementia, each person’s experience of PDD is different. Some people will develop many symptoms whilst others may have just a few. They also range in severity from person to person, but for everyone affected, symptoms will get worse over time and people will need more support with day to day life.

Some of the most common symptoms of PDD include:

• Mood changes – some people will experience anxiety, depression and feelings of frustration and agitation.
• Hallucinations and delusions – sensory experiences, thoughts and beliefs that feel real but are only happening in the mind. Some people with Parkinson’s can experience hallucinations and delusions as a side effect of Parkinson’s medications even if they do not have dementia.
• Communication difficulties – it can become difficult to find the correct words when speaking and speech can become slower and slurred.
• Changes in memory and thinking – issues with memory are less common with PDD compared to other types of dementia such as Alzheimer’s disease. In some cases it may become difficult to carry out tasks such as planning activities and following instructions.

Shelle’s father was diagnosed with Parkinson’s in 2003.

At the time it was a relief to have a label for the symptoms that he’d been experiencing for a couple of years. Over the next 15-16 years his Parkinson’s symptoms continued to get worse. The biggest problem with dad was that his speech had got really, really poor. So it was quite difficult for him to explain things to us, to help identify what was going on with him. He ended up in hospital and the geriatric consultant identified and diagnosed Parkinson’s dementia.

I had suspected this for a while but my concerns were dismissed by his healthcare team. I kept being told it’s just Parkinson’s, this is what Parkinson’s does, this is how Parkinson’s progresses. Whereas I know of other people with Parkinson’s who have not shown dementia symptoms so there obviously is a difference. The consultant diagnosing dementia helped validate our concerns.

Are there treatments for Parkinson’s disease dementia?

Although there is currently no cure for Parkinson’s disease, treatments are available that can help to control symptoms and maintain a good quality of life. The development of Parkinson’s disease dementia adds to the complexity of the condition and over time support with daily tasks like eating and washing will be needed.

A doctor will carry out a review of any Parkinson’s medications because side effects can sometimes make dementia symptoms worse. Medications should always continue to be taken unless instructed by a medical professional.

Medications prescribed to help with the symptoms of PDD are the same as for Alzheimer’s disease. These medications cannot slow down dementia but can help with symptoms. You can read more about them and how they work here.

Speech and language therapy, occupational therapy and physiotherapy can help someone living with PDD, giving practical tips, living aids and advice to help manage symptoms.

Activities such as music and art, or doing things a person enjoys, can help to improve general wellbeing and can play a role in reducing stress and anxiety.

Shelle explains that her father was offered symptomatic treatments and highlights the importance of research:

My dad was on Parkinson’s medication for many years, but it was just about managing the symptoms and these don’t work long term. As with all the diseases that cause dementia, finding new treatments and one day a cure, as well as understanding more about prevention is absolutely key and research is vital to that.

How can research help?

While existing treatments help address and manage dementia symptoms, research is the only way to find treatments that can slow down diseases like Parkinson’s and one day a cure. This is why Alzheimer’s Research UK fund research into different diseases that cause dementia.

Work being led by Dr Angelika Zarkali at the University College London aims to understand the mechanisms underpinning visual hallucinations in Parkinson’s disease and DLB. Dr Zarkali will work with people who have Parkinson’s disease and DLB using a combination of high-resolution brain imaging, brain activity studies and data analysis to understand what causes hallucinations, comparing brain structures of people who hallucinate with those that do not.

Projects like these enable us to understand more about symptoms like hallucinations, which can be scary and disruptive for the people who experience them. Having a better understanding of the brain changes associated with symptoms in Parkinson’s disease and DLB will help develop more accurate diagnosis and estimation of disease progression. This will help guide the development of preventative and personalised medicine for people affected.

If you’re interested in taking part in dementia research, visit our pages here.

Where to go for support

If you’re worried about symptoms of Parkinson’s disease or dementia, the first thing to do is visit your GP. You can find out more information about how dementia is diagnosed here.

Other helpful organisations:

• Parkinson’s UK
• The Lewy Body Society

If you have any questions about dementia or taking part dementia research, our Dementia Research Infoline is here to help – contact them by phone on 0300 111 5111, or by emailing infoline@alzheimersresearchuk.org