There are two main types of dementia that affect some people with Parkinson's - they are called Parkinson's dementia and dementia with Lewy bodies.

If you have Parkinson's and are worried about dementia, keep in mind that some of the symptoms of dementia are similar to those caused by other health conditions.

For example, side effects from medication, infections, thyroid problems, vitamin deficiencies, stress and depression can cause symptoms similar to dementia. 

Mild memory and thinking problems in Parkinson's

If you have Parkinson’s but don't have dementia, you may still experience mild memory and thinking problems as part of your condition. This is common.

You might experience a slowness in thinking (bradyphrenia) which becomes worse when your Parkinson’s medication isn’t working at its best.

Dementia is only diagnosed if your thinking and memory problems are serious enough to affect your ability to carry out everyday tasks.

If you're worried, speak to your GP, specialist or Parkinson’s nurse. You can also call our helpline on 0808 800 0303 to speak with a nurse adviser. 

Find out more: see our information on mild memory and thinking problems in Parkinson's.

‘Dementia’ describes a set of symptoms that gradually get worse over time and affect daily life. Dementia symptoms happen when nerve cells in the brain become damaged and eventually die.

Not everyone with dementia has the same symptoms, but the condition usually involves problems with memory, thinking, communication and mood. 

There are many different types of dementia. The most common type is Alzheimer’s.

Parkinson's dementia and dementia with Lewy bodies are the two types of dementia most likely to affect people with Parkinson's.

Some people have 'mixed dementia'. This is when someone has two different types of dementia, such as dementia with Lewy bodies and Alzheimer's.

Parkinson's dementia and dementia with Lewy bodies share the same types of symptoms. In both of these conditions, there are Lewy bodies within brain cells.

Because Parkinson's dementia and dementia with Lewy bodies are so similar, you may hear both of them being called 'Lewy body dementia', or read about them being grouped together under the term 'Lewy body dementia'.

There are motor and cognitive symptoms involved in both Parkinson's dementia and dementia with Lewy bodies. However, the order in which movement and dementia symptoms appear is different (see 'Diagnosis: Parkinson's dementia or dementia with Lewy bodies?' below.) 

What are Lewy bodies?

Lewy bodies are abnormal protein deposits that form within brain cells. 

We all have proteins in our brain, and this is normal, but in Lewy body dementia, proteins (such as alpha-synuclein) clump together, forming Lewy bodies. 

Diagnosis: Parkinson's dementia or dementia with Lewy bodies?

During assessment, a specialist (such as a neurologist) may look at when the dementia symptoms first appeared before reaching a diagnosis of Parkinson's dementia or dementia with Lewy bodies. 

If there have been motor symptoms (such as tremor or rigidity) for at least one year before dementia symptoms occur, specialists will often give a diagnosis of Parkinson's dementia.

If dementia symptoms occur before or at the same time as motor symptoms, specialists will usually give a diagnosis of dementia with Lewy bodies.

However, it should be noted that in some cases of dementia with Lewy bodies, no motor symptoms develop at all.

There’s no single test - diagnosis is made through several different assessments, usually starting with an appointment with your GP or Parkinson's nurse.

Some people find it helps to go to the appointment with someone who knows them well, who can give the GP or Parkinson's nurse information about changes they've noticed.

Your GP can discuss your symptoms with you and carry out a physical examination, including blood and urine tests, to rule out other potential causes of the symptoms (such as infections, thyroid problems and vitamin deficiencies). 

Your GP may also review your medication, in case your symptoms are side effects.

If your GP thinks you have dementia, they can refer you to a specialist, such as a neurologist, psychiatrist or geriatrician.

You might be referred to a memory clinic or memory service. In some areas of the country, you can refer yourself to these services.

The specialist will look at your medical history and carry out some pen-and-paper tests to assess your memory and thinking. 

Your specialist might also arrange for brain scans, which can help to identify the cause of your symptoms.

Once a correct diagnosis is made, the specialist should discuss your treatment plan with you. You'll then normally be discharged back to the care of your GP.

But if you feel you need to see the specialist again, you can ask to be referred back.

The experience of Parkinson's dementia varies from person to person - not everyone is the same.

Symptoms often fluctuate from hour to hour and day to day, and at times, especially in the early stages, they're so mild that they’re hardly noticeable. 

If you have Parkinson's dementia, you might experience the following:

Memory and thinking problems

You may experience forgetfulness, slowed thinking and difficulty concentrating. You might find it harder to follow conversations, and remember some words and names. This can make communication difficult.

You may also find it increasingly difficult to make decisions, plan activities and solve problems. This can make everyday activities harder.

Sleep disturbances

You might experience changes in your energy levels and sleeping patterns, so you could find yourself sleeping more during the day.

Changes in appetite

You may find that your appetite changes. Feeling tired and a lack of activity during the day can mean you eat less. Changes in appetite can also be a sign of depression or anxiety, which are common in people with dementia.

Mental health changes

You might find that at times you feel less engaged with what’s going on around you. You may also lack interest in activities you used to enjoy (apathy).     

You might experience anxiety, depression or agitation. You may have sudden outbursts of anger or distress, although this is not common. 

You may have hallucinations where you see, hear or feel things that aren’t really there.

You may talk about things you believe that aren’t based in reality (delusions).  You might feel paranoid, although these thoughts may be irrational.    

Reviewing your medication

If you’ve been diagnosed with Parkinson's dementia, your specialist or Parkinson's nurse should look at what medication you’re taking. 

This is because some of the side effects of Parkinson’s medication can make the symptoms of dementia worse. But reducing the dose or stopping these drugs may mean that the motor symptoms of your Parkinson’s are not as well controlled as before.

For this reason, treating the dementia symptoms needs to be balanced with managing physical symptoms.

Dementia medication

You may be prescribed dementia drugs. This depends on the stage of dementia and your general health. 

If you're prescribed these drugs, you may be asked to do more pen-and-paper tests of memory and thinking to see how your symptoms change.

The dementia medications used for Parkinson’s dementia are the same as those used to treat Alzheimer’s. They're called cholinesterase inhibitors. Some people find they help with their symptoms.

Very low doses of antipsychotics or neuroleptics might be prescribed to treat severe mood and behavioural symptoms, such as aggression. But doctors prescribe these drugs with extreme caution because they can cause serious side effects.

Speak to your GP, specialist or Parkinson’s nurse for advice about medication. 

Non-drug treatments and services

Physiotherapy, speech therapy and occupational therapy may help you manage your symptoms. 

There are various care and support services available that can also help you manage with your symptoms. Call our helpline on 0800 800 0303 to find out more.

The experience of dementia varies from person to person - not everyone is the same.

Symptoms can fluctuate from hour to hour and day to day, and at times, especially in the early stages, they're so mild that they’re hardly noticeable. 

If you have dementia with Lewy bodies, you might experience the following:

Fluctuating attention and confusion

You may swing from feeling alert to confused. You might stare into space, or have problems saying words in the right order. This can happen randomly, and last for varying amounts of time.

Sleep disturbances

You may feel sleepy during the day and fall asleep suddenly. You might talk in your sleep or act out your dreams. 

Mood changes

You may find you have times where you feel down or depressed, or lose motivation or interest 
in activities you used to enjoy (apathy).

Hallucinations and delusions             

You might experience hallucinations, where you see, hear or feel things that aren't really there. It's common to see small children or animals.

You may also talk about things you believe that aren’t based in reality (delusions).  You might feel paranoid, although these thoughts may be irrational.

Changes in visual perception

You might have difficulties recognising objects and the spaces between them. You may find it hard to judge distances and movements.

You might also misunderstand things you see, such as mistaking a pattern on a rug for an animal. 

Memory, decision-making and planning problems

You may have problems retrieving information from memory. You might take a long time finding an answer to a question, or recalling a word or name.

You may also find it difficult to make decisions, plan activities or solve problems. 

Parkinson’s-like symptoms

You might develop symptoms such as slowness of movement, stiffness and tremor.

Other common symptoms include dizzy spells and fainting. Sometimes blood pressure is affected.

You might also experience constipation, incontinence and swallowing problems.

There’s no cure for dementia with Lewy bodies, but there are treatments that can help with symptoms:

Cholinesterase inhibitors

Research has found that drugs used to treat Alzheimer’s, called cholinesterase inhibitors, can help with the symptoms of dementia with Lewy bodies.

You might find these drugs help thinking, memory and attention problems. Some people find they help with hallucinations and delusions too.

Parkinson's medication

You may benefit from taking Parkinson’s drugs, especially if you have symptoms like stiffness or rigidity.

But some side effects of Parkinson’s drugs make dementia symptoms worse, especially confusion. Specialists should try to find a balance.


Very low doses of these drugs might be prescribed if hallucinations and delusions are becoming a huge problem.

But these drugs are prescribed with caution because they can cause serious side effects, including severe rigidity and immobility, which can be dangerous.

About half of people with dementia with Lewy bodies react badly to antipsychotics. 

Other treatment options

Other medications might be prescribed to treat specific symptoms, such as sleep disturbance. It’s always a good idea to speak to your GP or specialist about other options. 

Non-drug treatments can also help manage symptoms, such as physiotherapy, speech therapy, occupational therapy, and care and support services.

Admiral nurses (dementia specialist nurses) can also provide support. They can be contacted on their helpline 0800 888 6678 and their website is

We still don’t fully understand why some people with Parkinson’s get dementia and others don’t, but there are factors that increase the risk. 

The likelihood of developing most types of dementia increases with age, and this is true for people with and without Parkinson's.

You’re more likely to develop dementia if you’re 65 or over, and your risk increases as you get older. A family history of dementia also increases your risk. 

You're at a greater risk of Parkinson's dementia if you were diagnosed with Parkinson’s in later life, or have been living with the condition for many years. 

If you have hallucinations or delusions early on in your Parkinson's, this may also mean you have an increased risk of developing dementia.

As with Parkinson's dementia, we still do not fully understand what causes dementia with Lewy bodies. Again, age is a risk factor - the condition is rare in people under 50.

Researchers are working hard to uncover what causes Lewy bodies to develop within brain cells, and what their role is in Parkinson's and Lewy body dementia.

Find out more: see Lewy bodies: The Story So Far. 

If you've been diagnosed with dementia, you might want to make some important decisions about your finances, your Will, and what sort of health and social care you’d like in the future.

You may also want to choose someone you trust to handle your affairs by setting up power(s) of attorney.

Find out more: see our information 'Putting your affairs in order'. 

Accessing support services

People with dementia may eventually need more support and help with things like shopping, housework, cooking or personal care.

Despite this, it’s important they continue to use their existing strengths and skills for as long as possible. 

If you regularly provide support or care for someone with dementia, you have a right to a ‘carer’s assessment’. This is done through your local authority.

After your assessment, if your local authority agrees you have needs, they will arrange services to help you. To find out more, contact our helpline on 0808 800 0303.

It's also important that you look after yourself if you're a carer. See our information on this for more.

Parkinson’s UK also has local advisers and local groups that can offer advice and support to anyone affected by Parkinson’s and dementia.

Go to or contact our helpline on 0800 800 0303 for more details.

The Alzheimer’s Society and Dementia UK's Admiral Nurses can also provide support. See the 'More information and support' section for contact details.

Practical advice

If you're supporting or caring for someone with dementia, there are some practical things you can do to help reduce their agitation or confusion:

  • Keep to a daily routine as much as you can to help them
  • Remember when certain things, like meal times, will happen.
  • Try to use familiar objects and phrases.
  • Avoid unfamiliar environments – these can 
  • be quite stressful and confusing.
  • Encourage someone with dementia to keep up with hobbies and keep engaging and interacting with people. 

Helping with communication

Difficulties with communication can be upsetting and frustrating for the person with dementia. But there are some basic things you can do to make it easier.

The Alzheimer’s Society has tips on communicating with people with dementia. You can find this and more helpful advice on the Alzheimer’s Society website.

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Dementia with Lewy bodies (PDF, 219 KB)

Parkinson's dementia (PDF, 219 KB)

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Last updated October 2019. We review all our information within 3 years. If you'd like to find out more about how we put our information together, including references and the sources of evidence we use, please contact us at [email protected]