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Dementia with Lewy bodies (DLB) is a type of dementia caused by Lewy bodies.


Lewy bodies are clumps of protein in the cells of the brain. These cause a range of symptoms, some of which are shared by Alzheimer’s disease and some by Parkinson’s disease. For this reason, DLB is often wrongly diagnosed. About 1 in 10 people with dementia has DLB.




Everyone experiences dementia differently. Alzheimer’s disease and DLB can both cause problems with staying focused and decision-making. Other symptoms of both conditions include memory loss and difficulties with the way the person sees things around them. However, common symptoms of DLB also include hallucinations, problems staying fully awake, difficulties with movement and very disturbed sleep. These are not usually seen in Alzheimer’s disease. The way someone is affected by DLB will depend partly on

on where the Lewy bodies are in the brain:

Lewy bodies at the base of the brain are closely linked to problems with movement. These are the main feature of Parkinson’s disease.

Lewy bodies in the outer layers of the brain are linked to problems with mental abilities, which is a feature of DLB and other types of dementia.


When DLB starts to affect someone, early symptoms may not cause too many difficulties. Gradually though, these get worse and cause problems with everyday living.

These are described in more detail in the following sections:

Mental abilities and alertness

Problems with attention and mental abilities are very common in DLB. For example:

The person may become confused and what they say may not make sense. These problems are likely to vary a lot throughout the day, from hour to hour or even over the course of a few minutes.

A person may have difficulty staying alert during the day. They may become less aware of what’s going on around them and appear to ‘switch off’.

A person may have difficulties judging distances and seeing objects clearly in three dimensions. This is because the brain makes links with other information to make sense of what we see. For example, the person may not be able to recognise the edge of a step on the stairs and know to change how they approach this.

A person may struggle with planning, organising and making decisions. Day-to-day memory is often affected in people with DLB,

but usually much less in the early stages of Alzheimer’s disease, where it is the main feature.

Some people also experience depression, anxiety or apathy.  

A common early symptom for people with DLB is visual hallucinations (seeing things that are not there). The person might describe seeing people or animals. For some people this is disturbing. Hallucinations in other senses – such as hearing, smell or touch – can also happen in DLB, although these are less common.

Visual hallucinations are one of the reasons why a person with DLB may stop driving, because this is no longer safe. 

Most people with DLB also have delusions (persistently thinking things that are not true) at some stage. 

Movement problems

Up to two-thirds of people with DLB have movement difficulties when they are diagnosed, and this increases as DLB progresses. The movement- related symptoms of DLB are similar to those of Parkinson’s disease, and include slow and stiff movement of limbs. Their facial expressions may also be limited.

The person’s posture may become increasingly stooped, and they may shuffle when they walk. They may also have difficulty with their balance and their limbs may sometimes tremble. This, combined with difficulty seeing objects properly, can make them prone to falling and getting hurt.


Sleep problems

Not sleeping well is a common symptom of DLB and can start many years before a person is diagnosed. They may fall asleep very easily during the day, but then have restless, disturbed nights. If the person has rapid eye movement (REM) sleep behaviour disorder, they may physically act out their dreams. This kind of very disturbed sleep is a feature of DLB (and Parkinson’s). 

Problems with how the body works

DLB affects the body in many ways that don’t relate to either dementia or movement. These can include the things we do automatically but don’t usually think about. For example, DLB can cause problems with:

problems passing urine – for example, needing to pee very often or in a hurry, or not being able to stop it coming

erectile dysfunction (not being able to get or keep a firm erection)

losing some sense of smell or taste (or both)

low blood pressure when standing up – this can cause dizziness and fainting.

Getting a diagnosis of DLB

Having a diagnosis of dementia can allow a person to get the support they need to live well. It is important to know the specific type of dementia a person has, especially if it’s possible they may have DLB. This is because the drugs used to treat hallucinations and delusions in other types of dementia can cause a bad reaction in a person with DLB.

DLB can sometimes be difficult to spot, and a diagnosis should be made by a specialist with experience of the condition. People with DLB are often mistakenly diagnosed as having another type of dementia, such as Alzheimer’s disease.

DLB may be mistaken for delirium – particularly if the person is first seen by medical staff during an emergency admission to hospital.


During the assessment, the doctor will talk to the person and someone who knows them well. They will ask about the person’s medical history, when their symptoms started, and how well they have been able to get on with daily life.

The doctor may do some blood tests to rule out other causes of the person’s symptoms, such as a low level of vitamins in the body or hormone problems. They should check the person’s eyesight and hearing, as problems with these can play a part in the person’s symptoms.

The doctor should also check the person’s medications. Some drugs used to treat depression, allergies or incontinence can cause confusion.

The person will be asked to complete tests or activities designed to
show if they are having problems with thinking and perception. How well a person with DLB functions can vary a lot from day to day. These tests can sometimes miss symptoms if the person does one when they are having a ‘good day’ and can concentrate much more than on a ‘bad day’.

The doctor may also look at a person’s muscle stiffness and balance to see if the disease has affected their movement. If the person is showing any movement-related symptoms, they may be referred to a neurologist (who can help with movement problems).

Brain and heart scans

If the person shows signs of DLB, they may have a brain scan to help confirm the diagnosis.

A CT or MRI scan may rule out other brain conditions such as a brain tumour, excess fluid or a bleed on the brain. If it still not possible to make a diagnosis, a more specialised scan of the brain can be carried out. This can show the difference between DLB and other types of dementia. Doctors may scan the nerve cells in a person’s heart, as these can show similar changes to those in the brain of a person with DLB.

If there is still doubt, another type of brain scan can confirm a diagnosis of DLB if it shows loss of a particular type of cells (dopamine nerve cells) at the base of the brain.

Treatments for agitation and distress

DLB can sometimes cause a person to become agitated and distressed. This may be because they are having hallucinations or delusions, they are very tired and emotional (from sleep problems), or they may be struggling to understand what is going on around them. Positive interactions with other people, or activities matched to the person’s abilities and interests, can help. For example, they may benefit from music therapy, physical exercise and hand massage.

Support for hallucinations and delusions

If someone is having visual hallucinations or delusions, it is unhelpful to try to convince them that what they are seeing is not there, or that what they believe is untrue. Instead, carers can offer them reassurance, remind them that they are there to support the person, and try gently distracting them.

Hallucinations that are not distressing to the person may not need to be stopped. Some may even be comforting, such as the sight of a friend or family member sitting by the bed.

It is important to get a person’s eyesight and hearing checked regularly. Support them to keep their glasses or hearing aids clean and working properly. Problems with these can make difficulties with seeing or sensing things worse.

Please see this factsheet for more information:

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