Dementia is a group of symptoms. It’s caused by different diseases that damage the brain. Dementia is progressive, which mean symptoms may be relatively mild at first, but they get worse over time. Symptoms include:

  • Memory loss
  • Confusion and needing help with daily tasks
  • Problems with language and understanding 
  • Changes in behaviour

Last review - June 2024 (details below).

Dementia is an invisible disability

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    Alzheimer'sis the most common form of dementia. The next most common is vascular dementia. 
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    More than 55 million people around the world are estimated to be living with dementia
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    Early-onset Alzheimer's can occur in individuals as young as their 30s and 40s
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    Dementia is not a normal part of ageing
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    Dementia i not just about forgetting things

What causes dementia?

Dementia is not a natural part of ageing. It is caused when a disease damages nerve cells in the brain.
Nerve cells carry messages between different parts of the brain, and to other parts of the body. As more nerve cells are damaged, the brain becomes less able to work properly. 
Dementia can be caused by many different diseases. These diseases affect the brain in different ways, resulting in different types of dementia. 

Types of dementia

Around 19 out of 20 people with dementia have one of four main types. Dementia affects everyone differently, however each type has some common early symptoms.  
A person may also have mixed dementia, where they have symptoms of more than one type.

Alzheimer's disease

Alzheimer’s disease is the most common type of dementia. For most people, the first signs of Alzheimer’s are problems with their memory, thinking, language or perception.  It is a progressive neurological condition that affects mental function and memory. It is a constantly developing condition that affects how the brain cells transmit messages. ]]

Symptoms of Alzheimer's disease

Not everyone with Alzheimer’s will experience the same symptoms; however, memory loss is a key symptom. For others, memory loss is so severe and debilitating that it significantly impacts their daily life.
Symptoms are variable and broad and may include:

  • Forgetting recent events, conversations or appointments
  • Misplacing items or putting them in the wrong place - and being unable to go back over their steps to find them again
  • Forgetting the names of people, objects or places
  • Language difficulties such as struggling to find the right words or repeating themselves
  • Increasing confusion and disorientation, e.g. getting lost in familiar places

Other symptoms may include:

  • Mood changes
  • Feeling unsettled by unfamiliar situations or changes in routine
  • Becoming withdrawn
  • Difficulties in making decisions
  • Changes in how things are seen and heard
  • Obsessive or repetitive behaviours

Vascular dementia

Vascular dementia is the second most common type of dementia (after Alzheimer's disease). Everyone experiences it differently. Symptoms vary depending on the person, the cause and the areas of the brain that are affected.

Signs and symptoms of vascular dementia

The most common symptoms of vascular dementia during the early stages are:

  • Problems with planning or organising, making decisions or solving problems
  • Difficulties following a series of steps (such as when cooking a meal)
  • Slower speed of thought
  • Problems concentrating, including short periods of sudden confusion.

A person in the early stages may also have difficulties with memory and language.

Dementia with Lewy bodies (DLB)

Dementia with Lewy bodies (DLB) is a type of dementia caused by Lewy bodies, which are clumps of protein in the cells of the brain. Lewy bodies cause a range of symptoms, some 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.
The way someone is affected by DLB will depend partly 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.

Everyone experiences dementia differently. Both DLB and Alzheimer’s disease can cause:

  • Problems with staying focused
  • Difficulties with making decisions
  • Memory loss
  • Problems with the way the person sees things around them.

However, DLB also causes symptoms that are not usually seen in Alzheimer's disease. These include:

  • Hallucinations
  • Problems staying fully awake
  • Difficulties with movement  
  • Very disturbed sleep.

For more information: Dementia with Lewy bodies (DLB): what is it and what causes it? | Alzheimer's Society (

Frontotemporal Dementia (FTD)

Frontotemporal dementia (FTD) is one of the less common types of dementia. It is sometimes called Pick's disease or frontal lobe dementia. The first noticeable FTD symptoms are changes to personality and behaviour and/or difficulties with language.

The word ‘frontotemporal’ refers to the two sets of lobes (frontal and temporal) in the brain that are damaged in this type of dementia. FTD occurs when disease damages nerve cells in these lobes.

Frontotemporal dementia affects everyone differently. It’s symptoms vary a lot and depend on which areas of the frontal and temporal lobes are damaged. Symptoms include:

  • Loss of motivation
  • Difficulties planning, organising and making decisions
  • Loss of inhibitions
  • Showing repetitive or obsessive behaviours
  • Difficulties with speech and language

For more information: Frontotemporal Dementia (FTD) | Alzheimer's Society (


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The content on this page has been reviewed by Alzheimer’s Society (June 2024). For further information, please visit

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