What is dementia?

Print copy below
The content below is reflective of our leaflet.

Dementia is an umbrella term for a range of progressive conditions that affect the brain.

The brain is made up of nerve cells (neurones) that communicate with each other by sending messages. Dementia damages the nerve cells in the brain so messages can’t be sent effectively, which prevents the brain from functioning normally.

There are over 200 subtypes and causes of dementia, but the four most common are: Alzheimer’s disease, vascular dementia, frontotemporal dementia and dementia with Lewy bodies. It is possible to have not just one but two types of dementia. The most common is a combination of Alzheimer’s disease and vascular dementia, known as mixed dementia.

Dementia can affect a person at any age but it is more commonly diagnosed in people over the age of 65 years. A person developing dementia before age 65 is said to have young onset dementia.

There are over 850,000 people living with dementia in the UK and this is set to rise to over one million by 2025.

Symptoms of dementia

Regardless of which type of dementia is diagnosed and what part of the brain is affected, each person will experience dementia in their own unique way.

The symptoms of dementia can include:

Memory problems

People with dementia might have problems retaining new information. They might get lost in previously familiar places and may struggle with names. Relatives might notice the person seems increasingly forgetful, misplacing things regularly.

Cognitive ability, ie, processing information

People with dementia may have a problem with their concentration level which can also impact on their short term memory. They may also have difficulty with time and place, for example, getting up in the middle of the night to go to work, even though they’re retired. There may be a difficulty when shopping with choosing the items and then selecting the right money to pay for them. For some people, the ability to reason and make decisions may also be affected. Some people with dementia may get a sense of restlessness and prefer to keep moving than sit still; others may be reluctant or lack the motivation to take part in activities they used to enjoy.


People with dementia may repeat themselves often or have difficulty finding the right words. Reading and writing might become challenging. They can lose interest in seeing others socially. Following and engaging in conversation can be difficult and tiring, and so a formerly outgoing person might become quieter and more introverted. Their self-confidence might also be affected.

Mood and behaviour

People with dementia might experience changes in personality, behaviour, mood, and have some elements of anxiety and depression due to the changes they are experiencing.

Types of dementia

These are the most common types of dementia:

Alzheimer’s disease

Alzheimer’s disease is the most common type of dementia in the UK. It is a physical condition caused by changes in the structure of the brain. This is due to a build-up of proteins, resulting in ‘plaques’ and ‘tangles’ which damage the brain cells’ ability to transmit messages and which eventually lead to deterioration in the brain cells. Signs of Alzheimer’s tend to develop gradually over time and can affect concentration, memory, communication and word finding and skills such as reading, writing, numeracy, planning and sense of direction.

Medication is available which may help to increase concentration and slow progression but it does not prevent or cure Alzheimer’s disease.

Vascular dementia

Vascular dementia is the second most common type of dementia. It is caused by problems in the blood supply to the brain cells, commonly due to strokes or a series of small strokes, known as Transient Ischaemic Attacks (TIAs), which cause areas of localised cell damage in the brain.

Changes in a person’s condition as a result of TIAs or a larger stroke are often sudden, before their condition plateaus. But the damage caused often means the person does not function in quite the same way as they did before. This is often referred to as a step wise progression.

Frontotemporal dementia

Frontotemporal dementia is a progressive condition which means that the symptoms worsen over time. This tends to affect people aged 45 to 65 years and males and females in equal measure. The areas of the brain most affected are the:

  • frontal lobes which are important for personality, social functioning, decision making, problem solving, insight, empathy, motivation and planning. Dementia that predominantly affects the frontal lobes can be called frontal dementia, behavioural variant frontotemporal dementia or Pick’s disease
  • temporal lobes which are important for speech, word finding, comprehension and language ability. The hippocampus (important for memory formation) is also located in the temporal lobe. Dementia that predominantly affects the temporal lobes can be called semantic dementia or primary progressive aphasia

Often frontotemporal dementias are not recognised and diagnosed until the person has had signs and symptoms for four to five years as the early signs are often missed or misattributed by the person, their family and health professionals.

Dementia with Lewy bodies

Dementia with Lewy bodies is a progressive condition which means that the symptoms worsen over time. It affects movement and motor control. A person with dementia with Lewy bodies might:

  • be prone to falls
  • have tremors (similar to Parkinson’s disease)
  • have trouble swallowing
  • shuffle when they walk
  • experience disrupted sleep patterns due to intense dreams/ nightmares
  • have visual and auditory hallucinations due to the nerve
    cell damage

Memory is often less affected than with other types of dementia, but a person might experience sudden bouts of confusion which can change on an hourly basis.

Getting a diagnosis of dementia

If someone is showing symptoms associated with dementia it is important to visit a GP as soon as possible. Some conditions might look like dementia as they affect a person’s memory, concentration or behaviour but are treatable if addressed quickly. These include: infections, thyroid problems, delirium, confusion, vascular problems related to circulatory issues, vitamin B12 deficiency, sleep apnoea, stress, anxiety and depression.

To establish if dementia is present, a GP will take a medical and family history of the person and will screen them for mental health and cognitive issues by: asking questions, testing concentration, assessing short term memory, identifying mood and behaviour changes.

The GP may then request blood tests, an MRI or CT scan to examine the structure of the brain. If other physical health conditions are suspected they may also request blood tests and X-rays to check for any conditions that may mimic dementia.

Once the GP has ruled out potentially treatable causes of the changes observed, they may also refer the person to a memory service/clinic, or to a specialist for further investigation and assessment.

If a diagnosis of dementia is given, the GP should then ensure that the person with the diagnosis and their family are made aware of any specialist advice and support services in their area, as well as referring them for further assessments and interventions that may help. This support can come from a range of organisations, including health and social care professionals and the voluntary sector.

If you have any questions about getting a diagnosis of dementia, you can speak to an Admiral Nurse on our free Dementia Helpline. Call 0800 888 6678 (Monday-Friday 9am-9pm, Saturday and Sunday 9am-5pm, every day except Christmas Day) or email helpline@dementiauk.org.

Who gets dementia and can it be prevented?

About 10% of young onset dementias can be due to genetic mutations such as some forms of frontotemporal dementia, Huntington’s disease and rare varieties of Alzheimer’s disease.

However, in older age most cases of dementia are not thought to be inherited and recent research suggests that you can delay or prevent dementia by making some changes to your lifestyle. Everything that keeps your heart healthy can also keep your brain healthy. So, eat a balanced healthy diet, keep weight within recommended levels, keep hydrated, don’t smoke, avoid drinking too much alcohol, have regular check-ups with your GP and keep your cholesterol and blood pressure under control. If you have been diagnosed with type two diabetes you will need to follow any advice you have been given to manage this effectively and ensure that your blood sugar levels remain under control.

Stay physically active and mentally stimulated with different activities so that you use different parts of the brain. For example, walking, gardening, singing, art, music, reading, and other hobbies and interests are thought to help prevent or delay the onset of dementia.

There is no compelling research that says doing puzzles will improve brain health, however, learning another language is helpful because different parts of the brain are stimulated and this can enhance cognitive function.

Sources of support

Dementia UK leaflet on Getting a diagnosis of dementia


Dementia UK leaflet on the Emotional impact of a diagnosis


Dementia UK leaflet on Understanding Lewy body dementia


Dementia UK resources on Sources of support and advice



Order hard copies of our information leaflets