A group of symptoms
The NHS describes dementia as a syndrome. A syndrome is a group of related symptoms. With dementia, these symptoms come from an ongoing decline in how the brain works.
Dementia can affect:
- memory, especially remembering recent events
- thinking speed and concentration
- language, such as finding the right word or following a conversation
- understanding and judgement, such as planning or making decisions
- mood and behaviour, such as becoming withdrawn, anxious or easily upset
- movement and perception, such as judging distances or balance
Memory loss is the best-known symptom, but it is not always the first one. In some types of dementia, changes in behaviour, language or vision come first.
Dementia is progressive. This means the symptoms slowly get worse over time. How fast this happens varies a great deal from person to person.
What causes dementia
Dementia is caused by diseases that damage brain cells and the connections between them. Different diseases cause different types of dementia.
- Alzheimer’s disease is the most common cause. Proteins called amyloid and tau build up in and around brain cells. Amyloid forms clumps called plaques. Tau forms tangles inside cells. The NHS says this process starts years before symptoms appear.
- Vascular dementia is caused by reduced blood flow to the brain, for example after strokes or damage to small blood vessels.
- Dementia with Lewy bodies is caused by tiny clumps of protein, called Lewy bodies, inside brain cells.
- Frontotemporal dementia affects the front and sides of the brain first.
Some people have more than one type at the same time. This is called mixed dementia.
How the brain is affected
Different parts of the brain do different jobs. The symptoms a person has depend on which areas are damaged first.
| Brain area | What it helps with | Possible symptoms when damaged |
|---|---|---|
| Hippocampus (inside the temporal lobes) | Making new memories | Forgetting recent conversations or events |
| Frontal lobes | Planning, behaviour, self-control | Poor judgement, loss of motivation, personality changes |
| Temporal lobes | Language and recognising things | Word-finding problems, losing the meaning of words |
| Parietal and occipital lobes | Vision, sense of space | Misjudging distances, getting lost, trouble reading |
As brain cells stop working, levels of chemical messengers can fall. In Alzheimer’s disease, one of these is acetylcholine, which is involved in memory. Some dementia medicines work by helping to keep more of it available. See treatment.
Stages of dementia
Dementia is often described in three broad stages. Alzheimer’s Society stresses that these are only a rough guide. Symptoms may appear in a different order, overlap, or not appear at all. It is more helpful to focus on what the person needs now.
Early stage
Symptoms start to affect daily life. The person can still do many things by themselves, or with a little support. They may repeat questions, lose track of dates, or find it harder to manage money or plan a meal.
Middle stage
Symptoms become more severe and wide-ranging. The person starts to need help with basic tasks, such as washing, dressing and going to the toilet. Changes in behaviour and mood are more common.
Later stage
The person needs more constant care. Eating, drinking, walking and communicating become harder. Many people are cared for by professional carers at this stage, at home or in a care home.
How fast does it progress?
There is no set timeline. Alzheimer’s Society says speed can depend on:
- the type of dementia
- age, with dementia often progressing faster in younger people
- other health conditions, such as heart disease or diabetes
- sudden events, such as an infection or a stroke, which can cause a sudden worsening
Some people need support soon after diagnosis. Others stay independent for years.
How common is dementia?
- The NHS says more than 944,000 people in the UK have dementia, and about 1 in 11 people aged over 65.
- The NHS expects the number to rise to more than 1 million by 2030, mainly because people are living longer.
- Alzheimer’s Society says around a million people in the UK have dementia, and projects this will rise to 1.4 million by 2040.
- Alzheimer’s Society estimates that one in three people with dementia in England and Northern Ireland, and around one in two in Wales, do not have a diagnosis.
- Alzheimer’s Society says more than 70,800 people in the UK have young-onset dementia, where symptoms start before age 65.
Different organisations use slightly different methods, so figures vary.
Not a normal part of ageing
Dementia becomes more common with age. But the NHS states clearly that dementia is not a natural part of ageing. Many people live into their 90s and beyond without it.
Some changes are common as we get older. We may take longer to recall a name, or need more time to learn something new. That is different from dementia, where problems keep getting worse and start to affect everyday life. The early signs page has a table comparing the two.
Why a diagnosis matters
The NHS says an early diagnosis can help people get the right treatment and support, and plan for the future. In some cases, treatment may help slow the progress of symptoms for a while.
A diagnosis can also rule out other conditions that cause similar symptoms and can be treated. If you are worried, the first step is your GP. Read about getting a diagnosis.
Where to find support
You do not need to face this alone. Specialist dementia nurses and advisers are available by phone across the UK. See support and helplines for numbers and opening hours.