This page is part of PrimeCarers' guide to dementia care. It sits alongside how long does someone live with dementia?, which looks at what a diagnosis means for the years ahead, and what are the 7 stages of dementia?, which sets out how someone's needs tend to build once a diagnosis is confirmed.
The short answer
- Four types cause most diagnosesAbout 19 in 20 people with dementia have Alzheimer's disease, vascular dementia, dementia with Lewy bodies, or frontotemporal dementia. Each one tends to start differently.
- Alzheimer's disease is by far the most commonIt accounts for 60 to 70 in every 100 diagnoses, and it is usually the type people picture when they hear the word dementia.
- Dementia with Lewy bodies needs doctors to knowCertain antipsychotic medicines can cause a severe reaction in someone with Lewy body dementia, so telling any doctor, paramedic or hospital the diagnosis matters.
- The type shapes what happens nextIt changes which medicines can help, how quickly things tend to change, and what to plan for, so it is worth asking the specialist to confirm it in writing.
Figures on this page come from the Alzheimer's Society, the NHS, Dementia UK and a 2024 update to the Lancet Commission on dementia prevention, referenced as they come up.
The four main types
The four types behind most dementia diagnoses
Dementia is a name for a set of symptoms, memory loss, confused thinking, changes in mood or behaviour, caused by several different diseases that damage the brain in different ways. About 19 in 20 people with dementia have one of four main types, and knowing which one your relative has changes what tends to come next.
Alzheimer's disease
60 to 70 in every 100 people with dementia
- Cause
- A gradual build-up of two proteins, amyloid and tau, damages and eventually kills brain cells.
- Often the first sign
- Short-term memory lapses: repeating a question, misplacing things, or struggling to find a word.
- Pattern
- Develops slowly, over years rather than months.
Vascular dementia
The second most common type, affecting around 150,000 people in the UK
- Cause
- Reduced blood flow to the brain, most often after a stroke, a series of smaller strokes, or narrowed blood vessels deep in the brain.
- Often the first sign
- Trouble planning, organising or following steps, such as the stages of cooking a meal.
- Pattern
- Can appear suddenly after a stroke, or arrive in a series of steps rather than a steady decline.
Dementia with Lewy bodies
Less common than Alzheimer’s disease or vascular dementia
- Cause
- Clumps of a protein called alpha-synuclein, known as Lewy bodies, build up and disrupt the brain’s messages.
- Often the first sign
- Visual hallucinations, alertness that rises and falls through the day, and disturbed sleep.
- Pattern
- Shares features with both Alzheimer’s disease and Parkinson’s disease.
Frontotemporal dementia
Less common overall, but the type most often diagnosed before 65
- Cause
- Damage to nerve cells in the brain’s frontal and temporal lobes, which govern personality, behaviour and language.
- Often the first sign
- A change in personality or behaviour, or a language problem, usually without early memory loss.
- Pattern
- Most people are diagnosed between 45 and 65.
Alzheimer's disease is the most common type by a wide margin, and vascular dementia the second. Dementia with Lewy bodies and frontotemporal dementia are both less common on their own, but frontotemporal dementia is the type most likely to affect someone still of working age. It is also possible to have more than one type at once, called mixed dementia, most often Alzheimer's disease together with vascular dementia. About 1 in 20 people with dementia have a rarer type instead, some linked to Parkinson's disease and some to a hereditary condition, and a memory clinic can say more if one of these is suspected.
None of these diseases has a single cause, but the same handful of things raise the risk of most of them. Age is the biggest factor, and dementia becomes noticeably more common from the mid-60s onward, although it is not a normal part of ageing. A family history of dementia raises the risk too, and so does depression left untreated for a long time, though low mood can also be an early symptom of dementia rather than a cause of it, which can make the two hard to tell apart. Conditions linked to poor blood flow and heart health, including cardiovascular disease, high blood pressure, high cholesterol and diabetes, raise the risk of most types and vascular dementia especially. A 2024 update to the Lancet Commission on dementia prevention estimated that treating 14 of these modifiable factors well, including hearing loss, physical inactivity and social isolation as well as the ones above, could prevent or delay up to 45% of dementia cases worldwide.
Alzheimer's disease
Alzheimer's disease: the most common type, and how it tends to start
Alzheimer's is the type most people picture when they hear the word dementia, and it is the type your relative is most likely to have. It develops slowly, so the earliest changes are often put down to stress, tiredness or simply getting older.
How Alzheimer's disease tends to show itself
0 of 8 ticked
Early on
As it moves on
None of this points to a single day on which Alzheimer's begins. What are signs that dementia is getting worse? goes through what else to check first, because a urine infection, dehydration or a new medicine can look like a sudden decline and is often treatable.
Vascular dementia
Vascular dementia: caused by a reduced blood supply to the brain
Where Alzheimer's disease comes from a build-up of protein, vascular dementia comes from the brain's blood supply. Anything that blocks or narrows the blood vessels feeding the brain starves it of oxygen and nutrients, and where that damage happens decides how the symptoms show themselves.
The three patterns vascular dementia tends to follow
- Stroke-related vascular dementia
- Follows a stroke that damaged an area of the brain involved in thinking. Symptoms can appear suddenly, within weeks of the stroke.
- Subcortical vascular dementia
- Caused by disease in the brain's smallest blood vessels, deep inside the brain. It tends to develop more gradually, with slowed thinking and difficulty planning among the earliest signs.
- Mixed dementia
- Vascular dementia alongside Alzheimer's disease, the most common combination when someone has more than one type at once.
Because it shares its cause with heart disease and stroke, vascular dementia is the type most directly affected by the risk factors above: keeping blood pressure, cholesterol and blood sugar well controlled, and stopping smoking, all lower the risk of a further decline as well as a first one. A carer who visits regularly can help spot the signs that another stroke may have happened, sudden confusion, weakness down one side of the body, or slurred speech, and get help quickly.
Dementia with Lewy bodies
Dementia with Lewy bodies: fluctuating alertness, vivid hallucinations, and a medicine to be careful with
Dementia with Lewy bodies sits between Alzheimer's disease and Parkinson's disease, and it can look like either one at first. What tends to set it apart is how much someone's alertness changes from one hour to the next, and how early hallucinations tend to appear.
Alertness that rises and falls through the day
Vivid, detailed visual hallucinations
Disturbed sleep, including acting out dreams
Movement changes similar to Parkinson's disease
What is sundowning? covers a related pattern, confusion and distress that gets worse in the evening, which can affect people with any type of dementia but is often more pronounced here.
Frontotemporal dementia
Frontotemporal dementia: changes in personality or language, often before memory is affected
Frontotemporal dementia is the type most likely to catch a family off guard, because it rarely starts with memory loss. It damages the parts of the brain that govern personality, behaviour and language first, so the first sign is often a change in who someone seems to be rather than what they can remember.
| What tends to change first | What can follow | |
|---|---|---|
| Behavioural variant | Personality and behaviour: reduced empathy, apathy, socially inappropriate actions, or a new repetitive habit, often with little awareness that anything has changed. | Language and memory difficulties, as the illness moves on. |
| Language variant (primary progressive aphasia) | Language: losing the meaning of familiar words, or speech becoming slow, halting and hard to produce. | Personality and behaviour changes, usually later in the illness. |
Behavioural variant
- What tends to change first
- Personality and behaviour: reduced empathy, apathy, socially inappropriate actions, or a new repetitive habit, often with little awareness that anything has changed.
- What can follow
- Language and memory difficulties, as the illness moves on.
Language variant (primary progressive aphasia)
- What tends to change first
- Language: losing the meaning of familiar words, or speech becoming slow, halting and hard to produce.
- What can follow
- Personality and behaviour changes, usually later in the illness.
Frontotemporal dementia is mostly diagnosed in people under 65, and it is the type most often responsible for a dementia diagnosis at that younger age.
Because it usually affects people in their 50s and 60s, frontotemporal dementia often disrupts a career, a marriage or a family in ways the other types are less likely to. The earliest changes, apathy, a lapse in judgement, an odd new habit, are easily mistaken for a mental health problem or a difficult patch in life rather than dementia, which can delay a diagnosis by a year or more. If personality or language has changed markedly in someone under 65, it is worth asking the GP about frontotemporal dementia by name.
Getting a diagnosis
How a diagnosis is reached, and why the type matters
A diagnosis usually takes a few months from the first GP appointment to a specialist confirming the type, and it is worth seeing the process through rather than stopping once dementia itself has been confirmed.
- 1
See the GP first
The first appointmentThe GP asks about symptoms and how they affect daily life, such as cooking, paying bills or personal care, and carries out a physical check. - 2
Rule out other causes
Blood and urine testsMemory and thinking problems can also come from an infection, an underactive thyroid, a vitamin deficiency, depression, or a medicine's side effects, and these are checked and treated first. - 3
A memory or cognitive test
In the GP surgeryA short set of questions and simple tasks gives a first read on memory, thinking and orientation, and decides whether a referral is needed. - 4
Referral to a memory clinic
A specialist assessmentA psychiatrist, geriatrician or neurologist carries out a fuller assessment and may arrange a CT or MRI brain scan, which helps show which type of dementia is most likely. - 5
The diagnosis, and what happens next
A written care planNHS guidance says the specialist should discuss which type of dementia it is, or say when it will become clearer. From here, claiming Attendance Allowance and asking for a care needs assessment are usually the next two things worth doing.
This NHS diagnosis pathway is the same whichever type is eventually found. What is found at the end of it matters for more than curiosity. It changes which medicines can help and which to avoid, as dementia with Lewy bodies shows most starkly, how quickly things are likely to change, and what to plan for at home. At what point should someone with dementia go into care? and what does dementia care cost? are the next two questions most families ask once a diagnosis is confirmed, and Attendance Allowance is worth claiming as soon as your relative needs help or supervision, whatever their savings.
Questions
Questions families ask about the types of dementia
Alzheimer's disease, vascular dementia, dementia with Lewy bodies and frontotemporal dementia. Together they account for about 19 in every 20 dementia diagnoses. The four main types sets out what causes each one and what tends to come first.
Alzheimer's disease, which accounts for 60 to 70 in every 100 diagnoses. It develops slowly, usually starting with short-term memory lapses, and is the type most people picture when they hear the word dementia.
Yes. This is called mixed dementia, and the most common combination is Alzheimer's disease together with vascular dementia. It can make the symptoms harder to separate and the diagnosis take a little longer.
No, though the two are closely related. Vascular dementia is caused by a reduced blood supply to the brain, which can follow a stroke, a series of smaller strokes, or disease in the brain's smallest blood vessels, but not everyone with vascular dementia has had a stroke. Signs that dementia is getting worse explains what to check if symptoms change suddenly.
Mainly because of medicine safety. Up to half of people with dementia with Lewy bodies have a severe reaction to antipsychotic drugs, which are sometimes given for hallucinations or distress in other types of dementia. Dementia with Lewy bodies explains what to tell doctors and why.
It is mostly diagnosed in people under 65, and it is the type most often responsible for a dementia diagnosis at that younger age, but it can occur later in life too. It tends to start with a change in personality, behaviour or language rather than memory loss.
Through a GP appointment, blood tests to rule out other causes, a memory or cognitive test, and usually a referral to a memory clinic, where a specialist may arrange a CT or MRI brain scan. How a diagnosis is reached sets out each step.