Dementia Support Line
What causes young-onset dementia?
The causes of young-onset dementia, also known as early-onset dementia, are different from those in older people. The young-onset of some of the most common types of dementia are described on this page.
- Young-onset dementia
- You are here: What causes young-onset dementia?
- Diagnosing young-onset dementia
- Living with dementia as a younger person
- Treatment for people with young-onset dementia
Download or order a printed copy of our booklet Understanding young-onset dementia.
What are the causes of young-onset dementia?
The causes of young-onset dementia are mostly the same diseases that usually cause dementia in older people, such as Alzheimer’s or vascular (blood vessel) disease.
It’s often difficult to say why one person gets dementia earlier than another. We do know that genetics can play an important role for younger people.
Dementia can also happen in younger people because of non-genetic causes, such as severe damage to the brain caused by an early stroke, traumatic brain injury, or heavy alcohol use.
However, often there is no obvious cause or risk factor to explain why someone has developed young-onset dementia.
You’ll find more information below on:
- Common types of dementia, and their causes and symptoms
- Is young-onset dementia hereditary?
What are the symptoms of young-onset dementia?
The symptoms of young-onset dementia depend mostly on the type of dementia – for example, whether it’s Alzheimer’s disease, vascular dementia, Lewy body dementia, frontotemporal dementia, or a rarer type of dementia.
Each type has its own set of common symptoms and can be quite different from one another, particularly during the early stages.
Types of dementia
Learning disabilities and dementia
People with Down’s syndrome and other learning disabilities are more likely to develop dementia when they are younger. Dementia in people with Down’s syndrome is usually caused by Alzheimer’s disease, but not always.
The reasons why people with Down’s syndrome are at increased risk of Alzheimer’s disease are not well understood. It is thought to be due to chromosome 21, which most people with Down’s syndrome have an extra copy of. This leads to an overdevelopment of a protein (amyloid precursor protein) which forms plaques on the brain. These plaques are a feature of Alzheimer’s disease. By the age of about 40, almost all people with Down’s syndrome have changes in the frontal lobe of their brain. However, not everyone will develop the symptoms of dementia.
Can young-onset dementia be inherited?
It is uncommon for young-onset dementia to be caused by a single disease gene. However, it is relatively common for younger people with dementia to have a gene that carries a higher risk of dementia.
Around one in ten people with young-onset dementia have a single gene that causes dementia. This is known as ‘familial dementia’ because it runs in families.
If a person has several close relatives who have dementia, there is a greater chance that their dementia may have been caused by a gene. This is especially the case if these relatives had dementia when they were young.
If you have been diagnosed with familial dementia, you may be worried about other members of your family getting it too – particularly children. This can be a very difficult subject to think about, so it’s important to ask for help from specialists in genetic diseases.
Genetic testing
If anyone in your family is worried about inheriting dementia, they should talk to their GP first. If the GP thinks there is reason to be concerned, they can refer the family member to a local genetics service. Here, they can receive genetic counselling and be tested for certain genes.
Reasons for concern might include:
- Having a close relative, such as a mother, father, brother or sister, who has been diagnosed with frontotemporal dementia.
- Having more than one relative diagnosed with any dementia at 65 or younger, particularly if they developed symptoms at an early age during their 40s or 50s.
A person should consider carefully whether they want genetic testing. There are both advantages and disadvantages to knowing whether they have a genetic disease.
Familial Alzheimer’s disease is a very rare form of Alzheimer’s disease. It is caused by genetic mutations (changes in genes) that run in families. Three genes have been found to have these rare mutations – PSEN1 (presenilin 1), PSEN2 (presenilin 2) and APP (amyloid precursor protein).
There is a 50% risk of a parent passing on the familial Alzheimer’s disease mutation to their children. People with the condition usually have a strong family history of the disease and will know a range of family members who were affected at a similar age, along with one of their parents.
Symptoms of familial Alzheimer’s disease usually start in someone’s 30s, 40s or 50s. The earlier the symptoms start, the more likely it is that the disease is genetic. Familial Alzheimer’s disease is very rare and probably accounts for fewer than 1 in 100 people with Alzheimer’s disease.
In some families, there is a single faulty gene that will definitely cause FTD if it is passed down from a parent to a child. This is known as ‘familial FTD’.
About 10 to 15 in every 100 people with FTD have this type. Any child of a person with familial FTD has a 1 in 2 chance of getting the same gene. It most often causes behavioural variant FTD.
The three main gene mutations causing FTD are in the progranulin (GRN), microtubule-associated protein tau (MAPT) and chromosome 9 open reading frame 72 (C9ORF72) genes. Different gene mutations are associated with different types of FTD symptoms.
The children or siblings of someone with one of these gene mutations have a 1 in 2 chance of carrying the same mutation. Affected families can ask their GP to be referred to their local NHS Genetics Service for further support, including genetic counselling..
The progression of dementia
Dementia is a progressive and terminal condition, which means that symptoms get worse over time and eventually either cause or contribute to a person dying.
It’s very hard to predict how quickly the symptoms of dementia will progress for any one individual. Some types of dementia may progress more quickly than others. However, in general any predictions about either the progression of symptoms or life expectancy will be very approximate as there is a large amount of variation from person to person.
As dementia progresses, a person will need more help and support with daily living. Keeping active and involved may help to keep some their mental skills going for longer. Unfortunately, this won’t necessarily slow down the spreading of disease in the brain.
Alzheimer's disease affects around 1 in 3 younger people with dementia and is the most common type. Younger people are much more likely to have an unusual form of Alzheimer’s disease where the main early symptoms are not problems with memory. Instead, they could be difficulties with vision, language, thinking or behaviour. For more information on unusual types of Alzheimer’s disease, see Rarer Types of Dementia.
Vascular dementia is caused by problems in the blood supply to the brain. It is closely linked to diabetes and to cardiovascular diseases such as stroke and heart disease.
Symptoms of vascular dementia vary from person to person. Early memory loss is less common. However, other symptoms are more common in vascular dementia, including slower speed of thought and problems with:
Physical symptoms (such as limb weakness) are common in vascular dementia when a person develops it after a stroke.
Frontotemporal dementia is caused by damage to the lobes at the front and/or sides of the brain. It is much more common in younger people with dementia than in older people.
FTD is most often diagnosed in people between the ages of 45 and 65. This is different to Alzheimer’s disease, vascular dementia and dementia with Lewy bodies, which all become more likely as people get older. There are three different types of FTD which cause different changes as the first symptoms.
Dementia with Lewy bodies is caused by the build-up of tiny protein deposits (Lewy bodies) in the brain. DLB is less common in younger people with dementia than in older people. Lewy bodies also cause Parkinson’s disease and about one-third of people with Parkinson’s eventually develop dementia.
Symptoms of dementia with Lewy bodies can include hallucinations and varying levels of alertness. People can also develop the features of Parkinson’s disease (such as slower movement, stiffness and trembling limbs).
Alcohol-related brain damage (ARBD) is caused by regularly drinking too much alcohol over several years. People diagnosed with ARBD tend to be in their 40s and 50s, and it is more common in men.
Rarer types of dementia are more common in younger people than in older people. There are also a range of conditions that can cause symptoms similar to dementia in younger people.