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.

Download or order a printed copy of our booklet Understanding young-onset dementia.

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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.

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. 

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