Is dementia hereditary? | Dementia and genetics

Dementia is not usually hereditary, but there are certain types which are. These are caused by genetic factors but are very rare.

Key points

• Dementia isn’t usually hereditary but there are some rare types that are caused by faulty genes.
• Having a parent who carries a gene for hereditary dementia gives you a 1 in 2 chance of inheriting the gene yourself.
• Carrying a gene for dementia doesn’t mean you’ll definitely develop the condition.

Does dementia run in families?

Dementia can run in families, but inherited dementia is extremely rare. It is caused by an inherited mutation of certain genes.

What causes dementia?

There are numerous different types of dementia and each has a different cause.

Alzheimer’s disease is caused by a build-up of proteins called amyloid and tau in the brain. Vascular dementia is caused by reduced blood flow in the brain.

Some factors that lead to dementia developing can be inherited. For example, there are forms of hereditary heart disease, which in turn can lead to vascular dementia.

Which types of dementia are hereditary?

Hereditary types of dementia are usually prefaced with ‘familial’. This just means that it comes under the same category as the more common type but is caused in part by genetics.

Familial Alzheimer’s disease

Less than 1% of cases of Alzheimer’s disease are familial.

Alzheimer’s disease accounts for 60% of all cases of dementia.

Familial frontotemporal dementia (fFTD)

30-40% of cases of frontotemporal dementia are familial.

Frontotemporal dementia accounts for around 2% of all cases of dementia.

Familial vascular dementia (CADASIL)

According to Dementia UK, around 1000 people in the UK have this familial vascular dementia. This is around 0.1% of all dementia cases (there are about 982,000 people currently living with dementia in the UK).

Vascular dementia accounts for around 15% of all cases of dementia.

Read more about these rare types of dementia.

Do people with hereditary dementia start showing symptoms younger?

The vast majority of non-genetic dementias occur in people aged over 65. However people with hereditary dementia tend to start developing symptoms at a younger age – in fifties, forties and even thirties.

Are there tests for dementia genes?

If a parent or grandparent has been diagnosed with a familial form of dementia, it’s very understandable that you may wish to find out if you carry the gene that caused it too.

The NHS does offer tests for single genes if you have a strong family history of dementia.

There are three sorts of testing:

1. Diagnostic testing – For people who already have dementia and want to find out if it’s caused by a faulty gene.
2. Predictive testing – For close relatives of a person who has been diagnosed with familial dementia who want to find out if they also carry the gene.
3. Pre-Implantation Genetic Diagnosis (PGD) – This is part of IVF and can test whether embryos carry the gene before they are implanted into the womb.

The Alzheimer’s Society has in-depth information on genetic testing and whether it’s recommended.

If you are interested in genetic tests for dementia it’s advisable to speak to your doctor. Home testing kits for dementia are not recommended.

Can I reduce my risk of hereditary dementia?

As with any genetic condition, there is no guarantee that you’ll develop dementia if a hereditary type runs in your family.

You may not carry the gene at all – if it only runs in one side of your family then you only have a 50% chance of inheriting it.

Even then it’s possible that you won’t go on to develop dementia, but you do have an increased risk.

Reducing your risk of dementia in general

Age is the greatest risk factor for developing dementia, with any person having around a 1 in 50 chance of getting it at age 65-69, increasing to around 1 in 3 by age 90+.

However, around 4 in every 10 cases of dementia are caused by preventable lifestyle factors.

You can reduce your risk of dementia by leading a healthy lifestyle and keeping your brain active, including:

• Eating a healthy diet with plenty of whole food including vegetables, fruit and whole grains.
• Exercising regularly.
• Not smoking.
• Drinking no or minimal alcohol.
• Socialising regularly.
• Partaking in hobbies that stimulate the brain, such as playing an instrument, learning a new language, doing puzzles, playing chess and reading novels.

Podcast: Jess Crawford aged 29 reveals what it was like finding she has inherited the gene for frontotemporal dementia

You can read about Jess’ s journey with Pre-Implantation Genetic Diagnosis (PGD) on her blog, FTD and Me.