Is dementia hereditary?

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1. Can dementia be passed down through the family?
2. Can Alzheimer’s disease be inherited?
3. Can vascular dementia be inherited?
4. Can frontotemporal dementia be inherited?
5. Rare types of dementia and Alzheimer’s disease that can be passed down

1. Can dementia be passed down through the family?

Many people affected by dementia are concerned that they may inherit or pass on dementia.

The majority of dementia is not inherited by children and grandchildren. In rarer types of dementia there may be a strong genetic link, but these are only a tiny proportion of overall cases of dementia.

2. Can Alzheimer’s disease be inherited?

In the vast majority of cases (more than 99 in 100), Alzheimer’s disease is not inherited.

The most important risk factor for Alzheimer's disease is age. Because Alzheimer's disease is so common in people in their late 70s and 80s, having a parent or grandparent with Alzheimer's disease at this age does not change your risk compared to the rest of the population.

However, if somebody has developed Alzheimer’s disease at an earlier age (for example, less than 60 years-old) there is a greater chance that it may be a type of Alzheimer’s disease that can be passed on.

3. Can vascular dementia be inherited?

In most cases, vascular dementia itself is not inherited. However, the underlying health issues that sometimes contribute to this condition, such as high blood pressure or diabetes, may be passed on from one generation to another. 

Other than in a few, very rare cases, parents cannot pass on vascular dementia to their children. However, a parent may pass certain genes that increase the risk of developing vascular dementia.

The sort of genes that increase the risk of vascular dementia are often the same ones that increase the risk of high blood pressure, diabetes, heart disease and stroke.

For this reason, having a healthy lifestyle, such as eating well and staying physically active, are probably more important for preventing vascular dementia than they are in Alzheimer's disease.

4. Can frontotemporal dementia (FTD) be inherited?

Sometimes, yes. FTD is relatively rare compared with Alzheimer’s disease or vascular dementia, but it can be passed on directly from parent to child. A diagnosis of FTD can therefore cause a great deal of worry to someone who has children or grandchildren. 

Most FTD is not directly inherited, but about 40 per cent of people who develop the condition will have at least one close relative diagnosed with some kind of dementia. This can include FTD, Alzheimer’s disease or amyotrophic lateral sclerosis (ALS) (sometimes known as motor neurone disease). In general, the greater the number of relatives who have had dementia – particularly FTD or ALS – the greater the chances of developing ‘familial’ FTD.

Of the different types of FTD, the behavioural form is the one that is inherited most often. The type of FTD which starts as primary progressive aphasia (struggling with communication) is only rarely inherited.

There are lots of different genes causing familial FTD, each with its own pattern of inheritance. If you are concerned about either passing on an FTD gene or inheriting the disease from your parents, you can ask your GP to refer you to a genetic testing service in your area. These people are specially trained to guide you through the process of finding out whether you have a gene that causes FTD. You can also get in touch with a specialist support group at Rare Dementia Support, who can provide information and advice about how to cope with having a heritable form of FTD in your family.

5. Rare types of dementia that can be passed down

The good news is that these kinds of dementia are very unusual. 

Young-onset, familial Alzheimer’s disease

Not all kinds of Alzheimer’s disease are the same. Most people with the condition develop it during their 70s and 80s, but in a small proportion of cases, it can affect people in their 50s and 60s. This is known as ‘young-onset’ Alzheimer’s disease.

About 3 per cent (1 in every 33 people) people develop Alzheimer’s disease before they are 60 years of age. In these cases, the condition is much more likely to have been caused by a faulty gene being passed down from parents to children. In general, the earlier a person develops Alzheimer’s disease, the greater the chance that it is due to a faulty inherited gene. So in the really rare cases of a person developing Alzheimer’s disease in their 30s and 40s, it’s almost always because of a faulty gene. 

So, while the vast majority of people with Alzheimer’s disease do not pass on faulty genes to their children, this can sometimes be the case in younger people with the condition. 

Other rare types of dementia

Other rare types of dementia that can be passed down through the family include Huntington’s disease and Familial Prion disease. These diseases have a 50/50 chance of being passed on because they are caused by a single faulty ‘dominant’ gene. 

This means that, if you inherit a healthy gene from one parent and a faulty gene from the other parent, the faulty one will always be the one that is used – because it’s the ‘dominant’ gene. 

For more information, care and support services, please refer to the Huntington’s Disease Association or the National Prion Clinic at UCL.