“Dementia” is an umbrella term for a wide range of symptoms resulting from conditions that damage the brain. Some forms of dementia have a genetic link.

These include Alzheimer’s disease, Lewy body dementia, and frontotemporal dementia (FTD), among others.

However, multiple causes, rather than a single gene, often contribute to dementia.

Although scientists have identified a genetic link for some cases, further research would be beneficial to fully understand how a person’s family history contributes to their risk of developing dementia.

Keep reading to learn more about the link between genetics and various forms of dementia.

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“Dementia” is an umbrella term for a decline in mental ability as a result of disease or injury. Dementia can cause memory problems, personality changes, and impaired reasoning.

An individual with dementia may become forgetful, have limited social skills, and have reduced cognitive abilities to an extent that interferes with their daily functioning.

Dementia becomes more common as people age. Around 1 in 3 people aged 85 or older have some form of dementia. However, it is not a typical part of aging, and many individuals do not develop it.

There are various types of dementia, including:

  • Alzheimer’s disease: This is the most common form of dementia. Changes in the brain, including an unusual buildup of protein, cause the condition.
  • FTD: This is a rare form of dementia. It often occurs among people younger than 60.
  • Lewy body dementia: This condition happens because of an accumulation of atypical proteins, called Lewy bodies, in the brain.
  • Vascular dementia: This occurs when blood vessels in the brain become damaged and do not allow proper flow of blood and oxygen.
  • Mixed dementia: This is a combination of multiple types of dementia — most commonly a combination of Alzheimer’s disease and vascular dementia.

Changes to even small parts of a gene can cause dementia.

A gene is made up of a chemical called DNA. If someone inherits a genetic mutation that causes a health condition, they are more likely to develop that condition. Early-onset Alzheimer’s disease is an example of an inherited genetic disorder.

Additionally, genetic variants — changes to genes — can affect a person’s risk of disease. Doctors call this a genetic risk factor.

If someone has a genetic risk factor for dementia, then certain environmental and lifestyle factors can affect their chances of developing the condition. These can include:

A person whose parent has early-onset Alzheimer’s disease has an increased chance of developing the disease. However, this is not necessarily the case for late-onset Alzheimer’s disease.

A person’s risk for late-onset Alzheimer’s disease may depend on the age of onset, as well as whether the person has gene susceptibility — for example, mutations in the apolipoprotein E (APOE) gene.

While a specific gene does not seem to directly cause the disease, a variant of the APOE gene on chromosome 19 appears to increase a person’s risk. This gene plays a role in making proteins that carry cholesterol and other lipids in the blood.

Experts have identified three single-gene mutations that they associate with early-onset Alzheimer’s disease:

  • APP gene
  • PSEN1 gene
  • PSEN2 gene

Mutations in these genes may cause the atypical protein production involved in the disease.

Most people who develop Alzheimer’s disease are in their mid to late 60s.

Learn more about Alzheimer’s disease here.

Vascular dementia is the second most common cause of dementia, accounting for 1 in 5 cases.

It typically has multiple causes or related health conditions, such as high blood pressure and diabetes. Cerebral vascular disease — a condition that affects the blood vessels of the brain — is the most usual cause.

There is little data from studies examining the heritability of vascular dementia. In most cases, vascular dementia is not an inherited disorder, but the contributing health issues can pass from one generation to the next.

Lewy body dementia typically affects people over 65 years of age and can cause:

  • hallucinations
  • cognitive problems
  • parkinsonism, or symptoms of Parkinson’s disease

A growing body of research suggests that there is a genetic aspect to Lewy body dementia. However, compared to other neurodegenerative disorders, scientists know very little about the genetics involved in this condition.

Learn more about Lewy body dementia here.

Doctors do not fully understand why some people get FTD and others do not. In some cases, it may relate to a person’s genes. Around 3 in 10 people with the condition have a strong family history of it.

In some families, a single genetic variation that can cause FTD passes from parent to child. Doctors refer to this as familial FTD. It occurs in 10–15% of individuals with the condition.

Any child of a person who has familial FTD and carries an autosomal dominant gene has a 1 in 2 chance of receiving the same gene. This means the child needs to receive one affected gene from their parents to get the disease.

There are other forms of familial FTD in which there is no identifiable genetic cause or the genetic basis is not necessarily autosomal dominant.

Susceptibility genes can also increase a person’s risk of developing FTD. However, having the gene does not always mean that a person will develop the condition.

Learn more about FTD here.

Yes, some forms of early-onset dementia are genetic. For example, around 10% of individuals develop Alzheimer’s disease before age 60, and genetics are much more likely the cause in those cases.

Typically, the earlier someone develops Alzheimer’s disease, the more likely it is that the condition is the result of an inherited gene mutation. Therefore, if someone develops Alzheimer’s disease in their 30s or 40s, genetics are usually the cause.

Learn more about the symptoms of early-onset dementia here.

An individual can undergo genetic testing for dementia, but it is expensive and not always accurate.

The tests look for specific mutations involved in the condition. However, the tests cannot detect all possible causes of dementia. For example, experts estimate that 1% or fewer cases of Alzheimer’s disease are due to a specific mutation in certain genes. In other cases, the cause is unknown or multiple factors are involved.

Additionally, someone may have a certain mutation but never develop dementia. Therefore, doctors may not recommend genetic testing for dementia as a routine screening tool.

Genetic testing can be useful in families with a known genetic mutation for the disease. Tests can show which family members have the mutation and may develop Alzheimer’s disease.

If someone is considering genetic testing, they should first discuss their options with a doctor and/or a genetic counselor. The person should be fully aware of what the results of the test can mean before undergoing it.

Some forms of dementia, including Alzheimer’s disease and Lewy body dementia, have a genetic component. This means an individual may have an increased chance of developing these types of dementia if they have a family history of it.

However, dementia is often complex and can have multiple contributing factors.

In most cases, doctors do not recommend genetic testing for dementia. The testing can be expensive and is not always accurate. However, in some cases of strong family history, testing may be a useful tool to find out which family members have specific gene mutations.

A person who is considering genetic testing should discuss their options with a doctor or a genetic counselor.