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Everything you need to know about genetic testing for Alzheimer’s disease

TV presenter and journalist, Fiona Phillips, recently shared her Alzheimer’s disease diagnosis at the age of 61. Fiona has been an ambassador for Alzheimer’s Society and has undergone genetic testing for Alzheimer’s due to her family’s history with the disease (both her mother & father had Alzheimer’s). 

Since Fiona shared her diagnosis, many of our patients have been in touch with questions, particularly those with a family history of Alzheimer’s disease and dementia. In this latest article we want to share everything you need to know about genetic testing for Alzheimer’s disease:

What is Alzheimer’s disease?

Alzheimer’s disease is a physical illness which damages a person’s brain, eventually leading to dementia. Alzheimer’s disease is the most common cause of dementia, which describes a set of symptoms that over time can affect memory, problem-solving, language and behaviour. Alzheimer’s disease is the most common type of dementia.

In Alzheimer’s disease ‘plaques’ composed of proteins (called amyloid and tau) build-up in the brain, making it harder for the brain to function properly. Often there are other ‘vascular’ factors that cause harm to the brain. These could be high cholesterol lipoproteins as well as high blood pressure.

What are the causes of Alzheimer’s disease?

Alzheimer’s disease is the most common cause of ‘dementia’. The many causes of dementia all cause difficulties in memory, problem-solving, and thinking. Symptoms can be subtle at the start. It may take years before they are severe enough to cause a problem in your day-to-day life.

I have heard of a blood test to check for the risk of Alzheimer’s disease. What is the test?

Last year Chris Hemsworth revealed he had a high risk of Alzheimer’s disease after a genetic APOE test.

Testing for the gene changes that have been linked to early-onset Alzheimer’s might be useful for someone with a family history of the disease or for someone showing symptoms of early-onset disease. At Coyne Medical we offer APOE gene testing, in the form of a blood test, as an add-on to our health and genetic screening services. Please do get in touch if you would like to discuss APOE gene testing in more detail.

What is the APOE gene?  

APOE is a gene located on chromosome 19. There are three variations of APOE you can inherit, called ‘alleles’, epsilon (ε) 2, 3 and 4. You inherit any two combinations of ε2, ε3 or ε4, as you get one copy from each parent. For example your APOE genes could be ε2/ε2, or ε2/ε4 . ε4 is the variant which carries an increased risk. If you inherit two copies of ε4 your risk of Alzheimer’s dementia is 8 to 12 times the risk of someone with two copies of ε2.

APOE genes alone won’t guarantee someone gets Alzheimer’s disease. Lots of other factors will influence this. Blood pressure, diet, cholesterol and physical activity levels all have an impact.

About 1% of cases develop dementia due to an inherited genetic mutation in a single gene. One example is the amyloid precursor protein gene (APP). There may be a family history of dementia starting at a very early age, from 30 onwards. In these cases, it is important to talk to your doctor and consider your options for testing.

Dr Lucy Hooper
Coyne Medical