Should I get a genetic test to find out if I will get dementia?
My father has Alzheimer's. I saw that there are genetic tests that tell you the risk. Does it make sense to get one?
It's one of the most frequent questions from those caring for a parent with dementia, and it's a legitimate question. The short answer is that, in most cases, it doesn't make sense — and the reason isn't the cost.
What the test measures
The most talked-about gene is called APOE and has several variants. The APOE4 variant is the strongest known genetic risk factor for Alzheimer's disease. About a quarter of people have one copy, and only 2 to 3% have two.
It's a risk factor, not a sentence. Many people with APOE4 never develop dementia, and many people without APOE4 do. The test returns an altered probability, not a definitive answer.
Why guidelines don't recommend it
The test is not recommended for people without symptoms for a simple reason: the result doesn't change what needs to be done. There is no treatment that starts because of an APOE4 result. And the measures that reduce risk — moving your body, treating high blood pressure and diabetes, quitting smoking, correcting hearing, maintaining a social life — are exactly the same with or without the gene. You should already be doing them anyway.
There's also the other side. A positive result can bring years of anguish about a disease that may never arrive. A negative result can give a false sense of security and lead to neglecting precisely what makes a difference — because most cases of dementia occur in people without this variant.
This is being re-evaluated as new treatments emerge, and it is possible that guidelines may change. But today, this is the understanding.
When genetic counselling makes sense
There are situations where it does, and these should not be confused with the common case. There are rare forms of Alzheimer's, familial and early-onset, caused by mutations that are directly transmitted. They are suspected when there are several cases in the family with onset before the age of 60 or 65, across successive generations.
If this is the case in your family, talk to your doctor and ask for a referral to genetic counselling — not a test bought online. In that consultation, what is gained and what is lost by knowing is discussed, before any analysis.
About direct-to-consumer tests
Some companies sell genetic tests by mail, with results delivered without support. A result about dementia risk delivered by email, without anyone to explain it, is the worst possible way to receive this information. If you ever take the test, do it with clinical support.
What to do with fear
Having a parent with dementia is frightening, and the fear is reasonable. But the test doesn't solve it: at best, it exchanges one uncertainty for another. What is truly in your hands is everything else — and the good news of the last decade is that this part is greater than previously thought.