Actor Chris Hemsworth has announced that he has a high risk of suffering from Alzheimer’s in the future as he carries two samples of the APOE4 gene, a situation that only 2% to 3% of the population shares. Does that mean that people with a family history of Alzheimer’s should have a genetic test?
The answer is no, warns Juan Domingo Gisbert, chief investigator of the Neuroimaging Research Group of the Pasqual Maragall Foundation.
Who should take a genetic test?
«In principle no one. EWe are facing a very sensitive issue that not only affects the person, but all their first-degree relatives, siblings, children, parents. The important thing is to go to a Genetic Council that explains what it means, and what it does not, to have a genetic risk of Alzheimer’s, not only to understand the test result, but also to put the test result in context.
If my parents have had Alzheimer’s, do I have to take a test?
«The test is not recommended. What you have to do is go to the Genetic Council because, today, what can be done if the test is positive, or negative, is the same. Namely, take care of all cardiovascular risk factors because it is known that everything that is good for the heart is good for the brain: Control hypertension, prevent obesity, exercise, cholesterol, healthy balanced diet, stay active intellectually and avoid depression. Also, if a person is afraid of suffering from Alzheimer’s because he notices that his memory fails him, we have good news. There is a revolution in the world of Alzheimer’s. A few weeks ago, the results of the first drug, lecanemab, which has been shown to significantly reduce cognitive and functional decline, were presented. Surely in a couple of years we will have drugs that really change the course of Alzheimer’s.”
What types of genetic Alzheimer’s are there?
«In genetic Alzheimer’s we must distinguish two types, which are very different. On the one hand, there is the one determined by causative mutations, which is less than 1% and they are very aggressive cases that are detected before the age of 50 and occur in certain families”.
With biomarkers and drugs that modify the course of the disease, we are going to change the disease
«In 99% of Alzheimer’s cases we talk about genetic risk factors. That is, as in the case of Hemsworth, it is that these two copies of the Apoe4 gene increase the risk, but it does not mean that he will have the disease, it is possible that he will never have it. And it can happen that a person without that gene ends up suffering from Alzheimer’s. I insist, it is only a risk, only a genetic susceptibility. Therefore, taking a genetic test thinking that the disease is going to be ruled out is not advisable.
If, despite everything, I want to take a test, where can I go?
«In some Autonomous Communities there are Genetic Counseling Units, and also in private centers. But I insist I would never recommend taking a genetic test from those that offer at home; What you have to do is go to a Genetic Council. The consequences of a wrong interpretation of a result can be counterproductive at a psychological level. It is very important to know how to handle information.”
What risk factors?
“The most important is age. Many people with a history come from long-lived families and as Alzheimer’s is a neurodegenerative disease, the risk would be greater.
So, is there currently a genetic screening to find out which people have more or less risk of developing the disease?
“In the case of autosomal dominant genetically determined Alzheimer’s, there are mutations that are perfectly identified and that are the cause of the disease. In this case, screening is indicated for people whose father or mother is known to have this variant of the disease and want to know if they will have it or not. This is done through genetic counseling programs. But it represents a very small percentage of Alzheimer’s cases, it is below 1%. And they are very identified families.
“However, the vast majority of cases are so-called sporadic Alzheimer’s. In these, there are genetic risk factors, but it does not mean that whoever has this risk factor will end up developing the disease or that someone who does not have it will not develop it. What the test tells us is the risk of developing a disease throughout your life, but not if you are going to have it a no ».
In addition to genetic tests, can the disease be predicted?
“In the world of Alzheimer’s, everything is changing very quickly. We now have biomarkers that allow us to detect the most frequent alterations that occur in the disease decades before the symptoms appear. and those biomarkers right now they are easy to obtain, just a blood test. With which, we begin to have biomarkers in the blood that will allow us to identify in which person the pathological process has started, even if they are completely healthy. With biomarkers and drugs that modify the course of the disease, we are going to change the disease.”