“My Dad (or my mum, or my sister, etc) has been diagnosed with Alzheimer’s disease… I am fine but I worry a lot: will I develop the disease too?” This question is recurrent among people who have experienced Alzheimer’s disease in their family. Fortunately, for most people, the answer to that question is “no, it is not likely”. Indeed, genes are rarely the direct cause for Alzheimer’s disease. Scientists have not yet identified any single cause for Alzheimer’s disease. This is why you hear doctors or scientists talk about risk factors. These are the factors that will influence your risks of developing the disease.
The primary risk factor for developing Alzheimer’s is AGE. This means that the older you are, the more risks you have to get the disease. The likelihood of developing the disease doubles every 5 years after the age of 65 (65 years old: only 3% risks, 75 years old: 12%, 85 years old: almost 50%).
Research has shown that family history is also a risk factor. People who have a parent or sibling or child who has developed the disease are more likely to get it.
This mean that their risk of developing Alzheimer’s is slightly increased compared to the general population. This is only a 2 to 3 % increase. (Note that the risk increases if more than one family members has the disease.)
Two forms of Alzheimer’s disease
Sporadic or late-onset Alzheimer’s
In this form of Alzheimer’s, genes do NOT directly cause the disease. As we said above, genes may nevertheless influence the risks of developing it (see family history as a risk factor). In the majority of sporadic Alzheimer’s cases, the disease occurs after 70. Sporadic Alzheimer’s is also called non-inherited Alzheimer’s disease. It is the most common form of the disease.
Familial or early-onset Alzheimer’s
In this form of Alzheimer’s, genes directly cause the disease. A person who develops this type of Alzheimer’s has inherited an abnormal variation or mutation of one of the following 3 genes: PS1, PS2 and APP. A person who inherits one of these mutated genes will certainly develop Alzheimer’s. In addition, this person has 50% chance of passing this gene to his/her children. However, family members who have not inherited these mutated genes are not more likely to get the disease than the general population.
Most cases of familial Alzheimer’s occur before the age of 60 (however, it is not because someone gets the disease early that it is necessarily a familial form of Alzheimer’s). It is a very RARE form of Alzheimer’s.
As you know, there is no preventive treatment available for Alzheimer’s disease. Thus, genetic testing has its limitation. However it may provide individual peace of mind.
If familial Alzheimer’s is detected, important issues are at stake: employment, health insurance, future plans, etc.
“My Dad has Alzheimer’s, will I get the disease too?” Now you know that the answer in the vast majority of the cases would be: “Don’t worry. Your risks of getting Alzheimer are only 2% higher compared to other people.”.
In sum, relax and make sure to use your brain!