Alzheimer's is a complex disease and its onset and progression are influenced by a combination of genetic (how hereditary Alzheimer's is) and environmental (lifestyle) factors.
In terms of genetic architecture, we can classify Alzheimer's disease into two main groups:
- Hereditary early-onset Alzheimer's disease:
- It is a rare form of the disease that usually affects people under 65 years of age.
- It accounts for less than 5% of all cases of Alzheimer's disease.
- It has been related to mutations in three specific genes: PSEN1, PSEN2 and APP. The heritability of this type of Alzheimer's disease is around 90%.
- Late-onset Alzheimer's disease:
- It is the most common form of the disease (about 95% of cases) and usually affects people over 65 years of age.
- Although the exact cause is not clear, several genetic variants associated with the disease have been identified (heritability around 70%). Among these variants, it can be found the ε4 combination of the APOE gene. People who inherit one copy of the ε4 form from one of their parents have an increased risk of developing Alzheimer's, and those who inherit two copies (one from each parent) are even more at risk. However, having one or even two ε4 copies of the APOE gene does not guarantee that someone will develop Alzheimer's disease. In the image below you will find the frequency of the different configurations of the APOE gene in European population (with and without Alzheimer's). There are three configurations of the APOE gene (ε2, ε3, or ε4). Find out your APOE haplotype at ADNTRO!
It is important to note that although genetic factors may increase risk, they do not determine with certainty who will develop the disease. Many people with genetic risk factors never develop Alzheimer's, while others without these factors do. Therefore, it is crucial to consider both genetic and non-genetic factors when assessing individual risk.
At ADNTRO you can learn about your genetic predisposition to late-onset Alzheimer's disease. And if you want to know more about the genetics behind Alzheimer's, the pathophysiology, symptoms and the APOE haplotype, this article on Alzheimer's is of interest to you!
