Is Alzheimer’s a Hereditary Condition?

Alzheimer's disease is the most frequent cause of dementia in the current population. Its development is related to the changes that occur with aging, but also with genetics, lifestyle and environmental factors. Is Alzheimer's hereditary?

One of the greatest concerns of relatives of a patient with this disorder is the possible risk of inheritance. Although more than 90% of cases correspond to sporadic Alzheimer's, between 5% and 10% are hereditary.

This means that, due to certain genetic mutations, several members of the same family can develop the disease. The risk is higher if it is a relative in the first degree, such as a father or a brother.

What is Alzheimer's Disease?

Before explaining why Alzheimer's is hereditary, it is important to review what it means to have this disease. As we mentioned, it is a mental disorder that arises when the brain cells deteriorate and die.

As a result there is a decrease in the capacity of memory and mental function, which prevents the patient from remembering important things or people. In addition, it drastically affects his personality and markedly diminishes his quality of life.

This neurological pathology, which is also progressive, does not have relevant symptoms in its initial stages. However, as time passes, the thoughts begin to be confused and it is difficult to reason and maintain the memory.

When is Alzheimer’s is hereditary?

Doctors suspect that Alzheimer's is hereditary when there is a family history where several members of the same family were affected (usually three direct relatives). In these cases, the possibility of transmitting the pathology to the children is up to 50%.

However, it is the least common type of Alzheimer's, since more than 90% is sporadic or late-onset, whose causes combine multiple factors, including, to a lesser extent, genetics. It should also be noted that when Alzheimer's disease is hereditary, it usually manifests before the age of 65. There are even cases in which it originates from the age of 30.

What are the causes of hereditary Alzheimer's?

Alzheimer's is hereditary when there are genes involved in its evolution that have been transmitted by the paternal gametes (ovum and sperm). In spite of this, the fact that there is a family member with this disease does not necessarily mean that their direct relatives will inherit it. Next we review its possible triggers.

Risk Genes

Some genes have been identified that could increase the risk of this type of dementia. The one with greater influence is known as apolipoprotein E-e4 or APOE-e4, which could be a factor in 20 or 25% of cases. A person who inherits this gene from their parents has a higher risk of developing the disease.

It is important to mention that the mutated gene does not jump generations and is transmitted indefinitely from one to another. It can be detected through a blood test, but this does not serve to predict whether Alzheimer's will develop or not.

Deterministic Genes

 

The deterministic genes linked in familial Alzheimer's may be responsible for the majority of cases of early onset. These, in particular, would be responsible for the accumulation of β-amyloid peptide in the brain.

This toxic protein has been detected as responsible for brain agglomerations that cause damage to nerve cells. In addition, it is also associated with cases of deaths from Alzheimer's disease. The genes are:

Beta-amyloid peptide (APP) precursor protein

Presenilina1 (PSEN1)

Presenilina 2 (PSEN 2)

Predisposition to suffer Alzheimer's

So far there is no 100% effective test to predict Alzheimer's disease. However, there is a test called genetic testing that helps to know if the person has a predisposition or not.

It is a blood test that indicates whether someone with affected relatives has genes involved in the disease. If so, the doctor may suggest continuous evaluations to determine if there are signs of the disease.

When the test shows the presence of the mutation the individual has a high probability of suffering from this disease. Therefore, although there is no precise information to prevent it, it is essential to receive professional advice.

In summary, it is important to know the family history to determine if Alzheimer's is hereditary. When there are several affected relatives, periodic medical evaluations are recommended to observe changes and symptoms that indicate the disease.