Genetics and Alzeheimer’s: Identifying Those at Risk

Alzheimer’s disease is a degenerative disorder that leads to problems with memory, focus, judgment, and the ability to function comfortably. It typically occurs in individuals over the age of 65 but can start earlier in some cases.

There are several types of Alzheimer’s disease, which are differentiated based on their underlying causes and age of onset. While the exact cause of Alzheimer’s is unknown, some factors, such as genetics, lifestyle choices, or injury, can increase the risk of developing it. This blog explores Alzheimer’s disease causes, its types, and the role played by genetics in developing it.

What is Alzheimer’s Disease?

Alzheimer’s disease is a degenerative brain disease leading to changes in the brain and a buildup of protein deposits. This can eventually lead to the shrinking of the brain and death of brain cells. Alzheimer’s is also the most common cause of dementia, which is a gradual decline in memory, behaviour, thinking, and functioning. Some common Alzheimer disease causes include:

1. Genetic Mutations
2. Age
3. Gender
4. Injury or Head Trauma
5. Lifestyle

What are the Types of Alzheimer’s Disease?

The different types of Alzheimer’s include:

1. Early Onset Alzheinmer’s: This occurs in individuals below the age of 65, and most diagnosed with early onset Alzheimer’s are diagnosed by the age of 40 to 50 years of age.
2. Late-onset Alzheimer’s: Late-onset Alzheimer’s is the most common form, occurring in individuals who are 65 years or older and may be hereditary.
3. Familial Alzheimer’s Disease: Familial Alzheimer’s disease (FAD) has been linked to the presence of specific genes. It is most commonly observed in those with early-onset Alzheimer’s.

How Do Genetics Affect Alzheimer’s Disease? 

While family history is not essential for the development of Alzheimer’s, studies show that those with parents or siblings affected by the disease are also more likely to develop it. Two categories of genes have been identified that influence the development of Alzheimer’s disease:

1. Risk Genes

The most common risk gene linked to Alzheimer’s is the APOE-e4. While everyone inherits a copy of an APOE gene from each parent, those with the APOE-e4 form are at a greater risk of developing Alzheimer’s. Those who inherit two copies of this gene from both the mother and father are at an even greater risk of getting Alzheimer’s disease.

The risk of developing Alzheimer’s from the APOE-e4 gene can differ across populations. According to a study published in the Nature Reviews Neurology journal, there is a significant correlation between the presence of the APOE-e4 gene and an increased risk of Alzheimer’s and other types of dementia in India. While they increase the risk of developing the disease, those with these genes are not guaranteed to get Alzheimer’s.

2. Deterministic Genes

Deterministic genes are usually a direct cause of a disease. Three deterministic genes have been observed to lead to the development of Alzheimer’s disease. These include the beta-amyloid protein precursor on chromosome 21, presenilin 2 on chromosome 1, and presenilin on chromosome 14.

Genetic studies conducted on a smaller scale in India have also identified additional genes, such as glutathione S-transferase T1, as risk factors for dementia and Alzheimer’s.

How Is Alzheimer’s Disease Diagnosed?

The diagnosis of Alzheimer’s disease includes several steps. Medical professionals may look at current symptoms, family history, current and past health conditions, current and past medications, alcohol consumption, diet, and lifestyle. The following tests may be conducted to make a diagnosis:

1. Physical (like blood pressure and heart rate)
2. Biomarkers (like certain forms of PET scans to measure amyloid and tau protein levels in blood and spinal fluid)
3. Brain image (like MRIs and CT scans)
4. Mental status (short-term memory, long-term memory, and orientation and awareness)
5. Blood tests (to eliminate other possible reasons for symptoms or measure the amount of beta-amyloid or tau proteins)

Can Alzheimer’s Be Prevented?

Currently, there is no proven method for Alzheimer’s prevention. However, studies suggest that lifestyle habits may play a role in preventing Alzheimer’s. These include proper exercise, not smoking, eating a varied and nutritious diet, and consistent learning, which may reduce the risk of Alzheimer’s and certain forms of dementia.

Additionally, genetic tests can be conducted to determine the presence of genetic markers and risk factors (such as the APOE-e4 gene) for Alzheimer’s disease. While genetic tests are not recommended for those being evaluated for the condition, individuals with a family history of Alzheimer’s disease could consider them.

Individuals with symptoms or a family history of Alzheimer’s should consult a medical professional for further guidance on testing and prevention methods. Genetic test pricing for Alzheimer’s varies based on region. For accurate and quick testing, book a genetic test for Alzheimer’s with Dr Lal PathLabs.

FAQs 

1. How much of Alzheimer’s disease is genetic?

Individuals who inherit one copy of the APOE-e4 gene have a greater risk of developing Alzheimer’s, and those with two copies are at a greater risk. However, not all those with Alzheimer’s have this gene, and not all individuals with the gene will develop Alzheimer’s. Environment, lifestyle habits, and dietary choices also play a role in developing this disease.