Some research suggests that people may have an increased risk of developing Alzheimer’s disease if a relative has the disorder. However, the causes of the condition are unclear.
Alzheimer’s disease is a chronic, progressive condition that affects memory, thinking, and movement.
Current research suggests that multiple factors may contribute to the development of Alzheimer’s, including genetics.
This article explains the potential links between genetics and Alzheimer’s disease.
According to the Alzheimer’s Association, genetic risks for Alzheimer’s fall into two categories: risk genes and deterministic genes.
When a person has risk genes, they have an increased risk of developing a disease. Deterministic genes may directly cause a disease to develop.
Researchers have found several risk and deterministic genes for Alzheimer’s.
Risk genes
Several genes present a risk for Alzheimer’s. The gene with a
According to the National Institutes of Health (NIH), around
Someone who inherits the APOE4 gene from both biological parents has a higher risk of developing Alzheimer’s disease than a person who inherits the gene from only one.
Having this gene may also mean that an individual displays symptoms at an earlier age and receives an earlier diagnosis.
While every person inherits an APOE gene of some form, the APOE3 and APOE2 genes have a much
The trisomy 21 gene may also
Deterministic genes
According to the NIH, researchers have identified
- amyloid precursor protein (APP)
- presenilin-1 (PSEN1)
- presenilin-2 (PSEN2)
These genes are responsible for an excessive buildup of amyloid-beta peptides, a toxic protein that clumps together in the brain. This buildup causes nerve cell damage and death, which is characteristic of Alzheimer’s disease.
These genes are known as “dominant genes,” which means that if either parent has the condition, they can pass on the gene to their children, who are highly likely to develop the disease.
The NIH suggests that changes in the above genes account for 10% to 15% of early onset Alzheimer’s cases, which is when Alzheimer’s disease occurs before the age of 65 years. However, not all people with early onset Alzheimer’s have these genes.
Effect of genes in other types of dementia
Some types of dementia have links to other genetic development issues.
For example, Huntington’s disease is a dominant genetic condition that alters chromosome 4. It causes cognitive (thinking) changes that worsen as the condition progresses. When these changes
Dementia with Lewy bodies or Parkinson’s dementia may also have a genetic component. For example, Parkinson’s has known associations with several genes, including:
- SNCA
- PARK7
- PRKN
However, as with all forms of dementia, the cause of these conditions is typically dependent on several factors.
Researchers have identified several risk factors for Alzheimer’s disease,
- Age: The most significant risk factor for Alzheimer’s disease is age. The risk increases after a person turns 65 years.
- Family history: Having a close relative with Alzheimer’s disease can increase the risk of developing it.
- Head trauma: People with previous instances of severe head trauma may be at higher risk of developing Alzheimer’s disease.
- Heart health: Health issues affecting the heart or blood vessels may increase the chance of developing Alzheimer’s disease. Examples include high blood pressure, stroke, and diabetes.
- Lifestyle factors: Various lifestyle factors may increase the risk of Alzheimer’s, including physical inactivity, alcohol and smoking, sleep issues, and a lack of mental stimulation.
Alzheimer’s disease
Early symptoms may include periods of forgetfulness or memory loss. Over time, a person may experience confusion or disorientation in familiar settings, including at home.
They may need more assistance with daily living, such as brushing their teeth, getting dressed, and cutting food. They may also experience:
- agitation
- restlessness
- personality withdrawals
- speech issues
People age 65 and over live, on average,
Learn more about the stages of Alzheimer’s disease and their outlook.
Seeking medical assistance for someone who has symptoms of Alzheimer’s is vital, even though the discussion might be difficult. A doctor can rule out other conditions that might cause similar symptoms.
Before an appointment, family members need to list any medications the person with symptoms is taking. The doctor can review the list and ensure symptoms are not side effects of current medications.
Keeping a symptom journal over time may help a doctor establish potential patterns.
A doctor may sometimes recommend genetic testing when people show early Alzheimer’s symptoms. This may guide possible treatments and assist in future family planning.
However, genetic testing results may affect a person’s emotional well-being if it leads to an unwanted outcome. Working with a doctor or counselor during and after genetic testing can help people better understand the results and implications.
Alzheimer’s disease has links to several genes. Some, such as the apolipoprotein E4 gene (APOE4) gene, increase the risk of developing the disease but do not always lead to an Alzheimer’s diagnosis.
Others, such as the amyloid precursor protein (APP) gene, directly cause the disease to develop. However, this is a rare type known as familial Alzheimer’s that occurs in 10% to 15% of those with early onset Alzheimer’s disease.
People can speak with a healthcare professional if they start showing signs of Alzheimer’s disease, particularly individuals over 65 years.
