If a parent or other close relative has been diagnosed with Alzheimer’s, you are probably wondering is Alzheimer’s disease hereditary, which is a good question since some forms of dementia, for example Huntington’s, most definitely are.
What causes Alzheimer’s and is Alzheimer’s disease hereditary?
Alzheimer’s is a progressive brain disease and at present there is no known cure. Most cases of Alzheimer’s disease are seen in people aged 65 and above, but it can affect younger people, even those in their thirties. Symptoms of Alzheimer’s disease include short term memory loss, confusion, language problems, hallucinations, and eventually death.
Because Alzheimer’s disease affects so many families, it is not surprising that many of us become concerned that we could be at risk of developing the disease in later life. Thankfully, 99% of Alzheimer’s cases are as a result of age rather than hereditary factors, and the older you get, the more likely you are to develop Alzheimer’s disease, although there is some suggestion that having a close relative with the disease does slightly increase your chances of developing Alzheimer’s.
Is Alzheimer’s disease hereditary?
Approximately 1% of the population are at greater risk of developing Alzheimer’s disease due to an inherited gene. There are three identified genes: PS1, PS2, and APP, all of which are known to cause an inherited type of Alzheimer’s disease. Unlike the more common form of Alzheimer’s, this version is more likely to develop at an earlier age.
Only a very small minority of people are affected worldwide by a fault on chromosome 21 in the APP gene. This causes abnormal levels of the amyloid protein to accumulate in the brain, which is known to be linked to Alzheimer’s. Chromosome 14 defects in the PS1 gene affect slightly more families, and finally, a defective chromosome 1 on the PS2 gene is a very rare genetic abnormality, mainly affecting families in the US.
If the genetic defect is present in a family, only 50% of the next generation will inherit Alzheimer’s and subsequently go on to develop the disease at an earlier than normal age.
Can hereditary Alzheimer’s disease be tested for?
When the hereditary form of Alzheimer’s disease is known to be present in a close family member (parent or sibling) and the affected gene has been identified, it is possible for other family members to be gene tested to predict whether they are at risk of developing the disease. However, this is a difficult decision to take and not everybody wants to know whether they are facing a loaded gun, so genetic counseling is strongly recommended prior to any testing.
Are there any other hereditary risk factors associated with Alzheimer’s disease?
Research into the causes of Alzheimer’s disease has indicated that the presence of a particular type of a gene called apolipoprotein E has been linked to an increased risk of developing the disease. Although scientists are not sure why the inherited apolipoprotein E gene is linked to Alzheimer’s, it has been found to be present in half of all cases of Alzheimer’s disease.