Is Alzheimer’s Hereditary?
There is still a lot that science does not know about how and why some people develop Alzheimer’s disease. There is not a complete understanding of all the genetic factors that contribute to getting the disease, for example. Some people who develop Alzheimer’s disease also have a family member with Alzheimer’s disease, but a so-called “family history” is not always associated with developing the disease. It is very likely there is a combination of genetic, medical, and lifestyle risk factors that work together in concert in many people who develop Alzheimer’s disease.
For families that do have a loved one with the illness, it is understandable to have concerns about whether other family members might also develop Alzheimer’s. Scientific studies reveal that there is a small, increased risk if other family members develop the disease.
There are several factors that influence the risk of developing Alzheimer’s.
Age
Age is the most significant risk factor. Most of the time Alzheimer’s disease is diagnosed in someone who is in their mid-60s or older. This is called, “Late-Onset Alzheimer’s Disease.”
At age 65 there is a 2% risk of developing Alzheimer’s disease, meaning 2 out of every 100 people 65 years or older will develop Alzheimer’s each year. At age 85 the incidence increases to about 30-40 of every 100 people who are likely to develop Alzheimer’s disease or a related dementia.
Family History
Having a history of Alzheimer’s or another form of dementia “in the family” increases risk.
If you have a first-degree relative such as a parent or sibling who develops Alzheimer’s, your risk increases by 30%. A 65-year-old with a family history has a 30% higher risk such that in a group of 100 people with family history, and average of 2.6 people will develop Alzheimer’s disease. It is indeed an increased risk, but a relatively small one.
Genetic Factors
There are two known genetic factors that cause rare types of Alzheimer’s disease. Familial Alzheimer’s is caused by rare genetic abnormalities that cause early-onset disease in the 40s or mid-50s. There are only a few hundred families worldwide with this genetic makeup.
People with Down’s Syndrome have a higher-than-normal risk of developing Alzheimer’s disease. Unfortunately, the main genetic abnormality they have, three copies of chromosome 21, leads to an increase in the presence of amyloid which is thought to be the abnormal protein that causes disruption and cell death in nerve cells in the brain.
APOE
The most widely studied and known genetic factor specific for Alzheimer’s disease is APOE (apolipoprotein E). These proteins are involved in cholesterol management and transport in the bloodstream. There are three versions of APOE, and we all inherit two copies each from our parents.
Having one or two copies of “APOE” is known to increase the chance an individual will develop Alzheimer's Disease. In people with one APOE gene, 25% develop the disease by age 85. That incidence level rises to 55% for people with two APOE genes.
However, keep in mind this is not a definitive test. Not everyone who has the ApoE gene develops Alzheimer’s.
Because the link between ApoE and Alzheimer’s is not fully understood, testing for this gene is not routinely recommended. Currently most insurance companies, including Medicare, are not currently paying for ApoE testing. The testing is being used in medical research, and increasingly there are genetic tests commercially available that include the APOE gene marker. Click here for a listing of commercially available testing services.
Please note: We strongly recommend getting this testing done only if you have access to a physician, genetic counselor, or other knowledgeable provider who can help you interpret your test results and overall risk.
Please talk with your own/loved one’s healthcare provider before using any of this information.
