If you have a family member who has been diagnosed with Alzheimer’s disease, you may have wondered at one point in time, how likely the disease is to be passed on genetically. Which inheritable traits should families know about and should you pursue genetic testing?
Learn more from a recent Harvard Health article that provides the answers to these and other common questions about the genetic link to Alzheimer’s.
Alzheimer’s and Inheritable Traits
Just how likely are family members of those with Alzheimer’s to get the disease themselves? “People think that if Dad and Mom or an aunt or uncle had Alzheimer’s, they are doomed. But, no, that’s not true,” says Dr. Gad Marshall, assistant professor of neurology at Harvard Medical School.
“Even though family history adds to the overall risk, age still usually trumps it quite a bit. It means your risk is higher, but it’s not that much higher if you consider the absolute numbers.”
As Dr. Marshall notes, the most common form of the disease is age-related Alzheimer’s, which means the risk of the disease comes from a person’s age and not their genetic predisposition. The older a person is, the higher risk they have of getting Alzheimer’s, and this pertains to everyone, whether they’ve had a family member with the disease or not.
The statistics show that after age 65, everyone develops a 2% increased risk per year of getting diagnosed with Alzheimer’s. Other Harvard Health statistics show that:
- A family history of Alzheimer’s raises the yearly 2% risk factor to approximately 2.6%, so the overall relative risk does not rise dramatically. “That means going from 20 cases in a group of 1,000, to 26 in 1,000, or six additional cases in 1,000, so the absolute increase is relatively small,” Marshall explains.
- People in their 70s with a family history of Alzheimer’s have a 6.5% risk, compared to the general population with a 5% risk, so again, the genetic linked risk factors are relatively small.
- The overall risk of getting Alzheimer’s increases by approximately 30% for those who have a close relative who has been diagnosed with the disease. Harvard Health warns that this is a “relative risk increase, meaning a 30% hike in your existing risk.”
- Those who live to be 70 have a 5% chance of getting Alzheimer’s, so that number represents a higher risk than those who are in their 60s with a family history of the disease.
Inheriting the “Alzheimer’s Gene”
The gene that is largely responsible for increasing the risk of Alzheimer’s is called the Apolipoprotein E gene, or the apoE4 gene for short. This gene is involved in making a protein that helps carry cholesterol (and other fats) and vitamins throughout the body (including the brain). This gene variant does not cause Alzheimer’s, but rather, is thought to increase the risk of getting the disease.
Although it’s not completely clear exactly how the apoE4 gene increases the risk of getting Alzheimer’s, scientists believe it is associated with multiple factors, including environmental factors (like smoking or pollution), genetics and lifestyle factors (such as diet and exercise).
Inheriting one copy of the “Alzheimer’s gene” from one parent is said to raise the risk of getting Alzheimer’s and getting two copies (which is extremely rare) increases a person’s risk even more. But, it’s very important to understand that not everyone who gets the apoE4 gene will be diagnosed with the disease.
Taking Part in Genetic Testing
After questioning the likeliness of inheriting Alzheimer’s, perhaps the second most common question is: “Should I take part in genetic testing?” Dr. Marshall answers this question, saying, “It’s not going to be helpful since it won’t tell you whether you will develop the disease. It will only tell you if you are at a greater or lower risk.”
Dr. Marshall elaborates, saying that often the testing is complex and that many companies are ill-equipped to perform the testing. He also points out that if a person does test positive for a genetic form of Alzheimer’s (like early-onset familial Alzheimer’s), it could impact their ability to procure some types of insurance.
In conclusion, it’s always best to consult with a professional, such as a trusted healthcare provider, before considering any type of genetic testing.
Does the “Alzheimer’s gene” run in your family? Which inheritable traits are you most concerned about? We’d like to hear your thoughts in the comments below.