Many people worry about developing Alzheimer’s disease, especially if a family member has had it.
Having a family history of the disease does not mean for sure that you’ll have it, too. But it may mean you are more likely to develop it.
People’s genes, which are inherited from their biological parents, can affect how likely they are to develop Alzheimer’s disease.
Genetic risk factors are changes or differences in genes that can influence the chance of getting a disease. These risk factors are the reason some diseases run in families.
There are two types of Alzheimer’s—early-onset and late-onset. Both types have a genetic component.
Most people with Alzheimer’s have late-onset Alzheimer’s disease ,in which symptoms become apparent in their mid-60s.
Researchers have not found a specific gene that directly causes the late-onset form of the disease.
However, one genetic risk factor—having one form, or allele, of the apolipoprotein E (APOE) gene on chromosome 19—does increase a person’s risk.
APOE ɛ4 is called a risk-factor gene because it increases a person’s risk of developing the disease. However, inheriting an APOE ɛ4 allele does not mean that a person will definitely develop Alzheimer’s.
Some people with an APOE ɛ4 allele never get the disease, and others who develop Alzheimer’s do not have any APOE ɛ4 alleles.
Early-Onset Alzheimer’s Disease
Early-onset Alzheimer’s disease occurs between a person’s 30s to mid-60s and represents less than 10 percent of all people with Alzheimer’s.
Some cases are caused by an inherited change in one of three genes. For other cases, research shows that other genetic components are involved.
Researchers are working to identify additional genetic risk variants for early-onset Alzheimer’s disease.