While a combination of genes plays a role in determining risk for Alzheimer’s Disease, Apolipoprotein E (APOE) has been established as the strongest genetic determinant of risk for this neurodegenerative disorder. There are three different isoforms or “types” of this gene 

• APOE3 – The most common type  

• APOE2 – The least common type 

• APOE4 – The “risk factor” type 

Each person inherits one copy of the APOE gene from their mother and father respectively. Any combination of the three types is possible. The increase in risk presented by the APOE4 gene can vary based on multiple factors such as sex and ethnicity. However, have one allele or “copy” of the APOE4 gene roughly increases risk of developing Alzheimer’s disease 2- to 4-fold, and having two “copies” of the APOE4 gene increases risk by 8- to 12- fold.  

It is important to note that while genetics plays a role in the risk of developing Alzheimer’s disease, it is only one factor. Other important influences include sex, age, lifestyle, environmental exposures, medical/pharmacological history, etc. Together, these factors show that genetics is just one part of a more complex picture.