Image: DNA sketch

Science has revealed three specific genes directly associated with developing AD; amyloid precursor protein (APP) on chromosome 21, presenilin 1 gene on chromosome 14, and presenilin 2 gene on chromosome 1.23 Individuals who inherit a mutation in APP or presenilin 1 gene are virtually guaranteed to develop AD. Individuals with trisomy 21 (Down Syndrome), who live beyond the age of 40, frequently develop AD. Individuals who inherit a mutation in presenilin 2 have a 95% chance of developing the disease. Individuals with these genetic mutations often develop early onset AD.23

Another gene that increases the risk for developing AD is the apolipoprotein E (APOE)‑e4 gene.9 Individuals who inherit one APOE‑e4 gene have three times risk of developing AD. Individuals who inherit two APOE‑e4 genes have 8 to 12 times risk of developing AD.24 It is estimated 40 to 65% of people diagnosed with AD have at least one copy of the APOE‑e4 gene.25-27