Incidence and Prevalence
Alzheimer’s disease (AD) is always devastating when it strikes, but when it occurs in people less than 60 years old the devastation is brought into even sharper focus. This is because of the loss of work productivity and tremendous emotional and financial strain placed on other working family members and young children. Fortunately, young-onset AD represents about 1% of all people with the disease. Nevertheless, studying these individuals led to important discoveries about how AD occurs. We think there is much more to be learned by studying this often neglected group of AD sufferers.
Prior Genetic Research
Efforts to find the genetic basis of AD began in the 1980’s and focused on families that transmitted young-onset AD from one generation to the next. Even among suffers of young-onset AD, families that transmit the disease from generation to generation are very rare (probably about 10% of young-onset AD). Genetic studies with these families led to the discovery of AD-causing mutations in three genes: amyloid precursor protein, presenilin 1, and presenilin 2. It is hard to overstate the importance of finding these mutations on AD research. These mutations lent vital support to one view of how AD occurs, and these mutations are the basis of nearly every model system of AD from mice to cell models.
New genetic causes
What about the 90% of individuals without a family history? There is good evidence for alternative genetic causes of young-onset AD that has not been previously explored. Specifically, Wingo and colleagues found evidence that young-onset AD is likely inherited as a recessive illness in some instances. In other words, young-onset AD can occur when someone inherits two mutations in the same gene. This is a new hypothesis, and one they are vigorously pursuing to identify new genetic causes of the disease at the Emory University ADRC.