Discovered in 1993, APOE4 exists in about 20% of the population and increases the risk of developing Alzheimer’s disease by up to twelve times. It increases levels of amyloid in the brain, which is one of the prime suspects for the cause of Alzheimer’s. A new study, conducted by David Holtzman and his team at Washington University School of Medicine in St. Louis, revealed that APOE4 and its affect on the tau protein might be critical in understanding how the Alzheimer’s disease develops. “Once tau accumulates, the brain degenerates. What we found was that when APOE4 is there, it amplifies the toxic function of tau, which means that if we can reduce APOE4 levels we may be able to stop the disease process.” Said Holtzman.