Please post the studies you are looking at and I'll read them. Old people get AD. Old people typically have multiple health issues that can cause death.
A good example in prostate cancer. Many men are diagnosed with it. Some die of it. Most die of unrelated diseases including over all old age.
Ad is not a slow a progressing disease as is prostate cancer but 74% in 4 years is unlikely.
News 
Market Data 
Discover 
