Alzheimer's is a strange disease yet to yield to modern medicine. Cancer can be pretty devastating in its own way but Alzheimer's exacts quite a different toll by stripping a person of his or her personality.
It's quite odd and perhaps impossible really to imagine what it would feel like to lose memory slowly and inexorably to a point where one no longer recognizes one's closest family members or friends.
I do not even know how to analyze this disease ... where does this fit in in the story and context of human evolution for example. And why is it that this scourge is only rearing its ugly head now and not before in our civilization's history. Well, that's perhaps simple. The average human life span is increasing thanks to modern medicine and that unfortunately creates other demons that were so far latent — from cancer to heart disease to Alzheimer's.
Well, humanity has seen and come to terms with other challenges and I hope we'll deal with this challenge effectively as well.
Here's one perspective ...