> why we would want to detect Alzheimer’s

At a personal level, I've been through this with my grandfather.

I want to know. My family wants to know. I want to prepare because there are things I want to do today that I know I won't be able to do in the future.

In many ways, it's just like many terminal cancer diagnoses. You're going to lose that person, but you have some time.

But it is a wildly variated, almost meaningless diagnosis. 3 of my 4 grandparents got Alzheimer's diagnosis as well as my mom and mother-in-law. The variation of progression and symptoms is so wide that it really seems like a catch-all. One grandmother was fine until about 72 and in 2 years forgot who people were and 4 years had lost all executive function and passed away. The other one was diagnosed in her early 80s and lived to be 96 with no major progression, like slightly more repeating, but never forgetting people or not knowing how to talk etc. Similar dichotomy between my mother and mother-in-law but with considerably different presentations of symptoms.

It's a weird disease and IMO not even really a disease it's a bunch of different causes of cognitive impairment under one umbrella but shouldn't be separated out much further to find actual causes and treatments.