Hi MNL. There is just so much we're still learning about Alzheimer's. I'm so glad your Mom has you to be helpful with your Great Grandmother...and concerned about her.
When my Mom was first diagnosed...(9 years ago)...I tried to read everything I could find about this disease. It is one of several different types of dementia...but seems to be the one we hear the most about. I was told there are more than 60 different kinds of dementia!
One of the first things I found out is that there is "familial" Alzheimer's...that means it is genetic in some cases. Several articles suggested that if a parent has it, it is more likely to show up in larger families...and the older siblings are more prone than the younger ones. I would think this suggests that as more children are born into the family, there are parts of the brain of the oldest kids that are not stimulated as much???
There is also proof that a very hard bump to the head can bring on this disease as a person ages. (Of course THIS was my biggest worry when I fell forward on the icy cement sidewalk a few years ago! Two big black eyes...broken nose...broken teeth...broken arm...ARGH!!) ....(Have to admit, I had a pretty good time telling people it was a skateboarding accident!)
When my own 5 siblings and I were first aware of the changes in our Mother, we all started noticing our OWN challenges...so much that some of us asked our doctors about it. Lots of "stuff" going on in our lives brought on extra stress...and we were told we WERE acting "normal"! (Yep, you're right...there are six of us...and I'm up near the top...another thing to worry about!)
I've found worrying about something I don't know for SURE just makes life worse! So much effort is going into Alzheimer's research! We have to just look for miracles around the corner. Bless you for being concerned...and stay around here a while...you'll find some great answers and ideas that will help both you and your Mom with your Great Grandma's care. Hope I helped a little.......Pam