My MIL is 87 and resides in an Alzheimer's unit nearby. My grandmother is 90, and after 3 strokes has also developed dementia (on top of almost total loss of most physical functions). We have a full time nurse in my grandmother's house, as she kept running away from the nursing home (wheeled herself down to the front door, called a cab, LEFT)....we gave in, and she is much happier. DMIL doesn't really recognize us, or anything else any more. She is quite confused most of the time, but is physically relatively healthy- she just thinks she is about 4 and is waiting for her mommy and daddy to come and get her.
We have learned to laugh alot, especially our 4 kids (ages 11-21). It is hard when the grandmas don't remember your name, what you do, or what is going on in your life- but sometimes the grandmas are VERY funny! DMIL, a very prim and proper lady all her life, now cusses like a sailor, burps and farts- all with glee! She is, in many ways, much happier now. We also liken her attention span to Dug (the dog) in UP!.....and when things get a little tense working with her and trying to get her back to task, all it takes is for someone to say 'Squirrel' and we get fits of giggling (and she giggles right along!) and the tension is broken.
It IS hard! I hate trying to take care of parents and my own children. DH hates dealing with any of it, and leaves most of the stuff to me....and I really wish at times there was someone who could be mom, wife and caretaker to me! But- we live and learn.....nothing I can do to change it, so we might as well grin and bear it. We do a lot of grinning and laughing whenever we can....and we just keep putting one foot in front of the other.
BTW, I told my kids that if I ever get like the grandmas, to go ahead and shoot me or throw me in front of the bus....they offered to do it last week!