OTHER CAUSES of "Alzheimers" before writting off grandma to alzheimers, do these two things first:
1- have her/him tested for Urinary tract infetion (believe it or not weakness, and mental changes occur with UTI's) a course of antibiotics will make an amazing change.
2- rule out PARA-THYROID disease, aka elevated calcium levels in the blood. This will make grandma/grandad act like they have alzhimers, when instead it's a totally reversable illness.
I speak from first hand experience, the diagnosis of Alzhimers is a quick label for family members who display mental changes with fatigue, argumentaiveness, or just stare into space, there is a chance it is one of these two common illnesses, both are 100 curable.