Install the ones that make you push them down to get water, they shut off automatically as the "handle" rises.
Take said older person to the doctor. They might have early stages of dimentia, Alzheimer's or any number of other issues. Don't wait, get them evaluated immediately. I went through this with 3 immediate relatives.
I agree with Naomie but you may also try posting notes around to make sure they remember. Also a phone call to touch base.
Have heart if you get a positive diagnosis, there are a lot of medications that can help to slow down the effect of memory robbing disorders.
Thanks so much Kathy I think the notes will work!