Excessive tissue usage; how do we stop it?

Ha! Tissues!! Ugh... my MIL is continuously with a tissue or paper towel square. They are everywhere... She folds them; wipes her forehead when hot; sticks them in books; and tears them into smaller pieces, etc.

My MIL had that. I hand her a towel or facecloth and she is now focused on those.

Buy the stuff at the Dollar Store.
If it is Toilet Paper limit the rolls to 1 and get the single ply stuff.

If you can redirect to another type of paper try a news paper or magazines.

Not a whole lot you can do if this has become a focus. To take the paper away will increase anxiety and may turn the focus to other more destructive things.

Getting to anxiety...is this person on a medication for anxiety? It might help.
But with dementia there is often a "thing" that becomes a focus. Tearing paper, spitting, humming, moaning, pacing, counting just to mention a few things.
As long as the "thing" that your loved one has going is not harmful I would learn to deal with it. (my Husband made noises, sometimes so loud I had to go outdoors to talk on the phone....crazy as it sounds I miss it now)