Any suggestions for a way to lock all exterior doors so mom can't access to prevent her from exiting the house in the middle of the night?

First off, stop sleeping on the couch, you aren't resting and you are number one, not her. I do think the dead bolt in the reverse might work, but it isn't really safe for you since to get out fast, you would have to find a key. I have a night time walker too, so I do know it gets better as their mind deteriorates, she will get to where you could put a lock up high and she will not be able to reason out to get a chair. Bottom line here, is if she gets out and something does happen, please don't guilt yourself over it, there is just so much that is humanly possible to do when they are determined. Mine is a night time eater, she gets frozen waffles out and ice cream which I find on the counter the next morning, boxes of open cereal all over the place. I need a good lock for cabinets and refrigerator, so far none of the baby type ones have worked. It isn't that she figures them out, as frail as she seems, she can yank the plastic thingies right off. So far, mine just walks around the house at night and hasn't tried to get out. I fenced the back yard so that if she did
go out that way, she couldn't get out of the yard. I am also lucky that I live in town and the neighbors all know she is batty and keep an eye out for her. If your mom isn't afraid of bears, how about prowlers/buglers? Tell her there has been a prowler in the neighborhood and she has to stay inside or he will "get" her.

Marty, if your Mom sleeps all day and is up all night, try to see if you could reverse that pattern. I realize it won't be easy, but that might stop her feeling the need to go out at night to walk.

Are there any easy chores she could do to help you, chores must be done during day night. If she starts to doze off, carefully awaken her and just walk around the house. Would it be possible for you to go outside mid-morning and take her for a walk, then again mid-afternoon. After all that, Mom might sleep through the night. It's worth trying.

I don't know if this will help or work w/your mom, but I have heard that if you place a big, black mat in front of the door, she will perceive it as a hole and not try to walk on/over it.

When we put our pool in, we had to have pool alarms. It didn't matter that we already had burglar alarms. Anyway, they were $100 a piece, but they go up on the door and they would wake the dead. (They are awful.) We took them down, as soon as we passed inspection. But, they would let you know that she opened the door.

Could you get an coded lock, like people have on the exterior side of their doors and turn it around? It just takes 4 numbers to open it, but she won't know them. On other doors, I would dead bolt them with a key. Everyone needs a key, but her.

Oh yes, I forgot to ask, have you tried drugs? A neighbor of mine who also has a "wanderer" at night swears by tylenol PM, and Xanax is my friend when mine is especially active at night.

There are many ways to lock the doors but I would be very concerned about fire, ambulance access and so forth. At 92 is she alone most of the time?

Just did some reading and found that they suggest hanging a curtain over the door or otherwise disguise the door, possibly painting it the same color as the wall. Also, suggest using a sliding bolt door lock that is installed close to the floor.

Also, something you may already be doing. Have a real good current photo with vital statistics in case you need it. Don't wait to call 911 if she gets out.

Something else I thought of, and I don't know if this would be within the realm of possibility. Have a screened porch with a locked door that she could sit in.

Once again thanks for the input. This site has been a great help. Long time reader, first time talking. We have the doors alarmed and it is loud. What I am trying to do is have a situation where the doors are locked and she will realize that she can't walk at night. If the doors are unlocked, she will continue trying to leave the house which creates a horrible situation for me. eg I will have to physically restrain her, be awakened all night and never feel at ease that she won't somehow wind up on the streets in the middle of the night. If the doors are locked it will be an initial confrontation but the reality will be she can't leave the house at night. Maybe that will encourage her to be up during the day (wishful thinking). I just have to figure a way to do it safely.

Just put one of the old fashion chain locks on the top of the door. We did that and also on the basement door we put a pushpad combination lock, comes in handy for the grandkids too. We cut her door in half, dutch door, and put a lock on the outside hallway side. You know, like Mr Ed had? Worked like a charm.(ps) I also hung bells from yarn on her bed and from ceiling so I heard her at least.