If a person has dementia, will moving their personal belongings increase confusion?

Yes, they should, unless items are being moved for reasons of safety. Your MIL's safety, that is. Not the items' safety.

It would confuse ME if someone cleaning moved things around. I have come in after cleaning people have done the bathroom and everything is moved and I have a heck of a time putting things back just the way I want them. When papers get moved by me or someone else I have a difficult time readjusting my mind as to where things are.
So...short and simple if possible leave all personal items where they belong and where the person is more apt to be able to retrieve them. Hard enough to not get frustrated when you misplace something let alone someone moving things.
If things have to be removed that is one thing but other items that pose no danger should be left alone.

ROUTINE - ROUTINE - ROUTINE is the rule with the dementia care environment and schedule - NO CHANGE. All items should be left in place as she knew before she became impaired. Also the day's routine should stay the same, meals at the same time, activity, no rush to get ready for medical appointments, little travel, try to keep everything the same for the highest level of functioning.

Why does the person who does the cleaning rearrange items? Can this person understand and respect a request to leave things as they are? Move them to clean and then immediately put them back where they were. What is hard about that?

If this relative who is doing the cleaning has some problem understanding this simple concept, then I hope you can hire a cleaning person who will do as instructed.

Sometimes change is inevitable. I had to completely rearrange our bedroom when a hospital bed was brought in for my husband. By moving objects we made it possible for me to continue to sleep in the same room with him. That was a higher priority than keeping all the objects in place. Plus he needed a lot of new objects in that room.

Sometimes objects need to be removed because they now pose a risk.

We can't always keep everything exactly the same, but things should only be moved for well thought-out reasons.

Yes, absolutely. Say the elder has low vision called macular degeneration even a bottle of medication moved an inch or two away from its usual spot will cause severe confusion! They won't be able to function.

Yes, it is upsetting AND confusing, and highly distressing. The things should be wiped for dust with a baby wipie, the table cleaned, and the things put back the way the were exactly. That family member is trying to exert control and when it comes to things, unless there is a fire or health hazard, the person with dementia should be allowed to keep her things the way he/she put them.

Well, obviously it is confusing and upsetting your MIL so it should be kept to a minimum. Change is inevitable, though, and you have to clean. I would try to keep her stuff in the places she expects to find them. Depends too, on whose house it is. Relative may feel justified in what she's doing if it's her house.

I took care of my mom for 6/7 years while she suffered with dementia. Each stage brought new challenges. I made it a practice to keep things generally in the same order for her to find them and function better in a predictable environment. Cleanliness and safety are certainly a consideration but I know I, personally, like my own belongings generally where I put them. Nothing remains the same in the dementia world but they need some sense of order for them. I tried labelling things but after a while they ignored the signs. I say, within reason, keep things in places that make sense to her.

My general rule of thumb is that things should be placed and/or done the way my grandmother wants them UNLESS it is something that would adversely affect her health or others.

My Mom's Dr was actually able to notice that Mom had dementia because of her confusion in the 'new environment' of his office. He took me aside and explained the importance of consistent surroundings. He said that not only does it help her to function at her 'current' best' but it also gives her greater ease and confidence as the familiar environment provides visual clues and cues that she is in a safe and known place.