My father is 95 and has advanced stage dementia. Sometimes he sleeps for two days, other times he is up all night rearranging things. A new development is that he takes off all his clothes in bed and removes the sheets from the bed. He fights me when I try to get him cleaned up. Not even the caregivers can touch him sometimes. I am at my wits end. We have a new caregiver coming tomorrow. I hope that she will be able to handle him.
We haven't had the clothes issue yet but she hates to have her clothes off. It's a terrible chore in the morning to get her undressed to be cleaned then undressed at night to have her clothes changed again. She gets very upset and fights me at night to the point of where I end up distracting her in some manner just to get the job done. Sometimes that works, sometimes it doesn't. it's just part of the disease I think. I have given my grandma a little basket full of trinkets. She loves it. There are things to sort and lay out on her table, little tiny books to look at the pictures in, a pencil and paper for her to think she's at school and taking notes, a few hair things in there for her to mess with, and various little toys for her to organize. She takes these things out of the basket, does her little thing with them, then puts them back in. It's a break from the routine. I have sometimes the great grand-children of her look at photo albums with her to distract her from her day. I have found though routine is huge and helpful when dealing with her. Perhaps as suggested above, a routine will help you out as well.
Discuss his new behaviors with his doctor, especially any behaviors put him or family members at risk. Who is up with him, for example, when he is up all night? Try to resolve any safety issues and to be patient and reassuring with behavior that is just strange but not hurtful.
There is adoptive clothing available that fastens in the back and is difficult for the wearer to remove. This helps prevent nursing home patients from wandering the halls naked. In his own home you may have a lesser need for dad to keep his clothes on all night, unless he gets excessively cold or it is very unsettling to the rest of the household. But if need be, take other member's advice about trying clothes he might enjoy wearing more, or as a last resort clothes he cannot take off.
Dementia involves damage in the brain. Our brains control all aspects of our bodies, and damage in the brain can impact pretty much anything. That includes our sensations of temperature, how things feel against our skin, our internal clocks that tell us when and how long to sleep, how we perceive pain, and the list goes on and on. Yes, your father's unusual behavior is caused by his dementia.