My Mother started doing this in October of last year. She has vascular dementia. I agree that he should be checked for a UTI, especially if there are any other sudden changes. Is he more confused? Can you ask him about it? My Mother was still able to give some answers back then. She was able to say that her leg just didn't go where she told it to.
Good Luck with it. If you are unsure, then have a Doctor take a look at him. We are lucky that our Doctor is very aware of dementia and age related medicine. (He has been in the business about 35 years and has many of the same patients he started with, so he has quite an aged patient group.)
