Senior dogs do get dementia.
Symptoms of Dog Dementia Senior Dog Care: Older Dogs, Aged Minds: Dealing With Dog Dementia
Lady will be 15 in a couple of months and has some loss of vision, mostly night vision. She has started waking up in the middle of the night and barking because she can't find her water bowl. Last night she was wandering around barking all night, but she'd had a seizure from her blood sugar dropping too low earlier in the evening (she's diabetic) so I thought that was the reason.
I have also noticed that when I talk to her sometimes she looks in the opposite direction. I thought her hearing was going, but who knows?
I have also noticed she startles easily. I haven't noticed any housebreaking issues, though, and her appetite is great.
Maybe she is starting to show signs of dementia, too? I really don't care as long as she is happy. She's never been the sharpest tool in the shed. I call her my little Forrest Gump!