No, not in me, I'm still middle-aged, but in my 20 year-old cat.
Last night, I got up about 2am and sat on my bed stroking Ginger for a while. She got down, walked over to the sofa, jumped up onto a fake fur throw and used it as a litter box. She made no attempt to go the litter box room, which isn't far away, and didn't use the floor, she simply seemed to view the sofa as the right place to pee. I was glad I was awake since I was able to clean up right away but then I had to set her up in my dressing room since I had no idea what she would use as a litter box next.
For the past year, her litter box habits have been very messy since she either gets into the box and goes over the side or simply goes on the lino/newpaper around the boxes, but at least she went to the right place.
Is this a sign of senility in a cat? She has seemed more "out of it" lately but I thought that was our heat wave. Has anyone else experienced this in an elderly cat?