Sleeps like the dead. Unless his stomach is growling he doesn't wake up when someone comes in the room or makes normal household noises.
Unless of course, it is about 3:00 am. Then he gets up and wanders the house - yowling. I've read that it's not unusual for elderly cats to wander at night, to seem confused and to vocalize. My crabby ol' man cat qualifies as elderly and he's certainly doing those things. It has been suggested that I open the door and allow him to make the choice. But how can I punish him if he has kitty-Alzheimer's? Sigh-h-h. He's lucky I love him. Oh well, I've played the caretaker role before ... .