have you ever all of a sudden forced to do graveyard shift?

Night shift is hard for most people, but not all. I worked midnight to 8 for many years, and I had no problems with it. I do think some people are natural 'night owls', meaning that their bodies sleep clock seems to adjust to nights better. For some, it's a matter of readjustment to sleeping in the daytime that's the problem. Daytime noises interfere with good sleep, as well as people who think that you can sleep whenever you choose during the day. It's important to have and keep a regular sleep pattern! The worst job I had was at a hospital where every two weeks you'd switch shifts: two weeks of days, then two of afternoon shift, and then finally two weeks of midnights. That was really rough! Your body clock and rhythms never got a chance to fully adjust, and when you had days off they'd be spent sleeping and catching up on sleep. That's when I finally went to permanent graveyard shift, and it was much easier after the adjustment. Still, I feel sorry for your uncle, it's hard to switch like that!