I am certainly neither an MD, DO, or PA-C. As such, my opinion on this matter should be taken with a grain of salt. Although I usually don't sleep on flights, the few times I have been in a cabin with a lie flat (or semi lie flat) bed, I have probably dozed a few times.

I know alcohol dehydrates the body, and that coupled with lower cabin pressure and low humidity in the air may serve to dry the body or more substantially than usual. That said, I usually have a drink or two on a long flight, or where it is free. I've never had any problems, but I'm not 60 either.

I'm going to go ahead and keep trying to sleep on flights. If I die up there due to sleeping, c'est la vie (actually c'est la mort). At least I'll go painlessly. All in all, though, I'm not too worried about it.