I used to work at a place where a number of people worked rotating shifts. They complained about it, but not a single one died from it.
I have had a few 12-hour jetlags, and guess what? After a few days, you readjust and you go on with your life.
This is horse****.
A friend of mine used to work days. Then a month later - nights. Month after that it was swing.
Lather, rinse, repeat. Every 30 days.
It was brutal. By the time he got used to one routine, it was time to change.