Ah. I did not know that.

When I was growing up, there was a 24/7 coal-mine near-by and everyone was on two-week rotations for their shift. Which (naturally) sucked. Eternal jet-lag. I thought that letting people simple pick their preferred, and stick to it would solve the suckiness...

I once visited a Ford factory in England where the manager told us the night shift workers were paid very well (more than London front office in their first two years at Goldman Sachs) because their life expectancy might be shortened by as much as 20 years.