Sleep studies - now that really gets my blood pressure up!
Almost every single study that I have ever seen is based on shift workers. What a laugh. Shift workers such as truckers, cops and nurses work regular shifts which they often are advised of months in advance. They then work a night shift or a day shift for a defined period before switching again with a bunch of time off in between to allow them to adjust. Boy, the stress that must cause!
I do not know of a single study that studies the crazy disruptive life of aircrew where day shift and night shift are meaningless terms depending where on the planet you find yourself. Any pilot knows what bodyclock time means and we become obsessed with sleep routines and sleep disruption. But few outsiders, researchers included, have ever come close to understanding this disruption and what it does to the body and mind.
A NASA study did some work on this years ago but the research has been largely ignored by the dumbos who write crew rosters, especially in regard to the idiotic principle of 24 hour layovers. Pretty much the Cathay standard!
Anyone at a scientific institute willing to step up to the plate? I doubt it..