From his medical column at Pajamas Media:
A study in a recent edition of the Journal of the American Medical Association attempted to demonstrate the effects of a protected sleep period on interns and residents when they were obliged to work shifts longer than 30 hours…Unsurprisingly, they got more sleep (about an hour more per night) when they were given such a protected period rather than when they were not. They were more alert, both subjectively and objectively, when they had slept 3 hours a night instead of only 2.