I'm guessing this was awhile ago because I was a co-author on what is now called "the sleep study" in short hand.
https://pubmed.ncbi.nlm.nih.gov/15509817/ How residents were assigned shifts changed dramatically after this study was published. It's one of my more cited publications. (Yeah, yeah, "mine" is relative. It was a research team, not an individual effort.)
Unintended consequences? Once residents were required to be given more time off between shifts, we found continuity of care matters almost as much as sleep. Too many changes in a patient's care team can also lead to significantly more medical errors. Reducing medical errors is a game of whack-a-mole sometimes.