The Chicago-based Accreditation Council for Graduate Medical Education announced late Tuesday that its board has approved the rules first outlined in June.
Council CEO Thomas Nasca says the new rules aim to ensure patient safety and a humanistic learning environment for doctors-in-training.
Maximum work shifts for first-year residents only are being cut from 24 hours to 16 hours. The 80-hour-weekly limit remains, but strategic napping is strongly recommended.
Also, medical residents are to tell patients they're being supervised by more experienced physicians.
The rules affect more than 110,000 new doctors being trained at U.S. hospitals. They take effect next July.