Doctors in training sometimes say there's a good reason they're called residents: they live at the hospital. Many work 30 hours at a stretch with no sleep. That can be a prescription for costly — and deadly — mistakes. A 2004 study of intensive-care units found that residents working a 30-hour shift made 36% more serious mistakes than those working a 15-hour one. For this reason, the Institute of Medicine has proposed new guidelines limiting shifts to 16 continuous hours if no rest will be granted and mandating 5-hour naps for longer shifts. But not everyone agrees with the plan. Some residents believe the grind helps them learn, and they question whether they'd get any sleep during a mandatory break, having patients' cases fresh in their minds and knowing that they'd have to go back to work. An alternative would be to shorten residents' workweeks (not their shifts) and lengthen the term of residency.