Weaver MD, Landrigan CP, Sullivan JP, et al. - Researchers intended to evaluate the impact of these work-hour regulations on physician safety. Between 2002-2007 and 2014-2017, all medical students matched to a United States residency program were invited to participate in prospective cohort studies. They compared the incidence of each outcome before and after the 2011 accreditation council for graduate medical education (ACGME) work-hour limit. Conditions were examined using generalized linear models adjusted for potential confounders. In physician safety and health, the 2011 ACGME work-hour limit was correlated with meaningful enhancements. Surveillance is required to observe the ongoing effect of work hours on physician safety, health, and well-being.