In 2011, the Accreditation Council for Graduate Medical Education (ACGME) instituted a 16-h limit on consecutive hours for first-year resident physicians. We sought to examine the effect of these work-hour regulations on physician safety.

All medical students matched to a US residency program from 2002 to 2007 and 2014 to 2017 were invited to participate in prospective cohort studies. Each month participants reported hours of work, extended duration shifts, and adverse safety outcomes, including motor vehicle crashes, percutaneous injuries, and attentional failures. The incidence of each outcome was compared before and after the 2011 ACGME work-hour limit. Hypotheses were tested using generalized linear models adjusted for potential confounders.

Of all first-year resident physicians nationwide, 13% participated in the study, with 80,266 monthly reports completed by 15,276 first-year resident physicians. Following implementation of the 16-h 2011 ACGME work-hour limit, the mean number of extended duration (≥24-h) shifts per month decreased from 3.9 to 0.2. The risk of motor vehicle crash decreased 24% (relative risk [RR] 0.76; 0.67-0.85), percutaneous injury risk decreased more than 40% (relative risk 0.54; 0.48-0.61), and the rate of attentional failures was reduced 18% (incidence rate ratio [IRR] 0.82; 0.78-0.86). Extended duration shifts and prolonged weekly work hours were associated with an increased risk of adverse safety outcomes independent of cohort.

The 2011 ACGME work-hour limit was associated with meaningful improvements in physician safety and health. Surveillance is needed to monitor the ongoing impact of work hours on physician safety, health, and well-being.