The word resident retains a very literal trace of the origins of this form of medical training. In the late 19th and early 20th centuries, young physicians specializing in a medical field lived, or “resided,” inside the hospital or in nearby accommodations.
This is also where terms such as house staff originated. These were the hospital’s “in-house” physicians, available to follow patients from admission through discharge. Although residents no longer typically live in hospitals, the term recalls a training model built around an almost constant hospital presence.
Discussing their working hours therefore means reconsidering how much of that tradition remains useful and how much needs to adapt to modern medicine.
On-call shifts are an essential part of medical residency. During these shifts, future specialists handle emergencies, make clinical decisions, and develop skills that are difficult to acquire in a classroom. However, working extended hours with little recovery time can also lead to fatigue, impair concentration, and make learning more difficult.
Striking a balance between clinical training and resident well-being is an international challenge. In the United States, resident physicians are limited to 80 work hours per week; in the European Union, the limit is 48 hours, and in Japan, it is 60.
In Mexico, a regulation established under the Mexican Official Standard (NOM) published in 2022 states that residents must not work more than two 24-hour on-call shifts per week, must have at least three days between shifts, and must not exceed 80 work hours per week.
Does reducing the frequency of on-call shifts actually improve learning? To explore this question, researchers conducted a study titled Impact of 24-hour call frequency (every 3rd vs every 4th day) on academic performance of general surgery residents, reporting on the General Surgery Residency Program at Tecnológico de Monterrey in The American Journal of Surgery.
Comparing Two On-Call Schedules
In March 2020, the residency program changed its on-call schedule. Previously, residents worked a 24-hour shift every third day, a system known as ABC, equivalent to approximately 92 work hours per week. After the change, shifts were scheduled every fourth day under the ABCD system, bringing the estimated workload down to 84–85 hours per week and providing longer recovery periods.
The researchers conducted a retrospective study of 63 residents who completed the five-year specialty program over a 10-year period. Of these, 33 trained under the ABC schedule and 30 under the ABCD schedule.
In total, the researchers analyzed 1,140 grades across two areas: the academic curriculum, which assesses theoretical knowledge through examinations, and clinical performance, which evaluates clinical reasoning, surgical skills, and patient care.
To account for factors beyond the on-call schedule, the statistical analysis adjusted for age, sex, each resident’s year of training, course type, and the period of the COVID-19 pandemic. It also accounted for the fact that each resident contributed multiple grades throughout their training.
Fewer On-Call Shifts, Better Academic Results
Residents under the ABCD schedule earned higher academic grades, with a median score of 88.57 compared with 85.50 among those following the ABC schedule.
Clinical performance scores showed a slightly different pattern. Residents under the ABC schedule had a median score of 93, compared with 91.57 for those under ABCD. However, this difference was not statistically significant. There was also no significant difference in the unadjusted overall average.
The main difference emerged when researchers analyzed all grades throughout residency and adjusted the results for the other variables. In this model, the ABCD schedule was associated with an average increase of 3.93 points compared with ABC. Both groups also showed improvement as they progressed through the program, as would be expected during a training process.
These findings suggest that more time between on-call shifts may support learning. One possible explanation is that residents have more opportunities to sleep, recover, and study. However, the study did not directly measure sleep, fatigue, stress, or time spent studying, so these potential mechanisms require further investigation.
The Need for Research in Medical Education
One of the main arguments against reducing work hours is that it could limit residents’ exposure to patients and surgical procedures. This study did not include the number of operations performed or directly assess surgical competence. Therefore, the researchers cannot determine whether the change in on-call schedules affected hands-on clinical experience.
The study also has limitations: it was a retrospective analysis conducted at a single institution. The timing of the schedule change coincided with the COVID-19 pandemic, making it difficult to completely separate the effects of these two factors, although the analysis accounted for the pandemic period. The findings show an association, but they do not prove that the ABCD schedule alone caused the improvement in academic performance.
Despite these limitations, the study provides evidence drawn from 10 years of residency training and comprehensive academic records. It also raises an important point: better-organized on-call schedules do not necessarily undermine learning and may actually strengthen it.
Research in medical and surgical education helps turn experiences and perceptions into measurable evidence. Regulations governing residency programs should not be based solely on tradition or the assumption that working longer hours always means learning more.
Academic performance, surgical experience, clinical competencies, resident well-being, and patient safety must all be evaluated together.
With measurable evidence, institutions and health authorities can make informed adjustments to work hours, on-call frequency, and recovery periods. In this way, each reform can become an opportunity to build safer, more humane, and more effective residency programs without compromising the quality of medical training.
Key refernce
Mauricio Gonzalez-Urquijo, Alfredo Verastegui, Diego Maldonado, et al. Impact of 24-hour call frequency (every 3rd vs every 4th day) on academic performance of general surgery residents, The American Journal of Surgery, Volume 262, 2026,117211, ISSN 0002-9610
Author
Mauricio González-Urquijo. Professor and researcher at Tecnológico de Monterrey’s School of Medicine and Health Sciences and a Level I member of Mexico’s National System of Researchers (SNII). He is a specialist in Angiology and Vascular Surgery, trained at the Pontifical Catholic University of Chile, and completed advanced training in endovascular aortic surgery at McGill University in Montreal, Canada. He holds a PhD in Clinical Sciences and conducts research in vascular surgery and medical education.
