Doctors work long shifts because of a combination of historical tradition, training requirements, staffing shortages, and a genuine medical tradeoff: fewer shift changes mean fewer opportunities for critical patient information to get lost. The current U.S. standard allows residents to work up to 24 consecutive hours, with an additional 4 hours for handoff tasks. That 28-hour ceiling exists not because anyone thinks sleep deprivation is good, but because the alternative introduces its own serious risks.
The Handoff Problem
Every time one doctor goes home and another takes over, patient information has to transfer between them. This transition, called a handoff, is where things go wrong. Miscommunication during patient handoffs contributes to an estimated 80% of serious medical errors. That’s not a small margin. It means the most dangerous moment in your hospital stay may not be the procedure itself but the shift change afterward.
This creates a genuine paradox. A tired doctor is not an ideal doctor. But a fresh doctor who doesn’t know your case, who received an incomplete summary from the last shift, carries a different kind of risk. Hospitals that promote schedule continuity, keeping the same physician on a patient’s care longer, have seen better outcomes after discharge. So the system tolerates long shifts partly because splitting them up doesn’t automatically make things safer. It just trades one type of danger for another.
How We Got Here
The culture of extreme physician hours traces back over a century to the earliest surgical residency programs, where trainees were expected to essentially live in the hospital. That tradition went largely unchallenged until March 5, 1984, when an 18-year-old named Libby Zion died at a New York hospital while under the care of overworked, undersupervised residents. The case triggered a grand jury investigation and eventually led New York State to adopt the first formal regulations on resident work hours: an 80-hour workweek cap, 24-hour shift limits, and mandatory supervision requirements.
Those New York rules became the blueprint for national standards. The Accreditation Council for Graduate Medical Education (ACGME) now enforces similar limits across all U.S. residency programs. Residents cannot be scheduled for more than 24 hours of continuous clinical work, must get at least 14 hours off after a 24-hour shift, and should have 8 hours between scheduled work periods. Before these rules, 100-plus-hour weeks were routine and largely unquestioned.
What the Research Actually Shows
You might assume that stricter hour limits would clearly improve patient safety. The evidence is more complicated. A major national trial published in the New England Journal of Medicine compared surgical residency programs using flexible, less-restrictive duty hours against programs following standard ACGME limits. The rate of death or serious complications was virtually identical: 9.1% in the flexible group and 9.0% in the standard group. Resident satisfaction with their education and well-being didn’t differ significantly either.
That doesn’t mean fatigue is harmless. Being awake for 24 hours impairs cognitive function to a degree comparable to a blood alcohol concentration of 0.10%, which is above the legal driving limit in every U.S. state. The National Institute for Occupational Safety and Health has highlighted this comparison directly. Doctors at the end of a long shift are measurably slower, less accurate, and worse at complex decision-making. The reason this doesn’t always show up in patient outcome data is that hospitals build safeguards around it: supervision layers, checklists, team-based care. But the biological cost to the physician is real and cumulative.
Training Demands Compress the Timeline
Residency isn’t just a job. It’s the final phase of medical education, and specialty boards require trainees to hit specific benchmarks within a fixed number of years. General surgery residents, for example, must perform at least 850 major operations over their five-year residency, including 250 by the start of their third year and 200 during their final chief year. These cases don’t schedule themselves neatly into 8-hour windows. Emergencies come in at 2 a.m. Complex surgeries run six or eight hours. If you cap shifts too tightly, residents either take longer to finish training or graduate without enough hands-on experience.
This pressure is unique to medicine. Unlike most professions, a doctor’s competence depends on sheer volume of clinical exposure. You can’t simulate your way to surgical skill. You need hundreds of real cases under real conditions, and the training window is already five to seven years after medical school depending on specialty. Shorter shifts would mean either extending that timeline, which delays careers and worsens the physician shortage, or accepting less-experienced doctors entering practice.
Not Enough Doctors to Go Around
Staffing shortages are a major, often overlooked reason shifts stay long. The Health Resources and Services Administration projects an overall shortage of 141,160 physicians in the U.S. by 2038. That gap spans nearly every specialty: 70,610 primary care doctors, 10,660 anesthesiologists, 7,660 OB-GYNs, 7,270 cardiologists, and shortages in 30 of the 35 specialties modeled. Within primary care alone, the projected shortfall includes roughly 39,000 family medicine physicians and 20,600 internists.
When there aren’t enough doctors, the ones who are available work more. It’s straightforward math. A hospital that can’t recruit a second overnight hospitalist doesn’t close its doors. The one hospitalist covers a longer shift. Rural hospitals and underserved urban centers feel this most acutely, but even well-resourced academic medical centers struggle to staff every rotation adequately. Cutting shift lengths without adding physicians simply creates coverage gaps, and in emergency medicine and critical care, gaps can be fatal.
How the U.S. Compares Globally
The United States is not the global norm. European countries cap physician work at 48 hours per week under the European Working Time Directive, compared to the 60 to 80 hours permitted in North America. A comparison of regulations across 14 high-income countries found this split consistently: European nations prioritize worker protections while North American systems prioritize training volume and continuity.
European doctors do complete their training, and European hospitals function. But the systems are structured differently. Many European countries have more physicians per capita, different models of team-based care, and training timelines that stretch longer to compensate for fewer weekly hours. The U.S. system was built around intensity and compression, and unwinding that without rebuilding the surrounding infrastructure would create new problems faster than it solves old ones.
The Cost to Physicians
None of this means the current system is healthy for doctors. Burnout rates among U.S. physicians have been rising for years, driven in large part by workload. Long shifts compound the problem because their effects don’t stay at work. Chronic sleep deprivation disrupts mood regulation, immune function, and cardiovascular health. Physicians in training often sacrifice relationships, exercise, and basic self-care during the years when those habits matter most. The system asks an extraordinary amount of the people inside it and frames that sacrifice as necessary for patient welfare, even when the evidence on that point is genuinely mixed.
The honest answer to why doctors work such long shifts is that no one has found a way to stop without creating a different set of serious consequences. Shorter shifts mean more handoffs, and handoffs are dangerous. Training requirements demand volume. The physician workforce is shrinking relative to demand. And a century of institutional culture has built hospitals, schedules, and expectations around the assumption that doctors will simply endure. Changing the hours means changing everything around them, and the system has been slow to do that.