To assess the clinical patient exposure of residents over 20 years following the statutory introduction of a maximum working week of 50 hours in 2005.

Retrospective analysis of longitudinal cohorts of residents who worked on the medical wards between 2001 and 2023 or the emergency department (ED) between 2007 and 2023.

Cantonal Hospital of Baden, a representative, large Swiss teaching hospital affiliated with the University Hospital of Zurich.

Residents in training working on the internal medical wards and the ED.

Annual Patient Exposure (APEX) of residents, which is the ratio of annual patients to residents and describes the annual number of patients treated per resident.

We assessed time trends of the APEX in annual cohorts of residents in training on the internal medicine wards (2001–2023) and the ED (2007–2023). We analysed the annual case severity (Case Mix Index and Emergency Severity Index (ESI)), patient age and the length of hospital stay (LOS) as a proxy for changes in the patient population over time and the readmission rate as a quality indicator.

The medical ward APEX even increased by 5.2% from 325 patients to 342, despite the workhour restrictions and the increased number of residents (+90%). Inpatients increased by 100% (from 3250 to 6507). Their LOS decreased from 12.4 to 7.5 days and the readmission rate decreased from 4.2% to 3.3%.

In the ED, the APEX decreased by 21% (from 3261 to 2576), but the case complexity (ESI) and the LOS increased substantially.

In contrast to the general belief, work hour restrictions and the increased number of residents did not reduce the inpatient APEX over 20 years. The reduced APEX in the ED may be compensated by the increase in case complexity and the LOS.