Inpatient hospital outcomes are the results of general trends in the characteristics of the concerned population, the evolution of the healthcare offer, the various management efforts to improve efficiency and effectiveness, as well as the hazard of unexpected health crises. Within the DRG-based French financing system, a 12-year longitudinal analysis (2012-2023) was performed at the Georges Pompidou University Hospital (HEGP) in Paris to provide and assess the simultaneous evolution of various inputs, outputs, and outcomes. Methods Explanatory variables extracted from the HEGP information system include the time of admission, patients' age, sex, the nature of stay, several morbidity conditions, the Elixhauser severity index (ESI), and two indicators of the physician and nursing staff load. Selected outputs and outcome measures include the number and length of stays (LOS), the inpatient stay mortality, the readmission (RA) rate, and 6 potentially avoidable complications (PACs). Relationships between explanatory conditions and outcomes are analyzed for the pre-COVID (2012-2019), per-COVID (2020-2023), and overall COVID (2012-2023) periods to contrast the longterm changes and the specific COVID-19 associated changes.

The pre-COVID period is characterized by a regular and significant increase in the total number of stays, day stays, the mean patients' age, the ESI, the RA rate, and a decrease in the intensive and surgical care percentages, the male gender ratio, the mean LOS, and the inpatient stay mortality. During ≥ 48 hours stays and the pre-COVID period, significant PACs increases associated with the nursing and physician staff loads concern pulmonary embolisms, pressure ulcers, sepsis, and prosthesis infections and wound dehiscence in the subgroup of surgical stays. After adjustment for stay and patients' characteristics, COVID inpatient stays are associated with higher rates of diabetes, pulmonary embolisms, sepsis, respiratory failure, renal failure, sepsis, inpatient stay mortality than non-COVID patients' stays but not with hypertension, obesity, or deep vein thrombosis.

This 12-year longitudinal analysis of patients at HEGP hospital provides valuable insights into input, output, and outcome indicators. When adjusting for confounding factors, the increasing activity associated with increased nurse and physician workload and various PACs increases needs to be related to the search for increased financial efficiency. The significance of COVID-19 several comorbidities depends on the selected stay and patients' characteristics adjustments. Results highlight the need for continued efforts to provide the best balance between efficiency-and effectiveness-oriented health strategies.