1 Health Care Management, Cape Breton University, Sydney, Nova Scotia, Canada.
2 Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
3 Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada caeastwo@ucalgary.ca.
4 Centre for Health Informatics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
5 Cancer Care Alberta, Calgary, Alberta, Canada.
6 Concordia University, Montreal, Quebec, Canada.
7 Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
8 Vice President's Office, University of Calgary, Calgary, Alberta, Canada.
9 Health Shared Services, University of Alberta, Faculty of Medicine and Dentistry, Edmonton, Alberta, Canada.
10 Quality of Care Unit, University Hospital Centre Grenoble Alpes, Grenoble, France.
11 Department of Medicine, McGill University, Montreal, Quebec, Canada.
12 Department of Oncology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.

Background: While the incidence of hospital adverse events appeared to be declining before 2019, the COVID-19 pandemic may have changed its course. This study aimed to evaluate adverse event incidence rates and trends during the pandemic and analyse differences in patient outcomes.

Methods: This retrospective electronic chart review included a random sample of adult patients admitted to four acute care hospitals in Calgary between 2017 and 2022. 18 adverse events and patient information were extracted. We calculated the observed and risk-standardised incidence rates of adverse events. Interrupted time series analysis was employed to determine the impact of COVID-19 on adverse events trends. Outcome differences were evaluated using mixed-effects logistic regression and negative binomial models.

Results: Among 10 673 patient admissions, 2310 adverse events were identified, resulting in an incidence rate of 21.64 (95% CI 20.77 to 22.54) per 100 patient admissions, or 26.85 (95% CI 25.77 to 27.97) per 1000 patient days. After adjusting for patient characteristics, seasonal variations and overall trends, the adverse event incidence rate increased by 14% (incidence rate ratio (IRR) 1.14, 95% CI 1.01 to 1.29) during the COVID-19 pandemic. In multivariable mixed-effects models, adverse events were associated with significantly longer hospital stays (IRR 3.13, 95% CI 2.97 to 3.30), increased odds of 30-day readmission (OR 1.4, 95% CI 1.17 to 1.68) and in-hospital death (OR 1.72, 95% CI 1.43 to 2.08).

Conclusion: The incidence of adverse events was high but relatively stable in acute healthcare settings before the COVID-19 pandemic and increased during the pandemic. Strengthening healthcare resilience and prioritising patient safety initiatives are crucial as we transition into the post-pandemic era.