COVID-19 and Emergency Department Visits: An Interrupted Time Series Analysis of Ontario and Alberta, Canada.

introductionEmergency department (ED) use declined drastically in the early stages of the COVID-19 pandemic. While the immediate effects of the pandemic are well-characterized, the longer term recovery patterns in ED use and regional differences in these patterns remain poorly understood. In Canada, provincial differences in public health policy responses may have influenced ED utilization during the pandemic, where Ontario implemented more restrictive and prolonged public health measures compared to Alberta, making Canada an ideal place to examine how regional variation in policy impacted ED use. Our objective in this study was to evaluate the impact of the pandemic on patterns of ED use in Ontario and Alberta and explore the potential differences in these patterns.

methodsOur primary outcome measure was the monthly count of all-cause ED visits in Ontario and Alberta. We obtained 146 entries of monthly counts of all-cause ED visits from April 2011-May 2023 (73,690,650 ED visits in Ontario and 27,132,554 in Alberta) from 206 EDs in Ontario and 113 EDs in Alberta and conducted a retrospective, interrupted time series analysis. Negative binomial regression models were used to estimate trends before and after the pandemic onset in March 2020 in each province and to test cross-provincial differences.

resultsOntario and Alberta experienced immediate and statistically significant reductions in monthly ED visits following the pandemic onset by 26.9% and 27.7%, respectively. Pandemic trend showed gradual recovery in both provinces. However, by May 2023 ED volumes in Ontario remained 5.5% below the expected volume, while Alberta's exceeded it by 2.5%. Relative risk (RR) estimates confirmed significant declines in ED volumes during the pandemic in Ontario (RR = 0.64) and in Alberta (0.72). No statistically significant cross-provincial differences were observed in the immediate reduction and the speed of recovery of the ED utilization during the pandemic.

conclusionOntario experienced a decline in ED visits followed by a steady recovery that did not reach pre-pandemic projections, raising concern for missed care. Alberta also experienced an immediate decline but demonstrated a slightly faster recovery, eventually surpassing pre-pandemic projections. Model parameters characterizing the ED use patterns in each province were not significantly different, despite differences in provincial public health policies introduced in the pandemic's early phases. Thus, broader national or individual level factors may have contributed more substantially to healthcare utilization than provincial policies during the COVID-19 pandemic.