The effect of the COVID-19 pandemic on hospital admissions and outpatient visits in Ontario, Canada.

Introduction: The wave-over-wave effect of the COVID-19 pandemic on hospital visits for non-COVID-19-related diagnoses in Ontario, Canada remains unknown.

Methods: We compared the rates of acute care hospitalizations (Discharge Abstract Database), emergency department (ED) visits, and day surgery visits (National Ambulatory Care Reporting System) during the first five "waves" of Ontario's COVID-19 pandemic with prepandemic rates (since January 1, 2017) across a spectrum of diagnostic classifications.

Results: Patients admitted in the COVID-19 era were less likely to reside in long-term-care facilities (OR 0.68 [0.67-0.69]), more likely to reside in supportive housing (OR 1.66 [1.63-1.68]), arrive by ambulance (OR 1.20 [1.20-1.21]) or be admitted urgently (OR 1.10 [1.09-1.11]). Since the start of the COVID-19 pandemic (February 26, 2020), there were an estimated 124,987 fewer emergency admissions than expected based on prepandemic seasonal trends, representing reductions from baseline of 14% during Wave 1, 10.1% in Wave 2, 4.6% in Wave 3, 2.4% in Wave 4, and 10% in Wave 5. There were 27,616 fewer medical admissions to acute care, 82,193 fewer surgical admissions, 2,018,816 fewer ED visits, and 667,919 fewer day-surgery visits than expected. Volumes declined below expected rates for most diagnosis groups, with emergency admissions and ED visits associated with respiratory disorders exhibiting the greatest reduction; mental health and addictions was a notable exception, where admissions to acute care following Wave 2 increased above prepandemic levels.

Conclusions: Hospital visits across all diagnostic categories and visit types were reduced at the onset of the COVID-19 pandemic in Ontario, followed by varying degrees of recovery.