Project Summary: The ongoing COVID-19 pandemic has had a dramatic impact on emergency care. Reports from around the country suggest that ED visits for non-COVID related conditions such as acute myocardial infarction and stroke have plummeted by 30-50%, and anecdotal data suggests that overall visit volume for non-COVID related conditions has also decreased. Conditional on presenting to the ED, the pandemic also is changing how ED providers approach the decision to admit a patient to the hospital. There may be a number of motivations involved in this decision-making, some related to system-level factors such as capacity constraints and some related to changes in assessments of the risks and benefits of hospitalization for individual patients. The emergency department (ED) is the primary source for hospital admissions in the US. Over 70% of hospital admissions among Medicare patients originate from the ED at an extraordinary cost to Medicare.1 Rates of hospital admission from the ED vary widely across regions, hospitals, and even across physicians within hospitals. A critical need exists to determine the extent to which factors related to the COVID-19 pandemic have altered provider decision-making in the ED and whether these decisions are associated with greater harm for patients. Lessons learned from these analyses will be vital to guiding ED providers in approaching the decision to admit during future phases of this pandemic as well as under similar circumstances that might arise. Moreover, there is a possibility that for some non-COVID related conditions hospitalization rates pre-COVID-19 were too high (low-value admissions), and that admission rates are now more optimal. Thus, there could be longer term improvements in the efficiency of the health care delivery system that can be gained by optimizing the use of inpatient hospital care, its most expensive component. The proposed study will utilize data on Medicare beneficiaries and their care providers to accomplish three key aims. Using nationally representative data from the Medicare program aim 1 will examine the extent to which the COVID-19 pandemic has impacted ED visit rates for specific diagnoses in parts of the country more and less effected by the pandemic. The second aim will then examine how admission decisions from the ED have been impacted. Finally, aim 3 will examine the impact of changes in admission on patient outcomes including 30-day mortality and ED revisits. The second and third aims will use rigorous quasi-experimental methods to compare changes in the outcomes of interest in areas of the country more and less impacted by the COVID-19 pandemic. Our central hypotheses are that the rate of admission will be decreased (across a broad array of non-COVID-19 related conditions) during the time of the pandemic, that greater decreases in admission will be seen for areas that were particularly impacted by COVID-19, and that these decreases in admission rates will be associated with worse clinical outcomes.

Project Narrative: This project seeks to determine whether practice patterns in the ED (primarily the decision to admit) are being impacted by the COVID-19 pandemic, the extent to which these changes depend on the local impact of COVID-19, and whether changes in patterns of admission are associated with worse clinical outcomes for non- COVID-19 related conditions. In addition to providing guidance during the pandemic, our results will help answer whether longer term improvements in the efficiency of the health care delivery system can be gained by optimizing the use of inpatient hospital care, its most expensive component.