Longitudinal Changes in COVID-19 Associated In-Hospital Mortality

Objective: As the COVID-19 pandemic has evolved, a key question for health care systems is whether in-hospital mortality has changed over time and if so, what factors contributed to these changes. Our goal was to leverage real-world data spanning two COVID-19 surges over the first year of the pandemic to determine the temporal trend of in-hospital mortality. Design: This was an observational, retrospective study based on real-world data for patients admitted with COVID-19. Generalized additive models (GAM) were used to evaluate the association of covariates with the composite outcome over time. Setting and Population: We identified a retrospective cohort of all patients who were hospitalized within the Yale New Haven Health (YNHH) system with an admission diagnosis of COVID-19 between March 1, 2020 and February 28, 2021. Main outcome: The primary outcome for the study was a composite endpoint of in-hospital mortality, defined as death during the index hospitalization or discharge to hospice. Results: Among 6,477 discharges over the study period, the mean age was 66.2 years (SD=17.6), 52.5% (n=3,401) were male and the overall composite mortality was 14.2% (n=920). Composite in-hospital mortality was significantly associated with increased age, comorbidity index, respiratory rate, and heart rate; decreased systolic blood pressure; male sex; and admission from a long-term care facility (LTCF). The significant temporal decrease in mortality that was observed for patients admitted from a location other than a LTCF was not seen in those admitted from a LTCF. Conclusions: We found that the adjusted in-hospital mortality rate declined over the first year of the pandemic, despite a second surge in COVID-19-related hospitalizations. Importantly, the decrease in mortality appeared to be driven by declines in risk in those not admitted from a LTCF. The observed decrease in mortality over time suggests that improved outcomes may be due to progressive, incremental learning and continuous evolution in hospital practice and policy over the course of the pandemic.