Clinical Characteristics, Risk Factors, and Outcomes Among a Large Midwestern U.S. Cohort of Patients Hospitalized With COVID-19 Prior to Vaccine Availability

Purpose: The COVID-19 pandemic posed unprecedented demands on health care. This study aimed to characterize COVID-19 inpatients and examine trends and risk factors associated with hospitalization duration, intensive care unit (ICU) admission, and in-hospital mortality.

Methods: This retrospective study analyzed patients with SARS-CoV-2 infection hospitalized at an integrated health system between February 2, 2020, and December 12, 2020. Patient characteristics and clinical outcomes were obtained from medical records. Backward stepwise logistic regression analyses were used to identify independent risk factors of ICU admission and in-hospital mortality. Cox proportional hazards models were used to evaluate relationships between ICU admission and in-hospital mortality.

Results: Overall, 9647 patients were analyzed. Mean age was 64.6 ± 18 years. A linear decrease was observed for hospitalization duration (0.13 days/week, R=0.71; P<0.0001), ICU admissions (0.35%/week, R=0.44; P<0.001), and hospital mortality (0.16%/week, R=0.31; P<0.01). Bacterial co-infections, male sex, history of chronic lung and heart disease, diabetes, and Hispanic ethnicity were identified as independent predictors of ICU admission (P<0.001). ICU admission and age of ≥65 years were the strongest independent risk factors associated with in-hospital mortality (P<0.001). The in-hospital mortality rate was 8.3% (27.4% in ICU patients, 2.6% in non-ICU patients; P<0.001).

Conclusions: Results indicate that, over the pandemic's first 10 months, COVID-19 carried a heavy burden of morbidity and mortality in older patients (>65 years), males, Hispanics, and those with bacterial co-infections and chronic comorbidities. Although disease severity has steadily declined following administration of COVID-19 vaccines along with improved understanding of effective COVID-19 interventions, these study findings reflect a "natural history" for this novel infectious disease in the U.S. Midwest.