ABSTRACT
Background. Understanding comorbidities that drive all-cause readmission in patients hospitalized with Coronavirus disease 2019 (COVID-19) can inform healthcare system capacity planning and improve post-discharge care. Methods. This was a retrospective cohort study of patients hospitalized for COVID-19 between April 2020-December 2020 (index cohort) across 760 hospitals in the Premier Healthcare Database. Patients who died or left against medical advice were excluded from the index cohort. Surviving patients in the index cohort were followed until May 2021. First readmission to the same hospital as the COVID-19 index admission was considered all-cause readmission. The all-cause 14-month risk (95% confidence interval) of readmission was calculated using the Kaplan-Meier approach. A multivariable Cox proportional hazards model adjusted for demographic variables, hospital characteristics, co-existing comorbidities, and COVID-19 severity was built to study the association between Elixhauser comorbidities and readmission. Results. Among 232155 unique patients in the index cohort, 36680 were readmitted to the same hospital at least once, followed through May 2021. The 14-month risk of readmission was 16.2% (95% CI:16.1% - 16.4%). The most frequent primary diagnosis on readmission was infectious disease (14240, 38.8%), of which 8754 (24%) were for COVID-19. With each additional comorbidity, the readmission hazard increased by 19% (HR, 1.19;95% CI:1.18 - 1.19). In the multivariable Cox proportional hazards model, many comorbidity categories were associated with an increased risk of readmission. Metastatic cancer (HR, 1.74;95% CI:1.60 -1.89), lymphoma (HR, 1.61;95% CI:1.47 - 1.77), drug abuse (HR, 1.51;95% CI:1.41 - 1.62), congestive heart failure (HR, 1.47;95% CI:1.44- 1.51), and alcohol abuse (HR, 1.46;95% CI:1.36- 1.56) were associated with the highest hazard for readmission. Conclusion. COVID-19 patients have a high risk of all-cause readmission and are frequently readmitted for COVID-19. With the continued emergence of COVID-19 variants, this study provides valuable insights into developing more informed discharge plans and improving post-discharge care for COVID-19 patients with existing comorbidities to prevent readmission.