Readmission Risk after COVID-19 Hospitalization: A Moderation Analysis by Vital Signs

Readmission to the hospital after hospitalization with coronavirus disease 2019 (COVID-19) is associated with significant morbidity and mortality. Hospital clinicians may identify the presence of a patient's comorbid conditions, overall severity of illness, and clinical status at discharge as risk factors for readmission. Objective data are lacking to support reliance on these factors for discharge decision making. The objective of our study was to examine risk factors for readmission to the hospital after COVID-19 hospitalization and the impact of vital sign abnormalities, within 24 hours of discharge, on readmission rates.

In total, 2557 COVID-19-related hospital admissions within the Lifespan Health System, a large multicenter health system (Rhode Island), of 2230 unique patients aged 18 years and older, occurring from April 1, 2020 to December 31, 2020 were analyzed. Risk factors associated with readmission within 30 days were identified and analyzed using Cox regression. A moderation analysis by vital signs at discharge on the risk of readmission was performed.

Clinical factors associated with readmissions included existing cardiovascular conditions (risk ratio 2.32, 95% confidence interval [CI] 1.10-4.90) and pulmonary disease (risk ratio 3.25, 95% CI 1.62-6.52). The absence of abnormal vital signs within 24 hours of discharge was associated with decreased 30-day readmission rates (risk ratio 0.70, 95% CI 0.52-0.94). Elevated C-reactive protein and d-dimer values and in-hospital complications including stroke, myocardial infarction, acute renal failure, and gastrointestinal bleeding were not associated with an increased risk of readmission. In moderation analysis, the presence of normal vital signs within 24 hours of discharge was associated with decreased readmission risk in patients who had primary risk factors for readmission including pulmonary disease (risk ratio 0.80, 95% CI 0.65-0.99), psychiatric disorders, and substance use (risk ratio 0.70, 95% CI 0.52-0.94).

Comorbid conditions, including pulmonary and cardiovascular disease, are associated with readmission risk after COVID-19 hospitalization. The normalization of vital signs within 24 hours of discharge during COVID-19 hospitalization may be an indicator of readiness for discharge and may mitigate some readmission risk conferred by comorbid conditions.