Patient emergency health-care use before hospital admission for COVID-19 and long-term outcomes in Scotland: a national cohort study

Background: The impact of pre-illness health care trajectories on longer-term personcentred outcomes for patients hospitalised with COVID-19 remains unclear. We sought to describe mortality and emergency hospital readmission following COVID-19 hospitalisation and assess the association with trajectories of healthcare use prior to COVID-19 admission. Methods: We undertook a national, complete retrospective cohort study using linked databases in all adult patients hospitalised in Scotland with COVID-19. We used latent class trajectory modelling to identify distinct clusters of patients based on emergency
hospital admissions in the two years before COVID-19 admission. Primary outcomes were mortality and emergency readmission up to 12 months after hospitalisation. We used multivariable regression models to explore associations between these outcomes and patient demographics, vaccination status, level of care received in hospital and previous emergency hospital utilisation. Findings: Between 01/03/2020 and 25/10/2021 33,580 patients were admitted to hospital in Scotland with COVID-19. Overall, 29.6% (95% CI 29.1%, 30.2%) of patients died within a year of COVID-19 hospital admission. Within 30 days of hospital discharge, 14.4% (95% CI 14.0%, 14.8%) of patients had experienced at least one emergency hospital readmission, increasing to 35.6% (34.9%, 36.3%) at one year. There were four distinct patterns of previous emergency hospital use: C1 “no admissions” (n=18,772, 55.9%); C2 “Minimal admissions” (n=12,057, 35.9%), C3 “Recently high” (n=1,931, 5.8%) and C4 “Persistently high” (n=820, 2.4%). Patients in high utilisation clusters (C3 and C4) were older, more multimorbid and more likely to have hospital-acquired COVID-19. All cluster groups had increased risk of mortality and hospital readmission relative to cluster C1. Mortality was highest in patients in “Recently high” C3, (C1 ref: post-hospital mortality HR 2.70 (95% CI 2.35, 2.81)) and readmission risk was highest in “Persistently high” C4 (ref C1: C4 HR 3.23 (95% CI 2.89, 3.61)). Interpretation: Longer term mortality and readmission rates for patients hospitalised with COVID-19 have been high, with one in three dying within a year and a third readmitted as an emergency. Pre-illness hospital resource trajectories were strongly predictive of mortality and readmission risk, independent of age, pre-existing comorbidity and vaccination status. This more precise identification of individuals at high risk of poor outcomes from COVID-19 will enable targeted support.