Risk of Hospital Readmission among People with Chronic Kidney Disease: A Population-Based Cohort Study

Background: People with chronic kidney disease (CKD) have higher risk of repeated hospitalization, and mortality than the general population. Given many unplanned readmissions may be avoidable, examining risks and reasons for readmission across CKD categories may inform targeted interventions and safer discharge planning. Thus, we estimated the association between estimated glomerular filtration rate (eGFR) and both readmission and mortality and identified diagnoses for readmission. Methods: Adults discharged from hospitals in Alberta, Canada from 2005-2021 were included. Pre-admission eGFR was categorized into eight groups (in mL/min/1.73 m 2 ): ≥60 (G1-2), 45-59 (G3a), 30-44 (G3b), 15-29 (G4), <15 not on dialysis (G5ND), on dialysis (G5D), prevalent kidney transplant recipients (G1T-5T), and unknown. The primary outcome was unplanned readmission or death within 30 days of discharge. Multivariable logistic regression, accounting for multiple admissions per participant, was used to estimate odds of the primary outcome, using G1-2 as the reference. Results were stratified by age and sex. The type, and frequency of each unplanned readmission was also determined. Results: The cohort comprised 2,992,810 admissions among 1,249,248 participants (median [IQR] admission per participant: 1 [1,3] admission; age: 61 [47,74] years). Among lower eGFR categories, heart failure was the most common readmission diagnosis, followed by acute kidney injury (AKI). Relative to G1-2, more impaired eGFR groups had significantly higher odds of the primary outcome, with the highest adjusted odds experienced by the G1T-5T group (aOR: 1.47; 95% CI: 1.12, 1.93) and G5ND group (aOR: 1.40; 95% CI: 1.34, 1.47). Stratified analyses showed that individuals <65 years and females with reduced eGFR had higher odds compared to counterparts in the G1-2 reference group. Conclusions: People with severe CKD had the highest risk of hospital readmission, suggesting the need to test interventions in this group to target volume and hemodynamic related readmissions such as post-discharge AKI and heart failure.