Factors associated with unplanned readmissions in a major Australian health service

<jats:p> Objective The aim of the present study was to gain an understanding of the factors associated with unplanned hospital readmission within 28 days of acute care discharge from a major Australian health service. Methods A retrospective study of 20575 acute care discharges from 1 August to 31 December 2015 was conducted using administrative databases. Patient, index admission and readmission characteristics were evaluated for their association with unplanned readmission in ≤28 days. Results The unplanned readmission rate was 7.4% (n=1528) and 11.1% of readmitted patients were returned within 1 day. The factors associated with increased risk of unplanned readmission in ≤28 days for all patients were age ≥65 years (odds ratio (OR) 1.3), emergency index admission (OR 1.6), Charlson comorbidity index &gt;1 (OR 1.1–1.9), the presence of chronic disease (OR 1.4) or complications (OR 1.8) during the index admission, index admission length of stay (LOS) &gt;2 days (OR 1.4–1.8), hospital admission(s) (OR 1.7–10.86) or emergency department (ED) attendance(s) (OR 1.8–5.2) in the 6 months preceding the index admission and health service site (OR 1.2–1.6). However, the factors associated with increased risk of unplanned readmission ≤28 days changed with each patient group (adult medical, adult surgical, obstetric and paediatric). Conclusions There were specific patient and index admission characteristics associated with increased risk of unplanned readmission in ≤28 days; however, these characteristics varied between patient groups, highlighting the need for tailored interventions. What is known about the topic? Unplanned hospital readmissions within 28 days of hospital discharge are considered an indicator of quality and safety of health care. What does this paper add? The factors associated with increased risk of unplanned readmission in ≤28 days varied between patient groups, so a ‘one size fits all approach’ to reducing unplanned readmissions may not be effective. Older adult medical patients had the highest rate of unplanned readmissions and those with Charlson comorbidity index ≥4, an index admission LOS &gt;2 days, left against advice and hospital admission(s) or ED attendance(s) in the 6 months preceding index admission and discharge from larger sites within the health service were at highest risk of unplanned readmission. What are the implications for practitioners? One in seven discharges resulted in an unplanned readmission in ≤28 days and one in 10 unplanned readmissions occurred within 1 day of discharge. Although some patient and hospital characteristics were associated with increased risk of unplanned readmission in ≤28 days, statistical modelling shows there are other factors affecting the risk of readmission that remain unknown and need further investigation. Future work related to preventing unplanned readmissions in ≤28 days should consider inclusion of health professional, system and social factors in risk assessments. </jats:p>