Social determinants of a critical care readmission to hospital over eleven years.

Introduction: Socio-economic factors may influence long term health outcomes. Approximately 5% of patients are readmitted to an Intensive Care Unit (ICU) following their initial discharge to a medical ward but prior to their hospital discharge. However, readmissions to an ICU during subsequent hospitalisations have rarely been investigated. Objectives/Aims: To identify socio-economic factors which influence risk of readmission to an ICU after discharge from hospital, over an eleven-year period. Method(s): Patients admitted to 23 adult public ICUs in Victoria, Australia between July 2007 to June 2018, were extracted from The Australian and New Zealand Intensive Care Society Adult Patient Database. De-identified data was matched using probabilistic methods and statistical linkage keys to the Victorian Admitted Episodes Database, to the Victorian Death Index and to socioeconomic data from the Australian Bureau of Statistics linked by residential area. Result(s): Of 228,912 ICU admissions examined, 183,635 (80%) were matched. 15,931 died in-hospital during their first admission, leaving 136,954 patients who accounted for a total of 167,704 ICU admissions. 21,650 (16%) patients had at least one more ICU admission over the eleven-year study period. Mortality on 1st, 2nd and 3rd readmissions were 11.4%, 10.1% and 8.2% respectively. After adjusting for age, acute and chronic illnesses, patients were less likely to be readmitted if from a higher socio-economic area (OR 0.976, 95%CI 0.971-0.982, P<0.001), mandarin was listed as preferred language (OR 0.57, 95%CI 0.41-0.78, P=0.001), in a married/ defacto relationship (OR 0.92 95%CI 0.88-0.96, P<0.001) or widowed (OR 0.74, 95%CI 0.69-0.79, P<0.001). Readmissions were more likely in men (OR 1.07, 95%CI 1.04-1.11, p<0.001) and separated/divorced patients (OR 1.17, 95%CI 1.10-1.24, p<0.001) and those with chronic obstructive pulmonary disease (OR 2.32, 95%CI 2.08-2.60, p<0.001). Conclusion(s): Subsequent hospitalisations includin