The impact of socio-economic status on outcomes after unplanned intensive care unit admissions in Australia: a retrospective observational cohort study.

OBJECTIVE: To examine the association between socioeconomic status and patient outcomes following unplanned intensive care unit admissions in Australia, using national data linked across public databases. METHODS: We conducted a national retrospective cohort study of all adult unplanned intensive care unit admissions in Australia between January 2017 and December 2019, using data from the Australian and New Zealand Intensive Care Society Adult Patient Database. Socioeconomic status was determined using the Australian Bureau of Statistics' 2016 Index of Relative Socio-Economic Advantage and Disadvantage (IRSAD), linked by patient postcode. The primary outcome was hospital mortality, adjusted for severity of illness, remoteness, year of admission, and intensive care unit, using a mixed-effects logistic regression model. RESULTS: A total of 245,867 intensive care unit admissions were included. Patients in the most disadvantaged quartile were less likely to be treated in tertiary or private hospitals. Still, there was otherwise no significant difference in demographic profile, intensive care unit interventions received, or reasons for admission. In the multivariate analysis, there were no significant differences in adjusted hospital mortality across IRSAD deciles (p = 0.3). DISCUSSION: In this national study, socioeconomic status was not associated with hospital mortality after adjustment for illness severity and hospital factors. These findings suggest that structural health system features, such as universal access to critical care in Australia, may mitigate the adverse effects of socioeconomic disadvantage among unplanned intensive care unit outcomes observed in other health systems. Further research is warranted to explore the pathways linking socioeconomic status, health access, and intensive care unit admission characteristics.