Neighborhood Deprivation, Antibiotic Prescribing Concordance, and 30-Day Outcomes After Emergency Department Encounters in Older Adults

Background: Older adults evaluated in emergency departments (EDs) frequently receive antibiotics, but the relationships among neighborhood deprivation, antibiotic decision concordance, and downstream outcomes remain incompletely defined. Methods: We conducted a retrospective cohort study of 1 365 957 ED encounters among adults aged ≥65 years at 119 CommonSpirit Health facilities across 15 US states (2015–2024). Census-tract Social Deprivation Index (SDI) was standardized for modeling. Indication-level concordance, overuse, and underuse were based on antibiotics administered during the index ED encounter and an encounter-level diagnosis-tier framework. Outcomes were length of stay (LOS), 30-day ED revisit, mortality, Clostridioides difficile infection (CDI), and desirability of outcome ranking (DOOR). Results: Associations between higher SDI and outcomes were statistically detectable but small in absolute magnitude. Guideline-concordant management was associated with shorter LOS, better DOOR, and lower revisit, mortality, and CDI risks; overuse was consistently associated with worse outcomes, whereas underuse showed mixed associations. Concordance mediated only a small share of SDI-associated outcome differences. Sensitivity analyses using a 4-level DOOR outcome, modified Poisson relative risks, and study-period stratification supported the principal interpretation. Conclusions: Neighborhood deprivation had small absolute associations with short-term outcomes. Indication-level concordance and avoidance of overuse were associated with more substantial outcome differences but explained little of the deprivation-associated variation.