High Utilisation Behaviour in Emergency Departments: Predictors in the subregion of Baixo Alentejo

Introduction: High Utilisation of Emergency Departments (EDs) is a behaviour present in a minority of patients, but spends a disproportionate share of visits and resources. Understanding their characteristics and predictors is essential for planning targeted interventions. Methods: A retrospective cohort study analysed all ED visits in 2024 at the Unidade Local de Saúde do Baixo Alentejo (ULSBA). Patient behaviour was classified as Control (≤ 3 visits), Moderate Frequent Use (MFU, 4–9 visits), or High Frequent Use (HFU, ≥10 visits). Variables included sociodemographic characteristics, comorbidities, outcomes, and utilisation measures. Descriptive, bivariate, and multivariate analyses were performed. Results: Among 50,626 patients accounting for 116,885 ED visits, 5,315 (10.5%) presented high utilisation, responsible for 31.7% of visits. These patients were more likely to be female and to present mental or social comorbidities. A bimodal age distribution was observed, with peaks under 30 years and over 60 years. Multivariate analysis identified female sex, mental and social comorbidities, and residence in Castro Verde or Moura as predictors of high utilisation. These patients were more likely to leave without treatment but less likely to die during ED episodes compared with controls. Discussion/Conclusion: High utilisations presents itself in heterogeneous populations, concentrated mostly in younger psychosocially vulnerable patients and older multimorbid adults. While they do not appear to drive ED overcrowding directly, their profiles reflect unmet needs in social and primary care systems. Tailored interventions across health and social services are needed to solve their issues and reduce avoidable ED use.