Characteristics and subgroups of frequent emergency department users in an academic hospital in Japan.

Aim Frequent emergency department (ED) users increase the burden on EDs. However, little is known about the characteristics and subgroups of frequent ED users in Japan. Methods We retrospectively analyzed data on patients who had visited the ED of an academic hospital in Japan between 2014 and 2015. We identified adult frequent ED users (four or more ED visits within 365 days prior to one's last visit) and sampled adult non-frequent ED users. We compared these groups to delineate the characteristics of frequent ED users and examined the association between frequent ED use and hospitalization rates. Additionally, to identify latent subgroups of frequent ED users, we undertook a cluster analysis. Results We identified 259 frequent ED users and 297 non-frequent ED users from 9,546 patients who had visited the ED in 2015. Frequent ED users accounted for 8.2% of all ED visits. Frequent ED users tended to be older, have comorbidities, and be receiving public assistance compared to non-frequent ED users. There was a significant association between frequent ED use and higher hospitalization rates, which was partially attributable to (older) age and comorbidities. In the cluster analysis, we identified four subgroups of frequent ED users: (i) older patients with malignant tumors and the highest hospitalization rates, (ii) patients with mental illnesses and the lowest hospitalization rates, (iii) patients who were at risk of cardiovascular diseases, (iv) others. Conclusions Frequent ED users tended to be older and have comorbidities. Four latent subgroups of frequent ED users were identified.