Figure 1 shows the patient flow in this study. The number of patients that were registered in the ORION system whose data were checked was 1,3901,47 during 2016 to 2018. Among these patients, 560,421 were transported and admitted to hospital during 2016–2018, excluding 798,154 patients who returned home from the ED, 17,370 patients who were transferred to another hospital from the ED, 14,061 who died in the ED and 141 patients who did not consult a hospital. Among these 560,421 patients, 32,492 had died by 21 days after hospital admission, 31,068 patients had been transferred to other hospitals by 21 days after hospital admission, 14,904 patients had missing data (outcome at 21 days: 2788 patients, diagnosis during hospitalization: 11,580) and 607 patients had inappropriate data. Finally, we included 481,886 patients in this study. Of them, 158,551 patients had remained hospitalized at 21 days after hospital admission and 323,335 patients had been discharged home by 21 days after hospital admission.
Table 1 shows the demographic and clinical characteristics of the patients in this study. The median of age was 75 (IQR: 59–83) years old, and the most common age group was high elderly with 206,707 patients (42.9%). Among the patients, 248,899 (51.7%) were men and 232,987 (48.3%) were women. The month with the highest number of patients was December, with 44,166 patients (9.2%), whereas that with the lowest number of patients was February, with 37,446 patients (7.8%). The day of week with the highest number of patients was Monday, with 75,486 patients (15.7%), and that with the lowest number of patients was Sunday, with 63,787 patients (13.2%). The most common reason for an ambulance call was acute disease, with 337,732 patients (70.1%), followed by inter-hospital transfer, with 59,571 patients (12.4%). The most common patient background factor was need for nursing care, with 102,096 patients (21.2%), followed by past history of psychiatric disease, with 19,634 patients (4.1%). The most common medical condition during hospitalization was injury, poisoning and certain other consequences of external causes, with 96,972 patients (20.1%), followed by cardiovascular disease (93,371 patients, 19.4%) and respiratory disease (69,966 patients, 14.5%).
Table 2 shows the results of the main analysis. Factors associated with the continuation of hospitalization at 21 days after hospital admission were elderly (AOR: 1.767 [95% CI: 1.730–1.805]), high elderly (AOR: 2.233 [95% CI: 2.191–2.276]), super elderly (AOR: 2.401 [95% CI: 2.337–2.466]) and female (AOR: 1.027 [95% CI: 1.013–1.040]). Compared to April, January (AOR: 1.069 [95% CI: 1.036–1.102]), February (AOR: 1.055 [95% CI: 1.022–1.089]), March (AOR: 1.066 [95% CI: 1.032–1.100]) and December (AOR: 1.032 [95% CI: 1.001–1.064]) were associated with the continuation of hospitalization at 21 days after hospital admission. Compared to Monday, Sunday (AOR: 0.844 [95% CI: 0.824–0.865]), Wednesday (AOR: 0.973 [95%CI: 0.951–0.996]), Thursday (AOR: 0.966 [95% CI: 0.944–0.989]), Friday (AOR: 0.970 [95% CI: 0.948–0.992]) and Saturday (AOR: 0.898 [95% CI: 0.877–0.920]) were inversely associated with the continuation of hospitalization at 21 days after hospital admission. Among the reasons for an ambulance call, traffic accident (AOR: 1.231 [95% CI: 1.183–1.282]), other trauma (AOR: 1.672 [95% CI: 1.630–1.716]) and inter-hospital transfer (AOR: 1.158 [95% CI: 1.134–1.181]) were associated with the continuation of hospitalization at 21 days after hospital admission. Among the patient background factors, past history of psychiatric disease (AOR: 1.078 [95% CI: 1.041–1.116]), no fixed address (AOR: 4.494 [95% CI: 3.632–5.314]), need for nursing care (AOR: 1.420 [95% CI: 1.397–1.443]), suicide attempt (AOR: 1.495 [95% CI: 1.238–1.806]), living in a nursing faculty (AOR: 1.115 [95% CI: 1.080–1.150]) and solitary person (AOR: 1.085 [95% CI: 1.050–1.120]) were associated with the continuation of hospitalization at 21 days after hospital admission. Compared to cardiovascular disease, only neoplasm (AOR: 1.301 [95% CI: 1.256–1.348]) was associated with the continuation of hospitalization at 21 days after hospital admission, whereas all other medical conditions were inversely associated with this outcome.