<title>Abstract</title> <bold>OBJECTIVE: </bold>To assess whether older adults who spend a night in emergency departments (ED) awaiting admission are at increased risk of mortality. <bold>METHODS: </bold>This was a retrospective review of a multipurpose cohort that recruited all patients ≥75 years who visited ED and were admitted to hospital on April 1 to 7, 2019, at 52 EDs across Spain. Study groups were: patients staying in ED from midnight until 8:00 a.m. (ED group) and patients admitted to a ward before midnight (ward group). The primary endpoint was in-hospital mortality, truncated at 30 days, and secondary outcomes assessed length of stay for the index episode. <bold>RESULTS: </bold>The sample comprised 3,243 patients (median [IQR] age, 85 [81-90] years; 53% women), with 1,096 (34%) in the ED group and 2,147 (66%) in the ward group. In-hospital mortality in ED vs ward group was 10.7% vs 9.5% (adjusted OR: 1.12, 95%CI: 0.80-1.58). Sensitivity analyses rendered similar results (ORs ranged 1.06-1.13). Interaction was only detected for academic/non-academic hospitals (p<0.001), with increased mortality risk for the latter (1.01, 0.33-3.09 vs 2.86, 1.30-6.28). There were no differences in prolonged hospitalization (>7 days), with adjusted OR of 1.16 (0.94-1.43) and 1.15 (0.94-1.42) depending on whether time spent in the ED was or was not taken into consideration. <bold>CONCLUSIONS: </bold>No increased risk of in-hospital mortality or prolonged hospitalization was found in older patients waiting overnight in the ED for admission. Nonetheless, all estimations suggest a potential harmful effect of staying overnight, especially without the proper hospitalist care.
