PurposeThe aim of this study is to analyse adverse health outcomes at hospital discharge adjusted to frailty degree measured by three instruments in patients admitted for medical diseases in an Acute Care for Elders (ACE). MethodsThis is a prospective observational study, including 194 frail patients aged 75 years or older. Patients were admitted to a tertiary hospital ACE for an acute medical illness or exacerbated chronic diseases from June 2022 to May 2023. Frailty was assessed by the FRAIL scale, the Clinical Frailty Scale (CFS) and the frail-VIG Index (IF-VIG). Health outcomes analysed were length of hospital stay, home destination at hospital discharge, development of delirium and functional decline. ResultsPatients were on average 85,14 years old, with 56 % women. Mean frailty punctuations were 2,83 for FRAIL scale; 4,1 for CFS and 0,3 for IF-VIG. Patients who did not return home were more fragile: FRAIL 3,1 vs 2,6; CFS 4,5 vs 4,0; IF-VIG 0,3 vs 0,2. Patients with a hospitalization longer than 10 days were more fragile: FRAIL 3,9 vs 2,6; CFS 4,5 vs 3,8; IF-VIG 0,3 vs 0,2. More frail patients had greater delirium incidence and prevalence: CFS 4,7 vs 4,1; IF-VIG 0,3 vs 0,2. These results are statistically significant. ConclusionsA greater degree of basal frailty during a hospitalisation in an ACE is strongly related with smaller return home rates at hospital discharge, as well as with longer mean stay-length and larger amounts of delirium.