Objectives: Diabetes mellitus (DM) and frailty are common in older patients with acute coronary syndromes (ACS). No data exists about its prognostic impact on long-term outcomes and their possible interaction in this setting.

Design: Observational prospective study.

Setting: Multicenter registry conducted in 44 hospitals in Spain.

Participants: Consecutive patients with ACS aged 80≥years.

Measurements: A comprehensive geriatric evaluation was performed during hospitalization, including frailty assessment by the FRAIL score. The impact of DM and frailty on the incidence of mortality/readmission at 24 months was analysed by a Cox regression model.

Results: A total of 498 patients were included (mean age 84.3 years). Prevalence of previous DM was 199/498 (40.0%). The rate of frail patients was 135/498 (27.1%). The incidence of mortality/readmission was higher frail patients (HR 2.49) (both p<0.001). In contrast, DM was not significantly associated to a higher rate of outcomes (HR 1.23, p=0.060) in the whole cohort. Among non-frail patients, patients with DM had a similar incidence of mortality or readmission (p=0.959). In contrast, among frail patients, DM was significantly associated with a higher incidence of events (HR 1.51, p=0.034).

Conclusions: Unlike frailty status, DM was not associated to poorer long-term outcome in elderly patients with ACS. Among frail patients the presence of DM seems to provide additional prognostic information.