PURPOSE: Our study was intended to examine time trends of management and mortality of acute coronary syndrome patients with associated diabetes mellitus. METHODS: We analyzed data from 5 nationwide registries established between 2001 and 2014, including consecutive acute coronary syndrome patients admitted to the Italian Intensive Cardiac Care Units. RESULTS: Of 28,225 participants, 8521 (30.2%) had diabetes: as compared with patients without diabetes, they were older and had significantly higher rates of prior myocardial infarction and comorbidities (all P < .0001). Prevalence of diabetes and comorbidities increased over time (P for trend < .0001). Cardiogenic shock rates were higher in patients with diabetes, as compared with those without diabetes (7.8% vs 2.8%, P < .0001), and decreased significantly over time only in patients without diabetes (P = .007). Revascularization rates increased over time in patients both with and without diabetes (both P for trend < .0001), although with persistingly lower rates in patients with diabetes. All-cause in-hospital mortality was higher in patients with diabetes (5.4 vs 2.5%, respectively, P < .0001) and decreased more consistently in patients without diabetes (P for trend = .007 and < .0001, respectively). At multivariable analysis, diabetes remains an independent predictor of both cardiogenic shock (odds ratio 2.03; 95% confidence interval, 1.77-2.32; P < .0001) and mortality (odds ratio 1.95; 95% confidence interval, 1.69-2.26; P < .0001). CONCLUSIONS: Despite significant mortality reductions observed over 15 years in acute coronary syndromes, patients with diabetes continue to show threefold higher rates of cardiogenic shock and lower revascularization rates as compared with patients without diabetes. These findings may explain the persistingly higher mortality of patients with diabetes and acute coronary syndromes. (C) 2019 Elsevier Inc. All rights reserved.