ABSTRACT: AIMS:The aim of this study is to determine the impact of diabetes mellitus on all-cause mortality and rehospitalization rates at 3 months and at 1 year in patients admitted with acute heart failure (AHF) stratified by left ventricular ejection fraction (EF). METHODS AND RESULTS:We analysed consecutive patients admitted to 47 hospitals in seven Middle Eastern countries (Saudi Arabia, Oman, Yemen, Kuwait, United Arab Emirates, Qatar, and Bahrain) with AHF from February to November 2012 with AHF who were enrolled in Gulf CARE, a multinational registry of patients with heart failure (HF). AHF patients were stratified into three groups: HF patients with reduced (EF) (HFrEF) (<40%), HF with mid-range EF (HFmrEF) (40-49%), and HF patients with preserved EF (HFpEF) (?50%). Analyses were performed using univariate and multivariate statistical techniques. The mean age of the cohort was 59 ± 15 years (ranging from 18 to 99 years), and 63% (n = 2887) of the patients were males. A total of 2258 (49%) AHF patients had diabetes mellitus. The mean EF was 37 ± 14%. A reduced EF was observed in 2683 patients (59%), whereas 962 patients (21%) had mid-range and 932 patients (20%) had preserved EF. Multivariable analyses demonstrated no significant differences in all-cause mortality between diabetics and non-diabetics in all the three types of HF; at 3 months follow-up: HFrEF [adjusted odds ratio (aOR), 1.30; 95% confidence interval (CI): 0.94-1.80; P = 0.119], HFmrEF (aOR, 0.98; 95% CI: 0.51-1.87; P = 0.952), and HFpEF (aOR, 0.69; 95% CI: 0.38-1.26; P = 0.225); and at 12-months follow-up: HFrEF (aOR, 1.25; 95% CI: 0.97-1.62; P = 0.080), HFmrEF (aOR, 1.07; 95% CI: 0.68-1.68; P = 0.783), and HFpEF (aOR, 1.07; 95% CI: 0.67-1.72; P = 0.779). There were also no significant differences in rehospitalization rates between diabetics and non-diabetics in all the three types of HF; at 3 months follow-up: HFrEF (aOR, 0.94; 95% CI: 0.74-1.19; P = 0.581), HFmrEF (aOR, 0.82; 95% CI: 0.53-1.26; P = 0.369), and HFpEF (aOR, 1.06; 95% CI: 0.64-1.78; P = 0.812); and at 12-months follow-up: HFrEF (aOR, 0.93; 95% CI: 0.73-1.17; P = 0.524), HFmrEF (aOR, 0.81; 95% CI: 0.56-1.17; P = 0.257), and HFpEF (aOR, 1.29; 95% CI: 0.82-2.05; P = 0.271). CONCLUSIONS:There were no significant differences in 3 and 12 months all-cause mortality as well as rehospitalization rates between diabetics and non-diabetic patients in all the three types of AHF patients stratified by left ventricular ejection fraction.