OBJECTIVES The study sought to compare the prevalence, clinical correlates and prognostic impact of diabetes in Southeast Asian versus white patients with heart failure (HF) with preserved or reduced ejection fraction. BACKGROUND Diabetes mellitus is common in HF and is associated with impaired prognosis. Asia is home to the majority of the worlds diabetic population, yet data on the prevalence and clinical significance of diabetes in Asian patients with HF are sparse, and no studies have directly compared Asian and white patients. METHODS Two contemporary population-based HF cohorts were combined: from Singapore (n 1,002, median [25th to 75th percentile] age 62 [54 to 70] years, 76% men, 19.5% obesity) and Sweden (n =19,537, 77 [68 to 84] years, 60% men, 24.8% obesity). The modifying effect of ethnicity on the relationship between diabetes and clinical correlates or prognosis (HF hospitalization and all-cause mortality) was examined using interaction terms. RESULTS Diabetes was present in 569 (57%) Asian patients versus 4,680 (24%) white patients (p amp;lt; 0.001). Adjusting for clinical covariates, obesity was more strongly associated with diabetes in white patients (odds ratio [OR]: 3.45;. 95% confidence interval [CI]: 2.86 to 4.17) than in Asian patients (OR: 1.82; 95% CI: 1.13 to 2.96; P-interaction = 0.026). Diabetes was more strongly associated with increased HF hospitalization and all-cause mortality in Asian patients (hazard ratio: 1.50; 95% CI: 1.21 to 1.87) than in white patients (hazard ratio: 1.29; 95% CI: 1.22 to 1.36; P-interaction = 0.045). CONCLUSIONS Diabetes was 3-fold more common in Southeast Asian compared to white patients with HF, despite younger age and less obesity, and more strongly associated with poor outcomes in Asian patients than white patients. These results underscore the importance of ethnicity-tailored aggressive strategies to prevent diabetes and its complications. (C) 2017 by the American College of Cardiology Foundation.