BACKGROUND: Ischemic heart disease (IHD) is the leading cause of mortality in the world with an increasing incidence. One of the interventions to treat IHD is coronary artery bypass grafting (CABG) and people with diabetes mellitus (DM) account for approximately one quarter of all patients who undergo coronary revascularization. Furthermore, people with DM have a higher risk of mortality due to heart failure (HF). OBJECTIVE: We aim to describe the risk of developing HF after CABG in patients with versus without DM. METHODS: Through a large nationwide register-based cohort study, patients who underwent CABG from January 1, 2000 to December 31, 2020 were included. In addition to Cox regression, g-formula methods based on multivariable Cox regression were performed to estimate the absolute risk (AR) and risk difference (RD) of the association between DM status and HF outcome, and between DM status and mortality. RESULTS: A total of 34,855 patients were included in this study, consisting of 6909 (19.8%) DM patients. The AR of HF after CABG in the 10th year was 35.1% versus 26.4% for patients with versus without DM (p <
0.001), respectively. The RD of HF for each exceeding year (3.7 percentage point (pp.) in the 1st year versus 8.6 pp. in the 10th year) was higher for patients with DM compared to those without DM. CONCLUSION: The risk of HF was significantly higher up to ten years after CABG in patients with DM compared to those without DM.