In this study of 19,824 ST-elevated myocardial infarction (STEMI) patients from the J-PCI OUTCOME registry (January 1, 2017, to December 31, 2018), we investigated the association between door-to-balloon time (DTB) and 1-year post-discharge cardiovascular outcomes. Patients with DTB >
90 min were older and had higher comorbidities. The incidence of 1-year major adverse cardiovascular events (MACE) showed an incremental increase: 3.7 %, 4.8 %, and 7.7 % for DTB ≤60, DTB 60-90, and DTB >
90 groups, respectively. Adjusted hazard ratios (aHR) compared to the DTB 60-90 group were 0.83 (DTB ≤60, p = 0.03) and 1.25 (DTB >
90, p = 0.005). Subgroup analysis revealed higher risk for MACE in DTB >
90 group for patients aged <
70, men, no history of coronary revascularization, and those with cardiac arrest or cardiogenic shock. Conversely, DTB ≤60 group without previous history had a lower MACE risk (aHR 0.80, p = 0.02). This study, the largest of its kind, demonstrates that a DTB below 90 min is associated with lower 1-year MACE risk, supporting current guidelines, and indicating additional benefits for specific patient subgroups, especially those experiencing their first acute coronary event. The findings suggest the importance of early intervention in primary prevention and emphasize the need for prompt detection of vulnerable plaque.