KEY POINTS: The association between aspirin use and risk of the first cardiovascular event was NS in patients with CKD. Compared with nonusers, aspirin users had an increased risk of significant bleeding events. Aspirin prescription for the primary prevention of cardiovascular disease in patients with CKD needs careful consideration. BACKGROUND: Despite the high cardiovascular risk in patients with CKD, the role of aspirin in primary prevention remains unclear. This study aimed to investigate the association between aspirin initiation in adults with CKD without prior cardiovascular disease (CVD) and the first cardiovascular and bleeding events using Korean nationwide cohort data. METHODS: Among individuals aged 40-79 years with an eGFR between 15 and 59 ml/min per 1.73 m RESULTS: During a mean follow-up of 6.9±2.9 years, the incidence rates for the primary efficacy outcome in aspirin users and nonusers were 8.0 and 9.0 per 1000 person-years, respectively. Aspirin therapy initiation was not associated with the primary efficacy outcome (hazard ratio, 0.93
95% confidence intervals, 0.86 to 1.04). However, the primary safety outcome of major bleeding was more frequent in aspirin users than in nonusers (6.7 versus 4.7 per 1000 person-years). The hazard ratio for this outcome in aspirin users versus nonusers was 1.45 (95% confidence intervals, 1.32 to 1.59). CONCLUSIONS: No association was observed between aspirin use and the risk of nonfatal atherosclerotic CVD or cardiovascular death in patients with CKD stages G3 and G4 without prior CVD. Aspirin use was associated with higher risk of major bleeding.