Data sources and study population

This study used the Korean NHIS database. The NHIS is an obligatory health insurance system that covers over 98% of the Korean population, including approximately 50 million people¹⁷. The NHIS database includes all beneficiaries' medical records, including demographic data, outpatients’ visits, hospitalization, medical history, general health check-ups, procedures, prescribed medications, diagnoses, and mortality. The diagnostic code was based on the International Classification of Diseases, 10th revision (ICD-10). Among adult (age ≥ 18 years) patients with end-stage renal disease (ESRD) requiring maintenance dialysis, 23,317 patients who experienced a first-time ASCVD event between January 1, 2013, and December 31, 2018, were identified. The index date was defined as the date when the patient was diagnosed with ASCVD for the first time during the study period. If a patient had an admission, the index date was defined as the discharge date. To address the beneficial effect of statin therapy in patients on dialysis after a new ASCVD event, we excluded patients with preexisting ASCVD by eliminating all cases with inpatient, outpatient, or emergency room claims for ASCVD during six months preceding the cohort entry date. This study was conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines¹⁸. All methods were performed in accordance with the relevant guidelines and regulations. This study was approved by the Institutional Review Board (IRB) of Daejeon St. Mary’s Hospital (IRB number: DC21ZESE0018). The IRB of Daejeon St. Mary’s Hospital waived the requirement for informed consent because the data analyses were performed retrospectively using anonymized data derived from the Korean NHIS database, which is publicly available via the official website (https://nhiss.nhis.or.kr/).