The supplementary online content provides additional information and detailed analyses from the study by Yagi R et al. (2024) published in *JAMA Internal Medicine*. The supplementary materials include: 1. **eTable 1**: A classification system for ECG abnormalities. 2. **eTable 2**: ECG categorizations from 2015 and 2016. 3. **eTable 3**: Sensitivity analysis adjusting for medication use, including hazard ratios (HRs) for endpoints adjusted for various factors such as age, sex, BMI, comorbidities, blood pressure, glucose, LDL, and estimated glomerular filtration rate. 4. **eTable 4**: HRs for overall death and CVD admission, adjusted for similar factors as in eTable 3. 5. **eTable 5**: Proportion of follow-up ECGs in individuals with ECGs in 2016. 6. **eTable 6**: Association of minor ECG abnormalities with the composite endpoint, adjusted for multiple comparisons using the Benjamini-Hochberg method. 7. **eTable 8**: Number of echocardiogram and catheterization procedures within one year after baseline ECG. 8. **eFigure 1**: Schoenfeld residual plots, adjusted for similar factors as in eTable 3. 9. **eFigure 3**: Comparison of risks of new major ECG abnormalities across subgroups by baseline CVD risk, including overall population, low CVD risk population, and moderate-high CVD risk population, adjusted for similar factors as in eTable 3. These supplementary materials provide comprehensive insights into the study's methodology, results, and statistical analyses.The supplementary online content provides additional information and detailed analyses from the study by Yagi R et al. (2024) published in *JAMA Internal Medicine*. The supplementary materials include: 1. **eTable 1**: A classification system for ECG abnormalities. 2. **eTable 2**: ECG categorizations from 2015 and 2016. 3. **eTable 3**: Sensitivity analysis adjusting for medication use, including hazard ratios (HRs) for endpoints adjusted for various factors such as age, sex, BMI, comorbidities, blood pressure, glucose, LDL, and estimated glomerular filtration rate. 4. **eTable 4**: HRs for overall death and CVD admission, adjusted for similar factors as in eTable 3. 5. **eTable 5**: Proportion of follow-up ECGs in individuals with ECGs in 2016. 6. **eTable 6**: Association of minor ECG abnormalities with the composite endpoint, adjusted for multiple comparisons using the Benjamini-Hochberg method. 7. **eTable 8**: Number of echocardiogram and catheterization procedures within one year after baseline ECG. 8. **eFigure 1**: Schoenfeld residual plots, adjusted for similar factors as in eTable 3. 9. **eFigure 3**: Comparison of risks of new major ECG abnormalities across subgroups by baseline CVD risk, including overall population, low CVD risk population, and moderate-high CVD risk population, adjusted for similar factors as in eTable 3. These supplementary materials provide comprehensive insights into the study's methodology, results, and statistical analyses.