Table 4.

C-index values

		# variables in model	Derivation Cohort	Validation Cohort
	n Deaths		22,097 819 (3.7%)	11,048 410 (3.7%)
Prediction models utilizing all covariates
Model 1	RSF	499	0.6815	0.6710
Model 2	Cox	499	Did not converge
Model 3	I1-penalized Cox	499	Did not converge
Model 4	AIC-penalized Cox	499	Did not converge
Prediction models utilizing covariates selected by variable selection methods
Model 5	RSF	20	0.6992	0.6934
Model 6	Cox	20	0.6954	0.6975
Model 7	I1-penalized Cox	59	0.7003	0.6978
Model 8	AIC-penalized Cox	22	0.7005	0.6980

Models 1–4 utilize all 499 demographic, clinical, and ECG variables available.

Models 5–6 utilize 20 variables selected by RSF variable selection method (Demographic/clinical: age, waist-to-hip ratio, smoking, income, systolic blood pressure, body mass index. ECG: SDNN, ventricular rate, T-wave area (lead I), P-wave intrinsicoid duration (leads V3, V4), P-wave duration (lead V2), T-wave amplitude (lead I), RMS-SD, T-wave axis, P-wave axis, P-wave amplitude (lead I), T-wave area (lead aVL), QT duration, P-wave area (lead V2))

Model 7 utilizes 59 variables selected by lasso approach from top 100 RSF variables (Demographic/clinical: age, waist-to-hip ratio, smoking, systolic blood pressure, income, body mass index, hypertension, education, diastolic blood pressure, marital status, alcoholic drinks per week, treated diabetes. ECG: SDNN, P-wave intrinsicoid duration (leads I, aVL, V2, V4, V5, V6), ventricular rate, P-wave duration (leads I, aVL, V2, V3, V6), RMS-SD, T-wave axis, P-wave axis, R-wave duration (leads aVF, V1, V4), P-wave area (leads I, V1), QRS intrinsicoid duration (lead I), T-wave intrinsicoid duration (leads I, III, aVL), P-wave amplitude (leads I, aVL, V5), T-wave area (leads aVR, V3), R-wave amplitude (leads II, V1, V5, V6), R-wave intrinsicoid duration (leads II, aVF, V1, V3, V4), P’-wave area (lead V1), R-wave area (leads III, aVL, V3, V6), T-wave amplitude (lead V1), QTc duration, P’-wave amplitude (lead V2))

Model 8 utilizes 22 variables selected by AIC stepwise approach from top 50 RSF variables (Demographic/clinical: age, waist-to-hip ratio, smoking, systolic blood pressure, income, body mass index, hypertension, education, marital status. ECG: ventricular rate, P-wave duration (lead V2), T-wave axis, P-wave axis, R-wave duration (lead V4), P-wave area (lead I), P’-wave intrinsicoid duration (lead aVL), QRS intrinsicoid duration (lead I), T-wave area (leads aVR, aVL), P-wave amplitude (lead I), R-wave intrinsicoid duration (lead aVF), R-wave area (lead V5))