Waist-to-hip ratio and risk of sudden cardiac death: a UK Biobank Cohort Study

Background Sudden cardiac death (SCD) remains a major contributor to cardiovascular mortality, often occurring unexpectedly in individuals without overt heart disease. Obesity is an established risk factor, but traditional anthropometric indices such as body mass index (BMI) may not adequately reflect central adiposity, which plays a key role in arrhythmogenic risk. We investigated the association between various anthropometric indices and the risk of SCD, with a focus on waist-to-hip ratio (WHR), a surrogate for visceral adiposity. Methods We analyzed 495,983 participants (age 40–69 years) from the UK Biobank with ≥1 year of follow-up and complete anthropometric and clinical data. Anthropometric indices included BMI, WHR, waist-to-height ratio (WHtR), relative fat mass (RFM), body shape index (BSI), and weight-adjusted waist index (WWI). SCD was defined using national death and hospital records with ICD-10 codes. Cox proportional hazards models were adjusted for demographics, lifestyle, and cardiometabolic comorbidities. Dose–response relationships were explored using restricted cubic splines, and the combined effect of WHR and cardiometabolic risk burden was assessed. Results Over a median follow-up of 12.3 years, 2,621 SCD events occurred. Among all indices, WHR demonstrated the strongest linear association with SCD risk, whereas BMI showed a U-shaped relationship (Fig A). WHR had the highest predictive performance (AUC = 0.672) and low collinearity with BMI (r = 0.43). Cumulative hazard curves demonstrated a stepwise increase in SCD risk across WHR quartiles (Q1–Q4), with the highest quartile showing the steepest cumulative hazard over time (Fig B). The association between WHR and SCD remained robust in fully adjusted models (HR for Q4 vs. Q1: 1.95; 95% CI: 1.58–2.41; p < 0.001).As shown in stratified analysis (Fig C), the risk of SCD increased progressively with the number of cardiometabolic risk factors (RF: hypertension, diabetes, dyslipidemia, smoking, and regular physical activity) and was consistently higher among participants with high WHR across all RF categories. Even among those with no risk factors, individuals with high WHR had significantly increased risk ((HR: 1.57, 95% CI: 1.25–1.96). The highest risk was observed in participants with both high WHR and ≥ 4 risk factors (HR 5.76, 95% CI: 4.48–7.41) Conclusion WHR was a strong and independent predictor of sudden cardiac death and outperformed BMI and other anthropometric indices. Its linear and graded association with SCD, even in individuals without traditional risk factors, supports incorporating WHR into routine cardiovascular risk assessment. WHR is a simple, low-cost, and scalable tool that can identify high-risk individuals who may benefit from early interventions to reduce SCD.