Long-term risk of sudden cardiac death according to cumulative smoking exposure and smoking cessation in the Copenhagen City Heart Study

Abstract Smoking is a major risk factor for cardiovascular disease, but the long-term relationship between cumulative smoking exposure, smoking cessation, and sudden cardiac death (SCD) remains incompletely understood. We investigated these associations in 10,038 participants from the Copenhagen City Heart Study who were followed for a median of 28.6 years. Smoking exposure was assessed using smoking status, cumulative pack-years, and years since smoking cessation, and SCD events were identified using standardized adjudication criteria. Cause-specific Cox proportional hazards models accounting for competing risks were used to estimate associations with SCD. During 188,870 person-years of follow-up, 890 participants experienced SCD. Compared with never smokers, the adjusted hazard ratio for SCD was 1.88 (95% confidence interval [CI] 1.54–2.29) among current smokers and 1.34 (95% CI 1.09–1.66) among former smokers. A clear dose–response relationship was observed, with progressively higher SCD risk across increasing categories of cumulative smoking exposure, reaching a hazard ratio of 2.50 (95% CI 1.89–3.32) in the highest exposure category. Among former smokers, SCD risk declined with increasing time since smoking cessation and approached that of never smokers only after prolonged abstinence. These findings provide long-term population-based evidence that cumulative smoking exposure is strongly associated with SCD risk and that smoking cessation is associated with gradual but prolonged risk reduction. The results reinforce the importance of smoking prevention and early smoking cessation to reduce the burden of SCD.