SUDDEN cardiac death risk increased substantially with cumulative smoking exposure and declined only gradually following smoking cessation, according to long-term findings from the Copenhagen City Heart Study.
Researchers analysed data from 10,038 participants who were followed for a median of 28.6 years.
Smoking exposure was assessed using smoking status, cumulative pack-years, and time since smoking cessation.
During 188,870 person-years of follow-up, 890 participants experienced sudden cardiac death.
Compared with never smokers, current smokers had a significantly greater risk of sudden cardiac death. Former smokers also remained at elevated risk.
At 20 years, sudden cardiac death incidence was 2.4% among never smokers, 3.2% among former smokers, and 3.8% among current smokers.
Sudden cardiac death consistently represented a substantial proportion of cardiac mortality across all smoking groups.
A clear dose-response relationship emerged when cumulative smoking exposure was assessed using pack-years. Compared with never smokers, risk increased progressively across exposure lengths.
Further analyses showed that both smoking intensity and smoking duration independently contributed to risk.
Each 10-cigarette per day increase in smoking intensity was associated with higher sudden cardiac death risk, while each 10-year increase in smoking duration was also associated with increased risk.
Among former smokers, risk declined with increasing duration of abstinence.
Participants who had stopped smoking within the previous 0 to 6 years had more than double the risk of sudden cardiac death compared with never smokers.
Risk remained elevated for many years, including among those who had quit for 15 to 26 years.
Only those with the longest duration of abstinence, between 26 to 67 years, showed a risk approaching that of never smokers.
The findings suggest that cumulative smoking exposure is strongly associated with sudden cardiac death risk, while smoking cessation offers meaningful but prolonged risk reduction.
The researchers concluded that preventing smoking initiation and promoting early cessation may be important strategies for reducing the long-term burden of sudden cardiac death.
Reference
Isozaki S et al. Long-term risk of sudden cardiac death according to cumulative smoking exposure and smoking cessation in the Copenhagen City Heart Study. Sci Rep. 2026;DOI:10.1038/s41598-026-67157-x
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