Smoking and the risk of sudden cardiac arrest in young-aged adults: a Korean nationwide population-based study

Aims Smoking is a risk factor for cardiovascular events. Regarding the different aetiology of sudden cardiac arrest (SCA) in younger individuals compared with the elderly, we investigated the linkage between smoking and the risk of SCA in young-aged adults. Methods and results In this retrospective analysis, an observational longitudinal cohort was obtained from the national health screening database in South Korea. Adults aged between 20 and 39 years who underwent health screening from 2009 to 2012 were included. Smoking status was categorized as non-smokers, ex-smokers, and current smokers. The burden of smoking was classified as mild (<10 pack-years), moderate (<20 pack-years), and heavy smokers (≥20 pack-years). The primary outcome was the occurrence of SCA during follow-up. Among 6 293 672 individuals, the mean age was 30.8 years, and the median follow-up duration was 9.7 years. Comorbidities such as hypertension, diabetes mellitus, or dyslipidaemia were rare. Non-smokers were most prevalent (55.2%), followed by current smokers (34.8%) and ex-smokers (10.1%). The incidence of SCA increased from non-smokers (0.06 per 1000 person-years), ex-smokers (0.08), to current smokers (0.14). Current smokers showed increased risk of SCA compared with non-smokers (adjusted hazard ratio 1.69, 95% confidence interval 1.57–1.81, P < 0.001). The risk of SCA was not increased in ex-smokers (0.96, 0.86–1.07, P = 0.420). Higher smoking burden was associated with accelerated risk of SCA (adjusted hazard ratio in heavy smokers 2.15, 1.90–2.43, P < 0.001). Conclusion In young-aged adults, current smoking was associated with significantly increased risk of SCA in long-term follow-up. The risk of SCA showed a dose-dependent association with cumulative burden of lifetime cigarette exposure.