Witnessed and unwitnessed sudden cardiac death: a nationwide study of persons aged 1–35 years

Abstract Aims The aim of this study is to compare clinical characteristics and causes of death among witnessed and unwitnessed sudden cardiac death (SCD) cases aged 1–35 years. Methods and results In this retrospective nationwide study, all deaths in persons aged 1–35 years in Denmark during 2000–09 were included (23.7 million person-years). Using the in-depth descriptive Danish death certificates and Danish nationwide registries, 860 cases of sudden, unexpected death were identified. Through review of autopsy reports and register data, we identified 635 cases of SCD of which 266 (42%) were witnessed and 326 (51%) were unwitnessed. In 43 cases (7%), witnessed status was missing. Clinical characteristics were overall similar between the two groups. We found a male predominance among unwitnessed SCD compared to witnessed SCD (71% and 62%, respectively, P-value 0.012), as well as more psychiatric comorbidity (20% and 13%, respectively, P-value 0.029). Unwitnessed SCD more often occurred during sleep whereas witnessed SCD more often occurred while the individual was awake and relaxed (P-value