Premature sudden death after out-of-hospital cardiac arrest: coroner-defined etiologies in a multi-ethnic southeast asian cohort

Background Out-of-hospital cardiac arrest (OHCA) is a leading cause of mortality globally, yet the underlying etiologies of OHCA deaths in young Asian populations remain poorly characterized. Understanding the causes of OHCA in this group is essential to refine risk stratification, guide family evaluation, and inform targeted prevention strategies. Purpose To characterise the etiologies of OHCA deaths in a multi-ethnic Southeast Asian cohort of young adults referred to the Coroner, and to examine sex-based differences. Methods We identified OHCA patients aged 16-50 years from the Singapore national OHCA registry between 2018-2021 and linked data to Coroner’s reports. Baseline demographics and comorbidities data were obtained from the national registry. Etiologies were assigned by the Coroner based on autopsy findings, imaging studies, and documented clinical records; where more than one contributing condition was present, the primary etiology was adjudicated and secondary etiologies were recorded. Etiologies were compared between males and females using chi-square tests. Results Among all OHCA deaths in this age group (n=1414), only 742 (52.5%) were referred to the Coroner and included in this analysis (median age 42 years, 76% males). Only 358 (48.2%) underwent postmortem autopsy, while 384 (51.8%) were certified by the Coroner without autopsy. The most common comorbidities were hypertension (21.6%), hyperlipidemia (16.2%) and diabetes mellitus (15.4%). Coronary artery disease (CAD; 36.7%) was the leading cause of OHCA, followed by cardiomyopathy (16.2%) and multiple injuries (12.2%; Table 1). Overall, 61.1% of etiologies were cardiovascular, including hypertensive cardiomyopathy, myocarditis, aortopathy, pulmonary embolism, and valvular heart disease. Cardiac causes were more common in males than females (66% vs. 46%; Figure 1A-B), and driven by higher CAD prevalence (43.6% vs. 14.8%, p<0.001). In contrast, non-cardiac etiologies including respiratory (12.6% vs. 3.8%, p<0.001), metabolic and endocrine (3.8% vs. 0.5%, p=0.003), and neurological disorders (12.6% vs. 4.5%, p<0.001) were more common in females. Conclusion Among Coroner-referred OHCA deaths in young, multi-ethnic Southeast Asian adults, there was a predominance of cardiovascular causes including CAD, particularly in men. Women had a substantially higher burden of non-cardiac causes, underscoring important sex-based differences in mechanisms of sudden death. The overall high burden of CAD and cardiovascular risk factors observed in patients with OHCA deaths suggests a potential role for cardiovascular risk factor screening and management. Furthermore, only around half of all OHCA deaths were referred for medicolegal evaluation, highlighting the need for more systematic postmortem investigation and sex-informed prevention strategies in this population.