Income-related disparities in sudden cardiac arrest among young adults: a nationwide cohort study

BACKGROUND: Socioeconomic disparities are associated with sudden cardiac arrest (SCA) in older populations, but evidence in young adults is limited. We investigated the association between income status, geographical region and SCA risk among young adults in South Korea. METHODS: Using the Korean National Health Insurance Service database, we identified 6 307 644 adults aged 20-39 years who underwent health screening between 2009 and 2012. Income status was defined by insurance premium quartiles and medical aid status. The primary outcome was incident SCA through December 2020. Multivariable Cox regression models were used to estimate adjusted HRs with 95% CIs. RESULTS: Over a mean follow-up of 9.4 years, 5340 individuals (0.08%) experienced SCA. Crude incidence rates were similar across income quartiles (0.09 per 1000 person-years) but highest among medical aid beneficiaries (0.28 per 1000 person-years; 95% CI 0.21 to 0.39). After multivariable adjustment, higher income was associated with lower SCA risk (adjusted HR for highest vs lowest quartile 0.67; 95% CI 0.61 to 0.73), while medical aid beneficiaries had substantially higher risk (adjusted HR 3.44; 95% CI 2.49 to 4.74). Geographical variation in SCA incidence was modest, and no significant interaction between income status and region was observed. Mediation analysis showed that modifiable risk factors explained only a small proportion of the income-SCA association. CONCLUSIONS: Lower income status, particularly receipt of medical aid, was independently associated with higher SCA risk among young adults. Socioeconomic disparities in SCA risk were not fully explained by lifestyle or metabolic factors.