Individual socioeconomic status and risk of out‐of‐hospital cardiac arrest: A nationwide case–control analysis

OBJECTIVES: Area-level socioeconomic status (SES) is associated with the incidence of out-of-hospital cardiac arrest (OHCA); however, the effects of individual-level SES on OHCA occurrence are unknown. This study investigated whether individual-level SES is associated with the occurrence of OHCA. METHODS: This case-control study used data from the nationwide OHCA registry and the National Health Information Database (NHID) in Korea. All adult patients with OHCA of a medical etiology from 2013 to 2018 were included. Four controls were matched to each OHCA patient based on age and sex. The exposure was individual-level SES measured by insurance type and premium, which is based on income in Korea. National Health Insurance (NHI) beneficiaries were divided into four groups (Q1-Q4), and medical aid beneficiaries were separately classified as the lowest SES group. The adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for the outcomes were calculated. Stratified analyses were conducted according to age and sex. RESULTS: A total of 105,443 cases were matched with 421,772 controls. OHCA occurred more frequently in the lower SES groups. Compared with the highest SES group (Q1), the aORs for OHCA occurrence increased as the SES decreased (aORs [95% CI] were 1.21 [1.19-1.24] for Q2, 1.33 [1.31-1.36] for Q3, 1.32 [1.30-1.35] for Q4, and 2.08 [2.02-2.13] for medical aid). Disparity by individual-level SES appeared to be greater in males than in females and greater in the young and middle-aged adults than in older adults. CONCLUSIONS: Low individual-level SES was associated with a higher probability of OHCA occurrence. Efforts are needed to reduce SES disparities in the occurrence of OHCA.