Objective To investigate the impact of pre-arrest comorbidities on future out-of-hospital cardiac arrest (OHCA) development using a nationwide dataset.

Methods This population-based, matched case-control study used the national health insurance claims data relevant to OHCA in South Korea from January 2009 to December 2018. Case patients were randomly matched to controls by age, sex and date of cardiac arrest. Controls were defined as patients who did not experience OHCA based on claim codes in national health screening data. The comorbidity burden was assessed using the Charlson Comorbidity Index (CCI).

Results A total of 191 370 OHCA patients were matched to 347 568 controls. The mean CCI in the case group was 3.76, which was significantly higher than that in the control group (1.75, p<0.001). Overall, OHCA was 1.35 (95% CI 1.34 to 1.35) times more likely to occur with every 1 point increase in the CCI. All other comorbidities constituting the CCI were associated with the OHCA risk (p<0.001). Patients with CCI ≥3 presented an OR of 3.71 (95% CI 3.67 to 3.76) for the risk of OHCA occurrence. This association was more pronounced in patients aged <70 years than in those aged ≥70 years (OR (95% CI) 16.07 (15.48 to 16.68) vs 6.50 (6.33 to 6.68)).

Conclusion A high burden of pre-arrest comorbidity was associated with a higher risk of OHCA development, which was more pronounced in patients with less advanced age.