Location of cardiac arrest and impact of pre-arrest chronic disease and medication use on survival

Introduction Cardiac arrest in a private location is associated with a higher mortality when compared to public location. Past studies have not accounted for pre-arrest factors such as chronic disease and medication. Aim To investigate whether the association between cardiac arrest in a private location and a higher mortality can be explained by differences in chronic diseases and medication. Methods We identified 27,771 out-of-hospital cardiac arrest patients ≥18 years old from the Danish Cardiac Arrest Registry (2001–2012). Using National Registries, we identified pre-arrest chronic disease and medication. To investigate the importance of cardiac arrest related factors and chronic disease and medication use we performed adjusted Cox regression analyses during day 0–7 and day 8–365 following cardiac arrest to calculate hazard ratios (HR) for death. Results Day 0–7: Un-adjusted HR for death day 0–7 was 1.21 (95%CI:1.18–1.25) in private compared to public location. When including cardiac arrest related factors HR for death was 1.09 (95%CI:1.06–1.12). Adding chronic disease and medication to the analysis changed HR for death to 1.08 (95%CI:1.05–1.12). 8–365 day: The un-adjusted HR for death day 8–365 was 1.70 (95% CI: 1.43–2.02) in private compared to public location. When including cardiac arrest related factors the HR decreased to 1.39 (95% CI: 1.14–1.68). Adding chronic disease and medication to the analysis changed HR for death to 1.27 (95% CI:1.04–1.54). Conclusion The higher mortality following cardiac arrest in a private location is partly explained by a higher prevalence of chronic disease and medication use in patients surviving until day 8.