One‐year survival after out‐of‐ hospital cardiac arrest: Sex‐based survival analysis in a Canadian population

Objective We investigated sex differences in 1-year survival in a cohort of patients who survived out-of-hospital cardiac arrest (OHCA) to hospital discharge. We hypothesized that female sex is associated with higher 1-year posthospital discharge survival. Methods A retrospective analysis of linked data (2011–2017) from clinical databases in British Columbia (BC) was conducted. We used Kaplan–Meier curves, stratified by sex, to display survival up to 1-year, and the log-rank test to test for significant sex differences. This was followed by multivariable Cox proportional hazards analysis to investigate the association between sex and 1-year mortality. The multivariable analysis adjusted for variables known to be associated with survival, including variables related to OHCA characteristics, comorbidities, medical diagnoses, and in-hospital interventions. Results We included 1278 hospital-discharge survivors; 284 (22.2%) were female. Females had a lower proportion of OHCA occurring in public locations (25.7% vs. 44.0%, P < 0.001), a lower proportion with a shockable rhythm (57.7% vs. 77.4%, P < 0.001), and fewer hospital-based acute coronary diagnoses and interventions. One-year survival for females and males was 90.5% and 92.4%, respectively (log-rank P = 0.31). Unadjusted (hazard ratio [HR] males vs. females 0.80, 95% confidence interval [CI] 0.51–1.24, P = 0.31) and adjusted (HR males vs. females 1.14, 95% CI 0.72–1.81, P = 0.57) models did not detect differences in 1-year survival by sex. Conclusion Females have relatively unfavorable prehospital characteristics in OHCA and fewer hospital-based acute coronary diagnoses and interventions. However, among survivors to hospital discharge, we found no significant difference between males and females in 1-year survival, even after adjustment.