Underuse of Bystander Defibrillation on Females During Out-of-Hospital Cardiac Arrest: A Retrospective Observational Study in Aotearoa New Zealand

Abstract

Introduction Early bystander CPR and defibrillation improve cardiac arrest survival. International studies show women receive fewer bystander interventions after out-of-hospital cardiac arrest (OHCA) than men. We investigated associations between sex and bystander interventions in OHCA in Aotearoa New Zealand. Methods Retrospective cohort study of adult OHCA with attempted resuscitation (January 2019–December 2023). Variables included demographics, ethnicity, socioeconomic deprivation, rurality, location type, and witness status. Logistic regression assessed associations between sex and bystander CPR and bystander defibrillation (shock delivered), adjusting for covariates. Results Of 9377 OHCA events, 29.6% occurred in females. Bystander CPR rates were similar between females (75.7%) and males (77.3%) (AOR 1.06, 95% CI: 0.94–1.18, p = 0.36). However, bystander defibrillation occurred in only 1.9% of females versus 5.4% of males. Females had 65% lower odds of receiving bystander defibrillation in unadjusted analysis (UOR 0.35, 95% CI: 0.26–0.47, p ' 0.001) and 39% lower odds after adjustment (AOR 0.61, 95% CI: 0.44–0.84, p = 0.002). Among shockable rhythm cases, sex disparity was not significant (AOR 0.83, 95% CI: 0.59–1.15, p = 0.26). Conclusion Despite equitable bystander CPR rates, females had significantly lower odds of receiving bystander defibrillation. In shockable rhythm cases, the disparity was not significant after adjustment for covariates, suggesting that patient and event characteristics mediate rather than confound this relationship. Findings highlight the need for targeted interventions addressing strategies to improve bystander defibrillation for females in cardiac arrest.