# Underuse of bystander defibrillation on females during out-of-hospital cardiac arrest: a retrospective observational study in Aotearoa New Zealand

## TL;DR

Women in New Zealand are less likely to receive bystander defibrillation during cardiac arrests, despite equal CPR rates, suggesting a need for targeted interventions.

## Contribution

This study identifies sex disparities in bystander defibrillation in New Zealand and explores how patient and event characteristics mediate these disparities.

## Key findings

- Females had 39% lower odds of receiving bystander defibrillation compared to males after adjusting for covariates.
- In shockable rhythms, the sex disparity in defibrillation was not significant after adjustment.
- Ethnicity and socioeconomic deprivation contribute to layered inequities in emergency cardiac care.

## Abstract

•High overall bystander CPR rates (76.9%) with no sex-based differences.•Only 1.9% of females received defibrillation vs 5.4% of males in cardiac arrest.•Females had 39% lower odds of bystander defibrillation despite equal CPR rates.•In shockable rhythms, patient and event characteristics mediate the sex disparity in bystander defibrillation.•Ethnicity and deprivation create layered inequities in emergency cardiac care.

High overall bystander CPR rates (76.9%) with no sex-based differences.

Only 1.9% of females received defibrillation vs 5.4% of males in cardiac arrest.

Females had 39% lower odds of bystander defibrillation despite equal CPR rates.

In shockable rhythms, patient and event characteristics mediate the sex disparity in bystander defibrillation.

Ethnicity and deprivation create layered inequities in emergency cardiac care.

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.

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.

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).

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.