Exploring gender differences and the "oestrogen effect" in an Australian out-of-hospital cardiac arrest population.

BACKGROUND: Recent studies have suggested gender differences in out-of-hospital cardiac arrests (OHCA) including outcomes favouring young women. We aimed to investigate these findings in an Australian OHCA population using the Victorian Ambulance Cardiac Arrest Registry (VACAR).

METHODS AND RESULTS: The VACAR was searched for adult presumed cardiac OHCAs between 2003 and 2010 where Emergency Medical Services (EMS) attempted resuscitation. Gender and age differences in survival to hospital arrival and to hospital discharge were examined using logistic regression adjusting for known predictors of survival. There were 10,453 OHCA meeting inclusion criteria (863 aged between 18 and 44 years). Women were less likely to be younger, have a witnessed arrest, receive bystander CPR, arrest in a public place, have an initial shockable rhythm or receive transport to 24-h cardiac interventional hospital. After adjusting for differences in pre-hospital factors, women were more likely to survive to hospital arrival than men (aOR 3.47, 95% CI: 2.19-5.50), but no gender differences were seen in survival to hospital discharge either overall or specifically in women aged between 18 and 44 years. Both younger men and younger women were more likely to survive to hospital discharge compared to older men and women.

CONCLUSION: Women were more likely to survive to hospital arrival despite less favourable baseline variables. However, this initial improvement in survival did not translate to better survival to hospital discharge either overall, or in women of a reproductive age. Further study is required to determine gender differences in the underlying causes of OHCA and in EMS transportation practices.