Sex differences in out-of-hospital cardiac arrest

Aims: The impact of resuscitation care initiatives on sex-differences in out-of-hospital cardiac arrest (OHCA) survival remains unclear. We aim to examine sex-differences in characteristics and survival. Methods and results: This Danish register-based study (2001-2020) included adult patients with a presumed cardiac cause of arrest. Temporal trends in survival were stratified by sex and subgroups: (i) bystander-witnessed status; (ii) bystander cardiopulmonary resuscitation (CPR); (iii) initial shockable heart rhythm; and age groups of <50, 50-75, and >75 years. To examine the association between sex and survival, we conducted adjusted logistic regression analyses. Among 50 066 OHCAs, women represented 34%. Women were older, had more chronic obstructive pulmonary disease, and lower prevalence of cardiovascular and cardiometabolic conditions than men. Women also had more OHCA at home (83.4 vs. 74.1%), fewer witnessed arrests (48.1 vs. 52.9%), half the probability of initial shockable heart rhythm (13.6 vs. 27.6%), and similar rates of receiving bystander-CPR. Survival rates improved over time for both sexes, but men had higher 30-day survival than women, even in subgroup and adjusted analyses [odds ratios (OR): 1.29; 95% confidence intervals (CI): 1.15-1.45, P < 0.001]. Sex-differences in survival were larger among those aged 50-75 years (in absolute and relative rates) and bystander witnessed arrests, while differences were smaller in those with initial shockable heart rhythms. Conclusion: Despite increases in 30-day survival for both sexes, women consistently had lower survival rates than men. Sex-differences were larger among those aged 50-75 years or with bystander witnessed arrests, but smaller in the subset of patients with an initial shockable heart rhythm.