Abstract Body: Background: Sex-based differences in survival following out-of-hospital cardiac arrest (OHCA) have been widely studied, but the joint effect of age and sex remains unclear.

Aims: To examine the joint effect of age and sex on OHCA outcomes, hypothesizing that older females have lower rates of return of spontaneous circulation (ROSC) and survival to hospital discharge.

Methods: We conducted a retrospective analysis of prospectively collected data from the British Columbia (BC) site of the Resuscitation Outcomes Consortium (ROC) Cardiac Arrest registry (2011–2016). EMS-treated adult OHCA patients were included; traumatic arrests and DNR cases were excluded. Patients were stratified into four age-sex groups: younger females (18–47 years), younger males (18–47), older females (≥53), and older males (≥53). To reduce misclassification bias, we excluded 833 patients aged 48–52. Multivariable logistic regression assessed differences in ROSC and survival between groups, using younger females as the reference and adjusting for Utstein predictors.

Results: A total of 6,454 cases were included in the analysis. Older females had the lowest rates of public location arrests (7.1%) and shockable rhythms (12.4%). Crude ROSC rate was lowest in older females (33.9%) compared to other groups: older males (35.4%), younger males (38.7%), and younger females (38.9%) (p = 0.33). Crude survival to hospital discharge differed significantly across groups, with older females having the lowest survival rate (6.1%) (p < 0.001) (Table 1). After adjusting for Utstein predictors, the odds of ROSC were significantly lower in younger males (OR 0.76, p = 0.01), older females (OR 0.75, p = 0.006), and older males (OR 0.63, p < 0.001), compared to younger females (reference group). For survival to hospital discharge, older females had the lowest odds (OR 0.30, p < 0.001), followed by older males (OR 0.42, p < 0.001). The odds of survival in younger males did not differ significantly from younger females (OR 1.02, p = 0.87) (Table 2).

Conclusion: Older females exhibited the lowest rates of ROSC and survival to hospital discharge. Adjusted analysis confirmed significantly lower odds of both outcomes in this group. The lower prevalence of shockable rhythms among older females may partially explain these disparities; however, further investigation is warranted to identify additional factors contributing to these disparities in outcomes.