Abstract Body: Background:
Bystander cardiopulmonary resuscitation (BCPR) is associated with improved survival after out of hospital cardiac arrest (OHCA). Adult females have better outcomes compared to males following OHCA, but are less likely to receive BCPR. Whether these sex differences exist across all ages is unknown. We hypothesized that adult and adolescent females will have higher survival outcomes, while there will be no difference between female and male children. We also hypothesized that more adult and adolescent females would receive BCPR, with no differences by sex in children.

Methods:
A retrospective cohort study was conducted utilizing the Cardiac Arrest Registry to Enhance Survival database. Adults were defined as ≥19 years of age, adolescents as 13-18 years, and children as <13 years. The primary outcome was survival to hospital discharge. Secondary outcome was BCPR. Multivariate analyses were conducted to assess differences by sex and age.

Results:
Of 869,828 OHCAs, 551,747 (63%) were males, 842,903 (97%) adults, 21,337 (2%) adolescents, and 5,588 (1%) children. In univariable analyses, 107,117 (39%) of females received BCPR compared to 197,435 (41%) of males (p<0.01). In adults, 39% of females and 40% of males received BCPR (p<0.01); in adolescents, 51% of both males and females received BCPR (p=0.8); and in children 47% of females and 48% of males received BCPR (p=0.05). In multivariable analyses, across all ages, males had lower odds of survival to hospital discharge compared to females (OR 0.94, 95%CI 0.92,0.96). Age differences were observed with higher survival in male children (aOR 1.30, 95%CI 1.16,1.47) and adolescents (aOR 1.33, 95%CI 1.09-1.62). Adult males had lower survival to hospital discharge compared to females (aOR 0.95, 95%CI 0.94,0.97). Males were more likely to receive BCPR (aOR 1.02, 95% CI 1.01,1.03) when considering all ages.

Conclusion:
We observed sex related differences in survival to hospital discharge following OHCA, with males having lower odds of survival compared to females. This difference varied across ages, with male children and adolescents having higher, and male adults having lower survival to hospital discharge. Males across all ages were more likely to receive BCPR, though only adult males had significantly higher rates of BCPR than females. Further work is needed to better understand the mechanisms behind these observations and implement interventions that improve outcomes and BCPR across sex and age.