Abstract Sat605: Changing relative distribution of out-of-hospital cardiac arrest cases by sex

Background: The incidence of out-of-hospital cardiac arrest (OHCA) varies by sex with a higher incidence reported in males. Nationally, >60% of OHCA cases are male. However, long term trends in distribution of OHCA by sex have not been examined. In this study, we assessed the relative distribution of OHCA cases over time by sex in Chicago, and in Illinois. Methods: We analyzed adult non-traumatic OHCA cases reported to Cardiac Arrest Registry to Enhance Survival (CARES) database and served by Chicago Emergency Medical Services from 2014-2023. Annual data were combined to create two-year cycles. The trends in distribution by sex were examined overall, by etiology and by age. Analysis of drug overdose cases was limited to 2018-2023. Results: Of 27,011 OHCA cases in Chicago during the study period, 60.8% were males. The relative distribution by sex changed over the 10-year period. Males accounted for 57.7% of the cases in 2014-2015, and it increased to 62.9% by 2022-2023. This increase was consistent across cycles (p for trend<0.001). When stratified by etiology, similar increase was seen in relative proportion of male cases with presumed cardiac etiology (from 57.9% in 2014-2015 to 61.7% in 2022-2023). Proportion of male cases with drug overdose related OHCA also increased (71.0% in 2018-19 to 77.5% in 2022-23). In the age group >50 years, a consistent increase has been observed from 56.2% to 60.4% in the same time frame. Similarly among those <=50 years of age, the proportion of males has increased from 64% to 71.2% (but the increase has been inconsistent). These patterns are also reflected in OHCA incidence in Chicago. The overall incidence increased (from 83 per 100,000 in 2015 to 109 per 100,000 in 2023), and both males and females have seen an increase, but the increase has been more drastic in males (from 97 per 100,000 in 2015 to 141 per 100,000 in 2023) compared to females (71 per 100,000 in 2015 to 79 per 100,000 in 2023). A similar pattern has been noticed in Illinois overall (although the underlying area covered has also increased over time). Conclusion: This overall trend is not driven by the pandemic nor is it solely driven by overdose either. While aging population may have some effect on distribution by sex, the pattern persisted even after stratifying by age. The possibility of increasing comorbidity burden (including hypertension) in males may have contributed but needs to examined further. Similar trends need to be studied nationally.