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Canadian Journal of Cardiology

FEMALE SEX IS NOT ASSOCIATED WITH INCREASED SURVIVAL AFTER NON-TRAUMATIC OUT OF HOSPITAL CARDIAC ARREST: A SYSTEMATIC REVIEW AND META-ANALYSIS

      Background

      Survival after out of hospital cardiac arrest (OHCA) remains low and there is increasing interest to determine if female sex is an important prognostic factor. Large prospective studies have demonstrated that females compared to males do not have improved survival to discharge. However, systematic reviews have reported significant survival benefits for females compared to males. The findings of these reviews may not be generalizable due to restricted inclusion criteria and pooling of adjusted and unadjusted effect estimates. This systematic review evaluates the relative and absolute associations of female sex with survival to discharge and survival to 30 days after non-traumatic OHCA.

      Methods and Results

      We searched Medline, Embase, CINAHL, Web of Science, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews from inception through June 2021 for published studies that evaluated female sex as a primary predictor or covariate in multivariable models of survival in adult patients with non-traumatic OHCA. Random-effects inverse variance meta-analyses were performed to calculate pooled odds ratios (ORs) with 95% confidence intervals (CI). The GRADE approach was used to assess evidence quality. Thirty studies with 1,068,788 patients were included in the meta-analyses. The proportion of female patients was 41% with an overall range of 19% to 56% and mean age of 65 ± 25 years. The pooled effect estimate did not demonstrate an association for female compared to male sex with survival to discharge (OR 1.03, 95% CI 0.95-1.12; I2=89%). Subgroup analysis of low risk of bias studies demonstrated an association between female sex and increased survival to discharge (OR 1.20, 95% CI 1.18-1.23; I2=0%) (Table 1). With high certainty in the evidence, the absolute increase in survival to discharge for females was 2.2% (95% CI 0.1%-3.6%). Female sex was not associated with survival to 30 days post-OHCA (OR 1.02, 95% CI 0.92-1.14; I2=79%) (Table 1).

      Conclusion

      In adult patients experiencing OHCA, with high certainty in the evidence from studies with low risk of bias, female sex was a small and not clinically important prognostic factor for survival to discharge. Differences in survival between men and women are likely to be related to the severity and type of disease leading to the OHCA, the response in the field, and the type of treatment in hospital. Future models that aim to stratify risk of survival post-OHCA should focus on sex-specific factors as opposed to sex as an isolated prognostic factor.
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