Elsevier

Resuscitation

Volume 85, Issue 9, September 2014, Pages 1212-1218
Resuscitation

Clinical Paper
Survival after out-of-hospital cardiac arrest in relation to sex: A nationwide registry-based study

https://doi.org/10.1016/j.resuscitation.2014.06.008Get rights and content

Abstract

Aim

Crude survival has increased following an out-of-hospital cardiac arrest (OHCA). We aimed to study sex-related differences in patient characteristics and survival during a 10-year study period.

Methods

Patients ≥12 years old with OHCA of a presumed cardiac cause, and in whom resuscitation was attempted, were identified through the Danish Cardiac Arrest Registry 2001–2010. A total of 19,372 patients were included.

Results

One-third were female, with a median age of 75 years (IQR 65–83). Compared to females, males were five years younger; and less likely to have severe comorbidities, e.g., chronic obstructive pulmonary disease (12.8% vs. 16.5%); but more likely to have arrest outside of the home (29.4% vs. 18.7%), receive bystander CPR (32.9% vs. 25.9%), and have a shockable rhythm (32.6% vs. 17.2%), all p < 0.001. Thirty-day crude survival increased in males (3.0% in 2001 to 12.9% in 2010); and in females (4.8% in 2001 to 6.7% in 2010), p < 0.001.

Multivariable logistic regression analyses adjusted for patient characteristics including comorbidities, showed no survival difference between sexes in patients with a non-shockable rhythm (OR 1.00; CI 0.72–1.40), while female sex was positively associated with survival in patients with a shockable rhythm (OR 1.31; CI 1.07–1.59). Analyses were rhythm-stratified due to interaction between sex and heart rhythm; there was no interaction between sex and calendar-year.

Conclusions

Temporal increase in crude survival was more marked in males due to poorer prognostic characteristics in females with a lower proportion of shockable rhythm. In an adjusted model, female sex was positively associated with survival in patients with a shockable rhythm.

Introduction

Major efforts have been launched in many countries throughout the past decade to improve bystander resuscitation attempts and advance care following out-of-hospital cardiac arrest (OHCA).1, 2, 3, 4, 5, 6, 7 In parallel, patient survival has increased1, 2, 3, 4, 5, 6 and in Denmark survival rates have approximately tripled during the past decade and was associated with a concomitant increase in bystander cardiopulmonary resuscitation (CPR).1 Nevertheless, it remains unknown whether efforts to improve survival have different impact on male and female patients. Dissimilarities may exist, as a number of studies have shown sex-related differences in survival outcomes after OHCA.8, 9, 10, 11, 12, 13, 14, 15, 16 Accordingly, female sex has been associated with improved survival upon hospital arrival,8, 9, 10, 12, 15, 16 as well as improved 1-month survival/survival at discharge in the reproductive age11, 13, 14 and at all ages.10, 12 It has been proposed that female sex hormones may be the underlying factor for such findings,10, 11, 12, 13, 14 yet there are still factors that are incompletely understood or even not yet identified that influence survival.17, 18 As a result, little is known about comorbidity and concomitant pharmacotherapy in relation to sex and subsequent survival; these parameters could vary according to sex and influence the chances of survival following an OHCA.

This nationwide OHCA study focused on: (1) sex-related differences in patient characteristics and crude survival during a 10-year study period; and (2) the association between sex and survival when taking patient characteristics (including comorbidity) into account in multivariable analyses.

Section snippets

Population and setting

This study was conducted in Denmark, which has approximately 5.6 million inhabitants.19 Patients were included from June 1, 2001 to December 31, 2010.

Definition and registration of OHCA

A patient was included when a medical condition of cardiac arrest resulted in a resuscitation attempt either by emergency medical services (EMS) personnel or by a bystander. Consequently, the definition excluded patients with late signs of death (e.g., rigor mortis) where resuscitation attempts were not given. The capture of OHCA cases is close to

Patient-related characteristics

The final study population comprised 19,372 patients (Fig. 1). There were fewer females (32.6%), and median age was five years higher in females (75 years vs. 70 years, p < 0.001) (Table 1). The distribution of comorbidities and use of medicine was different between the sexes (Table 2). Female patients were more likely to have a history of chronic obstructive pulmonary disease, malignancy, and psychiatric illness. By contrast, male patients were more likely to have a history of cardiovascular

Discussion

Our nationwide OHCA study focused on sex-related differences in patient characteristics and survival during a 10-year period. The study had two major findings. First, the increase in 30-day crude survival was more marked in male patients (3.0% in 2001 to 12.9% in 2010) versus female patients (4.8% in 2001 to 6.7% in 2010). This was mainly due to poorer prognostic characteristics in females with a lower proportion of a shockable rhythm, and a lower 30-day crude survival in females among patients

Conclusions

During a 10-year study period, the increase in crude survival after OHCA was higher in males compared to females. This was mainly due to a higher proportion of males with a shockable rhythm, and a higher crude survival in males among patients with a non-shockable rhythm. Other important factors for the higher crude survival in males were the higher age in females, and that females more frequently had severe comorbidities, experienced cardiac arrest at home, and received no bystander

Conflict of interest statement

The authors have no relevant disclosures to report.

Acknowledgments

We would like to extend our sincere thanks to the Danish Emergency Medical Services personnel who have completed the case report forms for the Danish Cardiac Arrest Registry.

This study was supported by the TrygFond Foundation, the Danish Heart Foundation (grant no. 12-04-R91-A4036-22679), and the Health Insurance Foundation (grant no. 2012B078) (all from Denmark). The Danish Cardiac Arrest Registry is supported by the TrygFond Foundation. Dr. Gislason is supported by an independent clinical

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    A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.06.008.

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