Clinical PaperSurvival after out-of-hospital cardiac arrest in relation to sex: A nationwide registry-based study☆
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.