ReviewAssociation of measures of socioeconomic position with survival following out-of-hospital cardiac arrest: A systematic review
Introduction
Cardiac arrest refers to sudden halting of cardiac mechanical activity, indicated by absence of signs of circulation.1 This may have a cardiac cause such as myocardial infarction, or non-cardiac cause such as drug overdose or airway obstruction.2 Out-of-hospital cardiac arrest (OHCA) is a particular healthcare challenge due to the need for rapid action and co-ordination of bystanders, emergency medical services (EMS), and hospital.3 The proportion of patients that survive OHCA varies between countries, but is generally low; a multicentre European study reported survival to hospital discharge in only 8% of patients who received cardiopulmonary resuscitation (CPR) (0–18% inter-country range).4
Work to understand predictors of OHCA survival may identify factors that could be targeted to improve survival, or highlight characteristics of populations with poor survival where interventions could be focused. Socioeconomic factors are one characteristic of interest. A recent systematic review found a generally consistent pattern of decreased OHCA survival in patients of lower socioeconomic position (SEP), such as 70% improved odds of 30-day survival in the most highly educated quintile relative to least,5 although several studies observed no such SEP-OHCA survival association.6 This was in addition to higher OHCA incidence in low SEP areas.6
Understanding which SEP measures, such as education or income, best identify likelihood of poor OHCA survival may help elucidate SEP-survival causal pathways and further guide targeting of interventions to subpopulations. Understanding whether the SEP-OHCA survival relationship differs by factors such as age and sex (effect modification) may also be informative here. While the previous review found insufficient evidence to draw conclusions around either of these aspects,6 we identified several additional relevant papers and therefore aimed to consider both aspects in more detail. We also considered the evidence for potential factors mediating any SEP-survival relationship, aiming to identify further potentially modifiable factors.
While population characteristics such as race and ethnicity may also be related to SEP in some settings, this is likely to vary significantly between countries. As we intended to review the global literature, we focused on economic factors such as education and income, considering these to be of broadest relevance.
Section snippets
Eligibility criteria
Eligibility criteria are detailed in Table 1. Briefly, primary studies considering the association of any SEP measure with any OHCA survival measure were eligible.
Study selection
MEDLINE and Embase databases were searched via Ovid using comprehensive search strategies (see supplementary materials), on 23 May 2019. All records were transferred into EndNote, duplicates removed, and initially screened by title or abstract to remove those clearly ineligible according to the Table 1 criteria. Full texts of
Results
The database searches yielded 3642 unique records, with 20 meeting the eligibility criteria. Reviewing their references yielded three more records. Fig. 1 outlines the number of records at each stage.
SEP-survival association
In almost all of the included studies, any association observed between a SEP measure and OHCA survival was in the direction of low SEP with decreased survival. The two exceptions are one study reporting an association of increased property value with decreased survival,11 and one reporting possible decreased survival in an intermediate income level relative to no income, but no association when comparing the most extreme categories.7 Though notably, several studies found no evidence of an
Conclusions
The current literature is generally supportive of any association of SEP with OHCA survival being in the direction of decreased survival with lower SEP, although an association is not seen in all studies. This further supports the need to reduce socioeconomic deprivation in society. It also suggests it may be appropriate to consider socioeconomic characteristics of populations when targeting CPR training and other resources to improve survival, especially given evidence of lower SEP being
Conflicts of interest
None.
Authors’ contribution
RC: Conceptualisation, Methodology, Data Curation, Analysis, Writing – Original Draft, Writing – Review & Editing. CB: Validation, Writing – Review & Editing. GC: Conceptualisation, Writing – Review & Editing. NH: Conceptualisation, Methodology, Writing – Review & Editing, Supervision.
Acknowledgement
Dr Halbesma is supported by a British Heart Foundation Intermediate Basic Science Research Fellowship (FS/16/36/32205).
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