A national population-based study of patients, bystanders and contextual factors associated with resuscitation in witnessed cardiac arrest: insight from the french RéAC registry

In the French national registry, we observed disparities in OHCA rate, patient’s age and initiation of bystander CPR according to the level of social deprivation of the place where OHCA occurred. These results persist after taking co-variables into account in multivariable analyses. This translates that the observed association between the social deprivation level of the place where a witnessed OHCA occurred and the CPR initiation by the bystander was not explained by differences in both the context, patients, and bystander characteristics included in the models.

In our study, we found more than one third of OHCA occurred in a high deprivation area. This over-representation of the most deprived areas in the OHCA caseload could support the impact of the area level of deprivation on OHCA incidence [13]. In the multivariable analysis, the OHCA area level social deprivation was negatively associated with the CPR initiation by the bystander. This observation is reinforced when considering that patients were younger in the most deprived areas. A challenge related to the optimised implementation of the chain of survival is the limitation of no-flow duration, that is bystanders’ ability to initiate CPR immediately after recognising OHCA [19]. Regardless the location of the OHCA, its aetiology or patient’s characteristics (e.g. gender, age), ROSC likelihood of occurrence and survival rate depend on the no-flow duration [25]. Regarding OHCA prognosis and outcome, patient’s age was described as negative predictor of overall survival and of survival with good neurological outcome [26, 27]. In our study, patients with OHCA in the area with the highest social deprivation level were younger and also with the fewest bystander-initiated CRP rate.

In the Korea nationwide registry, the temporal trend in bystander CPR increased in a different way considering the area average socioeconomic status. In ten years, the rate of bystander CPR increased by 22% in the least deprived areas versus 11% in the most deprived areas [28]. Public access to a defibrillator also varied widely depending on social factors. Lee et al. estimated that there were 12.7 defibrillators per 10,000 persons in the least deprived areas versus 4.9 defibrillators per 10,000 persons in the most deprived areas [29]. There are still considerable efforts to implement for improving the first link in the chain of survival. Until society becomes more aware, the use of mobile phone technology could bridge the current gap. Several software exists on smartphones that aim at helping to recruit laypersons to perform CPR while waiting the rescue teams [30]. Our findings point out the need to improve the bystander-initiated CPR rate in the most deprived area.

Our study has some limitations. We excluded numerous patients due to missing values or the impossibility to geocode the address, raising concerns about selection bias (Supplementary data, Table 1). However, results from Additional file 1: appendix 1 show differences between the included and excluded populations that are not clinically relevant although statistically significant, likely due to the width of the sample size. In addition, missing data in covariables included in the multivariable model concerned less 2% of the whole sample, minimizing the risk of selection bias. The sensitivity analyses carried on after the imputation of the missing data using a multiple imputation method provide similar results, supporting the robustness of our observations (Supplementary data, Table 2). As said above, we were not able to collect the bystanders’ individual socioeconomic position. We used a validated ecological index, the French EDI [31]. It was developed to allow comparison between European countries and used to approach the individual-level position in various studies [32‐35]. The EDI value was assessed from the residence address of the inhabitants of the area where OHCA occurred. Thus, the association between bystander CPR and OHCA-area deprivation may reflect an environmental effect as well, due to the area intrinsic characteristics as the effect associated with the characteristics of the whole daily population (i.e. the population generally occupying the area), or both. The underlying mechanisms remain to be investigated using more specific tools allowing for assessing the time-dynamic variation of areas social composition, (for instance the Mobiliscope project, www.​mobiliscope.​cnrs.​fr), as well as through a more qualitative approach to investigate the potential brakes and levers linked with CPR initiation by bystander. Finally, despite these limitations, we were able to provide a nationwide assessment of the association between the deprivation level of the area where OHCA occurred and CPR initiation by the bystander, supporting the idea of a need of improvement if the more deprived areas. This study constitutes the first steps for a future in depth analyse of the pathways linking the social deprivation of the area where OHCA occurred to bystander CPR initiation, through a causal perspective.