Socioeconomic inequalities in sudden cardiac arrest: An investigation into a psychobiological explanation

While SES gradients have been demonstrated in some cardiovascular disease outcomes, it remains unclear whether SES differences exist in out-of-hospital cardiac arrest (OHCA) and by what mechanism such inequalities
arise. One hypothesised ‘psychobiological’ pathway involves the chronic stress and altered autonomic nervous system activity, associated with SES, leading to an increased risk of OHCA. We investigated whether there is evidence for a causal relationship leading from socioeconomic status (SES) to OHCA and whether the hypothesised psychobiological pathway plays a role in this relationship.
According to our systematic search of the literature, the evidence on this relationship had a high risk of bias due to the use of neighbourhood level SES and cross-sectional study designs. We investigated the association between individual level income and OHCA longitudinally in a retrospective cohort. We found clear, consistent income gradients in women and men and most age groups. We also found SES gradients in measures of sympathovagal balance. We did not find evidence to suggest that this association was mediated by chronic psychosocial stress, however. We also did not find evidence for an association between SES and the diurnal rhythm of heart rate.
In conclusion, we found improved evidence for a causal relationship between SES and OHCA. We found some evidence for the role of a psychobiological mechanism in this relationship but not for the hypothesised role of chronic stress and diurnal rhythms of autonomic activity. Thus, low SES groups may be suitable target populations for interventions aiming to lower OHCA disparities.