Heartbeat: sex-based discrepancies in survival from sudden cardiac death

Sudden cardiac death (SCD) is a major cause of death worldwide, with a higher prevalence in men compared with women. To further understand sex differences in SCD presentation and outcomes, Skjelbred and colleagues looked at data on deaths in Denmark in 2010 and found that SCD accounted for 12.7% of all deaths with a male predominant (56% men, 44% women). The average age at SCD was higher in women (79 years) compared with men (71 years), with the greatest sex difference in SCD incidence rates in the age group from 35 to 50 years (incidence rate ratio 3.7, 95% CI 2.8 to 4.8) (figure 1). Women, compared with men, more often died at home (80.5% vs 69.7%, p<0.01) rather than in the hospital (16.8% vs 22.2%, p<0.01). The cause of SCD was coronary artery disease in about 40% of cases. Other causes (each <5%) included cardiac arrhythmias, heart failure, aortic dissection, valve disease and cardiomyopathy. In the accompanying editorial, Tan and Remme suggest that SCD risk relates not only to biological sex differences but also to societal and environmental factors. In men, the cause of SCD usually is coronary artery disease and the initial rhythm typically is ventricular fibrillation. In contrast, the cause of SCD in women more often is ventricular hypertrophy, aortic dissection or myocarditis and the initial rhythm is likely to be pulseless electrical activity or asystole. Women also are more likely to have an unwitnessed event at home, thus, not receiving prompt resuscitation. Even when witnessed, women are less likely to be resuscitated by bystanders; the combination of a longer delay to resuscitation plus the low frequency of a shockable rhythm results in lower survival rates. The authors urge increased research and action to reduce the risk of SCD in both women and men. ‘Clearly, to reduce the societal burden of SCD, we must focus our efforts on earlier recognition of SCA risk. Given the complex underlying causes of SCA and in view of the observation that our ability at early recognition has been stagnant over the last decades, we must adopt a more comprehensive strategy and reap the benefit of relatively new methods which have so far been poorly used in SCA research, for example, artificial intelligencebased analysis of large data sets, genetic analysis and metabolomic analysis. We must also recognise that we should direct our view to the group in society that has so far received insufficient attention in SCA research, that is, individuals who are in the care of their general practitioner and have not (yet) been referred to a cardiologist.’ (figure 2). Another study in this issue of Heart addresses sex (biological) and gender (sociocultural) differences in cardiovascular disease (CVD) risk factors. Based