Epidemiology

Due to its sudden nature and often unrecognised arrhythmic aetiology, the epidemiological characteristics of cardiac arrest are difficult to determine with precision. Nevertheless, estimates can be made. Because of fundamental differences in the underlying pathogenesis and system of care, epidemiological data for out-of-hospital cardiac arrests (OHCA) and in-hospital cardiac arrests (IHCA) are collected and reported separately.[2]​​ In the US, in 2023, the incidence of individuals of any age experiencing emergency medical services-assessed OHCA was 83.4 per 100,000.[2]​​​ In Europe, this figure has been reported as 84 per 100,000 population per year.[3]​ In the US, incidence of IHCA varies across hospitals, from 2.4 to 25.5 per 1000 admissions, resulting in 292,000 cases annually.[2][4]

Despite advances in the treatment of cardiac arrest, prognosis remains poor. According to the US Cardiac Arrest Registry to Enhance Survival (CARES), survival to hospital admission after emergency medical services-treated non-traumatic OHCA in 2023 was 26.1% for all presentations in adults, with higher survival rates in public places (38%) and lower survival rates in homes/residences (24.6%) and nursing homes (15.8%). Survival to hospital discharge after OHCA was estimated to be 10.2%.[2]​ Overall survival to hospital discharge after IHCA was 25.8% according to the UK National Cardiac Arrest Audit between 2022 and 2023. Survival was 52.9% when the initial rhythm was shockable, 17.1% when the initial rhythm was non-shockable pulseless electrical activity (PEA), and 11.5% when the initial rhythm was non-shockable asystole.[5] According to multiple studies, women with OHCA are older, less likely to present with shockable rhythms, and less likely to collapse in public compared with men. Despite these factors that are known to reduce survival, women have been shown to have equivalent or higher rates of survival to hospital discharge or to 30 days relative to men.[6]​​

If resuscitation attempts are unsuccessful, the situation is referred to as sudden cardiac death (SCD). Incidence of SCD increases with age; it is, around 50 per 100,000 person-years in the fifth to sixth decades of life, rising to at least 200 per 100,000 in the eighth decade of life.[7] At any age, men have higher SCD rates compared with women, even after adjustment for risk factors of coronary artery disease.[7] Ethnic background also has a large effect, with black people, particularly women, having a higher incidence of SCD compared to white people.​[7][8]​​​​​ In the Atherosclerosis Risk in Communities (ARIC) study, the sex-adjusted hazard ratio (HR) for SCD comparing black with white participants was 2.12, with a fully adjusted HR of 1.38. The reasons for this disparity are not fully understood, but lower socioeconomic status and a higher prevalence of cardiovascular risk factors (particularly diabetes and hypertension) have been shown to be important contributors.[8]

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