ORIGINAL RESEARCH Pre-hospital outcomes of adult out-of-hospital cardiac arrest of presumed cardiac aetiology in Queensland, Australia (2002–2014): Trends over time Katherine PEMBERTON , 1,2 Emma BOSLEY , 2 Richard C FRANKLIN 1 and Kerrianne WATT 1 1 College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia, and 2 Queensland Ambulance Service, Brisbane, Queensland, Australia Abstract Objective: To describe temporal trends in incidence of pre-hospital outcomes from adult out-of-hospital cardiac arrest (OHCA) of presumed cardiac aetiology attended by Queensland Ambulance Service (QAS) paramedics between 2002 and 2014, by age, gender, geograph- ical remoteness and socio-economic status. Methods: Cases included in this ret- rospective cohort study were identi- fied from the QAS OHCA Registry. Included cases were linked with Queensland Hospital Admitted Patient Data Collection and Queens- land Death Registry. Population data were obtained from the Australian Bureau of Statistics to calculate inci- dence rates for each year. Analyses were undertaken by four mutually exclusive pre-hospital outcomes: (i) no resuscitation (No-Resus); (ii) resuscitation, no pre-hospital return of spontaneous circulation (No-ROSC); (iii) resuscitation, pre- hospital return of spontaneous circu- lation not sustained to hospital (Unsustained-ROSC); and (iv) resusc- itation, pre-hospital return of spon- taneous circulation sustained to hospital (Sustained-ROSC). Trends over time were analysed for crude and specific rates for total OHCA events and for each outcome. Results: Between 2002 and 2014, there were 30 560 OHCA cases. Crude incidence significantly increased over time for No-Resus and Sustained-ROSC, and signifi- cantly decreased for No-ROSC. These trends were reflected in major cities, inner and outer regional areas. There was a significant increase in Sustained-ROSC in remote areas, and no significant trends in very remote areas. Conclusion: Incidence of withhold- ing resuscitation and ROSC sustained to hospital have indepen- dently increased over time. Factors of middle age, more rural location and lower socio-economic status should all be targeted in the develop- ment and implementation of future strategies. Key words: cardiac arrest, emer- gency medical services, epidemiol- ogy, pre-hospital. Introduction Out-of-hospital cardiac arrest (OHCA) is a leading cause of mor- tality. Incidence differs globally 1,2 and changes over time, depending on the sub-group of interest. 3,4 Patient outcomes from OHCA are routinely reported as proportions; 2,5–9 how- ever, incidence provides a more meaningful measure as it accounts for changes in population size and demography, better informing the true burden. Therefore, reporting incidence of outcomes from OHCA over time is preferable and essential to inform the impact of previous change and future direction. While there are published studies of tempo- ral trends in OHCA incidence, there are none reporting temporal trends in OHCA incidence by outcome. Several studies investigated OHCA incidence over time in the subgroup of patients who were in a shockable rhythm and received a resuscitation attempt; 10–12 all showed declining rates. Two studies examined trends over time in OHCA incidence of patients who received a resuscitation attempt, by initial rhythm. 13,14 The first study (1992–2002) reported a reduction in shockable cases, increase in asystolic cases and no changes in cases of pulseless electrical activity (PEA). 13 The second study (2003–2012) re- ported increases in annual overall incidence, and by presenting rhythm (ventricular fibrillation/ventricular tachycardia and PEA/asystole), in Correspondence: Ms Katherine Pemberton, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD 4811, Australia. Email: katherine.pemberton@my.jcu.edu.au Katherine Pemberton, BSc (Hons) (ParaSc), Critical Care Paramedic; Emma Bosley, BSc (Psych), PGBSc (Hons) (Psych), PhD, Director; Richard C Franklin, BSc, MSocSc (Health), PhD, Associate Professor; Kerrianne Watt, BSc (Hons) (Psych), PhD, Associate Dean. Accepted 14 June 2019 Key findings • Incidence of No-Resus and Sustained-ROSC significantly increased over time. • Evidence of a positive impact of remote-specific strategies. • Trends over time varied by SES – Sustained-ROSC increased over time for all categories. © 2019 Australasian College for Emergency Medicine Emergency Medicine Australasia (2019) doi: 10.1111/1742-6723.13353