Long term survival and disease burden from out-of-hospital cardiac arrest: a population-based cohort study
Authors: Ho A F W , Lim M J R , Earnest A , Ho J S Y , Graves N , Tiah L , Ong M E H 
Published: October 2022

Abstract

Background
Long-term outcomes of out-of-hospital cardiac arrest (OHCA) are important to evaluate the overall health burden of OHCA on society. The concept of disability-adjusted life years (DALY) have recently been utilised to measure disease burden in OHCA, but data in an Asian cohort remains limited. We aimed to quantify and identify predictors of long-term survival (up to 10 years follow up) in patients with OHCA, as well as to quantify the annual disease burden of OHCA estimated using DALY in a national multi-ethnic Asian cohort.

Methods
We conducted an open cohort study through the linkage of the Pan-Asian Resuscitation Outcomes Study and the Singapore Registry of Births and Deaths from 2010 to 2020 in Singapore [1]. We quantified long-term survival using the standardised mortality ratio (SMR) for each year of follow up and the annual disease burden using DALY. Predictors of long-term survival were identified using cox-proportional hazards models. Kaplan-Meier survival curves were constructed for the overall population, and by key characteristics. The proportion surviving (and 95% CI) was calculated for up to eight years post-OHCA.

Results
We included 802 cases in the analysis. The mean age was 56.0 (SD 17.8), 631 cases (78.7%) were male, and the majority (552 cases, 68.8%) were of Chinese ethnicity (Table 1). The proportion surviving at one year of follow up was 0.84 (95% CI: 0.81–0.87), at five years of follow up was 0.68 (95% CI 0.65–0.72), and at ten years of follow up was 0.62 (95% CI 0.57–0.67) (Figure 1). Age at arrest (HR 1.03, 95% CI: 1.02–1.04, p&lt;0.001), shockable first arrest rhythm (HR 0.75, 95% CI: 0.52–0.93, p=0.015) and Cerebral Performance Category (CPC) (HR 4.62, 95% CI: 3.17–6.75, p&lt;0.001) were independently associated with mortality (Figure 2, 3). At one year, the SMR was 14.9 (95% CI: 12.5–17.8), and this decreased to 1.2 (95% CI: 0.7–1.8) at three years, and 0.4 (95% CI: 0.2–0.8) at five years (Figure 4). The top three causes of death after OHCA based on ICD10 categories were pneumonia, chronic ischemic heart disease, and acute myocardial infarction. The total DALY increased from 304.1 in 2010 to 849.7 in 2015, followed by decreasing to 547.1 in 2018. The mean DALY decreased from 12.162 in 2010 to 3.599 in 2018.

Conclusions
Age at arrest and CPC category was independently associated with higher risk of mortality, while a shockable first arrest rhythm was independently associated with a lower risk of mortality in long-term OHCA survivors. Initial survivors of OHCA have an increased mortality rate compared to the general population for the first three years, but normalises to that of the general population subsequently, while the annual disease burden of OHCA quantified using DALY showed decreasing trends from 2010 to 2018. Further improvements in the surveillance and management of OHCA may be warranted to improve the long-term survivorship and decrease the burden of disease of OHCA globally.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Medical Research Council, Clinician Scientist Award, Singapore (NMRC/CSA/024/2010 and NMRC/CSA/0049/2013), Ministry of Health, Health Services Research Grant, Singapore (HSRG/0021/2012)