Incidence of stroke among survivors of sudden cardiac arrest: a population-based cohort study

Article information

J EMS Med. 2025;4(1):1-9
Publication date (electronic) : 2024 September 26
doi : https://doi.org/10.35616/jemsm.2023.00038
1Yong Loo Lin School of Medicine, National University of Singapore, Singapore
2National Registry of Diseases Office, Health Promotion Board, Singapore
3Department of Emergency Medicine, Singapore General Hospital, Singapore
4Division of Neurosurgery, Department of Surgery, National University Hospital, Singapore
5Division of Neurology, Department of Medicine, National University Health System, Singapore
6Pre-Hospital and Emergency Research Centre, Health Services and Systems Research, Duke-NUS Medical School, Singapore
7Programme in Health Services and Systems Research, Duke-NUS Medical School, Singapore
Correspondence to: Pamela Jia Min Tay Department of Emergency Medicine, Singapore General Hospital, Office C, 1 Outram Rd, Singapore 169608, Singapore E-mail: pamelatay93@gmail.com
*Celeste Zi Hui Ng, Huili Zheng, and Jun Wei Yeo are co-first authors.
**A list of the Singapore PAROS Investigators appears at the end of this article.
Received 2023 July 15; Revised 2024 January 6; Accepted 2024 July 19.

Abstract

Objective

Out-of-hospital cardiac arrests (OHCA) impose a significant health burden worldwide, with low survival rates. Despite improvements in short-term outcomes, data on long-term outcomes of OHCA remain sparse. We investigated stroke incidence in OHCA survivors and aimed to identify characteristics associated with the risk of developing subsequent stroke.

Methods

This was a retrospective cohort study of OHCA survivors in Singapore between 2010 to 2019. A combined dataset consisting of three population-based registries–Pan-Asian Resuscitation Outcomes Study (Singapore participants), Singapore Stroke Registry, and the Singapore Registry of Births and Deaths–was used to estimate the incidence of subsequent stroke and determine predictors using Cox regression hazard ratios for time-to-event analyses.

Results

In total, 882 OHCA survivors were analyzed. Of these, 15 (1.7%) subsequently developed a stroke (73.3% ischemic and 26.7% hemorrhagic). OHCA survivors who developed subsequent stroke were more likely to have had a previous stroke (hazard ratio [HR], 2.2; 95% confidence interval [CI], 0.61–7.96) or acute myocardial infarction (HR, 2.96; 95% CI, 0.82–10.70). OHCA survivors with stroke who underwent targeted temperature management showed a trend toward a reduced risk of developing stroke (HR, 0.47; 95% CI, 0.10–2.12).

Conclusion

In this population-based cohort study in a multi-ethnic Southeast Asian country, 1.7% of OHCA survivors developed stroke. OHCA survivors with a prior history of acute myocardial infarction or stroke showed a trend toward an increased incidence of stroke, while temperature management use exhibited a trend toward lower stroke incidence. Further randomized studies on the long-term outcomes of stroke and OHCA could potentially improve clinical outcomes.

INTRODUCTION

Out-of-hospital cardiac arrest (OHCA) continues to impose a significant disease burden [1,2] worldwide [3,4] despite improvements in prehospital and in-hospital cardiac arrest responses over the past decades. The global survival rate of OHCA patients was found to be 7.7% at 1 year after hospital discharge [5]. While there has been extensive research regarding short-term OHCA outcomes, relatively little is known about longer term outcomes in OHCA survivors. As increasing proportions of OHCA patients survive beyond 1 year in many communities around the world, there is emerging scientific interest in the long-term trajectories in the lives of OHCA survivors.

Strokes contribute significantly to the global burden of disease, being the second leading cause of deaths worldwide and the third leading cause of morbidity and mortality worldwide [5]. In Singapore, cerebrovascular disease was the third leading cause of death for most years since 1970, comprising 9% to 12% of all deaths [6]. Multiple studies have shown that increasing age is significantly associated with stroke prevalence. With Singapore’s aging population and high prevalence of stroke risk factors within the population, the incidence and health impact of strokes are expected to further increase. While number of studies look at long-term neurological outcomes and cognitive function in OHCA survivors, these mainly focus on memory and executive function as compared to the incidence of stroke.

This study aims to estimate the incidence of stroke in OHCA survivors in Singapore. We also looked to identify predictors or baseline characteristics of these patients that are associated with an increased risk of developing subsequent stroke.

METHODS

Study population

We obtained data from three different population-based registries: (1) Pan-Asian Resuscitation Outcomes Study (PAROS)–Singapore participants; (2) Singapore Stroke Registry; and (3) Singapore Registry of Births and Deaths. These were linked via the patients’ national registration identity card number, which is a unique identifier issued to every Singapore Citizen and Permanent Resident. Annual audits were carried out on data from each registry to ensure accuracy and reliability.

PAROS is an ongoing prospective multicenter registry of OHCA cases occurring in at least nine countries across the Asia-Pacific region [7]. Only data from Singapore was used for the current study. All OHCA cases conveyed by emergency medical service or presenting at public emergency departments were included in this study. OHCA was confirmed by absence of pulse, unresponsiveness, and apnea. The PAROS data was then linked with both the stroke registry and the death registry to determine survival status and subsequent occurrence of stroke in the OHCA survivors.

The stroke registry is maintained by the National Registry of Diseases Office, Ministry of Health Singapore, and collects epidemiological data on Singapore residents (aged 15 and above) diagnosed with stroke [8]. These cases are contributed by all public healthcare institutions in Singapore. Cases were identified using the International Classification of Disease 9th Revision (ICD-9) Clinical Modification codes 430 to 437 (excluding 432.1 and 435) prior to 2012, and the ICD-10 Australian Modification codes I60 to I68 (excluding I62.0 and I62.1) from 2012 onwards. All diagnoses of stroke were certified by a doctor based on clinical presentation. Dedicated registry coordinators extracted relevant clinical information after going through the patients’ electronic medical records. Further medical information was also obtained via ambulance, emergency department, and inpatient medical records or discharge summaries by registry coordinators.

The Singapore Registry of Births and Deaths is maintained by the Immigration and Checkpoint Authority and collects data on all live births, deaths and stillbirths occurring within Singapore and its territorial waters [9]. This also traces the causes and dates of all deaths of Singapore Citizens and Permanent Residents, in accordance with the Registration of Births and Deaths Act 2021 [10]. All identifiable data was removed by the Ministry of Health’s Unit for Prehospital Emergency Care prior to data analysis.

Study population and setting

Singapore is an urban city-state in Southeast Asia. Singapore has a unique healthcare system, whereby funding for public healthcare services is through a combination of compulsory savings, government subsidies, and price controls [11,12]. In 2020, cerebrovascular diseases (including stroke) were the fourth most common cause of death in Singapore [13]. The two risk factors with the highest prevalence amongst stroke patients remained consistent from 2010 to 2020, with 82.9% of the patients with stroke in 2020 having hyperlipidemia and 81.5% having hypertension [10].

Inclusion criteria and data collection

This study included all cases of OHCA in Singapore that occurred from April 1, 2010, to December 31, 2019, in the PAROS registry. From this population, patients who were not Singapore residents, younger than 18 years old, pronounced dead on scene or at the emergency department, or who died in hospital within 30 days from OHCA were excluded. We have provided a flowsheet showing selection criteria for OHCA cases in this study (Supplementary Fig. 1).

Each episode of stroke was consistent with the World Health Organization’s MONICA (Monitoring Trends and Determinants in Cardiovascular Disease) criterion [14]. Strokes in our defined population were ascertained and validated, whereby a recurring stroke within 28 days of a preceding episode was merged with the preceding episode, while a recurring stroke after 28 days of a preceding episode was counted as another stroke episode.

Statistical analyses

Baseline characteristics were presented as frequencies with proportions for categorical variables, and as median with interquartile range (IQR) for continuous variables. We used the Wilcoxon rank-sum test, Pearson chi-square test, and Fisher exact test to compare baseline characteristics between OHCA survivors with and without subsequent stroke where appropriate.

We performed Cox regression to identify factors associated with stroke after OHCA. The covariates investigated were: demographic factors (age, sex, and race), Utstein variables (bystander cardiopulmonary resuscitation [CPR], bystander automated external defibrillator [AED] use, CPR, bystander AED, witnessed arrest, first arrest rhythm, and prehospital return of spontaneous circulation [ROSC]), post-resuscitation therapeutics (such as emergency percutaneous coronary intervention, coronary artery bypass graft, targeted temperature management [TTM], or extracorporeal membrane oxygenation) and pre-existing comorbidities (previous acute myocardial infarction [AMI], previous heart disease, and previous stroke). For variables with few unknowns (n<10; bystander AED, prehospital ROSC), the unknown was excluded from the P-value calculation. For variables with substantial unknown (shockable first arrest rhythm, previous heart disease, and previous stroke), the unknown was included in P-value calculation. Since the event of death excludes a patient from a future stroke, competing risk from death was accounted by generating a sub-distribution hazard ratio for each factor in a Fine-Gray regression model. The level of significance was set at 5% and all analyses were performed using Stata V13 (Stata Corp.).

Ethics approval

This study was approved by the Centralized Institutional Review Board (CIRB Ref: 2018/2937) and was exempted from full review as only de-identified data was analyzed. The Ministry of Health’s Unit for Prehospital Emergency Care acted as a trusted third party to assist in removal of all identifiable information prior to data analysis.

RESULTS

A total of 21,592 OHCA cases occurred from April 2010 to December 2019. The excluded cases (non-mutually exclusive) were 20,710–they were foreigners (n=14), less than 18 years (n=369), pronounced dead at scene (n=284), died in the emergency department (n=17,358), died in the hospital within 30 days from OHCA without being discharged alive after OHCA (n=2,833) and/or had repeat OHCA events (n=69). A total of 882 OHCA survivors were subsequently analyzed in our study.

Baseline characteristics

Baseline characteristics are shown in Table 1. Eight hundred and sixty-seven OHCA survivors (98.2%) did not have a subsequent stroke while 15 OHCA survivors (1.7%) were found to have a subsequent stroke. OHCA survivors with stroke showed a trend towards older age (60 years [IQR, 51–70 years] vs. 64 years [IQR, 58–70 years], P=0.066). As seen in Table 1, there was a significantly higher proportion of previous stroke in OHCA survivors with subsequent stroke (n=5, 33.3%) as compared to OHCA survivors without subsequent stroke (n=106, 12.2%, P=0.001). There was also a trend towards higher proportion of OHCA survivors with subsequent stroke having had previous AMI (n=11, 73.3%) as compared to OHCA survivors without subsequent stroke (n=447, 51.6%, P=0.119).

Characteristics of OHCA survivors

Incidence and characteristics of stroke among OHCA survivors

Of the 15 OHCA survivors who had subsequent stroke, 11 patients (73.3%) presented with an ischemic stroke and the other four patients (26.7%) presented with a hemorrhagic stroke. Fourteen patients (93.3%) had previously known ischemic heart disease, five patients (33.3%) had atrial fibrillation, 12 (80.0%) had hypertension, 13 (86.7%) had hyperlipidemia, and five patients (33.3%) had diabetes mellitus (Table 2).

Characteristics of stroke among OHCA survivors with subsequent stroke

Predictors of subsequent stroke among OHCA survivors

There was no obvious trend seen in majority of the baseline patient characteristics (e.g., sex, ethnicity) and prehospital interventions (e.g., bystander CPR, bystander AED) in OHCA patients with stroke. Baseline probability of having had a previous stroke (hazard ratio [HR], 2.20; 95% confidence interval [CI], 0.61–7.96) or AMI (HR, 2.96; 95% CI, 0.82–10.70) appeared to be slightly higher in OHCA patients who subsequently developed stroke, although this was not statistically significant. Patients who underwent TTM also showed a trend towards a lower likelihood of developing stroke (HR, 0.47; 95% CI, 0.10–2.12), although not statistically significant (Table 3).

Hazard ratios of subsequent stroke after surviving OHCA

Predictors of death among OHCA survivors with subsequent stroke

We aimed to evaluate the significance of various patient factors (e.g., age, gender, previous atrial fibrillation, presence of hypertension) in OHCA survivors with subsequent stroke. None of the factors assessed were found to be significantly associated with mortality among OHCA survivors with subsequent stroke (Table 4).

Hazard ratios of death after surviving OHCA and having a subsequent stroke

DISCUSSION

In this nationwide, population-based study of OHCA patients who survived to 30 days post cardiac arrest, we found that: (1) 1.7% of OHCA survivors subsequently developed stroke; (2) previous stroke and AMI predisposes towards subsequent stroke after OHCA; or (3) TTM showed a trend towards decreased likelihood of subsequent stroke. While there has been increased interest in long-term outcomes of OHCA survivors in recent years, these mainly focus on neurological outcomes, cognitive function, and quality of life.

Current studies suggest a number of pathological links between stroke and cardiac arrest, with evidence pointing towards a higher incidence of cardiac death after an ischemic stroke. This is thought to be due to increased concentrations of cardiac enzymes and catecholamines, along with ongoing inflammation [15]. Most of the existing studies focus more on cardiac events after stroke, and less so on the occurrence of stroke after an OHCA. To the best of our knowledge, this is the first and largest study specifically investigating the incidence and factors affecting subsequent development of stroke in OHCA survivors in a multi-ethnic Asian cohort [16,17].

Byrne et al. [18] had a study population of 1,051 30-day OHCA survivors, and found that the absolute 5-year risk for OHCA survivors for stroke was 6.3% (95% CI, 4.1–8.5) as compared to 2.0% (95% CI, 1.6–2.5) for age- and gender-matched controls. Rey et al. [19] assessed long-term clinical outcomes in OHCA survivors, with a total of 201 surviving patients included in the final analysis. They reported a 6.5% (13 patients) incidence of stroke at the end of follow-up, with a reported 93% of OHCA patients presenting with favorable neurological outcome throughout follow-up. These reported values are substantially higher than our reported stroke incidence of 1.7%. Reported crude incidence rate of stroke was 256 per 100,000 population in Singapore in 2021 [8]. We postulate that the significantly different reported stroke incidence between our study and prior studies may be due to a number of different population and study factors.

A recent retrospective study in Singapore demonstrated that only 2.27% (260 out of 11,404) of OHCA survivors had favorable neurological outcome [20], in comparison to Rey et al. [19], where 93% of the study population had favorable neurological outcome. Although data on neurological outcomes was not included in our study, Liu et al.’s study [20] was also a population-based study conducted in Singapore from April 2010 to December 2018 which largely corresponded with our study period and population. We postulate that the poor neurological outcomes in Singapore OHCA survivors likely contribute towards lower reported stroke rates due to difficulty in assessing for symptoms in an individual with pre-existing severe cerebral disability. Given the vastly different OHCA survivor to discharge rate of about 4% in Singapore as compared to 13.6% in Victoria or 11.7% in Europe [21,22], it is expected that many other system and population factors are unaccounted for. Further research is needed to better understand the factors affecting OHCA survival and stroke incidence in Singapore.

Increasing age significantly increased the risk of subsequent stroke in OHCA survivors (HR 1.05 [1.01–1.09]), which is consistent with current findings, with more than 70% of strokes occurring above 65 years old, and a doubling of stroke incidence with each decade after 45 years of age [23]. Our findings of a trend towards increased incidence of stroke in patients with prior stroke (HR 2.20 [0.61–7.96]) and AMI (HR 2.96 [0.82–10.70]) are also congruent with prior studies demonstrating a strong association between AMI and stroke [24]. Cerebrovascular disease and cardiovascular disease are both known to share many similar risk factors such as diabetes, hypercholesterolemia, hypertension and positive family history of heart disease [15]. However further analysis into the trends of pre-existing comorbidities on stroke incidence was limited by the small number of patients with stroke post cardiac arrest.

TTM, also known as therapeutic hypothermia, involves the use of various cooling methods to induce hypothermia with the aim of improving neurologic outcomes. It is proposed that hypothermia reduces cerebral metabolic rate and oxygen demand, preserving energy stores, reducing lactate production [25] and the further development of acidosis. The effectiveness of TTM has been demonstrated in multiple studies showing improved neurological outcomes and mortality in OHCA survivors [26], and is also a part of recommended resuscitative guidelines for the International Liaison Committee on Resuscitation [27] and the American Heart Association Emergency Cardiac care guidelines [28]. In a randomized trial involving 77 comatose survivors of OHCA, treatment with moderate hypothermia was associated with improved outcomes [29]. Similarly, TTM also demonstrated improved neurologic outcome (55% vs. 39%, P=0.009) and reduced mortality in patients with OHCA due to ventricular fibrillation [30]. Implementation of TTM itself varies widely, with no current consensus as to the optimum temperature, duration, or specific cooling method. We found that OHCA survivors who underwent TTM showed a trend towards a lower risk of developing stroke (HR, 0.47; 95% CI, 0.10–2.12) (Table 3). This is a novel finding demonstrating the benefits of TTM on the incidence of stroke post cardiac arrest, and further studies should be done to better elucidate the effect of TTM. As TTM was only implemented in 260 cases (29%) out of the 882 OHCA survivors, further improvements in protocol and processes may serve to further improve outcomes. More research and clinical trials would be essential to establish TTM as part of standard protocol.

To our best knowledge, this is the most extensive open cohort study summarizing the incidence, demographics and factors affecting subsequent development of stroke in OHCA survivors. Use of population-based registries also ensures that data obtained is accurate and standardized, and minimizes the likelihood of missing information or cases.

There are a number of limitations to this study. The small number of OHCA survivors that developed a subsequent stroke limited further analysis into the various patient and resuscitation factors in OHCA. Larger studies would allow for more accurate analysis and data interpretation to elucidate any underlying trends. Functional status of OHCA survivors are often assessed using cerebral performance category (CPC) or modified Rankin scale as per Utstein guidelines, which have been shown to be predictive of long-term survival [31]. Information regarding CPC of OHCA survivors was not available in this study. This may have affected the accuracy of reported stroke incidence as patients with low CPC may not present with the stereotypical signs and symptoms of stroke, and subsequent deaths may have been attributed to other causes. As this was a retrospective cohort study, there may also have been confounding factors not accounted for. Other study methods such as the use of matched controls could also be considered in future. As our study was based on information collected from registries, information regarding patients who presented to private hospitals would not have been included.

In summary, incidence of stroke after OHCA was found to be 1.7% in our population-based cohort study in a multi-ethnic Southeast Asian country. OHCA survivors who developed subsequent stroke appeared likelier to have had a previous AMI or stroke, which is consistent with current studies demonstrating similar pathological risk factors toward the development of both cerebrovascular and cardiovascular disease. We also showed a trend towards decreased incidence of stroke after OHCA with use of TTM. Further studies on long-term outcomes of OHCA, in particular with relation to the incidence of stroke and TTM use may facilitate improvement in protocols and clinical care.

Notes

FUNNING

This study was supported by grants from the National Medical Research Council, Clinician Scientist Award, Singapore (NMRC/CSA/024/2010, NMRC/CSA/0049/2013 and NMRC/CSA-SI/0014/2017), National Medical Research Council, Clinician Investigator Salary Support Programme (NMRC/CSSP/0079/2018), and Ministry of Health, Health Services Research Grant, Singapore (HSRG/0021/2012). AFWH was supported by the SingHealth Duke-NUS Academic Medical Centre under the Clinician Investigator Advancement Programme (award number 15/FY2022/CIVA/03-A03).

CONFLICT OF INTEREST

No potential conflict of interest relevant to this article was reported.

AUTHORS’ CONTRIBUTIONS

Conceptualization: AFWH, CZHN, JWY; Data curation: MJRL, BYQT, PPP, MEHO, AFWH; Formal analysis: all authors; Methodology: CZHN, JWY, AFWH; Project administration: all authors; Resources: all authors; Software: all authors; Supervision: AFWH; Validation: ZHL; Writing - original draft: CZHN, JWY; Writing - review & editing: all authors.

Acknowledgements

The authors would like to thank Ms. Nur Shahidah, Ms. Pek Pin Pin and the late Ms. Susan Yap from Department of Emergency Medicine, Singapore General Hospital; Ms. Nurul Asyikin, Ms. Liew Le Xuan and Ms. Joann Poh from Unit for Prehospital Emergency Care, Singapore General Hospital for their contributions and support to the Singapore OHCA registry. We would also like to acknowledge the Singapore PAROS Investigators: Michael YC Chia (Tan Tock Seng Hospital, Singapore); Yih Yng Ng (Tan Tock Seng Hospital, Singapore); Benjamin SH Leong (National University Hospital); Han Nee Gan (Changi General Hospital, Singapore); Wei Ming Ng (Ng Teng Fong General Hospital, Singapore); Si Oon Cheah (Urgent Care Clinic International, Singapore); Desmond R Mao (Khoo Teck Puat Hospital, Singapore); Nausheen Edwin Doctor (Sengkang General Hospital, Singapore); Shalini Arulanandam (past Chief Medical Officer from Singapore Civil Defense Force).

Supplementary Material

Supplementary materials can be found via https://doi.org/10.35616/jemsm.2023.00038

Supplementary Fig. 1.

Selection criteria for out-of-hospital cardiac arrest (OHCA) cases occurring in Singapore during a study period of April 2010 to December 2019.

jemsm-2023-00038-Supplementary-Fig-1.pdf

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Article information Continued

Table 1.

Characteristics of OHCA survivors

Characteristic Without subsequent stroke (n=867) With subsequent stroke (n=15) P-value
Age (yr) 60 (51–70) 64 (58–70) 0.066
Sex 0.274
 Male 680 (78.4) 10 (66.7)
 Female 187 (21.6) 5 (33.3)
Ethnicity 0.879
 Chinese 626 (72.2) 11 (73.3)
 Malay 133 (15.3) 2 (13.3)
 Indian 87 (10.0) 2 (13.3)
 Others 21 (2.4) 0
Bystander CPR 0.297
 No 347 (40.0) 8 (53.3)
 Yes 520 (60.0) 7 (46.7)
Bystander AED 0.999
 No 706 (81.4) 13 (86.7)
 Yes 153 (17.7) 2 (13.3)
 Unknown 8 (0.9) 0
Witnessed arrest 0.328
 No 155 (17.9) 4 (26.7)
 Yes 712 (82.1) 11 (73.3)
Shockable first arrest rhythm 0.649
 Non-shockable 223 (25.7) 4 (26.7)
 Shockable 572 (66.0) 9 (60.0)
 Unknown 72 (8.3) 2 (13.3)
Prehospital ROSC 0.544
 No 188 (21.7) 2 (13.3)
 Yes 669 (77.2) 13 (86.7)
 Not applicable 10 (1.1) 0
Any ROSC 0.999
 No 1 (0.1) 0
 Yes 866 (99.9) 15 (100)
Emergency PCI 0.999
 No 525 (60.6) 9 (60.0)
 Yes 342 (39.4) 6 (40.0)
Emergency CABG 0.999
 No 865 (99.8) 15 (100)
 Yes 2 (0.2) 0
Hypothermia therapy 0.572
 No 610 (70.4) 12 (80.0)
 Yes 257 (29.6) 3 (20.0)
ECMO therapy 0.999
 No 859 (99.1) 15 (100)
 Yes 8 (0.9) 0
Previous AMI 0.119
 No 420 (48.4) 4 (26.7)
 Yes 447 (51.6) 11 (73.3)
Previous heart disease 0.411
 No 290 (33.4) 6 (40.0)
 Yes 325 (37.5) 7 (46.7)
 Unknown 252 (29.1) 2 (13.3)
Previous stroke from OHCA and SSR 0.001
 No 761 (87.8) 10 (66.7)
 Yes 106 (12.2) 5 (33.3)

Values are presented as median (interquartile range) or number (%).

OHCA, out-of-hospital cardiac arrest; CPR, cardiopulmonary resuscitation; AED, automated external defibrillator; ROSC, return of spontaneous circulation; PCI, percutaneous coronary intervention; CABG, coronary artery bypass graft; ECMO, extracorporeal membrane oxygenation; AMI, acute myocardial infarction; SSR, Singapore Stroke Registry.

Table 2.

Characteristics of stroke among OHCA survivors with subsequent stroke

Variable OHCA survivors with subsequent stroke (n=15)
Age (yr) 65 (63–72)
Type of stroke
 Ischemic 11 (73.3)
 Hemorrhagic 4 (26.7)
Previous IHD
 No 1 (6.7)
 Yes 14 (93.3)
Atrial fibrillation
 No 10 (66.7)
 Yes 5 (33.3)
Hypertension
 No 3 (20.0)
 Yes 12 (80.0)
Hyperlipidemia
 No 2 (13.3)
 Yes 13 (86.7)
Diabetes
 No 10 (66.7)
 Yes 5 (33.3)

Values are presented as median (interquartile range) or number (%).

OHCA, out-of-hospital cardiac arrest; IHD, ischemic heart disease.

Table 3.

Hazard ratios of subsequent stroke after surviving OHCA

Variable Unadjusted HR (95% CI)
Age 1.05 (1.01–1.09)
Sex
 Male 0.62 (0.19–2.03)
 Female 1.00 (ref)
Ethnicity
 Chinese 1.00 (ref)
 Malay 1.60 (0.36–7.16)
 Indian 1.10 (0.24–5.10)
 Others NA
Bystander CPR
 No 1.00 (ref)
 Yes 0.62 (0.21–1.87)
Bystander AED
 No 1.00 (ref)
 Yes 0.99 (0.21–4.58)
Witnessed arrest
 No 1.00 (ref)
 Yes 0.66 (0.18–2.40)
Shockable first arrest rhythm
 Non-shockable 1.00 (ref)
 Shockable 0.91 (0.24–3.43)
 Unknown 1.94 (0.32–11.77)
Prehospital ROSC
 No 1.00 (ref)
 Yes 0.64 (0.14–2.89)
Emergency PCI
 No 1.00 (ref)
 Yes 0.89 (0.29–2.72)
Targeted temperature management
 No 1.00 (ref)
 Yes 0.47 (0.10–2.12)
Previous AMI
 No 1.00 (ref)
 Yes 2.96 (0.82–10.70)
Previous heart disease
 No 1.00 (ref)
 Yes 1.32 (0.41–4.27)
 Unknown 0.84 (0.17–4.11)
Previous stroke
 No 1.00 (ref)
 Yes 2.20 (0.61–7.96)

OHCA, out-of-hospital cardiac arrest; HR, hazard ratio; CI, confidence interval; NA, not available as the number is too small to generate a valid estimate; CPR, cardiopulmonary resuscitation; AED, automated external defibrillator; ROSC, return of spontaneous circulation; PCI, percutaneous coronary intervention; AMI, acute myocardial infarction.

Table 4.

Hazard ratios of death after surviving OHCA and having a subsequent stroke

Variable Unadjusted HR (95% CI)
Age 1.09 (1.00–1.18)
Sex
 Male 0.24 (0.04–1.48)
 Female 1.00 (ref)
Previous AF
 No 1.00 (ref)
 Yes 0.58 (0.11–3.00)
Hypertension
 No 1.00 (ref)
 Yes 0.99 (0.11–8.91)
Hyperlipidemia
 No 1.00 (ref)
 Yes 0.32 (0.06–1.81)
Diabetes
 No 1.00 (ref)
 Yes 1.41 (0.24–8.49)

OHCA, out-of-hospital cardiac arrest; HR, hazard ratio; CI, confidence interval; AF, atrial fibrillation.