Long-term disability level of 1-month survivors after out-of-hospital cardiac arrest: a nationwide cohort study in Korea using data from 2009 to 2018

1. Background

Out-of-hospital cardiac arrest (OHCA) is a major health problem worldwide [1]. Despite recent advances in post-cardiac arrest care, OHCA survivors may experience long-term disabilities due to hypoxic brain injury [2, 3, 4]. Several studies reported that OHCA survivors have cognitive, emotional, and fatigue problems during long-term follow-up [5, 6, 7]. With increasing interest in determining the long-term outcomes of OHCA survivors, recent guidelines included recovery from cardiac arrest in the chain of survival to emphasize the importance of rehabilitation after post-cardiac arrest [8]. Recovery expectations and survivorship strategies that address treatment, surveillance, and rehabilitation should be provided to cardiac arrest survivors and their caregivers at hospital discharge to address the sequelae of cardiac arrest and optimize transition of care to independent physical, social, and emotional roles [9, 10]. However, previous studies mainly focused on functional outcomes using the Cerebral Performance Category (CPC) and modified Rankin Scale (mRS) scores. Limited evidence is available regarding physical function, particularly persistent disability, of OHCA survivors. To better understand the prevalence of long-term disability in 30-day OHCA survivors, we used the data from the National Health Insurance Service (NHIS) of Korea. This study aimed to evaluate long-term disability in a large and representative group of OHCA survivors using this nationwide population data on disability grade.

2. Material and Methods

3. Results

3.1 Study Populations

Of 224,520 OHCA patients identified during the study period, 25,598 (11.4%) survived at 30 days. We excluded 3143 patients with a follow-up less than 2 years. Among the 22,455 patients included, 13,552 patients survived at the 1-year follow-up. Disabilities had developed in 2269 (16.7%) 1-year survivors and 395 (4.4%) non-survivors (Fig. 1).

Fig. 1.Patient enrolment flow diagram. OHCA—out-of-hospital cardiac arrest. ED—emergency department.

3.4 Disability grade according to category

Fig. 2 presents a detailed disability grade according to the category. Most patients with an encephalopathic disability were grade 1 in both groups (77.0% vs. 78.8%). Among patients with a cardiac disability, grade 3 was the most frequent in both groups (54.4% vs. 60.0%). In the 1-year survivor group, 26 patients (25.2%) were assigned to grade 5, which was the second most frequent. Pulmonary disability was most severe in both groups; however, the order differed. Among 1-year survivors, grade 2 was the most frequent, followed by grades 1 and 3 (36.4% vs. 34.1% vs. 25.0%, respectively). On the other hand, grade 1 was the most frequent among non-survivors, followed by grades 2 and 3 (52.9% vs. 23.5% vs. 17.6%, respectively). With respect to physical disability, a mild disability grade was more frequent in 1-year survivors than in non-survivors (61.2% vs. 40.4%). The distribution of the degree of physical disability was relatively even in both groups. A detailed number of patients in each group are presented in Supplementary Table 1.

Fig. 2.Disability grade according to category. (A) Physical disability; (B) Encephalopathic disability; (C) Cardiac disability; (D) Pulmonary disability.

4. Discussion

The main finding of this study was that 11.9% of 30-day OHCA survivors had newly developed disabilities, including encephalopathic, physical, renal, and cardiac disabilities, among others. Further, approximately 80% of patients with disabilities had severe grade disabilities.

In this study, approximately 40% of OHCA survivors died within the 1-year follow-up. This rate was much higher than that in the previous study that reported a 1-year mortality of 8.2% when assessing long-term outcomes of OHCA survivors [16]. However, Chocron et al. [17], who evaluated an association between functional status at discharge and long-term survival, reported that survivors with unfavourable outcomes showed a 1-year mortality of 44.2%, which is similar to the result of our study. An explanation for this discrepancy might be that this study was not conducted in a country where withdrawal of life-sustaining treatment is not widely practiced. This suggests that our study included more patients with poor outcomes.

The prevalence of disability was higher in 1-year survivors than in non-survivors. This does not necessarily indicate that patients with a disability have a better chance of long-term survival. Rather, since diagnosing a disability requires a considerable observation period, most non-survivors might die before a diagnosis is made. The frequency of encephalopathic and intellectual disability was lower in non-survivors. Patients with these disabilities, which are mainly associated with cerebral function, had poor neurologic outcomes. As discussed above, patients with a poor CPC died earlier; thus, the mortality was higher before a diagnosis of disability in 1-year non-survivors.

Among 1-year survivors with disabilities, most patients are diagnosed with severe grade disabilities other than physical disabilities. This suggests that patients are more likely to develop severe disability. The reason for the discrepancy between physical and other disabilities might be due to differences in pathogenesis. Previous studies reported that patients admitted to the intensive care unit owing to critical illness developed physical dysfunction [18, 19, 20]. Thus, physical disability after OHCA might be caused by intensive care post-cardiac arrest, and not by hypoxic brain injury caused by cardiac arrest itself.

However, approximately 20% of patients with disabilities had a mild grade. As there was no established follow-up plan for OHCA survivors during the study period, it is possible that that there were more patients with a mild form of disability, who may have been lost to follow-up. Patients who are still in a comatose state or in an unresponsive state of wakefulness one month after cardiac arrest rarely recover [3, 21]. However, Peskine et al. [22] evaluated the long-term disability of patients who awakened during the first 2 weeks, and found that patients who developed a disability could recover within 18 months after cardiac arrest. This suggests that patients with a mild disability could potentially recover with rehabilitation. A previous randomized controlled trial found that early intervention in cardiac arrest survivors led to faster recovery with cost-effectiveness [23, 24]. In 2020, Korean guidelines for Cardiopulmonary Resuscitation were updated [25]. The guideline recommends that cardiac arrest survivors have multimodal rehabilitation assessment and treatment for physical, neurological, cardiopulmonary, and cognitive impairments before hospital discharge. Still, structured follow-up plans for individuals and specific rehabilitation system were not widely established and applied. Specific long-term care plans would be helpful for physicians to use. For example, it would be practical to set a particular follow-up date with multidisciplinary evaluation for impairment, such as at 4, 6, and 12 months after discharge. Telephone consultation might be an alternative approach for patients who cannot visit the outpatient clinic. Future multicentre study is needed to follow up patients and assess the effectiveness of early rehabilitation for long-term disability in OHCA survivors.

The World Health Organization (WHO) defines disability as the outcome of the interaction between a person’s health condition and the context in which the person lives [26]. It compasses three aspects of the interaction, including impairments, activity limitations, and participation restriction. However, the Korean disability grading system was mainly focused on measuring disability in terms of impairments. The reason for dividing people with disability into various grades is that not only do they have different medical needs, but also some benefits are determined by this definition of severity [27]. This study has strength in evaluating newly appeared disability after cardiac arrest as an objective measure. Still, accompanying limitation exists that subjective feeling and difficulty might not be not fully assessed.

Our study has several strengths. First, this was a large, nationwide study assessing patients admitted over a substantial period to all emergency departments. Second, most studies that evaluated the long-term outcomes of OHCA survivors generally used the CPC or mRS scores, which are mainly associated with neurological outcomes [2, 28]. This study used disability grade, which encompasses physical and medical disabilities, which cannot be differentiated with CPC and mRS. Furthermore, as the specialist of each department diagnosed the disability grade, with considerable time to confirm a diagnosis, this was a more objective measure of outcome. However, this study also has several limitations. First, there is an inherent methodological limitation of a nationwide observational study. The potential impact of confounding factors would be significant, and the generalizability of these data is thus limited. Second, the NHIS database does not include each CPR’s clinical data; therefore, we could not analyse the risk factors associated with a long-term disability. Third, data about the conditions for which patients are presented in the emergency room and the period of survival after the acute episode is missing. This information could be important to analyze specific risk factors for developing disability and the effect of disability on the patient’s survival. Fourth, there could be a possibility that disabilities can result not only from post-cardiac arrest syndrome and but also from other specific underlying disease progressions. Due to inherent limitation of population-based study, the specific reason for developing disability could not be proven. However, this type of study deals with a large number of patients so that it could provide valuable information about the trends of developing disability after cardiac arrest. Fifth, as approaches to measuring disability vary across countries, the results of this study would not be generalized to other developing countries.

5. Conclusions

Among 30-day OHCA survivors, 11.9% of patients developed various disabilities, including encephalopathic, physical, renal, and cardiac disabilities. Physicians should be aware of the risk of the development of such disabilities and efforts to treat these disabilities in OHCA survivors should be increased.

Author contributions

WYK—Conceptualization; WYK, YeJK, YounJK, SMK—Methodology; YeJK, YounJK, SMK—Data curation; WYK, YeJK, YounJK, SMK—Formal analysis; YeJK, YounJK, SMK—Validation; YounJK, SMK—Visualization; YJK, SMK—Writing original draft preparation; WYK—Writing review and editing; WYK—Supervision, all authors have read and approved the manuscript.

Ethics approval and consent to participate

Not applicable.

Acknowledgment

Thanks to all the peer reviewers for their opinions and suggestions.

Funding

This study was supported by a grant from the Asan Institute for Life Sciences, Asan Medical Center, Seoul, Korea (grant number: 2021IT0007).

Conflict of interest

The authors declare no conflict of interest. Won-Young Kim is serving as one of the Guest editors of this journal. We declare that Won-Young Kim had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to OK.

Supplementary material

Supplementary material associated with this article can be found, in the online version, at https://oss.signavitae.com/mre-signavitae/article/1496783716862574592/attachment/SV2021120802-Supplementary%20Table%201-layout1.docx.