Burnout Syndrome in Nursing: A Concept Analysis
Article information
Abstract
Purpose
This study aimed to define nurse burnout syndrome clearly and highlight its distinct characteristics within today's healthcare environments, especially in light of the WHO ICD-11 revision that reclassified burnout as an occupational syndrome.
Methods
A concept analysis was conducted using Rodgers' evolutionary method. A systematic literature review was performed using CINAHL and PubMed databases with search terms including 'Nurs*' AND 'Burnout' and related concepts.
Results
The analysis identified five defining attributes of nurse burnout syndrome: emotional exhaustion, depersonalization, reduced personal accomplishment, meaning depletion, and somatic complaints. Key antecedents included excessive workload, understaffing, emotional labor, poor organizational support, shift work patterns, and limited job control and autonomy. Consequences included organizational inefficiency, withdrawal behaviors, compromised care quality and patient safety, and deterioration of mental health.
Conclusion
This concept analysis provides an expanded definition of nurse burnout syndrome by identifying five core attributes: emotional exhaustion, depersonalization, reduced personal accomplishment, meaning depletion, and somatic complaints. The findings offer a comprehensive framework that clarifies the complexity of this phenomenon and guides the development of measurement tools and intervention strategies in nursing practice, education, and research.
INTRODUCTION
The World Health Organization's (WHO) International Classification of Diseases (ICD) underwent significant revisions in the definition and classification of burnout during the transition from ICD-10 to ICD-11 in 2019. Under ICD-10, burnout was classified under code Z73.0 and conceptualized as a "state of vital exhaustion". In contrast, ICD-11 reclassified burnout under code QD85, defining it as a syndrome resulting from chronic workplace stress that has not been successfully managed [1]. This revision represents a paradigmatic shift that reconceptualizes burnout not merely as a psychological state, but as an occupational syndrome requiring medical and organizational level management, thereby highlighting its significance within healthcare settings. In addition, several European countries, including the Netherlands, Sweden, and France, have officially recognized burnout syndrome as an occupational disease with established diagnostic and evaluation systems [2].
Burnout syndrome has become an increasingly critical concern in the nursing profession, given the distinctive characteristics of nursing practice [3]. As healthcare professionals who play pivotal roles in healthcare delivery, nurses experience elevated levels of occupational stress and burnout due to unique features of nursing work, including shift work and unpredictable patient condition changes. This phenomenon has been identified as a contributing factor to increased nurse turnover rates [4] and has been reported to directly impact not only individual job performance but also patient safety and quality of nursing care [3]. Consequently, there has been growing interest in burnout syndrome within the nursing discipline, necessitating systematic scholarly efforts to understand and manage this phenomenon comprehensively.
The COVID-19 pandemic, which emerged globally in late 2019, has introduced unprecedented changes to nursing practice environments and has further intensified the manifestation and severity of burnout syndrome among nurses. The pandemic's unique stressors-including infection control duties, excessive workloads, frequent patient deaths, and isolation from personal protective equipment (PPE) use-have created complex burnout patterns that exceed traditional conceptual frameworks [5].
Maslach and Leiter defined burnout in a more systematic manner and distinguished it into three core components. Burnout is not a single emotional state but rather a psychological syndrome that manifests in a multidimensional way through emotional exhaustion, depersonalization, and reduced personal accomplishment [6]. Burnout syndrome extends beyond the three core symptoms traditionally described in burnout-emotional exhaustion, depersonalization, and reduced personal accomplishment-to include various physical symptoms and cognitive impairments. Major physical symptoms reported include headaches, gastrointestinal problems, sleep disturbances, and chronic fatigue, while cognitive impairments may manifest as reduced attention, impaired decision-making, and memory decline. From a psychological perspective, burnout is often accompanied by emotional disorders such as depression, anxiety, and feelings of hopelessness [7,8].
A number of empirical quantitative studies of the nursing workforce-most of them cross-sectional in design and employing the Maslach Burnout Inventory-have tended to regard burnout as an outcome of nurses' work. However, the specific components and antecedents of burnout syndrome, as well as its impacts on individuals, organizations, and patients, have not been clearly elucidated [9]. Furthermore, burnout has been extensively discussed in nursing and related fields, there remains a lack of empirical studies confirming how well the existing conceptualizations of burnout syndrome operate in real-world nursing practice. Given these gaps, there is a compelling need for systematic concept analysis research to identify the unique attributes of nurse burnout syndrome and to refine its conceptualization within contemporary nursing practice contexts.
METHODS
1. Methodological Approach
Recognizing that burnout syndrome in nursing practice possesses unique attributes and contextual specificities that distinguish it from general burnout concepts, and that these concepts evolve dynamically according to temporal and sociocultural factors, Rodgers' evolutionary concept analysis was applied. This approach is grounded in the philosophical premise that concepts are not fixed entities but dynamic constructs that continuously change and evolve over time and across sociocultural contexts. Through this methodology, we can conduct in-depth analysis of conceptual attributes and dimensions to enhance theoretical understanding of specific phenomena and systematically examine how concepts are applied and interpreted in actual nursing practice [10].
As this study was a literature-based concept analysis and did not involve human participants, it was exempt from institutional review board (IRB) approval.
2. Data Sources and Sample
To clearly define the concept of nurse burnout syndrome and identify its key attributes, a literature search was conducted between June 1 and June 30, 2025, focusing on peer-reviewed English-language articles published within the past 30 years. Literature searches were performed using CINAHL and PubMed databases with the following search terms: 'Nurs*' AND 'Burnout', and 'Burnout OR emotional exhaustion OR depersonalization OR personal accomplishment'. In PubMed, Medical Subject Headings (MeSH) such as "Burnout" and "Nurses" were also applied.
The inclusion criteria comprised: (1) reference literature and theoretical papers that explain the concept of burnout syndrome, and (2) empirical literature that clearly addresses concepts and attributes related to burnout syndrome among nurses. Exclusion criteria were: (1) studies not involving nurses as the primary population, (2) non- English publications, (3) dissertations, conference abstracts, and grey literature, and (4) duplicate or overlapping datasets.
Following the initial search, duplicates were removed using EndNote and manual verification. Articles were then screened by title and abstract for adherence to inclusion and exclusion criteria, followed by full-text review to determine final inclusion for analysis. A total of 22 studies were ultimately included. The selected literature was systematically analyzed according to Rodgers' seven-step evolutionary concept analysis framework to identify the conceptual definition, attributes, antecedents, and consequences of burnout syndrome among nurses. The literature selection process is illustrated in the PRISMA flow diagram presented in Figure 1.
PRISMA flow diagram (adapted) of the study selection process. Page et al. (2021).
3. Coding and Synthesizing of Data
Following Rodgers' recommendations, each article was first reviewed comprehensively, then analyzed with focus on conceptual context, surrogate and related terms, attributes, antecedents, consequences, and exemplars. Articles were read multiple times with specific descriptions and definitions highlighted. To ensure methodological rigor, the coding process was independently conducted by two researchers. Inter-coder reliability was established through repeated discussions and consensus meetings until full agreement was reached on the categorization of attributes, antecedents, and consequences.
To identify attributes of burnout syndrome among nurses, we focused primarily on direct definitions. When authors did not provide explicit definitions, attention was given to statements that implied the meaning or usage of burnout syndrome within nursing contexts.
4. Related Term
Compassion fatigue is a psychological exhaustion phenomenon commonly observed among caring professionals, such as nurses, who are continuously exposed to others' suffering, presenting clinical manifestations very similar to nursing burnout. Compassion fatigue represents a "secondary traumatic stress reaction," characterized by the gradual depletion of nurses' emotional energy through continuous empathetic engagement with patients' suffering [11].
Recent studies indicate that compassion fatigue and burnout are independent yet overlapping concepts, with accumulated compassion fatigue potentially creating pathways to burnout through emotional exhaustion and reduced self-efficacy. Compassion fatigue is often referred to as "the cost of caring" and typically occurs in environments requiring sustained empathy through repeated interactions with patients experiencing psychological distress. Multiple studies have identified compassion fatigue as a significant factor influencing nursing burnout, with significant positive correlations reported between these constructs [8,12].
However, the two concepts demonstrate distinct etiological mechanisms. Compassion fatigue focuses on emotional energy depletion within caring relationships, while burnout is triggered by more structural and complex factors involving organizational structure, job demands, and personal resource interactions. Therefore, while these concepts are interrelated, they should not be considered identical. Prevention requires comprehensive approaches including organizational educational programs, enhanced awareness of empathetic exhaustion, and strengthened individual self-care strategies [12].
RESULTS
1. Attributes
Following Rodgers' evolutionary concept analysis methodology, the literature review revealed that burnout syndrome comprises multidimensional attributes. Five core attributes were identified that define the constitutive characteristics of burnout syndrome and provide a theoretical foundation for diagnosis and intervention design at both nursing practice and organizational levels.
1) Emotional exhaustion
Emotional exhaustion represents a core attribute of burnout syndrome, characterized by depletion of emotional resources due to excessive work demands and sustained occupational stress. This condition emerges as a response to chronic workplace stressors that persist beyond an individual's adaptive capacity [13]. It signifies depletion of emotional rather than physical energy [6,13].
Emotional exhaustion has been consistently identified as the most salient dimension of burnout among nurses, with empirical studies demonstrating its close association with staffing shortages and high patient-to-nurse ratios [14,15]. A systematic review of empirical quantitative studies on burnout in emergency nurses further emphasizes that those exposed to acute workload demands and persistent occupational stress are particularly vulnerable to severe emotional exhaustion [16].
2) Depersonalization
Depersonalization is recognized as one of the core components of burnout and is interpreted as a phenomenon that fundamentally conflicts with the identity and essence of the nursing profession, which is grounded in human-centered care [17]. It represents a coping mechanism for chronic occupational stress, whereby nurses detach psychologically from work and relationships to conserve emotional resources [6].
Low self-efficacy resulting from burnout has been identified as a factor that further intensifies such psychological distancing [9,18]. Over time, this distancing may lead to adverse consequences, including the loss of professional idealism, the development of impersonal attitudes toward patients, and the emergence of a cynical perception of one's work. As this process unfolds, nurses may shift from professional commitment and engagement toward a defensive stance, limiting themselves to the minimal fulfillment of required duties [9,18]. Ultimately, this trajectory can undermine nurses' job performance, degrade the quality of interpersonal relationships, and weaken their professional identity.
3) Reduced personal accomplishment
Reduced personal accomplishment refers to a diminished sense of efficacy, self-esteem, and professional competence in nursing practice. Maslach and Leiter identify it, alongside emotional exhaustion and depersonalization, as a core dimension of burnout. In addition, a sense of inefficacy and diminished accomplishment regarding one's professional competence has been identified as an attribute of nurse burnout [19].
A systematic review of empirical studies examining hospital nurses reported that burnout, particularly the dimension of reduced personal accomplishment, was consistently associated with diminished emotional and professional commitment to their organizations [3]. Furthermore, diminished personal accomplishment is closely associated not only with declines in nurses' individual wellbeing but also with compromised patient safety and reduced quality of healthcare services.
4) Meaning depletion
meaning depletion describes a state in which nurses no longer perceive their work as possessing existential or intrinsic meaning, representing a key psychological manifestation in advanced burnout. It stems from a gap between the fundamental value of nursing and one's professional identity, exacerbated by repetitive tasks, administration- centered culture, and insufficient recognition of caregiving. Such conditions can lead to viewing work as hollow, fostering existential doubt and disengagement, a phenomenon defined as a "failure to derive existential significance from work"[20].
A grounded theory study conducted with nurses in public hospitals employed in-depth interviews and theoretical sampling to explore the contextual formation of meaninglessness. The findings revealed that inefficient hospital systems and dehumanizing environments undermine nurses' motivation and reinforce their perceptions of meaninglessness [21]
5) Somatic complaints
Burnout syndrome extends beyond emotional exhaustion and work withdrawal, often involving a range of somatic complaints, underscoring its complex impact on nurses' overall health and functional capacity. Common symptoms include sleep disturbances, chronic fatigue, musculoskeletal pain, tension headaches, and gastrointestinal problems, interpreted as bodily warning signals to sustained emotional labor and occupational stress. Empirical evidence from studies on emergency nurses has demonstrated a significant association between burnout and somatic symptoms, indicating that physical fatigue can be a major barrier to job retention [7]. Certain dimensions of burnout have also been linked to medical conditions such as hypertension and gastrointestinal disorders, suggesting that occupational stress may extend beyond subjective emotional states to impair physiological functioning [22].
2. Antecedent
To understand the development of nurse burnout syndrome, organizational, environmental, and personal conditions that exist prior to its formation can be defined as antecedents. This study synthesized the major antecedents identified through literature review following Rodgers' concept analysis method.
First, excessive workload and understaffing represent one of the most prominent and consistently identified factors in nurse burnout development. Higher patient-to-nurse ratios significantly correlate with increased emotional exhaustion and turnover intention among nurses [14], serving as a structural cause that continuously depletes nurses' physical and psychological resources.
Second, emotional labor and emotional depletion arising from repetitive patient care processes constitute major psychosocial catalysts for burnout. Repeated situations requiring emotional suppression or overt regulation intensify emotional exhaustion, with environments involving patient deaths, family conflicts, and intensive care unit duties particularly exacerbating such depletion [3,16].
Third, sleep disorders and circadian rhythm disruptions caused by shift work patterns duties induce mental fatigue and decreased concentration among nurses, forming the physiological foundation for burnout development. Poor sleep quality demonstrates significant correlation with emotional exhaustion, a subdimension of burnout, with 12-hour shift workers reporting higher burnout levels compared to 8-hour shift workers [23].
Fourth, poor organizational support systems and conflicts with managers constitute core factors that diminish nurses' psychological resilience. Community refers to the quality of social relationships in the workplace and closely relates to burnout development [24]. When interpersonal tensions, conflicts, and feelings of alienation accumulate among colleagues, job satisfaction declines and organizational commitment weakens, ultimately leading to decisions to leave the team. Lower levels of leadership fairness, feedback adequacy, and supervisory emotional support correlate with higher emotional exhaustion and depersonalization among nurses [25], suggesting that mismatches in the community domain can trigger emotional isolation and exhaustion. Therefore, establishing and maintaining trust-based relationships in the workplace represents a crucial element in preventing burnout and creating sustainable work environments within organizations.
Fifth, limited job control and autonomy impede self-determination and function as burnout-inducing factors. When nurses have limited control over their work environment and lack autonomy in decision-making, their sense of self-determination becomes undermined, creating conditions that promote burnout. Research shows that limited work discretion correlates with elevated burnout levels and negatively impacts work engagement [26]. Rather than operating independently, these factors interact to progressively deplete nurses' emotional resources, ultimately culminating in the negative psychological state of burnout.
3. Consequences
1) Organizational inefficiency
Nurse burnout closely correlates with decreased job satisfaction and reduced work productivity. Emotional exhaustion and depersonalization impede nurses' work engagement, ultimately leading to diminished work efficacy. Nurse burnout levels consistently demonstrate negative correlation with organizational commitment [3], indicating that burnout weakens nurses' emotional bonds and sense of responsibility toward the organization, consequently functioning as a mechanism that reduces work motivation and productivity. This trend directly translates to deterioration in nursing service quality and can negatively impact overall organizational performance and efficiency.
Nurse burnout syndrome extends beyond individual job performance to adversely affect organizational culture. As depersonalization tendencies increase, the quality of communication among colleagues and across disciplines deteriorates, weakening collaborative nursing practice. Higher organizational burnout correlates with decreased teamwork levels and mutual trust, while conflict frequency increases [25]. This ultimately leads to weakened cohesion within nursing units and breakdown of service consistency.
2) Organizational withdrawal behavior
Burnout emerges as a major predictor of nurses' turnover behavior. Nurses with high burnout scores report turnover intentions at rates more than twice the average compared to other workplace transitions [14], while absenteeism rates also increase, posing a long-term threat to hospital operational stability.
Furthermore, nurses experiencing burnout demonstrate 1.85 times higher likelihood of being absent for one or more days in the past month due to personal health issues [27]. This research empirically demonstrates that burnout directly relates to increased absenteeism and significantly associates with decreased job performance. Such increases in turnover and absenteeism not only threaten hospital operational stability but also negatively impact overall organizational workforce management and operational efficiency.
Turnover and absenteeism intensify nursing workforce circulation, causing disruptions in new staff training and work continuity.
3) Compromised care quality and patient safety
Nurse burnout syndrome extends beyond individual emotional exhaustion to directly impact patient care quality and safety. A comprehensive analysis of 85 studies reports significant correlations between nurse burnout and poor patient safety climate and grades, hospital-acquired infections, falls, medication errors, increased adverse events, and low patient satisfaction [28]. Notably, the research emphasizes that nurses' self-assessed quality of care deterioration clearly associates with burnout.
In addition, a systematic review has suggested that nurse burnout is closely linked to higher turnover, reduced job satisfaction, and poorer patient care outcomes, supporting the view that burnout undermines both organizational performance and patient safety [3].
These studies consistently demonstrate that nurse burnout syndrome constitutes a structural risk factor that significantly impacts patient safety and organization-wide healthcare quality, rather than merely an individual problem.
4) Mental health deterioration
Burnout syndrome functions as a risk factor for various mental health problems including anxiety, depression, and post-traumatic stress disorder (PTSD). Research on intensive care unit nurses identified significant positive correlations between burnout levels and depression and anxiety scores [29]. Similarly, studies examining COVID-19 intensive care unit nurses and primary care nurses consistently report significant positive correlations between burnout and depression and anxiety [30]. These findings suggest that burnout acts as a direct mental health risk factor among nurse populations.
Consequently, nurse burnout syndrome functions as a chronic and structural factor that extends beyond temporary exhaustion to mental health deterioration, indicating the essential need for early intervention and systematic prevention.
4. Definition
Through Rodgers' evolutionary concept analysis conducted in this study, nurse burnout syndrome is defined as follows:
"Nurse burnout syndrome is a multidimensional syndrome arising from occupational stressors, characterized by five attributes: emotional exhaustion, depersonalization, reduced personal accomplishment, meaning depletion, and somatic complaints, constituting a complex phenomenon that generates extensive negative consequences at both individual and organizational levels."
This definition builds upon the multidimensional structure grounded in the Maslach Burnout Inventory (MBI), while incorporating the organizational and emotional antecedents and outcome variables emphasized in recent research, thereby encompassing the distinctive characteristics of burnout specific to the nursing practice context.
5. Model Case
Nurse Kim is an experienced nurse with seven years of clinical experience. She has demonstrated professional competence in the operating room environment, which demands high concentration and rapid decision-making. However, in recent years, she has experienced substantial occupational stress from chronic staffing shortages, unpredictably prolonged surgeries, and persistent tension regarding patient deterioration (Antecedents: Excessive workload and understaffing, Limited job control and autonomy). Particularly, the psychological pressure from unexpected complications during surgery leading to critical patient deterioration has become a persistent trauma (Antecedents: Emotional labor, Poor organizational support).
At some point, Nurse Kim began experiencing strong resistance to morning commutes and reporting extreme physical and mental exhaustion that persisted even after work (Attributes: Emotional exhaustion, Somatic complaints). She displayed cynical attitudes toward patient prognoses and showed hypersensitive reactions to minor complaints from patients and guardians, demonstrating tendencies toward emotional distancing. She exhibited passive attitudes in interactions with colleague nurses, with her previously active and collaborative demeanor diminishing (Attributes: Depersonalization). While she previously held strong pride in her expertise, she now excessively blames herself for minor work errors and recognizes diminished self-efficacy regarding her work capabilities. She experiences helplessness believing that no effort will improve the situation, along with skepticism about the meaning of her work (Attributes: Reduced personal accomplishment, Meaning depletion).
These burnout symptoms directly affected Nurse Kim's job performance. Decreased work efficiency and accuracy were observed through minor errors in pre- and post-operative verification procedures and delays in surgical instrument preparation. In the operating room environment where teamwork is essential, reduced communication and collaboration with colleagues negatively impacted overall team capability and organizational culture (Consequences: Organizational inefficiency, Compromised care quality and patient safety). She is currently seriously considering resignation and has experienced voluntary absenteeism due to chronic fatigue leading to hospital attendance avoidance (Consequences: Organizational withdrawal behavior). On a personal level, she reports sleep disorders, unexplained anxiety, and depressive symptoms, experiencing deteriorating mental health and overall quality of life decline (Consequences: Mental health deterioration).
This case clearly demonstrates how nurse burnout attributes manifest in actual clinical practice, warning that this syndrome can negatively impact not only nurses' individual psychological health but also organization-wide workforce management and patient safety. Therefore, it suggests the essential need for early detection, structural intervention, and preventive strategy development for burnout (Figure 2).
Antecedents, defining attributes and consequences of burnout syndrome in nursing.
DISCUSSION
This concept analysis identified five core attributes of nurse burnout syndrome: emotional exhaustion, depersonalization, reduced personal accomplishment, meaning depletion, and somatic complaints. These attributes extend the traditional three-dimensional model of Maslach and Leiter, suggesting that burnout in nursing practice encompasses broader psychological, existential, and physical domains [19].
Compared to systematic reviews of quantitative studies on hospital nurses, which have primarily emphasized the psychological dimensions of burnout such as emotional exhaustion, depersonalization, and reduced personal accomplishment [3], this analysis highlights the additional attributes of meaning depletion and somatic complaints, thereby underscoring the unique complexities of nursing practice. Recent qualitative and mixed-method studies increasingly point to existential distress and physical manifestations as critical but underexplored aspects [7,21]. This study therefore contributes to broadening the conceptualization of nurse burnout by critically integrating these dimensions, which have been relatively overlooked in prior frameworks.
In distinguishing burnout from related constructs, it is also important to note that secondary traumatic stress, while sharing symptoms such as emotional exhaustion, arises specifically from indirect exposure to patients' trauma and includes PTSD-like features such as intrusion and hyperarousal [11]. Likewise, job strain, defined within the Job Demand-Control model as the combination of high demands and low control, should be regarded as an antecedent condition rather than burnout itself, as it reflects contextual work characteristics rather than the psychological and somatic syndrome experienced by nurses [23,24].
Although some previous studies-such as cross-sectional surveys using the Maslach Burnout Inventory and qualitative grounded theory research with hospital nurses have classified meaning depletion and somatic complaints as consequences of burnout [20-22], the present analysis identified them as defining attributes. Previous studies have largely conceptualized meaning depletion as a consequence of job alienation or bureaucratic organizational structures [20,21]. In contrast, this analysis positions it as a defining attribute of burnout, thereby extending prior frameworks. This highlights how the erosion of professional identity and loss of existential significance are embedded directly within the burnout process.
Similarly, while earlier research tended to describe somatic complaints as secondary outcomes [7,22], this analysis redefines them as intrinsic attributes of the syndrome. Somatic complaints such as sleep disturbances, chronic fatigue, and gastrointestinal problems have been consistently demonstrated as core health-related manifestations closely intertwined with the burnout process itself, rather than mere aftereffects. This reconceptualization underscores the need to view burnout not merely as a psychological state but as a holistic health issue with embodied manifestations.
Thus, treating these domains as attributes expands the traditional three-dimensional model and better captures the complexity of nurse burnout syndrome. Taken together, this study critically examines how prior research has overemphasized the psychological dimensions of burnout, and it broadens the conceptualization by integrating existential and physical attributes. In doing so, it more accurately reflects the complex nature of burnout in nursing and offers substantial contributions for both scholarship and practice.
Nevertheless, several limitations warrant consideration. First, although the literature review was comprehensive, it may not have captured all cultural and contextual variations of nurse burnout, particularly in non-English language studies. Second, this analysis synthesized findings across diverse study designs, which may limit the comparability of results. Third, the identification of attributes was based on currently available literature; as the phenomenon evolves, additional attributes may emerge.
Future research should therefore focus on developing and validating measurement tools that reflect this expanded conceptualization, particularly incorporating meaning depletion and somatic complaints. Furthermore, intervention studies should address both psychological and physical dimensions of burnout to design holistic prevention and management strategies.
CONCLUSION
This concept analysis provides conceptual clarity regarding nurse burnout syndrome and expands its definition beyond the traditional three-dimensional model. Five core attributes-emotional exhaustion, depersonalization, reduced personal accomplishment, meaning depletion, and somatic complaints-were identified as constitutive elements of the phenomenon.
By integrating both traditional and newly identified dimensions, this study offers a comprehensive conceptual framework that reflects the psychological, existential, and physical complexities of burnout in nursing practice. This framework provides a foundation for developing valid measurement tools, guiding intervention strategies, and informing policy decisions aimed at supporting nurses' health and professional sustainability.
Ultimately, the findings emphasize the necessity of multidimensional approaches to prevent and manage nurse burnout, with the ultimate goal of enhancing nurses' well-being, ensuring patient safety, and improving the overall quality of nursing care.
Notes
Kuem Sun Han and Miran Jung have been members of the editorial board since March 2021 and January 2024, respectively, but they had no role on the decision to publish this article. Except for that, no potential conflict of interest relevant to this article was reported.
AUTHOR CONTRIBUTIONS
Conceptualization or/and Methodology: Lee, SY, Han, KS, Jung, M & Cha, S
Data curation or/and Analysis: Lee, SY, Han, KS, Jung, M & Cha, S
Funding acquisition: None
Investigation: Lee, SY, Han, KS, Jung, M & Cha, S
Project administration or/and Supervision: Lee, SY, Han, KS, Jung, M, & Cha, S
Resources or/and Software: Lee, SY, Han, KS, Jung, M & Cha, S
Validation: Lee, SY, Han, KS, Jung, M & Cha, S
Visualization: Lee, SY, Han, KS, Jung, M & Cha, S
Writing: original draft or/and review & editing: Lee, SY, Han, KS, Jung, M & Cha, S