Global Research Trend and Bibliometric Analysis of Current Studies on End-of-Life Care

The growing emphasis on evidence-based practice has led to a need for more research on healthcare disciplines, and for the synthesis and translation of that research into practice. This study explored the global research trend in regard to End-of-Life Care (EoLC), and assessed the impact and influence, on the scientific community, of relevant EoLC publications EoLC. Over 350,000 related publications on EoLC were retrieved from three databases (PubMed, Scopus, and Web of Science). Our analysis of the global research trend revealed an exponential rise in the number of related publications on EoLC since the year 1837. This study assessed the bibliometric information of 547 current journal publications on EoLC, sorted by relevance, from the three databases. The USA (47.3%) and the UK (16.1%) were the most productive countries, in terms of the number of relevant publications. The bibliometric analysis also revealed which EoLC research was most impactful and influential, from different parameters including documents, authors, sources, and organisations. The keyword analysis further suggested the growing importance of advance care planning and decision-making in regard to EoLC, as well as an episodic upsurge of EoLC publications related to the COVID-19 pandemic. There were few collaborations among the prolific research on EoLC. This study recommends increased research collaboration across the globe, for wider wisdom-sharing on EoLC issues.


Introduction
End-of-Life Care (EoLC) is culturally and contextually relevant, and has received substantial interest among researchers and industry practitioners. Many countries have promoted the implementation of EoLC, to varying degrees, according to their economic status, resources, and energy [1][2][3][4][5]. Literature review studies have been accepted as an effectual means to map the existing intellectual territory [6,7]. The review works on EoLC research have been done from various perspectives. For instance, in recent years, Yoong, S.Q. et al. [6] conducted a scoping review, to explore death doulas as supportive companions in EoLC. Syvyk, S. et al. [7] also conducted a systematic review and meta-analysis of studies on colorectal cancer disparities across the continuum of cancer care. Most of these reviews were for synthesising practice directions in the available literature. The Lien Foundation developed an index to rank the quality of death across countries, from the experts' views [8,9]. The index was re-named and refined as the 'Quality of Death and Dying Index' [10], and was compared across geographical regions. These cross-country comparisons were mainly from the service-provision perspective, and there have been few comparisons on research and publications across countries and various parameters.
The cumulative increase in the publication of studies on EoLC necessitated an assessment of the impact and influence of these publications on the scientific community. An assessment of the current articles, using a mapping approach, would provide a considerable year 2020 and onwards. This reduced the number of documents in each dataset (PubMed: 84,755; Scopus: 53,954; and Web of Science: 72,044). Each of these databases provided different impact metrics. To explore the most relevant studies, the first 200 articles, sorted by relevance in the 3 databases, were downloaded and merged in Excel. The final number of documents, after removing duplicates, was 547 articles. These included 173 articles from the year 2020, 218 articles from the year 2021, and 156 articles from the year 2022. Bibliographical information about the 547 articles was exported from the Scopus database. Figure 1 presents the search process for the selected studies. ensure the homogeneity and robustness of the analysis, the document type was set to Journal articles only. In order to explore current publications only, a time period was restricted to the year 2020 and onwards. This reduced the number of documents in each dataset (PubMed: 84,755; Scopus: 53,954; and Web of Science: 72,044). Each of these databases provided different impact metrics. To explore the most relevant studies, the first 200 articles, sorted by relevance in the 3 databases, were downloaded and merged in Excel. The final number of documents, after removing duplicates, was 547 articles. These included 173 articles from the year 2020, 218 articles from the year 2021, and 156 articles from the year 2022. Bibliographical information about the 547 articles was exported from the Scopus database. Figure 1 presents the search process for the selected studies.

Research Trend Analysis
This study sought to explore the research trend of studies on EoLC. Using descriptive analysis, the yearly number of journal publications on EoLC, as well as the cumulative number of publications, were assessed to provide a clear estimate of the growth trend in research on EoLC. The current number of publications was also used to determine the most productive countries, institutions, authors, and journal sources in the field of EoLC research.

Bibliometric Analysis
This study sought to determine the top 20 most impactful authors, documents, and journal sources on EoLC that had been published to date, as well as to determine the various network relations, using bibliometric analysis. Previous studies had presented the top 15 [13] and top 10 [14] parameters from the bibliometric analysis of related studies. The current research themes on EoLC were also explored. The bibliometric analysis was conducted using VOSviewer software (Leiden University, Leiden, The Netherlands). Using the VOSviewer software, different bibliometric maps were generated from the 547 included studies, and analysed, based on citation analysis and co-occurrence analysis of the

Research Trend Analysis
This study sought to explore the research trend of studies on EoLC. Using descriptive analysis, the yearly number of journal publications on EoLC, as well as the cumulative number of publications, were assessed to provide a clear estimate of the growth trend in research on EoLC. The current number of publications was also used to determine the most productive countries, institutions, authors, and journal sources in the field of EoLC research.

Bibliometric Analysis
This study sought to determine the top 20 most impactful authors, documents, and journal sources on EoLC that had been published to date, as well as to determine the various network relations, using bibliometric analysis. Previous studies had presented the top 15 [13] and top 10 [14] parameters from the bibliometric analysis of related studies. The current research themes on EoLC were also explored. The bibliometric analysis was conducted using VOSviewer software (Leiden University, Leiden, The Netherlands). Using the VOSviewer software, different bibliometric maps were generated from the 547 included studies, and analysed, based on citation analysis and co-occurrence analysis of the keywords. The citation analysis was used to reveal the relational networks that existed among the 547 included studies, and to assess the impact of each study in the scientific community, based on the number of times other authors had mentioned it in their work.
keywords. The citation analysis was used to reveal the relational networks that existed among the 547 included studies, and to assess the impact of each study in the scientific community, based on the number of times other authors had mentioned it in their work. The network from the citation revealed who had cited whom, and was used to reveal the citation relationships between authors and documents. The co-occurrence-of-keywords analysis was used to reveal the current research themes, based on the most active keywords explored in the studies on End-of-Life Care. The number of publications on a yearly basis was assessed from three databases (PubMed, Scopus, and Web of Science), to provide a clear estimate of the research growth trend in the subject area. Using descriptive analysis, the yearly number of publications on End-of-Life Care, as well as the cumulative publications on a year-to-year basis for each database, were obtained, and are shown in Figure 2. The plotted line graph of the cumulative publications in Figure 2 depicts an exponential growth trend of research publications on EoLC. Different results were obtained from the three databases. The results from Scopus revealed that publications on EoLC date back to the year 1837, whereas PubMed and Web of Science indicated the later years of 1850 and 1970, respectively. EoLC-related studies were published yearly from 1837 to 1963 and, though there were few years within that period in which less than 100 such studies were published, it was from 1990 onwards that researchers showed great interest in EoLCrelated studies, with over 1000 publications yearly. In the year 2021, the number of published journal articles on EoLC was the highest to date (Web of Science: 38,708; PubMed: The plotted line graph of the cumulative publications in Figure 2 depicts an exponential growth trend of research publications on EoLC. Different results were obtained from the three databases. The results from Scopus revealed that publications on EoLC date back to the year 1837, whereas PubMed and Web of Science indicated the later years of 1850 and 1970, respectively. EoLC-related studies were published yearly from 1837 to 1963 and, though there were few years within that period in which less than 100 such studies were published, it was from 1990 onwards that researchers showed great interest in EoLC-related studies, with over 1000 publications yearly. In the year 2021, the number of published journal articles on EoLC was the highest to date (Web of Science: 38,708; PubMed: 37,552; Scopus: 29,645). This year, 2022, as of 19 August, about 20,000 journal articles have already been published. The findings extended to the year 2023, with 13 articles identified in Scopus database, 7 from Web of Science, and 4 from PubMed. The findings included journal publications, conferences, books, and book chapters. The results indicate that researchers across the globe still have great interest in studies on EoLC. This is evident from the exponential rise in the number of cumulative journal publications since the year 1990.

Most Productive Countries for Current Research on EoLC
The 547 most relevant journal publications on EoLC were published by 63 countries across the globe. The study identified the top 20 most productive countries that have currently published more than five relevant journal articles on EoLC, from the year 2020. Table 1 presents the list of the most productive countries, their number of article publications, the percentage distribution of the publications, and the World Bank rating of the income levels of each of the top countries. The highest number of current relevant Journal publications on EoLC (200 articles, 36.6% of the total documents) was from the United States of America. This was followed by 102 articles (18.6%) from the United Kingdom. Subsequently, Australia and Canada published 54 articles (9.9%) and 52 articles (9.5%), respectively.
It is evident from Table 1 that all the top 12 countries working on EoLC have high income levels [15]. This is indicative of the fact that economically developed countries have identified the benefits of EoLC research, and are exploring its various dimensions.

Top Organizations with Highest Current Publications on EoLC
The study revealed 160 organizations affiliated with the 547 recent publications on EoLC, out of which, 20 top organizations with more than 9 journal publications on EoLC, from the year 2020, were identified. Table 2 presents the list of the top organizations, with their country of location and the number of current relevant publications on EoLC. The University of British Columbia Canada 9 It was found that the University of Toronto in Canada had published the highest number (34) of journal articles, out of the 547 included studies on EoLC from 2020 to date. This was followed by the University of Pennsylvania and the University of Washington, both in the United States of America, with 30 and 19, respectively, of the most relevant journal articles on EoLC. These results also indicate that three countries-the United States of America, Canada, and the United Kingdom-play dominant roles in the research on EoLC globally.

Results from Bibliometric Analysis of Publications from 2020 3.2.1. Citation Analysis of the Documents
The citation analysis of the documents provided information on the quality of the published document. A publication with a higher citation metric usually indicated that the quality of the document was very good, as it had been cited by many researchers. The bibliometric analysis revealed that, out of the 547 documents under study, only 8 documents had citation connections, and formed three main clusters.
This study further sought to identify the highly cited documents from the 547 current journal publications on EoLC. Table 3 presents the top 20 documents that have been cited more than 11 times.
The top 20 most-cited document was by Lovell N., Maddocks M., Etkind S.N. et al., 2020 [16], which postulated that palliative care is an essential component of the COVID-19 response, and aided care teams to rapidly adapt with the new ways of working. The second-most-cited document was authored by Van den Block L., Honinx E., Pivodic L. et al., 2020 [17], which investigated the effect of Palliative Care for Older People (PACE), for evidence on how to improve palliative care in nursing homes.

Authors and Co-Authors Analysis
The analysis of the authors and co-authors was done to identify the major research scholars in the field of EoLC. The bibliometric analysis revealed that the 547 documents were written by 2920 authors and co-authors. Table 4 presents the list of 20 top authors and co-authors with more than three relevant article publications on EoLC. The results indicate that these are the most impactful and most influential researchers in the current research on EoLC.

Source Distribution and Citation Relationship
The analysis of the distribution of EoLC publications among the various journal sources, and their citation relationship, provided an indication of the top journals where the researchers preferred to publish their research on EoLC. The bibliometric analysis revealed 212 sources from the 547 documents under study. Table 5 -3.113). The impact factors of the six top journals were above 2.000; this indicates that high quality articles were published in these journals.

Identifying the Most Active Keywords of EoLC Research
Co-occurrence analysis of the authors' keywords was employed, to identify the most common keywords that were used by the EoLC researchers. The bibliometric analysis revealed that there were 1215 keywords used in the 547 documents. Figure 3 presents the network visualisation map of the keywords' co-occurrence for the 20 most common keywords with a minimum of 10 occurrences.

Identifying the Most Active Keywords of EoLC Research
Co-occurrence analysis of the authors' keywords was employed, to identify the most common keywords that were used by the EoLC researchers. The bibliometric analysis revealed that there were 1215 keywords used in the 547 documents. Figure 3 presents the network visualisation map of the keywords' co-occurrence for the 20 most common keywords with a minimum of 10 occurrences.  The science mapping of the 20 most active keywords, with at least 10 occurrences, generated three clusters, with each representing the domain that was most relevant: these included palliative care, end of life care, and advance care planning. The statistical details of the most active keywords have been presented in Table 6. Quality of life 12 22 20 Supportive care 12 26 The results indicate that the most repeated keywords were 'Palliative care', followed by 'End-of-Life Care'. The total link strength, which defines the strength of inter-relatedness between keywords, also revealed 'Palliative care' and 'End-of-Life Care' as the most active keywords in this research field.

Discussion
This paper discusses the global research trend of, and bibliometric information on, the current most relevant articles on EoLC. Three databases-PubMed, Scopus, and Web of Science-were used to retrieve related articles on EoLC. It was observed that there has been an exponential rise in publications on EoLC since it first began in the year 1837, with a cumulative number of over 350,000 publications. The exponential rise in related publications on EoLC was also reported in previous studies [13,36]. The growing worldwide demand for care at the end of life, due to the ageing population, saturation in hospitals, and high prevalence of chronic illnesses [37], may account for the increasing research interest in this field.
A total of 547 of the most relevant articles on EoLC, from the year 2020 onwards, were sorted from the three databases. Bibliometric analysis, using VOSviewer Software, was performed on the information extracted, from the Scopus database, about the 547 articles. The results from the bibliometric analysis revealed that most of the countries involved in EoLC research were economically developed. The growing provision of palliative care in the health systems of several high-income countries may account for the great research interest in this field [38]. The United States of America was the country that had published the highest number (200) of the most relevant current articles on EoLC. This was followed by the United Kingdom. The results revealed that the University of Toronto, Canada, was the most productive affiliated organisation that had published the highest number of the most relevant articles on EoLC. The findings indicate that the United States of America, the United Kingdom, Canada and Australia, are the most productive countries of EoLC-related publications. Despite its having had no language limit, the study's findings are congruent with a previous study by Adu-Odoh et al. [13], which was limited to English language only, a factor which the authors had reported as having been a possible influence on their study findings. The document by Lovell N., Maddocks M., Etkind S.N. et. al. 2020, was the most cited publication. Most of the current relevant articles on EoLC were published by the American Journal of Hospice and Palliative Medicine and the Journal of Pain and Symptom Management. The collaboration connection among the prolific authors and co-authors in this research field was found to be weak, as also reported in similar studies [13,14]. International research collaboration is essential for helping to strengthen the quality of any research work [11].
It was found that the most active keywords in this research domain were 'Palliative care', 'End-of-Life Care', and 'Advance care planning'. Though it is not a surprising finding, we can see that the term 'End-of-Life Care' exists in different derivatives, such as 'End-of-Life', 'End of Life', and 'End of Life Care'. Similarly, the different forms of care for patients with life-threatening illnesses, such as 'Palliative care', 'Hospice', 'Hospice care', and 'Terminal care' were referred to, but 'Palliative care' was a more frequently used keyword in all the academic publications. Notably, Advance care planning, Communication, and Decision-making are increasingly popular themes in regard to EoLC [14]. Similarly, the term 'Dementia' is also popular in EoLC research. The keywords 'Quality of life', are a term which is usually referred to as the outcome of End-of-Life Care, and which also appears to be an important concept. These are the areas expecting to receive more research attention. An incidental finding is the popularity of COVID-19 in current EoLC publications. The high death toll of this infectious disease probably alerts patients and families to the need for EoLC.
There were limitations to this analysis, as only the first 200 publications, sorted by relevance from each of the three databases of PubMed, Scopus, and Web of Science, were included in the bibliometric analysis. Notwithstanding, the high co-occurrences of the keywords 'End-of-Life Care' with 'Palliative care' and 'Hospice care' confirmed the inclusion of most of the relevant publications. The sample size of 547 journal articles was also a limitation, though it was not easy to appraise the large number of papers, which were combined from multiple databases. Publications in all languages were included in the selection process, to capture the global essence of studies around the world. The time period restriction, to publications from 2020 onwards, may also have limited the search output, but to a more manageable level.

Conclusions
The results from this study give an indication of the impact and influence of the most relevant recent publications on EoLC in the scientific community. EoLC-related topics have attracted substantial research interest across the globe. The bibliometric analysis revealed the various relevant topics linked with EoLC. The global response to the COVID-19 pandemic has sparked research interest in COVID-19-related EoLC studies. Further studies on COVID-19-related EoLC studies should be extended, to explore the changes in care plans, and directions for End-of-Life Care improvement. This study also affirms the need for international cross-collaboration among prolific researchers in this field, to expand knowledge on EoLC issues globally.