A bibliometric study of medical tourism

ABSTRACT This bibliometric study analyzes 1535 publications from 1952 to 2020 on medical tourism. The aim of the study is to portray medical tourism publication trends from different perspectives such as the main subjects, word dynamics, authors’ originations and finally research gaps and future directions. The study shows that concepts like “perceived value” and “destination image” are among the emerging concerns in recent studies. The themes of research were grouped into six themes of marketing, economic & political, social & cultural, ethical, technological and governmental within these categories, factors affecting emotional aspects of tourists’ decision-making were found to be under-studies, compared to factors feeding the cognitive side of their choice of destinations.


Introduction
Medical tourism is described as travelling abroad to treat any kind of illness or to receive medical care, which is a modern trend in the healthcare field (Yu & Ko, 2012). Medical tourists fly around the world to explore emerging medical developments or innovative forms of treatment that may not be accessible or allowed in their home country. Medical tourism has become increasingly integrated with commercial tourism over time, and is now a key factor in choosing between existing travel destinations (Cannon Hunter, 2007). Statistics estimated that approximately 207.8 billion USD worldwide will be spent for medical tourism by 2027 (Grand view research, 2020(Grand view research, -2027. Medical tourism is a recent international economic and political phenomenon that has become increasingly important for developing countries, particularly those in Asia. Private hospitals in India, Malaysia and Thailand were spotted as highly popular destinations for medical tourism (Moghavvemi et al., 2017). Therefore, a bibliometric study is needed to recognize the appropriate strategies that encourage medical tourism, as it has high potential in future prospects.
Bibliometric analyses measure research output performance based on various indicators such as the number of published articles, citations and collaborating networks (Ghanbari Baghestan et al., 2019). The bibliometric approach is used to evaluate the research trends in particular area of research (Chahrour et al., 2020;Ebrahim et al., 2019), research productivity (Shonhe, 2020), manuscript characteristics that influence citations (Paracha et al., 2020), road mapping and research directions (Mukhlif et al., 2019;Qadir et al., 2019), and impact of published documents (Muhammad et al., 2017). Two of the most important indicators for a bibliometric analysis are the number of published articles and citations (Yusop et al., 2020).
While studies are currently being conducted in the area of medical tourism, few existing research have attempted to provide a visual presentation of the trends and patterns in this field. An examination of well-known databases containing all medical tourism studies conducted through the bibliometric method reveals no such documents. Therefore, a new and complete bibliometric study regarding the concept of medical tourism is necessary. The current study aims to explore the research status and publication trends in the medical tourism field; thus enabling researchers to grasp the historical development and current research hotspots of this field. To achieve this aim, both bibliometric and content analysis of the existing literature were carried out. The study presents a road map and potential opportunities for future research to researchers who aim to work on the concept of medical tourism.

Methodology
In this study, we applied a bibliometric method along with exploring the research themes of existing papers, to evaluate publication trends in the medical tourism field. To this end, the first step in the bibliometric method was to select the best keyword sets which cover all publications in the chosen field. Authors of the present study extracted the keyword sets on the main topic of "Medical Tourism". The alternative keywords were also selected based on the authors' experience and the title of published documents related to "Medical Tourists" which included phrases other than "Medical Tourist" in their titles. There are three main scientific databases, which index peer review publications and medical and scientific documents; PubMed, SCOPUS, and Web of Science (WoS). Databases, namely, Scopus and Clarivate Analytics Web of Science (WoS) which provide web-based citations to derive bibliometric data (Das, 2015;Ebrahim et al., 2020).
To select the best database, an initial title search was carried out on all three databases. The title search for "Medical Touris*" (consists of "Medical Tourism", and "Medical Tourist/s") retrieved 128, 932, and 536 documents from SCOPUS, and WoS, respectively, on 22 June 2020. Hence, the database selected for data collection was SCOPUS, as it provided a broad coverage (Aghaei Chadegani et al., 2013). The scope of the research was thus limited to those documents, which were indexed in SCOPUS in the period from 1952 to 2020. The final search terms were "Medical touris*" OR "Health* touris*" OR "Health care touris*" OR "Healthcare touris*" OR "Medical touris*" OR "Wellness touris*" OR "Wellbeing touris*" OR "Medica* travel*" OR "Patien* mobil*" which will hereafter be called "search term". A title search on SCOPUS based on the search term retrieved 1,535 documents consisting of 969 Articles, 197 book chapters, 102 review papers, 83 conference papers, while the rest were notes, letters, editorials, short surveys, books, and erratum.
The above mentioned documents were analysed by a R-Tool of the Bibliometric-package. The R-tool was specifically designed for research that involves quantitative bibliometric (Aria & Cuccurullo, 2017), and has been used for scientific mapping purposes. VOSviewer, a computer software suitable for bibliometric mapping was the second software used to analyse the data. The term VOS seen in the name of the software means "visualization of similarities" (Van Eck & Waltman, 2010). A brief demonstration of the bibliometric data that was collected can be seen in Table 1. Bibliometry is not an adequate substitution for qualitative peer evaluation . Thus, precautions should be taken while evaluating scholarly outputs using this method (Franceschini & Maisano, 2011). Examining the content of the studies alongside the bibliometric data provides a more insightful look at such scholarly works (Maghami et al., 2015). Therefore, in this study, the content of 26 most cited papers that examine the field of "Medical Tourism" were explored and the themes of research were categorized into common key research directions.

Results
One thousand five hundred and thirty-five documents were used to explore an overview of publications in the area of medical tourism. The publication trends and the cumulative number of publications are shown in Figure 1. From 1952 to 2005, the annual number of publications on medical tourism did not see any changes; remaining on less than 10 documents per year. From 2006 to 2015, there was an obvious increase in the annual number of publications, which reached its maximum of 172 documents in the year 2015. The trend of publications declined from 2015 to 2020. However, the total publications increased from one in the year in 1952 to 1535 in the year 2020, with a growth rate of 8.43% per year with each document containing an average of 11.2 citations. The first article written by Blake (1952) and published by Journal of the American Medical Association was entitled "Medical tourists in Great Britain". This article describes how London was Europe's centre for tuberculosis in 1952, and the treatments that were prescribed for it at that time.
The top 30 most repeated author's keywords (out of 2455 keywords previously presented in Table 1) are shown in Figure 2. Each colour represents a cluster. A cluster is a set of closely related nodes that the VOSviewer software assigns in a network. The VOSviewer software uses both a mapping and a clustering approach to calculate the strength of associations between keywords. Keywords that are closely associated are visualized as clusters, using specific colours (Khodabandelou et al., 2019;Van Eck & Waltman, 2010). Moreover, a relevant distance-based map is plotted, indicating clustered keywords from the author's suggested keywords in the documents (Kalantari et al., 2017).  As illustrated with yellow colour in Figure 2, the "perceived value" drives medical tourism and other variables such as "destination image", "satisfaction", "service quality" and "trust" as a cluster, and can be a predictor of "behavioural intention" in the context of medical tourism (Ekinci & Hosany, 2006;McKnight et al., 2002;Ryu et al., 2008). The red cluster displays the importance of "medical tourism" in developing countries such as India, Malaysia, and Thailand as argued by (Moghavvemi et al., 2017). Another aspect of the red cluster was globalization and its relationship with medical tourism as highlighted by Carrera and Bridges (2006). Their health tourism grew up to 3.9% annually and was worth 513 billion USD at the international level, involving 617 million individuals. Wellness and health tourism are shown in a cluster of green which demonstrates other aspects of tourism.
The 795 journals, books, etc. published 1535 documents in the area of medical tourism (Table 1). The top 30 sources published about 46% of all documents. Figure 3 shows that "Tourism Management" ranks first when journal impact is considered and ranks second when the frequency of publication is considered (Table 2). Table 2 shows that citation frequency of journals varied during the observation period. These variations have different reasons that can be based on journal rankings. As Figure 3 shows, Tourism Management (ISI, Q1), has the most cited articles in the field of tourism and hospitality.
This section will examine the research articles that were derived from the bibliometric data analysis and were explored in terms of their subject matters and research themes. In order to identify the most important research topics in the field of medical tourism, the papers that were most commonly cited can be evaluated. In this regard, times cited per year (TCpY) for each paper was found by dividing the total number of times cited by the number of years since it was published. Publications with the minimum of five TCpY were analysed based on all titles and abstracts. Another criterion used to select top papers was "authors' production over time"; which means the paper itself should have enough citations and the paper's author should be an expert in the area   of the research. The top 26 most frequently cited papers were categorized into common key research directions shown in Table 3. In our scholarly list, this number points to high-quality articles. Revision of the most cited articles over the years 1952 to 2020, show that the majority of these articles were published from 2006 to 2017. In a similar vein, international transfer to obtain healthcare has boomed during this period of time in the real industry scenario (Vijaya, 2010). The initial papers published on this topic have indicated very little knowledge about this scope, while the published papers from 2013 onward cover much broader scopes which can be categorized into six themes of "Marketing", "Economic & political", "Social & cultural", "Ethical", "Technological", and "Governmental" (respectively, based on the number of articles dedicated to each research theme).

Conclusion and implications
The study carried out a quantitative and content analysis on 1535 publications in medical tourism retrieved from SCOPUS database from 1952 to 2020. The annual publication in medical tourism has increased from 2006 to 2015, reaching a maximum of 172 documents in the year 2015. The trend of publications declined from 2015 to 2020. The analysis of author keywords shows that "perceived value", "destination image", "satisfaction", "service quality" and "trust" were emerging key terms in the publications, which can be used as a guideline for future research as well. Tourism Management Journal, the most impactful journal in the field of medical tourism, ranked second as the most productive journal with 29 publications. Through the analysis of research themes of topcited documents, the top six major factors were found to be marketing, economic & political, social & cultural, ethical, technological & governmental. Reviewing the content of the papers, we noticed that the factors which affect the decision of medical tourists in choosing their destinations is the main focus of the literature that can be divided into the above mentioned six themes of research. In order to further discuss the research trend, we can deploy psychological theory of cognition and emotion (Shiv & Fedorikhin, 1999). According to this theory, a person's behaviour (in this case choosing a medical destination) involves reciprocal interaction between emotion and cognition. On the one hand, people use various sources to collect information and rationally decide on a choice/behaviour (cognitive aspect), and, on the other hand, their emotion affects the cognition or their rational judgement and consequent behaviour. Within such a framework, the elements affecting the destination choice of a tourist, as discussed in literature, is a combination of cognitive and emotional factors. Cognitive factors have received more attention in studies while emotional factors are yet to be explored further in the future.
Regarding the importance of providing authentic sources of information to feed the cognitive aspect of decision-making of medical tourists, Crooks et al. (2010) argues about how patients consult and compare various sources of knowledge before deciding on a medical tourism destination. L. G. Turner (2011) also emphasized on setting standards to ensure that the clients of medical tourism businesses make educated choices. There is no doubt that medical tourism depends on effectively educating prospective patients about therapeutic choices, care facilities, accommodation incentives, travel arrangements and countries of destination. It's needless to say that marketing promotional activities and using advanced technologies facilitate this practice .
The role of the internet as the main source of information for medical tourists has been discussed in various studies. The research done by Moghavvemi et al. (2017) explored how private hospitals portray themselves online while trying to meet the perceived needs of medical tourists, and the way their websites promote medical tourism. Likewise, the research done by Penney et al. (2011) demonstrated that broker websites were widely varied in scale, quality, professionalism and knowledge depth. According to the literature on cognitive factors, people search for information and try to compare and choose medical destinations based on different criteria. These criteria are discussed in studies in above-mentioned six themes of research. For instance, factors like costs and service quality of health care system are explored in category of marketing and elements such as national economy, availability and reliability of medical infrastructure, transportation facilities as well as political stability of destination country and political economy are discussed under economic and political factors. Connell (2006) has underlined that the quality of a healthcare system is a focal element for the success of a medical tourism industry. Countries and hospitals help patients in identifying the best options to obtain high-level medical and tourism services (Habibi & Ariffin, 2019). Nevertheless, marketing factors such as cost, care, type of surgery and doctors play vital roles in the context of medical tourism. In this line, L. G. Turner (2011) argued that patients cross-national boundaries in search of accessible and opportune healthcare. He added that economic gradients, moving from higher to lower cost healthcare settings are significant, but the movement of patients is not guided by cost savings alone. Similarly, Hanefeld et al. (2014) claimed that patient's incentives are dynamic and factors beyond expense, including accessibility and distance clearly play an important role in marketing. Facilities provided by destination countries such as housing and transportation options, play key roles in boosting medical tourism (Ormond & Sulianti, 2017).
As mentioned above, emotional factors affecting the decision of tourists are comparatively under-studied in literature. A few factors such as emotional stress , trust and satisfaction (Ekinci & Hosany, 2006;McKnight et al., 2002;Ryu et al., 2008) are mentioned in the studies. All these cognitive and emotional factors together form patients' perceived value and their final decision about their destination (Habibi & Rasoolimanesh, 2020). Considering the recent outgrowth of rivalry between countries, and the above-mentioned gap in studying emotional factors involved in the destination choice of medical tourists, we may suggest that both researchers and practitioners need to pay more attention towards patient's emotional experience. Thus, exploring and then providing elements that improve the emotional experience of medical tourists becomes crucial. This can be done through various effective marketing strategies in order to gain competitive advantage in such an intensely competitive industry.

Data availability statement
The datasets generated and/or analyzed during the current study are available in the ZENODO repository http://doi. org/10.5281/zenodo.5025655 .

Disclosure statement
No potential conflict of interest was reported by the author(s).