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Observational Study

Diversity of academic general medicine

A cross-sectional bibliometric study of original English-language research articles in general medicine and cardiology in Japan

Takahashi, Noriyuki MD, PhDa,b,*; Matsuhisa, Takaharu MD, PhDb; Takahashi, Kunihiko PhDc,d; Ban, Nobutaro MD, PhDe

Editor(s): Li, Jinfeng

Author Information
doi: 10.1097/MD.0000000000029072
  • Open


1. Introduction

The production of scientific research is essential for the development of general medicine as an academic discipline.[1] The importance of research has frequently been discussed in the related fields of general practice, primary care, family medicine, and general internal medicine (GIM).[2-6] The diversity of research in general medicine is well documented. This research field includes topics such as quality of care, universal health coverage, patient complexity, and personality in patient care, and covers a broad spectrum of individuals, families, and communities.[4-7] These international research trends also exist in Japan.[8-10]

Publication trends in English-language academic papers in medical science have been widely studied using bibliometric analysis of databases such as Web of Science (WOS), Google Scholar, and Scopus.[11,12] The production of academic papers in the field of general medicine has been actively investigated. International comparisons of publication trends in general medicine and related fields in North America, Europe, and Australia were conducted in 2011 and 2019.[13,14] Some reports have described the diversity of general medicine research as indicative of the multidisciplinary nature of research fields in publishing and the classification of organ systems.[15-17] These characteristics have informed research on publishing trends in individual countries and regions, including Germany, the Netherlands, Taiwan, Saudi Arabia, and the USA.[16-20] Although there have been several attempts to understand the characteristics of related fields in general medicine compared with other disciplines, such comparisons have not focused on the diversity of the general medicine research field.[21,22]

In recent years, several studies have examined the production of scientific research in general medicine departments in Japan.[23-25] For example, Watari et al[23] used an online questionnaire survey to explore research areas investigated by general medicine department heads in university hospitals in Japan. However, previous studies have focused on a single specialty; no studies have compared the characteristics of general medicine research in Japan with that of other specialties. In Japan, the first university department of general medicine was established in 1981 at Kawasaki Medical School.[26] Additional medical schools across the country have since been established. As of 2017, approximately 80% of university hospitals had departments related to general medicine,[27] but it was not until 2018 that a third-party accreditation system for medical specialists was initiated in Japan.[28] University departments related to general medicine in Japan include family medicine, GIM, primary care medicine, and community medicine.[27]

Both academically and clinically, cardiology is one of the most influential disciplines worldwide and cardiology research has been explored using bibliometric analysis.[29] According to the Japanese Ministry of Health, Labour, and Welfare, cardiologists comprise the largest group of organ-specific physicians in Japan.[30] Whereas cardiology research is characterized by organ-specific specialization limited to the cardiovascular field, general medicine encompasses cross-disciplinary fields and a wide range of diseases. Therefore, cardiology research output provides a useful contrast to general medicine research, and permits an examination of the characteristic research profiles of the 2 disciplines.

The study aims were to characterize the research from university departments of general medicine in Japan by analyzing the output and range of original articles published in English, and to compare this research with that of another academic specialty, cardiology.

2. Methods

2.1. Study design and setting

We conducted a cross-sectional study to analyze original English-language papers published by heads (or equivalent faculty members) of university departments of general medicine and cardiology in Japan. A web-based survey of published articles was conducted from April 1 to 30, 2020.

2.2. Selection of named researchers in general medicine

We accessed the official websites of the general medicine departments of all 82 graduate schools, university medical schools, and hospitals affiliated with medical schools in Japan. According to a 2017 study by Takeoka et al,[27] the names of such departments include terms corresponding to general medicine, GIM, primary care medicine, family medicine, and community medicine. We targeted department heads because these individuals are usually responsible for creating a culture that both requires and promotes scholarship among the faculty. When we identified multiple general medicine departments under different names at a single university, we extracted information for each department separately. We included endowed chairs or professors that belonged to the main university, but excluded others (e.g., those belonging to an affiliated branch hospital). Departments of community medicine were excluded if the name of the department included a specialty (e.g., orthopedics, ophthalmology, virology) or nursing field. Departments designated as being in charge of community liaison or patient consultation were also excluded. Although we considered the person listed at the top of each departmental website as the department head, if that person held concurrent positions in another department(s), the person listed second for that department was also included if they held the position of lecturer or higher as of January 1, 2020. Individuals who held concurrent guest positions or could be confirmed as having retired or been transferred were also excluded. To avoid the accidental inclusion of specialists, we excluded adjunct physicians. To differentiate between adjunct and full-time researchers, we searched all faculty listed on the university websites for the names of each preselected department head and judged them to be adjuncts if they were also listed in other departments of organ-specific medicine. The official faculty database of each university, the Grants-in-Aid for Scientific Research database (, and Researchmap ( operated by the Japan Science and Technology Agency were used to confirm background information on each subject. Private department websites created by individual researchers or their departments were used only when their background was unknown.

2.3. Journal article search

To avoid mixing data on researchers with the same name, we first entered the English name of each subject at their listed affiliation (s) from 2010 to 2019 into a Google search to determine if there was another person by that name at the university. If 2 people with the same name were found, the university-listed affiliation was used to differentiate them. Next, we searched for the English names of the relevant individuals in the WOS Core Collection (WOSCC) and extracted original research academic papers published during the period 2010 to 2019. Other publication types, including review articles, letters to the editor, conference proceedings, and books, were excluded. If more than 1 affiliation appeared in the search results for an individual, the results were narrowed to include only those affiliations identified within the last 10 years.

The WOSCC was used because it enabled us to index the research fields of the targeted authors’ papers. The WOSCC is a citation database of English-language academic research[31] that has a broader coverage than the journals indexed on PubMed.[32] Several previous studies on medical research, including some in primary care, have limited searches to English-language articles in the WOS.[19,20,33] The WOS covers approximately 250 research fields in the natural sciences, the social sciences, and the humanities.[34] The WOS classifies each journal into between 1 and 6 fields.[35] The WOSCC was used in this study with the permission of Clarivate Analytics (Japan) Co., Ltd. (permission date: February 12, 2020).

2.4. Contents of the survey

We carried out the following calculations for each researcher, using the numbers of original articles and research field(s) for each journal in which they had been published.

  • The total numbers of articles and fields were calculated using simple addition.
  • The number of articles in each field was calculated by aggregating the number of original articles. The number of researchers publishing in a particular field was determined; if a given researcher had published multiple articles in that field, the number of researchers was counted as 1 regardless of the number of articles.
  • The total numbers of articles and different publication fields for each researcher were calculated.
  • The total number of articles in each field was calculated. However, if multiple fields were allocated to a particular article in the WOSCC, all fields were counted; thus, there was some overlap in the number of articles included in each field. To estimate the extent of such duplication, we calculated the total duplication rate by dividing the total number of articles by field (i.e., including duplications) by the total number of articles (i.e., without duplications).
  • We calculated the proportion of researchers in each field against the total number of published researchers, then stratified the fields according to these proportions. These data were plotted on the horizontal axis of a box plot. This generated 7 distinct layers of data. This criterion was developed to compare the general medicine and cardiology groups. The number of articles per person in each field (i.e., number of articles by field/number of researchers by field) was plotted on the vertical axis of the box plot.
  • For each researcher, data on the number of articles were transformed into the common logarithm and plotted on the horizontal axis of a scatterplot. The number of fields were transformed into the common logarithm and plotted on the vertical axis of the scatterplot. The common logarithm was used because the data were not normally distributed, and to facilitate the interpretation of the data before and after the transformation.

2.5. Setting of the reference group

Subjects in the cardiology group were searched for all 82 universities nationwide and extramural members were excluded. The heads of cardiology departments that also included basic medical sciences, such as physiology and molecular biology, were excluded. The selection of researchers, search method, and contents of the survey were the same as those for general medicine.

2.6. Statistical analysis

Descriptive statistical analyses and intergroup comparisons were performed using the Mann-Whitney U test for continuous variables.[36] The chi-square test was used to test the paper duplication rate.[36] The number of researchers in each field was stratified as a percentage of the total number of researchers. We then created box plots of these data, sorted into layers, and conducted comparisons between any 2 groups that fell into a specific layer. Scatterplots were generated to show the relationship between the number of articles and the number of fields by individual researchers in general medicine and cardiology. Data were excluded for researchers with no articles. An analysis of covariance was conducted to examine differences in the regression lines for the number of fields per researcher.[36] Statistical significance was set at a two-sided P value of ≤.05. IBM SPSS Statistics ver. 26 (IBM Corporation, Armonk, NY) was used for the statistical analysis.

2.7. Ethics approval and consent to participate

This study used only information published on public websites and databases. However, because we also collected and aggregated English-language articles related to individual researchers, we sought the approval of the Nagoya university ethics review committee (approval no. 2019-0547-3), of which the first author was a former member. The intention to conduct this study was announced on the first author’s university website, and all participants were given the opportunity to refuse participation. All information associated with a specific researcher was anonymized during the analysis.

3. Results

Of the 82 universities nationwide, 128 general medicine departments in 78 universities met the inclusion criteria, with 128 eligible research authors. In cardiology, 96 departments in 81 universities met the inclusion criteria, with 96 eligible research authors (Fig. 1). The total numbers of articles/fields of study recorded in the WOSCC during the 10-year period from 2010 to 2019 were 2,923/92 in general medicine and 10,190/99 in cardiology (Table 1).

Table 1 - Descriptive statistics for published research from the heads of university-affiliated departments related to general medicine and cardiology in Japan.

General medicine


Total numbers

Research authors









Numbers by field

Median number of articles



IQR of articles



Median number of authors



IQR of authors



Total number of articles with duplication



Duplication rate of total articles



Numbers by researchers

Median number of articles



IQR of articles



Median number of fields



IQR of fields



IQR = interquartile range.

Figure 1:
Flow chart of the selection of study subjects. aGraduate schools of medicine, medical schools, and hospitals affiliated with medical schools (main hospitals); bDepartments of general medicine, general internal medicine, primary care medicine, family medicine, community medicine, and other similar department names; cDepartments of cardiology, circulatory medicine, endovascular medicine, and other similar names; dOn January 1, 2020.

The median number of articles stratified by field of study was 8.0 (interquartile range [IQR] 2.0-51.0) in general medicine and 7.0 (IQR 2.0-39.5) in cardiology, with no significant difference between the groups (P = .723). The median number of researchers by field was also not significantly different (P = .813) between general medicine (5.0; IQR 2.0-20.0) and cardiology (5.0; IQR 1.0-20.0).

The duplication rates of the total number of articles in general medicine (1.33) and cardiology (1.29) were similar (P = .276). The number of articles by individual researchers differed significantly between the groups, with a median of 12.5 (IQR 3.0-30.5) articles for researchers working in general medicine and 81.5 (IQR 42.5-132.0) for those in cardiology (P < .001). The median number of fields covered by researchers in general medicine (8.0; IQR 4.0-12.0) was significantly lower than for cardiology researchers (16.0; IQR 10.5-22.0; P < .001).

Of the 3,894 papers (including duplicates) encompassing 92 fields of general medicine, most were in the category of general and internal medicine (11.9%; 465 papers; Fig. 2). Conversely, nearly half (48.7%; 6,417 papers) of the 13,170 papers (including duplicates) from 99 fields of cardiology were in the top category of cardiac and cardiovascular systems. The least represented field was primary health care, which contained 28 papers (0.7%) by researchers working in general medicine and only 1 paper (0.0%) by a cardiologist.

Figure 2:
Research field coverage of the surveyed articles (as a percentage of the total number of articles by field) in the 2 groups. General medicine group: 3,894 total articles (including duplicates) in 92 fields. Cardiology group: 13,170 total papers (including duplicates) in 99 fields. Research fields that comprised <2.0% each (75 in general medicine and 91 in cardiology) are not shown on the graphs, with the exception of primary health care).

Figure 3 shows the relationship between the proportion of the total number of researchers by field and the number of articles/individual researchers by field. The plotted numbers are the 92 fields of general medicine and 99 fields of cardiology. In the general medicine group, there was no field in which >75% of the researchers were published. Furthermore, the number of articles/field was significantly higher in general medicine than in cardiology for the layers that contained 10% to 20% and 20% to 30% of all researchers. The median number of articles for the layers with 10% to 20% of all researchers was 2.58 (IQR 1.88-3.78) in general medicine and 1.47 (IQR 1.19-1.76) in cardiology (P = .002). The median number of articles for the layers containing 20% to 30% of all researchers was 2.89 (IQR 2.41-5.08) in general medicine and 1.85 (IQR 1.81-2.19) in cardiology (P = .009).

Figure 3:
Box plots showing the number of articles/researcher/field stratified by the proportion of the total number of researchers in each field (92 fields in general medicine and 99 in cardiology). aIndicates number of articles by field/number of researchers in each field; bIndicates number of researchers by field/total number of researchers. Boundary values belong to the lower group; cValues on/in the boxes indicate the number of research fields in general medicine and cardiology.

Figure 4 shows the scatterplot generated after applying common logarithm transformation of data on numbers of published articles and fields for 118 researchers in general medicine (excluding 10 researchers with 0 articles) and 96 researchers in cardiology. The analyses of covariance showed that the assumption of parallelism could not be rejected with significant probability (P = .067 > .05). Therefore, we estimated the regression line, assuming a common slope of b = 0.5620, which showed a statistically significant difference between the 2 groups (P < .001); the intercepts were 0.239 for general medicine and 0.111 for cardiology. Statistically, researchers in general medicine had their work published in a significantly greater number of fields than those in cardiology, for the same number of articles.

Figure 4:
Scatterplots and regression lines of the number of articles and fields for each researcher transformed to the common logarithm.

4. Discussion

This is the first study to demonstrate the research output of physicians in charge of general medicine university departments in Japan who have published in English-language journals, compared with department heads in another specialty. A total of 128 researchers from 78 general medicine departments, and 96 researchers from 81 cardiology departments, were included in the study. We found that general medicine practitioners in Japan publish more multidisciplinary research than do researchers in cardiology and related departments. We suggest 2 possible reasons for this difference: researchers in general medicine departments in Japan may represent a heterogeneous group that publishes articles in different fields; and there may be a tendency for individual researchers in this group to publish in a relatively multidisciplinary manner.

Although there is an international trend for general medicine research to encompass numerous fields, the output from individual countries indicates their emphasis on specific areas. Studies of research in general medicine in recent decades have variously identified the top research categories as psychiatry and cardiology in Germany,[16] circulatory and respiratory systems in the Netherlands,[18] and medicine (general/internal) and public/environmental/occupational health in both Taiwan and Saudi Arabia.[19,20] Taking a different approach, Gehanno et al[37] assessed the variety of specialties covered by the top 4 general medical journals (The Lancet, New England Journal of Medicine, Journal of the American Medical Association, and British Medical Journal) and found that the top 3 fields were cardiology, neurology, and environmental/public health. Similarly, our study identified cardiac and cardiovascular systems as an active publishing field in general medicine for authors from Japan, but GIM was the predominant field. Interestingly, Watari et al[23] suggested that the 3 most common research themes in general medicine in Japan are GIM, medical management, and infectious disease medicine. Although we also found that GIM was the dominant research area, the second and third most common research areas differed between our study and that of Watari et al.[23] This may reflect differences in research methods (i.e., use of a questionnaire survey compared with bibliometric research) and classification (i.e., used of national grant categories compared with WOS categories).

The heterogeneous range of research by general medicine practitioners in Japan may reflect a cultural influence. In Japan, even physicians who are trained as specialists are often expected to serve their community as a generalist or traditional family doctor.[38] Publications in cardiology, gastroenterology, and endocrinology were in the top 10 specialties of organ-specific internal medicine from the general medicine university departments in this study. According to a 2018 national survey by the Ministry of Health, Labour and Welfare, the 2 largest groups of specialists in Japan are cardiologists (12,865 physicians) and gastroenterologists (19,054 physicians), and there are more certified endocrinologists (2,180 physicians) than certified family physicians.[30] The number of family physicians board certified by the Japan Primary Care Association (JPCA), a leading academic general medicine organization in Japan, was only 673 as of 2017.[39,40] This imbalance suggests that researchers trained in organ-specific specialties are sometimes affiliated with a general medicine department because of cultural attitudes toward the practice of general medicine in Japan.

The tendency of individual researchers to publish in a relatively multidisciplinary manner may be related to the diversity of the clinical practice of general medicine, which inherently provides a broad spectrum of health care.[15-20] In Japan, the contributions of university and hospital departments of general medicine to the literature on treatment of unknown fevers and diagnostics indicate a high affinity for multiorgan treatment.[41] Hospitalist practice, which is derived from the practice of GIM in the USA, is characterized by its relevance to organ-specific internal medicine and geriatric medicine.[42,43] However, our study showed that researchers in general medicine produced significantly fewer articles than their counterparts in cardiology, possibly because physicians working in the university hospital setting are expected to focus more on clinical practice than on publishing activities.[43,44] Hospitalists in Japan may feel a duty to contribute to non-research fields, such as clinical education and promotion of the establishment of general medicine as a specialty.[28,40,44]

Our finding indicating the lack of a dominant field in general medicine highlights another problem: only 0.7% of all publications were in primary health care, which should be a core research area for any university-affiliated department of general medicine. Carratalá-Munuera et al[45] found that articles from the primary health care field comprised only 0.73% of total academic publications worldwide, and they did not limit author affiliation to the primary health care field. In a study that limited author affiliation to departments/institutes of family medicine, Lin et al[19] found that 20.7% of all academic publications in the USA and 23.0% in Canada were in the primary health care category; in Taiwan, this figure was only 0.4%. In Japan, Aoki et al[46] reported that the proportion of domestically originated articles in the primary care field in major international journals was 0.15%. Komagamine et al[47] found that only 3.8% of conference presentations in JPCA annual meetings were eventually published as original articles, in contrast to a publication rate of >40% for presenters at annual conferences in other countries. These international comparisons of scientific output strongly suggest that much progress needs to be made in primary care-related research in Japan. However, the low number of primary health care articles identified in this study may have been influenced by the paucity of primary care journals in the WOSCC. The top 5 fields in both general medicine and cardiology in this study were represented by 165 journals in general and internal medicine, 138 in cardiac and cardiovascular systems, 65 in peripheral vascular disease, 143 in endocrinology and metabolism, 270 in pharmacology and pharmacy, and only 19 in primary health care (Journal Citation Reports; September 2020).[48] The Journal of General and Family Medicine, an official English-language journal of the JPCA, is included in the WOSCC as part of the Emerging Sources Citation Index, but is listed under the categories of general and internal medicine and not primary health care (Master Journal List search: September 22, 2020).[49] Therefore, the productivity of academic research in the primary care field in Japan may appear lower than it actually is owing to the classification of journals in the WOSCC.

Overall, the international trends in academic publishing suggest that the output of general medicine papers by Japanese researchers, either collectively or individually, lags behind that of other countries, slowing the maturity of general medicine as an academic discipline in Japan. According to Glanville et al,[13] the total number of primary care articles indexed in MEDLINE and Embase from Australia, Canada, Germany, the Netherlands, the UK, and the USA combined was 82,169 from 2001 to 2007. The number of articles by country ranged from 4,020 in Germany to 42,643 in the USA. Without adjustment for the number of researchers, language of publication, research funding, population of each country, and study design, such comparisons are limited. However, the present study showed that the number of primary care articles from Japan over 10 years (2,923) was relatively low. However, comparatively poor research productivity in general medicine is also a challenge in other countries. Some reasons for this paucity that have been highlighted are incompatibility with educational practices in undergraduate and postgraduate settings, unstructured research networks, and lack of research funding[50-53]; the situation is similar in Japan.[46,54] Further exploration of Japan’s unique barriers to research activity, and a more direct comparison of academic publishing productivity between Japan and other countries, are needed.

4.1. Limitations

The articles examined in this study do not necessarily represent the entire research output of any individual researcher. First, we did not examine Japanese-language articles. Second, we only included publications classified as original research articles in the WOSCC. Third, classification of articles by field of study using a single database (WOS) was used for practical reasons. The WOS categories were created by Clarivate Analytics as a convenient classification system for internal usage.[35] This system provides a surrogate model that may not fully reflect reality. Thus, the single use of WOS may be inappropriate to determine publication category. Combining WOS with other databases would have enabled us to conduct a more comprehensive search of publications in different academic fields.[32] Alternatively, it may have been useful to create our own categories that reflected the study focus and to examine these in future studies.

There are also several limitations to our methods. First, staff numbers may influence departmental research output.[24,55] Although an examination of staff numbers was beyond the scope of this study, general medicine departments may contain fewer researchers than cardiology departments if the number of specialists is taken into account.[30,39] Thus, the simple comparisons of article numbers for researchers shown in Table 1 require careful interpretation. However, taking into account the proportion of articles by research field could offset the effect of staff numbers (Fig. 2). Even taking into account differences in staff numbers between the 2 specialties, the general medicine field seems to be a heterogeneous group (Fig. 3) that contains researchers who conduct multidisciplinary research (Fig. 4). Second, it is very likely that the search results contained some overlap between articles, particularly for studies involving collaborations between authors. However, a detailed crosscheck of author names to avoid such overlap was beyond the scope of this research. Third, this survey only targeted the person of highest authority in each relevant university department, thereby excluding other researchers in the same departments, as well as those working in non-university research institutes. There were 2 reasons why it was impractical to expand the study population: it would have resulted in duplication of published articles by researchers working together in the same department; and the inclusion of less experienced individuals (i.e., a research career of < 10 years) would have introduced bias for lower publication rate. Previous studies have focused on the research output of the person of highest authority; for example, 1 study investigated the research of pharmacy school deans in the USA.[56] Fourth, our survey included researchers who met the study criteria as of January 1, 2020, and English-language articles that appeared in the WOS up to April 2020, creating a gap of approximately 3 months. In Japan, organizational and faculty changes typically happen in April, which is the first month of the academic year; however, such changes may not immediately be reflected on the official website of each university. Therefore, it is possible that some researchers were removed from their posts between January and April 2020. However, it is unlikely that this would have substantially affected the overall results, as there has been no unified national reorganization of university researchers.

5. Conclusions

The English-language articles produced by the heads of university departments of general medicine in Japan covered many fields, with most in GIM and few in primary care. The surveyed researchers were a heterogeneous group with a variety of research fields, and included individuals with a relatively multidisciplinary body of research. This study is important in that it identifies previously unknown publishing behaviors and research characteristics of researchers in university-affiliated general medicine departments in Japan, and compares such characteristics with those of researchers in cardiology departments.


We thank Michelle Kahmeyer-Gabbe, PhD, and Diane Williams, PhD, from Edanz Group ( for editing a draft of this manuscript.

Author contributions

Conceptualization: Noriyuki Takahashi, Takaharu Matsuhisa,

Kunihiko Takahashi, Nobutaro Ban.

Data curation: Noriyuki Takahashi.

Formal analysis: Noriyuki Takahashi, Kunihiko Takahashi.

Funding acquisition: Noriyuki Takahashi.

Investigation: Noriyuki Takahashi.

Methodology: Noriyuki Takahashi, Takaharu Matsuhisa, Kunihiko Takahashi.

Project administration: Noriyuki Takahashi.

Resources: Noriyuki Takahashi.

Supervision: Kunihiko Takahashi, Nobutaro Ban.

Validation: Noriyuki Takahashi, Kunihiko Takahashi.

Visualization: Noriyuki Takahashi, Takaharu Matsuhisa, Kunihiko Takahashi.

Writing - original draft: Noriyuki Takahashi.

Writing - review & editing: Noriyuki Takahashi, Takaharu Matsuhisa, Kunihiko Takahashi, Nobutaro Ban.


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bibliometric analysis; cardiology; general medicine; Japan; research field; research output; Web of Science Core Collection

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