Analysis of Publication Trends
A total of 2551 articles were included in the final analysis. The timeline was divided into three segments using the histograms and line charts (Fig. 2A) for the annual distribution of publications. The first phase was from 2000 to 2010, and the annual number of articles published was about 95, indicating the lack of research focus during this period. During the second phase (2011 to 2019), there was an upward trend of popularity with around 125 articles published during this period. During the third (2020 to present), the number of published articles had a vigorous growth averaging around 160 articles. The trend of average total citations per year and the average annual number of publications are roughly in line with each other. Interestingly, the average number of citations reached 160 in the last two years, with a clear upward trend. Overall, these findings suggest the increased research focus on trace elements and CKD which is expected to grow further.
Analysis Of Most Productive Countries
A total of 87 countries contributed to the research about trace elements and CKD, among which the top three countries with the highest number of publications were the USA (n = 1303), China (n = 970), and Japan (n = 580). For the parameters of citations, while the top two countries remained unchanged, Germany occupied the third position instead of Japan. The trend graph of the annual volume of national publications (Fig. 2B) shows that the USA has been ahead of other countries in the number of annual publications in this field. Among other countries, China experienced rapid growth since 2016 and even caught up with the USA for the first time in 2020. In addition, Japan, Italy, and Germany also have made significant contributions in this field. In terms of the degree of cooperation, it can be concluded from Fig. 2C that The United States, France, Germany, and Italy were among the most cooperative nations and frequently cooperate with other countries. Academic communications between Western Europe and North America have been observed to be particularly close, while it is relatively rare in South America and Africa. In Asia, except for China, Japan and India, there are few academic exchanges between other countries. The top 20 countries and institutions have been listed in Table 1 and the cooperation network analysis is shown in Fig. 2D.
Table 1
The top 20 countries/regions contributing to publications in research.
Country | Articles | Country | Total citations | Average Citations |
USA | 1296 | USA | 16266 | 37.83 |
China | 956 | China | 5720 | 19.72 |
Germany | 575 | Japan | 3397 | 32.98 |
Japan | 411 | France | 3133 | 17.12 |
Italy | 337 | Germany | 2961 | 38.96 |
Spain | 323 | Iran | 2957 | 33.99 |
United Kingdom | 298 | Turkey | 2561 | 28.78 |
Australia | 271 | Uk | 2272 | 45.44 |
Canada | 269 | Brazil | 1985 | 28.36 |
France | 265 | India | 1938 | 21.30 |
Brazil | 259 | Italy | 1875 | 19.95 |
Turkey | 236 | Poland | 1658 | 16.42 |
Denmark | 231 | Canada | 1641 | 71.35 |
India | 217 | Spain | 1568 | 14.00 |
Korea | 177 | Australia | 1395 | 22.87 |
Sweden | 169 | South Korea | 1350 | 30.00 |
Switzerland | 145 | Sweden | 1234 | 58.76 |
Poland | 95 | Belgium | 1110 | 13.06 |
Iran | 88 | Finland | 1066 | 11.34 |
Belgium | 78 | Denmark | 933 | 27.44 |
Analysis Of Most Influential Institutions And Authors
More than 2000 institutions were calculated to have made contributions to this field. Figure 3A presented that the University of São Paulo(n = 24), the Chinese Academy of Sciences (n = 23), and the University of Michigan (n = 15) published a great many articles about this topic, which are from Brazil, the USA, and China respectively. The interagency partnerships among those affiliations were drafted, and the main clusters together from different schools were established to conduct further research (Fig. 3B). It was apparent that institutions that came from the same or neighboring countries were prone to work with a network, and top-level research and development institutions in different countries were also inclined to make cooperative research, such as the collaboration between China medical university and the University of Michigan.
The most prolific authors and authors with the highest h-index have been listed in Table 2. Liu Y (n = 21), Zachara Ba (n = 17), and Mafra D (n = 16) occupied the top three positions for publishing the greatest number of articles. In terms of the highest h-index, Zachara Ba and Mafra D performed much better than other authors, and Fissell WH also yielded excellent results. In Fig. 3C, an overlay visualization map of co-authorship analysis has been presented in the form of clustering. As can be seen that each cluster was radiated by one or two core authors, notably, Zachara Ba’s team and Ding sm’s team research results are particularly outstanding. The achievement paths of high-yielding authors in different periods have presented in Fig. 3D, which hints at the fact that while the majority of authors began to express interest in this field around 2011, Zachara Ba has shown deep in this field of research since 2001. The research results from Liu Y, Mafra D, and Macmillan-crow have been updated until recently.
Table 2
The top 20 authors contributing to publications in research.
Authors | Articles | Author | Citations | Author | H-index |
Liu Y | 23 | Zachara Ba | 192 | Zachara Ba | 13 |
Mafra D | 17 | Manitius J | 150 | Mafra D | 11 |
Zachara Ba | 17 | Guo Ch | 148 | Fissell Wh | 10 |
Macmillan-Crow La | 15 | Wang Cl | 148 | Macmillan-Crow La | 10 |
Davenport A | 14 | Chen Pc | 123 | Roy S | 10 |
Ciechanowski K | 13 | Wasowicz W | 118 | Wasowicz W | 10 |
Wasowicz W | 13 | Navarro-Alarcon M | 111 | Fouque D | 9 |
Zhang Xl | 13 | Palomares-Bayo M | 110 | Guo Ch | 9 |
Fissell Wh | 12 | Mafra D | 108 | Kim J | 9 |
Roy S | 12 | Miranker Ad | 103 | Xu Tw | 9 |
Chen Y | 10 | Hemmelgarn Br | 102 | Almen T | 8 |
Guo Ch | 10 | Kinniburgh D | 102 | Chen Pc | 8 |
Kim J | 10 | Klarenbach Sw | 102 | Manitius J | 8 |
Nangaku M | 10 | Manns Bj | 102 | Miranker Ad | 8 |
Wang Y | 10 | Tonelli M | 102 | Nangaku M | 8 |
Argani H | 9 | Wiebe N | 102 | Navarro-Alarcon M | 8 |
Chlubek D | 9 | Adamowicz A | 88 | Wang Cl | 8 |
Ding Sm | 9 | Bello A | 88 | Bosscher D | 7 |
Fouque D | 9 | Field Cj | 88 | Deelstra H | 7 |
Gromadzinska J | 9 | Gill Js | 88 | Gromadzinska J | 7 |
Analysis Of Journals And Cited Journals
The top 10 productive and the most cited journals between 2000 and 2021 have been listed in Table 3, which shows a total of 2551 published articles. The journal with the most publications was Biological Trace Element Research (n = 91), followed by Journal Of Trace Elements In Medicine And Biology (n = 40), Nephrology Dialysis Transplantation (n = 40), and Kidney International (n = 40). The co-citation analysis of journals revealed that Kidney International was the most distinguished one (n = 2554) followed by Nephrology Dialysis Transplantation (n = 1823), and the American journal of kidney disease (n = 1510). The association strength between magazines is shown in Fig. 4, and it was found that magazines form clusters based on preference for subject orientation. Journal Of Renal Nutrition and Nutrients paid more attention to the nutritional status of patients with nephropathy, Biological Trace Element Research was partial to discussing the metabolism of trace elements in the kidney, while Nephrology Dialysis Transplantation and Kidney International preferred to discuss the role of micronutrients in the treatment of kidney disease, its complications and the corresponding characteristics in disease outcome.
Table 3
Top 10 journals with most publications and with most cited works in the field of research.
Journals | Articles | Journals | Citations |
Biological Trace Element Research | 91 | Kidney International | 2570 |
Journal Of Trace Elements In Medicine And Biology | 40 | Nephrology Dialysis Transplantation | 1823 |
Nephrology Dialysis Transplantation | 40 | American Journal Of Kidney Diseases | 1510 |
American Journal Of Kidney Diseases | 38 | Journal of Biological Chemistry | 1371 |
Kidney International | 34 | Journal of The American Society of Nephrology | 1320 |
Journal Of Renal Nutrition | 32 | Biological Trace Element Research | 987 |
Pediatric Nephrology | 29 | American Journal of Clinical Nutrition | 974 |
Peritoneal Dialysis International | 28 | Nephron | 898 |
Plos One | 28 | The New England Journal of Medicine | 895 |
Renal Failure | 25 | Biochemistry | 667 |
Reference Co-Citation Network Analysis
Co-citation refers to a reference cited by two and above. The most co-cited references were summarized into 5 clusters in Fig. 5A, in which the most important are in red and blue.
The red cluster is represented by an article by Tonelli M published in BMC Medicine in 2009, which is a meta-analysis measuring 19 trace elements in whole blood, serum, or plasma to find specificity in hemodialysis patients [6]. Another representative manuscript by Tonelli M (2018) evaluated the relationship between 25 trace element blood concentrations and adverse outcomes [5]. The red cluster made assumptions about the risk that the status of trace elements may affect clinical outcomes.
The blue cluster is represented by an article by Zachara Ba published in 2001[21], which explored the relationship between selenium homeostasis and oxidative stress parameters in patients with renal failure. Another research that is of great significance is from Girelli D published in 1993[22] in which the relationship between selenium status and dialysis treatment, dietary habits, and adverse clinical symptoms of chronic renal failure was investigated. The blue cluster emphasized exploring the association between individual elements and chronic renal failure, especially selenium.
The Burst detection function provided by CiteSpace is used to detect the situation that the reference amount has great changes in a certain period of time. In Fig. 5B, detailed information on the emergence of literature citations could be realized.
An Overview Of Research Hotspots And Frontiers
Keyword analyses revealed that the keywords with high frequency reveal the main topic of this field. The top 50 keywords with frequency to make a co-occurrence network was filtered in this study (Fig. 6A), and detailed rates of occurrence of individual subject headings have been presented in the Treemap in Fig. 6B. The keywords that garnered the highest attention among the researchers were “chronic kidney disease”, “oxidative stress”, “zinc”, “copper”, and “hemodialysis”. To refine the research theme and direction, the keywords were categorized into 6 clusters in terms of subject classification (Fig. 6C). In the red cluster and purple clusters, research was concentrated on the role of heavy metals of trace elements in nephropathy, including modification of CKD induced by environmental toxicants, heavy metals exposure and incidence of kidney problems, and the associated molecular mechanisms. The risk, outcomes, and survival status were the focal points of research in the green cluster and the influence of trace elements on complications of chronic renal failure such as cardiovascular events and cancer was emphasized in this cluster. In the dark blue cluster, multitudes of fundamental experimental research had been implemented to explore mechanisms of kidney injury, and hot research areas include oxidative stress and apoptosis. In the yellow cluster, nutritional status in patients of end-stage renal disease especially those in hemodialysis has been the theme of the investigators’ interest. In this period, zinc supplementation and vitamin requirement are considered a necessity for improving clinical outcomes and quality of life, because most hemodialysis patients are anemic or malnourished. Continuing from the yellow cluster, variation in micronutrient intake due to different eating habits was studied in the watery blue cluster. Moderate intake of protein and grains as well as dietary calcium absorption were also researched by researchers. Furthermore, the frontier hotspots were visualized according to the strongest citation bursts in Fig. 6D. It was concluded those renal complications and nutritional status of patients, risk factors associated with prevention and prognosis, and measures to reduce the prevalence of CKD have been the hotspots of research in recent years.