|Year : 2021 | Volume
| Issue : 1 | Page : 23-30
Thyroid disorders in children and adolescents: Systematic mapping of global research over the past three decades
Devi Dayal1, Brij Mohan Gupta2, Atul Gupta1
1 Department of Pediatrics, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 CSIR-National Institute of Science, Technology and Development Studies, New Delhi, India
|Date of Submission||25-Apr-2021|
|Date of Acceptance||07-Jun-2021|
|Date of Web Publication||14-Aug-2021|
Prof. Devi Dayal
Endocrinology and Diabetes Unit, Department of Pediatrics, Advanced Pediatrics Center, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012
Source of Support: None, Conflict of Interest: None
Background: Several countries research thyroid problems in children and adolescents. However, a scientometric assessment of global research in this field is unavailable.
Aim: We aimed to provide a comprehensive assessment of research in thyroid disorders in children during 1990–2019.
Methods: The data on pediatric thyroid disorders (PTDs) publications were retrieved from the Scopus database and analyzed using select bibliometric tools.
Results: There were 4658 publications over the 30-year period registering an average annual and 15-year cumulative growth of 6.9% and 149.4%, respectively, and averaging 24.0 citations per paper. Of the 144 participating countries, the top ten contributed 69.9% of the global share. The most productive countries were the USA, Italy, and UK, whereas Netherlands, Canada, and the USA were the most impactful. Of the 745 participating organizations and 1275 authors, the top 20 of each contributed 26.2% and 7.9% of publication share, and 42.8% and 14.6% of citation share, respectively. The top three most productive organizations were INSERM, France, National Institute of Health, USA, and National Cancer Research Institute, USA, whereas the top three most productive authors were S. Yamashita, L. Persani, and G. Weber. Journal of Clinical Endocrinology and Metabolism, Journal of Pediatric Endocrinology and Metabolism, and Thyroid were the journals that published most research in PTDs.
Conclusions: There is a substantial recent increase in the quantity of research on PTDs dominated by the North-American and Western-European countries. The vast disparities in pediatric thyroid research between high- and low-income countries need to be addressed through collaborations.
Keywords: Adolescents, bibliometrics, children, global publications, Graves' disease, hypothyroidism, scientometrics, thyroid disorders
|How to cite this article:|
Dayal D, Gupta BM, Gupta A. Thyroid disorders in children and adolescents: Systematic mapping of global research over the past three decades. Thyroid Res Pract 2021;18:23-30
|How to cite this URL:|
Dayal D, Gupta BM, Gupta A. Thyroid disorders in children and adolescents: Systematic mapping of global research over the past three decades. Thyroid Res Pract [serial online] 2021 [cited 2022 Aug 9];18:23-30. Available from: https://www.thetrp.net/text.asp?2021/18/1/23/323899
| Introduction|| |
Pediatric thyroid disorders (PTDs) are a group of diseases of the thyroid gland comprising hypothyroidism, hyperthyroidism, thyroid nodules, and malignancies and endemic goiter in iodine-deficient regions., Hypothyroidism accounts for almost 90% of PTD, which can be due to congenital or acquired causes., Hyperthyroidism is primarily caused by Graves' disease.
Although PTD are among the most common endocrine disorders in children, the exact burden of these disorders is unknown due to the lack of extensive epidemiological data. Congenital hypothyroidism occurs in 1:3000–1:4000 live births, whereas acquired hypothyroidism has a prevalence of 1%–2% in the pediatric population., About 6% of childhood cancers involve the thyroid gland, which approximates 2% of all thyroid malignancies in children and adults. Even as the global prevalence of iodine deficiency disorders as estimated by the total goiter rate has fallen from 13.1% to 3.2% over the past 25 years, it still constitutes a significant thyroid problem even in the developed countries. An estimated 4.8 million newborns were expected to be affected by iodine deficiency with its consequences of life-long productivity losses in the USA alone. Thus, collectively, PTD constitutes a significant disease burden in children and adolescents.
The past few decades have seen tremendous progress in PTD research, thus contributing to an improved understanding of these disorders and better disease outcomes and patients' quality of life. However, several questions on PTD still remain to be addressed through further research. For example, in the neonatal period, the etiological diagnosis of the various forms of congenital hypothyroidism and the decision to treat transient hypothyroxinemia is difficult. The reasons for wide regional variations in the occurrence of different types of thyroid dysgenesis are not known., Moreover, although several genes have been identified for various forms of thyroid dysgenesis, the genetically proven familial thyroid dysgenesis accounts for <5% of all cases., The long-term management of nodular thyroid disease in children is not as well elucidated as in adults. Similarly, the management protocols for Graves' disease, especially the timing of definitive treatment, is still evolving. Several aspects of pubertal development, both delayed and precocious puberty, in relation to a long-standing hypothyroid state also remain poorly understood.,
Bibliometric studies help identify the gaps in research and are therefore valuable for guiding further research in a particular field. Although a few scientometric studies are available on research in thyroid disorders in general, the PTD research remains less evaluated. Bhutani et al. examined 210 publications that appeared in a thyroid specialty journal during 2006–2013 and found that articles on PTD constituted only 3.3% of all contributions to the journal. Another bibliometric study by Kim et al. was limited to analyzing the characteristics of 100 highly cited publications (HCP) in thyroid research. In an analysis of Indian research output in thyroid disorders, Gupta et al. also demonstrated a meager contribution of publications in pediatric thyroidology of 2.8% over a 10-year period of 2007–2016. More recently, two scientometric studies analyzed research on the association between selenium and thyroid disorders and pediatric hyperthyroidism., However, none of these studies provided further analysis of research in PTD. Thus, the global architecture of PTD research remains unmapped. To address the lack of a comprehensive assessment of international research in PTD, we planned to undertake the present study.
We aimed to assess the quantity and quality of global research on PTD during 1990–2019 using appropriate bibliometric indicators on publications in this field as indexed in the Scopus international database (http://www.scopus.com). The records were analyzed by publication type and source, the annual and cumulative magnitude of publication growth, the media of research communication, characteristic features of HCPs, and identification of top countries, organizations, and authors in productivity, impact, and collaborations.
| Methods|| |
All publications on PTD during 1990–2019 were identified, retrieved, and downloaded from the Scopus database using a defined bibliometric search strategy [Appendix 1][Additional file 1]. Briefly, two combinations of keywords (thyroid* or hypothyroidism or hyperthyroidism) and (child* or pediatr* or paediatr* or toddler or adolescent* or juven* infant) were searched in “TITLE” (Title of paper) and “KEY” (Keyword) tags, and the search output was confined to the period' 1990–2019' using “date range tag.” The top ten countries in PTD research were identified by refining the search strategy by country. Countries were also classified into high-income, upper-middle-income, and lower-middle-income groups according to the World Bank criteria. The retrieved publications were analyzed by broad subject areas, publication type, country wise, author wise, organization wise, and journal wise using analytical provisions of the Scopus database. A complete counting method, wherein every contributing author or organization covered in multiple authorship publications is fully counted, was used. Similar to the methods used in our previous bibliometric analyses, we standardized the author names to avoid spelling errors in names and initials and used other specific fields such as affiliations to resolve the issue of synonyms or homonyms in authors' names.,, The qualitative assessment of publications was done using indices such as citations per paper (CPP), relative citation index (RCI), and H-index (HI). The CPP was obtained by dividing the total number of citations by the total number of publications. The RCI was defined as the number of citations to the publication divided by the average number of citations that an article usually receives in that particular field and then benchmarking the number obtained against the median relative citation ratio for all National Institute of Health (NIH)-funded papers. HI or Hirsch index was calculated by counting the number of publications, for which an author has been cited by other authors at least that same number of times. The activity index was used to reflect changes in research activity over time. To understand the long-term changes in publication growth and metrics, the 30-year study period was divided into two 15-year time periods. Citations to the publications were counted from the date of their publication until August 21, 2020.
| Results|| |
Publication types, average growth, and funding
Out of 4762 publication records obtained, 104 were deleted because of nonrelevance to time, leaving 4658 for further analysis. The original articles and reviews constituted 81.9% and 10.3%, respectively, of all publications followed by conference papers (2.6%), letters (2.5%), notes (0.9%), editorials (0.8%), short surveys (0.7%), book chapters (0.06%), and undefined (0.02%). The clinical studies were further distributed as controlled studies (1442 publications), follow-up studies (321), retrospective studies (260), case reports (645), cross-sectional studies (195), prospective studies (204), multicenter studies (108), case–control studies (182), clinical trials (266). The average annual growth rate of publications was 6.9%, up from 66 publications in the year 1990 to 259 publications in 2019. The 15-year cumulative growth was 149.4%, up from 1333 publications during 1990–2004 to 3325 publications during 2005–2019. However, the CPP decreased from 38.2 during the first to 18.2 during the second 15-year period [Figure 1]. Only 10.7% (502 out of 4658) received funding from 150 agencies; their number increased from 31 (2.3%) to 471 (14.1%) over the two 15-year periods. The average CPP of funded publications was better than the average CPP of all publications (26.6 vs. 24.0). The major funding agencies were the National Institutes of Health (101 papers) and National Cancer Institute, USA (41 papers), National Natural Science Foundation, China (31 papers), European Commission (20 papers), Medical Research Council, UK (16 papers), Wellcome Trust, UK (20 papers), Japan Society for the Promotion of Science (19 papers), Centers for Disease Control and Prevention, USA (13 papers), European Seventh Framework Programme (13 papers), and National Institute of Allergy and Infectious Disease, USA (12 papers).
|Figure 1: Total number of citations (dark red line), citations per paper, and number of publications on pediatric thyroid disorders during 1990–2019|
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Contribution by countries
Of the 144 countries which participated in PTD research, 91 contributed 1–10 papers each, 11 contributed 11–20 papers each, 19 countries 21–50 papers each, 11 countries 51–100 papers each, 15 countries 101–500 papers each, and 1 contributed 1358 papers. The top ten countries together contributed 69.9% to the global research output, with the USA leading the ranking with a 29.1% share [Table 1]. The publication share increased in all countries except Germany. Only three countries, namely, the Netherlands, Canada, and the USA, registered RCI higher than their group average of 1.3. The share of international collaborative papers of the top ten countries varied from 23.8% (Japan) to 58.5% (Canada), with an average value of 37.9% [Table 1]. Of the top thirty countries classified according to World Bank income criteria, the publication share of 22 high-income countries was 79.7%, whereas six upper-middle and two lower-middle countries contributed 13.5% and 4.4%, respectively [Figure 2]. The citation share of high, upper-middle, and lower-middle economies was 87.5%, 5.9%, and 2.2%, respectively. However, their respective CPP was 14.1, 15.7, and 30.1. India's share in the global output was 3.3%.
|Figure 2: Distribution of publication and citations share of countries classified according to the world bank criteria|
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|Table 1: Publication output and share of topmost productive countries in pediatric thyroid disorders research during 1990-2019|
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Most productive and impactful organizations
Of the 745 organizations that contributed to PTD research, 312 published 1–5 papers each, 205 published 6–10 articles each, 130 published 11–20 articles each, 84 contributed 21–50 articles each, 13 contributed 51–100 papers each, and one organization contributed 102 papers. The productivity of the top twenty most productive organizations varied from 39 to 102 publications; together, they contributed 26.2% of global publications share and 42.8% of global citations share [Table 2]. Eight organizations registered their publication output above the group average of 61.0, whereas seven registered their CPP and RCI above the group average of 39.2 and 1.6, respectively [Table 2].
|Table 2: Top 20 most productive organizations in pediatric thyroid disorders research during 1990-2019|
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Most prolific and impactful authors
A total of 1275 authors participated in PTD research; 1081 published 1–5 papers each, 149 authors 6–10 papers each, 37 authors 11–20 articles each, and 8 published 21–24 articles. Each of the 20 most productive authors contributed 14–24 publications; their collective contribution was 7.9% and 14.5%, respectively, to global output and citations. Nine of the most prolific authors registered their publications output above the group average of 18.4, while six registered CPP and RCI above the group average of 44.2 and 1.8, respectively [Table 3].
|Table 3: Most productive authors in pediatric thyroid disorders research during 1990-2019|
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Distribution of publications by research area
Clinical aspects of PTD were the most researched broad area that contributed 59.4% share to the global publications, followed by publications on pathophysiology, epidemiology, and disease outcome [Supplementary Table 1][Additional file 2].
Disorder-wise distribution of research
Hypothyroidism was the most researched PTD with 44.9% of publication share, followed by thyroid cancer (32.4%), hyperthyroidism (7.5%), autoimmune thyroiditis (6.0%), goiter (5.5%), iodine deficiency (3.4%), thyroid nodules (2.8%), and Hashimoto's thyroiditis (1.4%). The publication share increased in hypothyroidism, thyroid cancer, thyroid nodules, and autoimmune thyroid disease as against a decrease in hyperthyroidism, Hashimoto's thyroiditis, goiter, and iodine deficiency disorders during the two 15-year time spans [Supplementary Table 2][Additional file 3].
Media of research reporting
A majority (84.2%, 3921 articles) of the PTD research were published in 478 journals. The top 20 most productive journals accounted for 26.4% share of total output; the share increased from 21.5% to 28.7% between 1990–2004 and 2005–2019 [Table 4].
|Table 4: Top 20 most productive journals in pediatric thyroid disorders research during 1990-2019|
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Only 3.5% (163/4658) publications registered CPP of more than 100 and were assumed as HCPs; their total citations were 35,921 citations averaging 220.3 CPP. The citation range was 100–500, 501–1000, and 1001–1364 for 151, 9, and 3 publications, respectively. A majority (121/163, 74.2%) of HCPs were contributed by the USA. The National Institute of Health, USA contributed the largest number (19 papers) of HCPs, followed by INSERM, France, Hospital for Sick Children, University of Toronto, Canada and National Cancer Institute, USA (9 HCPs each), and Harvard Medical School, USA, and University of Toronto, Canada (7 HCPs each). M. B. Zimmermann contributed 7 HCPs, M. M. Hudson and K. Matthay 5 HCPs each), and L. Persani, J. Leger, M. Polak, P. Beck-Peccoz, and T. I. Bogdanova contributed 3 HCPs each. The largest number (29 papers) of HCPs were published in Journal of Clinical Endocrinology and Metabolism, followed by Cancer (8 papers), New England Journal of Medicine (7 papers), Journal of Clinical Oncology, Pediatrics, and Thyroid (6 papers each), Clinical Endocrinology (5 papers), and Endocrine Review, European Journal of Endocrinology, and The Lancet (4 papers each).
| Discussion|| |
The highlight of our study is the finding of a wide disparity in PTD research between high-income and low-income countries. The PTD research is dominated by high-income countries in the North-American and Western-European regions. Most of the intercountry collaborations were between the organizations and authors belonging to high-income countries. The pattern is similar to research in other fields and is largely due to the availability of financial support and commitment to research by the national governments., The infrastructure and funding are an essential requirement to carry out a highly organized and impactful research activity. Unfortunately, the paucity of research funding does not allow researchers in low-income countries to carry out impactful research. It is well known that the funded research is more impactful as compared to nonfunded research. In the present analysis also, the qualitative indices of largely unfunded research from the developing countries were inferior as compared to those from the resourceful countries. Thus, there is a need for addressing the disparities in PTD research by fostering research endeavors and collaborations between high- and low-income countries in order to improve the patient care practices in the low-income countries. For a long-term impact and sustainability, the strengthening of collaboration has to occur at the level of research organizations in resourceful and resourceless countries. The capacity-building initiatives at the level of individual researchers appear to have promising outcomes in the short term only. It is noteworthy that none of the organizations or researchers from the low-income countries figured in the most productive or impactful listings in the current analysis.
Another important finding was the decrease in the quality of research over the two time periods of the study. The primary indicator of the quality of publications, i.e., CPP, fell to more than half of its value, while the quantity of publications showed an impressive growth rate over the study period. However, this observation does not appear to be specific to PTD research. In general, the quality of medical research has shown a decline over the past few decades due to several factors, such as the growth in the number of researchers and the emphasis on quantity and not quality in hiring or promotions in jobs. The observation is also important in the context of research funding. The fall in CPP of PTD publications occurred despite an increase in the proportion of funded publications from 2.3% to 14.1% over the two 15-year time periods. The average CPP of funded publications was only marginally better than that of nonfunded publications (26.6 vs. 24.0). This is intriguing because research funding is considered an important determinant of citations and impact., A recent bibliometric study showed a considerable difference between the CPP of funded and nonfunded publications (77.2 vs. 18.6).
The journals were, understandably, the most preferred media for communication of PTD research. However, only three pediatric endocrinology subspecialty journals were among the top twenty journals that published PTD research. Other subspecialty journals that publish quality PTD research are poised to improve their impact in the future.,,,,,,,,,,
For the current bibliometric study, we used a single database similar to most of the previous scientometric reviews.,,,, Scopus database was chosen for its more extensive content coverage, search analysis tools, better citation accuracy, and funding information as compared to PubMed or Web of Science., Since Scopus does not cover all the published content, our study may have missed some of the data on PTD. Besides, some of the citations may have remained uncounted., For capturing additional data, a simultaneous search in the major scientific databases such as Scopus, PubMed, and Web of Science has been suggested but is very cumbersome to carry out., Despite the limitation of using a single database, our study accomplished the stated objectives within its protocol. We could identify the research gaps and trends in PTD research and suggest the potential use of our findings. The study thus provides the first global architecture of PTD research and a framework for authors, organizations, and countries to develop focus and collaborations on future research in this field.
| Conclusions|| |
The quality of PTD research has shown a decrease despite an impressive increase in quantity over the past three decades. The PTD research landscape is dominated by the North-American and Western-European countries, and a wide disparity exists between high- and low-income countries in PTD research. The disparities need to be addressed through collaborations between high- and low-income countries to improve the lives of children suffering from thyroid disorders in less-resourceful countries.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]