Abstract
BACKGROUND:
Neuromyelitis optica spectrum disorder (NMOSD) is a neuroimmune disease, i.e. under constant research. The aim of this bibliometric study is to perform a bibliometric indicator analysis of the worldwide academic production of NMOSD during the period 2017–2021.
METHODS:
A bibliographic search was assessed in the Scopus database to identify NMOSD-related articles published during the period 2017–2021. Collected publications were exported and analyzed in Scival (Elsevier). Bibliographic data were described through absolute values and percentages in descriptive tables. VOSviewer was used to visualize collaborative networks.
RESULTS:
A total of 1920 documents were collected, and the highest percentage of these belonged to the area of neurology. Friedemann Paul was the author with the highest scientific production, but Brian Weinshenker had the greatest impact worldwide. Three of the institutions with the highest production were North American. Multiple sclerosis and related disorders were the journal with the highest production of publications. Most papers were published in Q1 or Q2 journals.
CONCLUSION:
NMOSD-related articles are mostly published in first and second quartile journals, which would reflect a high interest of the scientific community. Publications with international collaboration reported a higher impact. Although African and South American regions have considerable prevalence of this disease, they do not have institutions with high productivity developing research on this disease.
Keywords: Bibliometrics, neuromyelitis optica spectrum disorder, scientific production
Introduction
Neuromyelitis optica spectrum disorder (NMOSD) is considered an immune-mediated disease of the central nervous system associated with the antibody aquaporin-4 immunoglobulin G (AQP4-IgG).[1,2] It has a very heterogeneous worldwide prevalence ranging from 0.7/100,000 persons to 6.8/100,000 persons.[3] The prevalence of NMOSD varies depending on the geographic area. According to studies in Asia and Latin America, the prevalence is approximately 1–4 cases/100,000 population. In contrast, in studies conducted in Europe and North America, the prevalence is lower, with about 0.5–2 cases/100,000 population. NMOSD is a rare disease, and the prevalence may be underestimated due to lack of awareness of the disease and difficulty in accurate diagnosis.[1,2,3,4]
The cardinal symptoms of this disease are optic neuritis and myelitis.[4] For a long time, this disease was considered a variant of multiple sclerosis, another neuroimmunologic disease. However, at the beginning of this century, it was discovered that AQP4-IgG plays a fundamental role as a specific marker of this disease distinguishing it from multiple sclerosis.[5] After several years, AQP4-IgG seronegative patients were reported.[6,7] Due to this diversity, in 2015, the term “NMOSD” was coined, and diagnostic criteria were established and are currently used worldwide.[8] In recent years, new drugs have been developed with different therapeutic objectives; however, there is still an unmet need.[9]
Bibliometric analyses use rigorous methods to explore scientific information to identify emerging trends in journals and specialties as well as patterns of collaboration between authors, institutions, and countries.[10] Several bibliometric studies related to neurological diseases such as stroke, Guillain–Barre syndrome, and Parkinson’s disease have been conducted.[11,12,13] In the field of NMOSD, a bibliometric analysis of multiple sclerosis and NMOSD in the Southeast Asian region was reported;[14] however, no bibliometric study of NMOSD worldwide has been reported to date.
Thus, the objective of this bibliometric study was to analyze through bibliometric indicators the global scientific production of NMOSD during 2017–2021.
Methods
Search strategy
On February 15, 2022, we conducted a literature search using a combination of MeSH terms and free terms related to “Neuromyelitis optica spectrum disorder.” To refine the search, we used Boolean operators “OR” and “AND,” and focused on the title and abstract of each publication. Our search formula in Scopus was: The asterisk is a truncator, which is usually placed when building a search strategy. There is no need to put “means” as it is only a truncator. OR “NMO spectrum disorder*” OR “Devic neuromyelit*” OR “Devic’s diseas*” OR “Devics diseas*” OR “Devic diseas*” OR “Devic syndrom*” OR “Devic’s syndrom*” OR “Devics syndrom*” OR “Devic’s neuromyelit*” OR “Devics neuromyelit*” OR “NMOSD” OR “myelooptic neuropath*” OR “neuropticomyelit*” OR “optic neuromyelit*”) AND SRCTYPE (“j”) AND PUBSTAGE (“final”) AND SUBJAREA (“MEDI”) AND LANGUAGE (“English”) AND (LIMIT-TO [PUBYEAR, 2021] OR LIMIT-TO [PUBYEAR, 2020] OR LIMIT-TO [PUBYEAR, 2019] OR LIMIT-TO [PUBYEAR, 2018] OR LIMIT-TO [PUBYEAR, 2017]).
Selection of information
We included papers in the English language and published during 2017–2021 in scientific journals and excluded papers undergoing peer review.
Data analysis
To obtain the bibliographic indicators, the Scival program (Elsevier) was used, which is a tool for evaluating scientific production that includes four sections for the analysis of information, which are: number of citations and publications, type of collaboration, countries with the highest scientific production. Finally, VOS viewer (version 1.6.10 Centre for Science and Technology Studies Copyright © 2023 Centre for Science and Technology Studies, Leiden University, The Netherlands) was used to analyze the dynamics of the collaborative networks.
Results
A total of 1920 documents related to NMOSD were collected in medicine. Of which 1416 were original articles, 289 reviews, 121 letters, 61 notes, 27 editorials, 20 errata, 11 short surveys, 2 conference papers, and 1 retracted. The subcategories with the highest percentage were neurology (1378, 71.8%), immunology and allergy (176, 9.2%), and general medicine (150, 7.8%).
Top ten authors publishing on neuromyelitis optica spectrum disorder
Friedemann Paul was the author with the highest number of publications (80 papers), whereas Brian Weinshenker had the highest impact with 41.3 citations per paper in his 32 publications. Romain Marignier and Toshiyuki Takahashi were the second and third most productive authors, respectively. Most authors were American (3), Japanese (3), and German (2) [Table 1].
Table 1.
Top ten authors publishing on neuromyelitis optica spectrum disorder
| Rank | Author | Documents, n (%) | Total citation | Citations pser document | h-index | FWCI | Country |
|---|---|---|---|---|---|---|---|
| 1 | Paul, Friedemann | 80 (4.2) | 2240 | 28.0 | 47 | 3.6 | INLINE |
| 2 | Marignier, Romain | 42 (2.2) | 971 | 23.1 | 38 | 4.1 | INLINE |
| 3 | Takahashi, Toshiyuki | 39 (2.0) | 503 | 12.9 | 42 | 1.9 | INLINE |
| 4 | Levy, Michael | 38 (2.0) | 1065 | 28.0 | 38 | 3.5 | INLINE |
| 5 | Fujihara, Kazuo | 37 (1.9) | 1135 | 30.7 | 16 | 6.7 | INLINE |
| 6 | Pittock, Sean Joseph | 36 (1.9) | 1281 | 35.6 | 81 | 7.2 | INLINE |
| 7 | Nakashima I | 35 (1.8) | 836 | 23.9 | 49 | 3.9 | INLINE |
| 8 | Leite, Maria Isabel S | 35 (1.8) | 1325 | 37.9 | 57 | 4.7 | INLINE |
| 9 | Ruprecht, Klemens | 32 (1.7) | 744 | 23.3 | 49 | 2.7 | INLINE |
| 10 | Weinshenker, Brian G | 32 (1.7) | 1323 | 41.3 | 88 | 6.5 | INLINE |
FWCI: Field-weighted citation impact
Top ten productive institutions on neuromyelitis optica spectrum disorder
The top 10 institutions with the highest number of papers are shown in Table 2. The Charité – Universitätsmedizin Berlin (Germany) was the institution with the highest scientific output (85), whereas Oxford University Hospitals NHS Foundation Trust had the highest impact (39.0 citations per paper). The University of Oxford (UK) and Mayo Clinic Rochester (USA) were the second and third institutions with the second and third highest scientific output with 79 and 71 published papers, respectively. Three of the 10 institutions are North American.
Table 2.
Top-10 institutions on neuromyelitis optica spectrum disorder
| Rank | Institution (country) | Documents, n (%) | Total citation | Authors | Citations per document | FWCI |
|---|---|---|---|---|---|---|
| 1 | Charité–Universitätsmedizin Berlin (Germany) | 85 (4.4) | 2300 | 138 | 27.1 | 3.3 |
| 2 | University of Oxford (UK) | 79 (4.1) | 2832 | 93 | 35.8 | 46 |
| 3 | Mayo Clinic Rochester (USA) | 71 (3.7) | 2207 | 110 | 31.1 | 4.9 |
| 4 | Harvard University (USA) | 60 (3.1) | 910 | 80 | 15.2 | 3.0 |
| 5 | Tohoku University (Japan) | 57 (3.0) | 1119 | 26 | 19.6 | 3.3 |
| 6 | Capital Medical University (China) | 55 (2.9) | 425 | 149 | 7.7 | 1.3 |
| 7 | National Hospital Organization, Japan (Japan) | 55 (2.9) | 610 | 57 | 11.1 | 1.8 |
| 8 | Johns Hopkins University (USA) | 53 (2.8) | 1184 | 80 | 22.3 | 2.8 |
| 9 | Oxford University Hospitals NHS Foundation Trust (UK) | 53 (2.8) | 2067 | 76 | 39.0 | 5.2 |
| 10 | Sun Yat-Sen University (China) | 50 (2.6) | 408 | 126 | 8.2 | 1.4 |
FWCI: Field-weighted citation impact, NHS: National Health Services
Bibliometric indicators of production and impact on neuromyelitis optica spectrum disorder
With respect to the journals, multiple sclerosis and related disorders, multiple sclerosis journal, and Frontiers in Neurology are the ones with the highest number of publications about study with 331, 86, and 85 documents, respectively. However, the journal with the highest impact was neurology with 24.2 citations per paper [Table 3].
Table 3.
Bibliometric indicators on neuromyelitis optica spectrum disorder
| Rank | Journals | Quartile | Scimago journal rank | Documents | Citations per document | CiteScore 2020 |
|---|---|---|---|---|---|---|
| 1 | Multiple sclerosis and related disorders | Q2 | 0.9 | 331 | 6.5 | 3.7 |
| 2 | Multiple sclerosis Journal | Q1 | 17 | 86 | 12.0 | 9.5 |
| 3 | Frontiers in Neurology | Q2 | 1.2 | 85 | 7.6 | 4.0 |
| 4 | Journal of Neuroimmunology | Q2 | 1.1 | 84 | 5.1 | 5.3 |
| 5 | Neurology: Neuroimmunology and NeuroInflammation | Q1 | 1.5 | 62 | 16.7 | 7.7 |
| 6 | Clinical and experimental Neuroimmunology | Q3 | 0.3 | 51 | 2.9 | 1.6 |
| 7 | Neurology | Q1 | 2.9 | 48 | 24.2 | 9.6 |
| 8 | Frontiers in immunology | Q1 | 2.6 | 47 | 13.2 | 8.1 |
| 9 | Journal of the neurological sciences | Q2 | 1.0 | 46 | 7.7 | 5.1 |
| 10 | Journal of Neurology | Q1 | 1.5 | 36 | 22.4 | 6.4 |
CiteScore quartile on neuromyelitis optica spectrum disorder
Table 4 shows the documents according to the quartile of the journal. A higher percentage was observed in Q2, followed by Q1 and Q3.
Table 4.
Documents according CiteScore quartile
| CiteScore quartile | 2017 | 2018 | 2019 | 2020 | 2021 | Total |
|---|---|---|---|---|---|---|
| Q1 | 139 | 109 | 134 | 138 | 163 | 683 |
| Q2 | 105 | 144 | 130 | 245 | 196 | 820 |
| Q3 | 52 | 43 | 60 | 72 | 80 | 307 |
| Q4 | 11 | 22 | 15 | 8 | 17 | 73 |
| Total | 307 | 318 | 339 | 463 | 456 | 1883 |
Type of collaboration on neuromyelitis optica spectrum disorder
Table 5 shows the type of collaboration and its bibliometric indicators. Most of the retrieved papers had only national collaboration (743 papers: 38.9%), followed by only institutional collaboration (643 papers; 33.7%), and international collaboration (427 papers; 22.3%). Nonetheless, international collaboration (8592 citations; 20.1 citations per paper) exceeds both national (6662 citations; 9.0 citations per paper), and institutional (3285 citations; 5.1 citations per paper). The rest of the documents belong to the category “single authorship” or “no collaboration” (98 documents: 5.1%).
Table 5.
Type of collaboration on neuromyelitis optica spectrum disorder
| Collaboration | Percentage | Documents | Citations | Citations per document | FWCI |
|---|---|---|---|---|---|
| International | 22.3 | 427 | 8592 | 20.1 | 3.0 |
| Only national | 38.9 | 743 | 6662 | 9.0 | 1.2 |
| Only institutional | 33.7 | 643 | 3285 | 5.1 | 0.8 |
| Single authorship (no collaboration) | 5.1 | 98 | 395 | 4.0 | 0.7 |
FWCI: Field-weighted citation impact
Discussion
NMOSD is a neuroimmune disease with heterogeneous epidemiology worldwide and constant research on its etiology, prognosis, and treatment in recent years. In this context, the aim of our study was to assess the characteristics of publications on this disease. Our analysis found 1920 publications during 2017–2021 with the neurology area being the most frequent.
Bibliometric studies have increased during the past years. This increase is because bibliometric analyses allow the evaluation of the production of public and private institutions. These studies are increasingly being considered by funders and politicians for decision-making.[10]
Although Friedemann Paul was the author with the highest scientific production, and Brian Weinshenker was the author with the greatest impact, presenting the highest number of citations per publication. One of his publications with the highest number of citations in which Weinshenker participated during our study period was a clinical trial on inebilizumab for the treatment of NMOSD.[15] The most productive authors were American, Japanese, and German. This is consistent with a bibliometric study in which these three countries led the scientific production in neurology worldwide.[16]
Regarding the most productive institutions, although Universitätsmedizin Berlin in Germany was the institution with the highest average of publications, the two institutions with the highest impact worldwide were Oxford University Hospitals and the University of Oxford. This may be since among their most cited publications during our study period are recommendations on autologous hematopoietic stem cell transplantation and other cell therapies in neurological diseases such as NMOSD and a proposed diagnostic algorithm for relapsing demyelinating syndromes in children, including NMOSD.[17,18] Although a high prevalence of NMOSD has been reported in African regions as well as a considerable frequency in South America;[3,19,20] no institution from these regions is present among the 10 with the highest production. This indicates that public and private institutions in these regions should be encouraged as their populations are the most affected.
The journal multiple sclerosis and related disorders published the largest number of papers related to NMOSD; however, the journal neurology had the greatest impact with the highest number of citations per paper. Neurology also has relevance in the topic of Guillain–Barré Syndrome as well as COVID-19 and the area of neurology.[12,21] Regarding the quartile of the journals, most publications were in Q1 or Q2 journals, and this distribution has been maintained in these 5 years. This could indicate that publications related to NMOSD have maintained interest and impact in the scientific community.
Regarding collaboration between authors, national collaboration was almost double that of international collaboration. However, the international one had the highest impact, more than double the national one.
Our study had some limitations. First, only the English-speaking literature was analyzed, which may have prevented the identification of more articles. Second, the information was obtained from Scopus, so those journals not indexed in this database were omitted; however, this database covers a wide range of journals.[22] Third, an analysis of the past 5 years was made so past publications that may have had greater relevance or impact were omitted; however, NMOSD is a disease that has had a change in diagnostic criteria in recent years, so the period covered represents the most current research.
Conclusion
The articles related to NMOSD are mostly published in first and second quartile journals, which would reflect a high interest of the scientific community. Publications with international collaboration reported a higher impact. Although African and South American regions have considerable prevalence of this disease, they do not have institutions with high productivity developing research on this disease.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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