Bibliometric evaluation based on scopus database: Global analysis of publications on diabetic retinopathy and comparison with publications from Turkey

Ayşe Nilüfer Köylüoğlu1, Bünyamin Aydın2, Can Özlü3

1Department of Eye Diseases, Kütahya Health Sciences University, Evliya Çelebi Research Hospital, Kütahya, Turkey
2Department of Endocrinology and Metabolism, Kütahya Health Sciences University, Evliya Çelebi Research Hospital, Kütahya, Turkey
3Department of Internal Medicine and Hematology, Kütahya Health Sciences University, Evliya Çelebi Research Hospital, Kütahya, Turkey

Keywords: Bibliometric analysis, diabetic retinopathy, Scopus analysis.

Abstract

Objectives: In this study, we aimed to review the scientific literature on Diabetic retinopathy (DR).

Materials and methods: Scopus bibliometric database was searched in English. Original research articles made between 1941-2021 containing the keywords "diabetic", "DM" and "retinopathy" and "article" in the title, abstract, and keywords were found. Publications were evaluated in terms of the institution, author, publication year, subject, number of citations, and the journal in which they were published.

Results: It was determined that there were 58,516 publications on DR, and the first publication was published in 1941. 41,996 of them were research papers. Only research articles were evaluated in our study. It was determined that there was an increase in the number of articles after the 1960s and that the year 2020 was the year in which the highest number of articles were published (6.3%). The United States (21.9%) and China (10.6%) were the countries with the highest number of articles. Turkey ranked 13th. The journals in which the highest number of articles were published were Investigative Ophthalmology and Visual Science (3.1%) and Ophthalmology (1.9%). The third leading institution with the most articles; Harvard Medical School (1.4%), University of Melbourne (1.1%), and Wilmer Eye Institute (1%).

Conclusion: The increase in scientific research on DR, both on treatment and prevention, causes an increase in the number of publications. The ranking of our country should be raised to higher levels in this regard.

Introduction

Diabetic retinopathy (DR) is the most common complication of diabetes mellitus (DM). It has long been considered a microvascular disease.[1] Diabetic retinopathy is one of the longterm complications of diabetes and the major leading cause of vision loss among the workingage population in industrialized societies. As of 2010, this complication affects more than 100 million people globally and is estimated to increase to >190 million by the year 2030.[2] This disease, especially in the early stages, is largely asymptomatic and causes patients with diabetes not to be diagnosed in a timely manner. After the disease develops, regular eye screening is needed to ensure its management.[3] The increased number of affected people has resulted in an increase in scientific research on this topic.

Developing evidence-based clinical, pathological, and experimental data from the last 20 years has now led to an expanded view of how diabetic retinopathy develops. However, most of the available treatments focus on the latestage.[2] This makes the treatment of DR difficult.[1] A better understanding of the pathophysiology associated with diabetes should therefore provide opportunities to prevent the disease at a much earlier stage. It is predicted that in the coming years, new pharmacological treatments based on understanding the causal mechanisms of DR will be developed and meet the need for both vascular and neuroprotection.[1] Laboratory and clinical evidence has shown that, in addition to microvascular changes, inflammation and retinal neurodegeneration may contribute to diabetic retinal damage in the early stages of DR. Further investigation of the underlying molecular mechanisms may provide targets for the development of new early interventions.[2,4]

In this study, we aimed to analyze the publications about diabetic retinopathy which is an important health problem worldwide, and compare Turkey’s status.

Patients and Methods

Research model

The research model is a situation analysis study, which is one of the qualitative research methods. The purpose of this study is to reveal results related to a specific situation. In order to create a model, Arıca et al.[5]’s study was taken as a model. With this evaluation method; studies on the subject are analyzed mathematically on the basis of various research parameters, including publication years, themes, authors and institutions, keywords, funding institutions, citations, methods, and samples.[5] In our study, we aimed to evaluate the current situation regarding DR research articles worldwide. The study was conducted in accordance with the principles of the Declaration of Helsinki.

The Scopus bibliometric database was searched in English using the same method as in a similar study. In the study, original research articles with the keywords “diabetic”, “DM” and “retinopathy” and “article” in their title, abstract, and keywords were found between January 1, 1941, and June 9, 2021. Duplications were included in the review only once. The obtained data were analyzed in the Excel spreadsheet created by the researcher.

Data analysis

Using the bibliometric data analysis technique; mathematical and statistical analyzes (frequency and percentage) were performed. Publications were evaluated in terms of the country, institution, author, publication year, subject, number of citations, and the journal in which they were published. In addition, a special evaluation was made for Turkey.

Ethics approval

The study complied with the Helsinki Declaration, which was revised in 2013. Ethics committee approval is not required as there is no human or animal research.

Results

It was determined that there were 58,516 publications on diabetic retinopathy and the first publication was published in 1941. Of these publications, 41,996 were research papers. Only research articles were evaluated in our study. It was found that the number of articles increased after the 1960s and 2020 was the year in which the highest number of articles were published (n=2,643, 6.3%) (Figure 1).

Figure 1. Distribution of articles by year.

The majority of the articles (n=34,125, 81.2%) were written in English. Chinese (n=1,585, 3.8%), Japanese (n=1,521, 3.6%), German (n=1,219, 2.9%), French (n=1,163, 2.8%), Spanish (n=548, 0.93%) Russian (n=535, 0.91%) were also the languages in which the most articles were published.

The United States (USA) (n=9,212, 21.9%), China (n=4,485, 10.6%), Japan (n=4,213, 10.3%), England (n=3,379, 8%), India (n=2,068, 4.9%) were the top five countries with the most articles on this topic. Turkey was in the 13th place with 905 articles (2.1%) (Figure 2).

Figure 2. The number of publications by country.

12,483 (29.7%) of the articles were published in open access (OA) journals. The highest number of articles on DR were published in the journals of Investigative Ophthalmology and Visual Science (n=1,309). The highest number of articles on DR in this journal was in the year 1998 (Figure 3).

Figure 3. Distribution of the number of articles by years and journals.

Articles were published in 28 different subject areas. Medicine (n=36,325, 86.5%), biochemistry/genetics/molecular biology (n=8,185, 19.5%), neuroscience (n=5,137, 12.2%), pharmacology/toxicology (n=1,619, 2.76%), nursing (n=1,266, 3%), engineering (n=1,161, 2.7%) were the areas with the highest number of publications.

The first three journals with the highest number of articles published were Investigative Ophthalmology and Visual Science (3.1%), Ophthalmology (1.9%), and Diabetes Care (1.8%) journals (Table 1).

Table 1. Top 10 journals with the highest number of articles on diabetic retinopathy (n=41,996)

The most repeated keywords in the articles were diabetic retinopathy (n=33,044, 78.6%) and human (n=33,983, 80.9%).

Financing institutions

Institutions that provide the most financial support for research articles were; National Eye Institute (n=2,337, 5.6%), National Institutes of Health (n=1,405, 3.3%), National Natural Science Foundation of China (n=867, 2.1%).

Distribution of the articles according to the institutions in which they were published

The three leading institutions with the most articles on DR were; Harvard Medical School (1.4%), University of Melbourne (1.1%), and Wilmer Eye Institute (1%) (Table 2).

Table 2. Top 10 institutions with the highest number of articles published (n=41,996)

Ronald E. Klein from the United States was the author who published the most articles on DR (Figure 4).

Figure 4. Authors who published the most on diabetic retinopathy.

Citation analysis

Forty-four of these articles were cited at least 1,000 times, 122 of the 500 times, and 1,937 at least 100 times. The most cited article was “The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus”[6] published in 1993 by the Diabetes Control and Complications Trial Research Group. This article was cited 20,708 times. 2,000 of the articles that could be accessed were never cited. However, the Scopus database only allowed the review of the least 2,000 articles for citation analysis (Table 3).

Table 3. Analysis of the 10 most cited articles[6-15]

Evaluation of Turkey’s research articles on diabetic retinopathy

Turkey was in 13th place in the publication ranking, 905 articles were published. There was a rapid increase in the number of publications after 2000, and the most publications were published in 2016 (80 articles) and 2020 (83 articles). The highest number of articles were published by Mehmet Çıtırık from Ankara Training and Research Hospital (Figure 5).

Figure 5. Authors who published the most on diabetic retinopathy from Turkey.

The institutions with the highest number of publications from Turkey were Istanbul University Faculty of Medicine (5%) and Health Sciences University (4.6%) (Table 4).

Table 4. Top 10 institutions in Turkey with the highest number of publications on diabetic retinopathy (n=905)

Discussion

With the use of oral antidiabetic drugs and insulin treatments, the life expectancy of patients with diabetes has increased. The incidence of DR, one of the main complications of diabetes, has increased, too. Diabetic retinopathy is seen all over the world between the ages of 20-65 and is among the major causes of blindness in patients with diabetes. While the incidence of DR development within 10 years in patients diagnosed with diabetes before the age of 30 is 50%, this rate rises to 90% after 30 years. The longer the duration of diabetes, the higher the likelihood of DR findings. The risk of developing blindness in patients with diabetes is 25 times higher than in patients without diabetes.[16,17] For all these reasons, scientific products on DR are also carried out globally, and the globally increasing diabetic and aging population causes the studies on DR to continue without losing speed. In order to analyze the situation, we examined the research articles on DR based on the Scopus database, which is the largest database that provides bibliometric analysis. In our study, we found that the number of publications on DR is increasing both in our country and in the world. We believe that this situation will encourage the researchers to publish on DR.

With the bibliometric analysis method, holistic evaluations of scientific research can be made. By comparing previous studies, gaps in research areas can be identified and even comparisons can be made at the level of countries.[18-21] Internet databases are frequently used in the bibliometric analysis. While this method was frequently used in social field analyzes in previous years, it has also been used in medicine and eye diseases, which is our field, in recent years. In fact, different databases can be analyzed and mapped with visualization methods.[18-25]

Heng Wong et al.[24] in a bibliometric analysis study in which 100 groundbreaking articles in the field of eye were examined, it was reported that most of the publications were from the USA, as in our study. In this study, all types of articles were examined, 83% of the publications were original research articles and 15% of the publications were DR.[24] This shows that DR, which is the subject of our study, is one of the important issues in the field of eye diseases. In our study, only research articles were also evaluated. In this meta-analysis study, it was determined that most of the publications were published in the journals of Archives of Ophthalmology, the American Journal of Ophthalmology, and Ophthalmology. In our study, the first three journals in which the most articles were published; Journals were Investigative Ophthalmology and Visual Science (3.1%), Ophthalmology (1.9%), and Diabetes Care (1.8%).

While the Web of Science (WoS) database included in Thomson Reuters’ publications was the only database for bibliometric studies until 2004, the number of bibliometric databases increased with the establishment of Scopus and Google Scholar in 2004.[26,27] Google Scholar was not evaluated in this study due to the difficulty in evaluating publication and citation data. In our study, SCOPUS, the largest database, was preferred for bibliometric analyzes.[26] PubMed, on the other hand, was evaluated in terms of comparison.

In the examination made with the same keywords in the PubMed database; It was determined that there were 38,245 publications, 36,274 research articles in total, and the maximum number of publications was in 2020.

In recent years, medical journals have switched to the OA publication model so that publications reach more people. In the OA model, the journal acts as a service provider by evaluating the article/product for the scientist (peer review) and providing the most widespread distribution. Before OA, some medical journals charged subscription fees from libraries as well as submission, color figure, or page fees from authors, while article processing/publication fee (APC) has become one of the main income items in the financing of journals with the OA model.[28] Lansingh and Carter[25] in their meta-analysis study, in which they examined publications in the field of ophthalmology, found that the articles published in the Scopus database did not show a significant difference between open and closed access articles in terms of the number of citations. In our study, 29.7% of the publications were in the form of OA. The citation numbers of these journals were not significantly different from other publications. Forty-four of the articles in our study were cited at least 1,000 times, 122 were cited 500 times, and 1,937 were cited at least 100 times. This shows that publications on DR have a very high citation potential.

As a result, the increase in scientific research on both treatment and prevention of DR causes an increase in the number of publications. The ranking of our country should be raised to higher levels in this regard.

The limitations of the study were that only research articles were evaluated and a single database was searched. Content analysis was not performed, only the characteristics of the publications were examined.

In conclusion, apart from developed countries, developing countries should also be encouraged to conduct research on this subject.

Conflict of Interest

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Financial Disclosure

The authors received no financial support for the research and/or authorship of this article.

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