AECOPD research in the past ten years: a bibliographic analysis based on Web of Science

Introduction

Chronic obstructive pulmonary disease (COPD) is currently one of the main diseases affecting the health of adults, especially the elderly, and can increase the risk of lung cancer (1,2). According to statistics, COPD caused more than 3 million deaths worldwide in 2015, accounting for 5% of all deaths. Compared to 1990, the number of deaths from COPD in 2015 increased by 10% and the prevalence increased by 44%. Furthermore, due to insufficient diagnosis and treatment of COPD, the morbidity and mortality of COPD can be underestimated (3). In China, there are approximately 100 million patients with COPD. The prevalence of COPD varies from 1.20% to 8.87% in different regions. The prevalence rate of people over 40 years old is as high as 13.7%. Males (7.76%) are higher than females (4.07%). Rural areas (7.62%) are higher than urban areas (6.09%) (4,5).

Acute exacerbations of COPD (AECOPD) can cause a significant decrease in lung function of patients and seriously affect the health and life of patients. It is the main reason for the hospitalization and death of COPD patients and places a heavy burden on the patient's family and the medical system (6,7). Therefore, AECOPD has been the focus of research in respiratory diseases in recent years (8-12). The main cause of AECOPD is respiratory viral infection and the main pathogenesis includes viral-bacteria coinfection, microbiome changes in the respiratory tract and host response to bacteria and bacterial susceptibility (8,9). Especially in recent 2 years, COVID-19 infection can cause AECOPD which is very dangerous (12). However, in recent decades, the diagnosis, evaluation, and management of AECOPD have not made significant progress. Recent clinical and translational studies have shown that the heterogeneity of the mechanisms and outcomes of acute exacerbations can be resolved by grouping them into etiological groups (13). It is expected that this will help better understand the pathophysiological process behind each type of exacerbation, thereby facilitating the intervention of precision medicine in AECOPD (13).

Bibliometrics is a quantitative analysis of published documents, analyzing the authors, research institutions, countries from which they come from, journals, etc., reflecting the current research status of a certain topic, and analyzing the frequency of use of keywords to reveal the changes of research hotspots (14,15). This study aims to use bibliometric methods to analyze the status and characteristics of AECOPD related research in the past 10 years [2010–2020] and provide references for future research.

Methods

Database

Similar to the previous bibliometric studies, we used the Science Citation Index Expanded (SCI-E) database as a data source to search. The SCI-E database is an open database in the Core Collection of the Web of Science (WOS) that provides literature citation data from the literature. It is currently an important data source for bibliometric research and scientific paper evaluation. The SCI-E database was founded and published by the American Institute of Scientific Information in 1957. The documents included in it are from 1900 to the present, and it is constantly updated and supplemented. The data provides various retrieval methods. Currently, subject retrieval is mainly used to obtain target documents in a specific field or topic quickly.

Search strategy

The subject search strategy was used and the search terms were: “AECOPD” or “acute exacerbation of chronic obstructive pulmonary disease.” Since this research aims to analyze the research hotspots of AECOPD and other related situations in the past 10 years, the period of the retrieval target is: 2010–2020. The final search time is May 24, 2021.

Data processing

After the search is completed, we export all the records of the results and the cited references in text format as the original data set and use CiteSpace software to analyze the original data set. The analysis content includes the annual distribution of the published documents, the source of the published documents (including countries, institutions, journals, authors), and the use of keywords, cooperation (centrality) between countries, institutions, and authors.

Statistical analysis

This research mainly describes the number of papers published in different years, countries, institutions, journals, and related information of authors, the number of papers cited, the frequency of the keywords used, and its relationship with time. Therefore, the number and percentage used in the study to represent data centrality scores are automatically generated by CiteSpace software. This study did not perform a comparative analysis, so it is not necessary to set a P value.

Results

General information

The search results have a total of 3,806 records, including 2,610 original articles, 628 reviews, 437 meeting abstracts, 55 editorial materials, 46 letters, 12 proceeding papers, 9 corrections, 5 early access, 3 book chapters, and 1 retracted publication (Tables 1,2, Figure 1). After 21 duplicate records were removed, the final number of AECOPD-related research documents published from 2010 to 2020 was 3,785. It can be seen that the number of AECOPD documents has shown a steady increase in the past 10 years (Figure 1); 3,785 articles have been cited 62,162 times, and the number of citations each year has also shown a significant increase. The average number of citations per article is 16.42, and the h-index is 97 (Figure 2).

Figure 1 Annual changes in the number of papers published.

Figure 2 Annual changes of the citation frequency.

Countries and institutions distribution of literature

From a quantitative analysis, the top five countries that have published related articles are the United States, China, the United Kingdom, Spain, and Italy (Table 3). The top 5 countries with centrality scores reflecting the cooperation in the research are: the United Kingdom, Australia, the United States, Spain, and France (Table 4). The top 5 institutions by the number of publications are: Kings Coll London, Univ British Columbia, Fudan Univ, Univ Alabama Birmingham, and Univ Barcelona (Table 5). The top 5 institutions by centrality score are the following: Univ British Columbia, Harvard Univ, Monash Univ, Univ Barcelona, and Hanyang Univ (Table 6). CiteSpace V software was used to generate a visualization map of countries (Figure 3). The number of nodes is 143, representing 143 countries and regions that have participated in AECOPD research in the past 10 years. The number of connections between nodes is 636, indicating that there is not much cooperation between countries in this field. Cooperation is mainly concentrated in a few countries, including the United States, the United Kingdom, Australia, Canada, Germany, Italy, Spain, and China. In the institution visualization map (Figure 4), the number of nodes is 237, and the number of connections between nodes is 776, suggesting that there is not much cooperation between institutions. As can be seen in Figure 4, cooperation is mainly concentrated between a few institutions.

Figure 3 The visual map of the countries, showing that the cooperation between countries is relatively limited in several countries.

Figure 4 Institution visualization map. Cooperation is concentrated on some institutions in the United Kingdom and the United States (middle), and there is also some cooperation between several research institutions in China (middle left).

Authors

Author analysis results show that the top 6 authors with published papers are: Sethi S, Yoo KH, Miravitlles M, Dransfield MT, Sin DD, and Rhee CK (Table 7). The top 3 authors by centrality scores are Sethi S, Torres A, and Anzueto A (Table 8, Figure 5). It can be seen that although Chinese and South Korean researchers have published many articles, they have relatively few collaborations with other authors and have not entered the top 10 with high centrality scores. The top 5 authors by citations are: Celli BR, Hurst JR, Vestbo J, Donaldson GC, and Wedzicha JA (Table 9). The top 5 authors by co-citation centrality score are: Hurst JR, Seemungal TAR, Miravitlles M, Bhatt SP, and Ram FSF (Table 10, Figure 6). The results of the citation analysis also show that related studies in European and American countries are cited more frequently than other countries, and the number of citations and the centrality of co-citation of studies in China and South Korea are not among the top 10.

Figure 5 The authors’ co-authored visualization map.

Figure 6 The author’s co-cited visualization map.

Journals

The 3,785 documents on AECOPD come from 738 journals; 29 journals published more than 20 documents on AECOPD in the last ten years (Table 11), accounting for 1,983 (52.39%) documents. The top 5 journals that publish papers in this field are: Am J Resp Crit Care, Chest, Eur Respir J, Thorax, and New Engl J Med (Table 12). Only Circulation and Am J Manag Care are cited with a centrality score of more than 0.05. Circulation is a professional journal for cardiovascular diseases, and Am J Manag Care is a professional journal for disease management (Table 13).

Keyword analysis

The keyword analysis results show that the top 5 most used keywords are: chronic obstructive pulmonary disease, acute exacerbation, mortality, management, and risk (Table 14). The keywords with the highest centrality score are: chronic obstructive pulmonary disease and acute exacerbation (Table 15). We use CiteSpace V software to generate a keyword co-occurrence map (Figure 7: N=332, E=2,138). For high-frequency keywords, CiteSpace is used to perform burst detection, and the results are shown in Figure 8. There is a time change in the utility of keywords, indicating the shift of research focus.

Figure 7 Keyword co-occurrence map. Identified in the figure are keywords that often appear together.

Figure 8 Top 25 keywords with the strongest citation bursts.

Discussion

The results of this study show that AECOPD research has continued to grow in the past decade. Important research comes mainly from several developed countries in Europe and North America. The cooperation between the institutions and authors in these countries is relatively close. Asian countries, including China and South Korea, have published many papers, while the collaboration is relatively small and the number of citations is few. The journals in this field are mainly respiratory professional journals and top comprehensive journals. Keyword analysis suggests that the research hotspots in the past ten years are gradually changing.

Research on AECOPD contains many aspects, mainly including risk factors for AECOPD (16,17), biomarkers (13,18), and management (19-21). In terms of risk factors, current research still believes that respiratory tract infection is the most common cause of AECOPD. Therefore, patients with COPD should actively prevent infection during the stable period (22). The 2020 version of the global initiative for chronic obstructive lung disease (GOLD) pointed out that respiratory virus infection is a risk factor for the deterioration of the condition of AECOPD patients and the prolonged hospital stay (23). In addition, smoking and air pollution are currently also important risk factors for AECOPD (24-26). These studies are also reflected in the keyword analysis of this study (Figure 8). Burst analysis shows respiratory virus infections [2010–2014], air pollution [2017–2018], and smoking [2018–2020] are all high-frequency keywords. In the research of AECOPD biomarkers, both procalcitonin and C-reactive protein are related to AECOPD and its prognosis (27,28). Many studies have shown that eosinophils can be used as a monitoring indicator for the hormone treatment of AECOPD (29-31). GOLD also recommends this (23). The keyword analysis of this study also shows that eosinophils are high-frequency keywords in 2018–2020 (Figure 8). For the management of AECOPD, there have been many studies in the past 10 years. Mainly in two aspects: drug treatment and non-drug treatment. In terms of drug treatment, the first is the medication strategy in the acute exacerbation period. It is necessary to clarify the treatment goals and rationally use antibacterial drugs, tracheal dilation drugs, and hormones (23,32,33). In terms of non-drug treatment, attention should be paid to oxygen therapy and non-invasive mechanical ventilation (23,34,35). More importantly, AECOPD should be prevented when COPD is stable. For high-risk patients, GOLD recommends that patients start treatment with a combination treatment plan that includes inhaled hormones (23,36,37). Our research shows that pathogenesis is one of the high-frequency keywords in this field in recent years. As mentioned above, the current trend is to classify AECOPD according to the cause and further adopt targeted treatment, which is also the precise treatment of respiratory diseases (38).

Our research results show that the most frequently cited journals in this field are mainly top-level journals in the field of respiratory sciences and top-level comprehensive journals, but the number one journal of co-cited centrality is Circulation-a cardiovascular top journal. COPD is closely related to cardiovascular disease, including common risk factors, pathophysiological mechanisms, and similar clinical manifestations, and simultaneously aggravate each other (39). It is often necessary to distinguish AECOPD from acute heart failure and coronary heart disease in clinical research. At the same time of treatment and management, it is necessary to treat both situations in many aspects, such as medication and rehabilitation (40-42).

This study also shows that the important research literature on AECOPD comes mainly from developed countries in Europe and North America, and the cooperation between them is also relatively close. However, these countries are significantly different from other countries in terms of tobacco control and air pollution. Especially in China, contrary to the trend of decreasing number of smokers in the United States, the number of smokers in China has increased significantly (43-45). Therefore, in this field, Chinese research should pay full attention to the impact of smoking and other risk factors on COPD patients. According to the main cause of AECOPD, we recommend future study focus on the prevention of respiratory viral infection to decrease the risk of COPD and AECOPD. In general, this study shows an overview and some problems of the research of AECOPD in recent ten years. According to our results, investigators may find some important focus to study.

The limitations of this research: Bibliometrics uses an indirect method to describe the research overview of a certain topic and cannot fully present more than 3,000 search results documents. It can only reflect the general situation of the current research through the primary data. Most of the target documents of this study are clinical studies. Clinical research is closely related to basic research. When there is a breakthrough in basic research, it may impact clinical research or even rewrite the guidelines. Therefore, while understanding the research situation in this field, we should also pay close attention to related basic research.

Acknowledgments

Funding: Medical Science and Technology Project for Social Development in Xuzhou (KC16S126).

Footnote

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://dx.doi.org/10.21037/apm-21-2756). All authors reported they received funding support from Medical Science and Technology Project for Social Development in Xuzhou (KC16S126).

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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(English Language Editor: J. Chapnick)