The quality of life of patients with chronic obstructive pulmonary disease: a bibliometric analysis

Introduction

Chronic obstructive pulmonary disease (COPD) is a highly prevalent and mostly preventable respiratory disease characterized by persistent respiratory symptoms and restricted lung airflow (1). The natural course of COPD is characterized by symptom exacerbation and quality-of-life reduction (2), and the development of COPD involves complex pathogenic processes primarily centred around airway inflammation, oxidative stress, mitochondrial dysfunction, ageing, and iron ion metabolism (3). Cigarette smoke and other harmful particles are the primary causative factors of COPD. COPD has a high clinical mortality and mutilation rate and is often accompanied by complications such as chronic pulmonary emphysema (4). COPD can progressively deteriorate lung function and lead to various respiratory symptoms such as coughing, sputum production, shortness of breath, and respiratory distress, which reduces patients’ quality of life (QOL). These symptoms result in reduced exercise capacity and decreased social activity.

QOL is a comprehensive indicator for assessing the health and well-being of individuals, which is affected by a variety of factors (5). Recent research indicates that QOL is a critical measure of the effectiveness of pulmonary rehabilitation in patients with COPD (6). QOL is particularly relevant for patients with the exacerbator chronic bronchitis and exacerbator emphysema phenotypes, who have shown to experience the poorest QOL (7). Interestingly, spirometry, traditionally a staple in COPD diagnosis and management, may not be necessary for including patients in palliative care research or clinical care. This is especially pertinent for those with poor QOL and a high risk of adverse outcomes (8). However, it is important to note that telemonitoring has not been effective in improving QOL for patients with moderate to severe COPD, underscoring the need for alternative management strategies (9). The recent guidelines further reinforce the importance of QOL, recommending it as a management goal for those with COPD (10).

Bibliometrics is a widely used method for analyzing knowledge carriers and evaluating scientific research quantitatively and qualitatively. Compared to a literature review, based on a large number of literature and targeted analysis, bibliometrics makes it possible to quickly identify the overview of specific research fields and development frontiers (11). With the advent of scientific databases such as Web of Science, literature research has become more accessible (12). Web of Science is one of the most reliable sources of comprehensive scholarly databases. It is considered the most extensive and important bibliometric analysis database in most fields (13,14).

Clinical research is essential for the development of new medical treatments, diagnostic tools, and preventive measures. As the scientific literature continues to grow, it is becoming increasingly difficult for researchers and institutions to identify impactful research. Bibliometrics can help analyze the impact and hot trends of clinical research, strengthen teamwork, and gradually become one of the solutions to solve related challenges.

Given the growing focus on the QOL of patients with COPD, this area is garnering increasing attention. A thorough analysis of the related literature could yield more profound insights into research themes, active researchers, and research institutions. It could also guide practitioners and patients in making informed treatment decisions. There are many bibliometric studies on COPD, including mitochondria and the progress of COPD research (15). Still, there are few bibliometric studies on patients’ QOL with COPD.

Data visualization is a useful tool for visualizing bibliometric results. Thus, we conducted a bibliometric study based on the Web of Science database to characterize the research situation regarding the QOL of patients with COPD over the past 31 years. We completed a visual analysis of the research personnel, hotspots, and other related factors to gain a macroscopic understanding of the current development status of this field. These findings will provide valuable references for future research into the QOL of patients with COPD.

Methods

Literature search

We searched the Web of Science Core Collection database for literature published since the database’s inception. The main subject terms used were “chronic obstructive pulmonary disease” and “quality of life”, including the abbreviated forms “COPD” and “QOL”, respectively, and they were connected with the operator “OR” and the operator “AND”. Document type: unlimited. Articles were exported in plain text format along with their citation information. The data retrieval took place on December 25, 2022.

Statistical analysis

For bibliometric and data visualization, quantitative and visual analyses were conducted using the R package “bibliometrix” (16) (https://www.bibliometrix.org/; The R Foundation for Statistical Computing, Vienna, Austria). This package can be used for analysis of authors, journal sources, literature status, publishing countries, institutions, citation and time series relationships, etc. Statistical indicators include the number of publications, citations and outputs of core authors, author collaborations, major journals, major research countries and collaborations, and key research themes. During the keyword analysis process, to avoid the frequency impact of related vocabulary, the two categories of terms, “chronic obstructive pulmonary disease” and “quality of life”, were removed since they constituted the search content.

Results

Retrieval overview

A total of 9,220 documents were retrieved using the Web of Science platform. One document published in 2023 was excluded, resulting in a total of 9,219 documents being included in the analysis. The main period of publication of the retrieved documents was from 1992 to 2022, with some earlier journals included. Subsequent analyses were conducted using a timeline-based approach, with the base period being from 1992 to 2022. The results of this retrieval included 1,168 journals, with an annual growth rate of 13% in the number of articles published, an average citation frequency of 35.46 times per document, and a total of 32,508 authors (Table 1).

Distribution of publication volume by decade

Figure 1 depicts the distribution of the number of articles published in the research field of QOL in patients with COPD for patients with COPD across different years. In the initial phase [1992–2001], there were 478 publications, representing an average of fewer than 100 manuscripts annually. In the subsequent phase [2002–2012], the cumulative number of publications increased to 2,728, indicating a significant growth in publication volume. In the final phase [2013–2022], the total number of articles was 5,961, with a peak value of 675 manuscripts in 2020. Although the annual publication volume growth rate was slightly slower during this phase, it fluctuated consistently around the peak value.

Figure 1 The distribution of annual article publications from 1992 to 2022.

Distribution of core authors in the field

Globally, 32,508 authors published articles in this field, but only 9,098 published more than 1 article, with 527 having published more than 10. The top 30 authors, based on publication quantity, were considered to be the core authors in this analysis.

Analysis of citations among the core authors

As detailed in Table 2, the h-index, g-index, m-index, and other relevant metrics were calculated for the past 31 years. While Ambrosino N had the highest publication quantity, Wedzicha JA and Jones PW had the highest total citation counts in the field. Wedzicha JA also had the highest h-index, while Wouters EFM had the highest g-index.

Wedzicha JA is a researcher at the London School of Medicine, whose article published in the New England Journal of Medicine in 2010 (17) has been cited 1,846 times. The article describes a large-scale administrative cohort study with 2,138 participants and a maximum follow-up period of 3 years. The study found that although acute exacerbations become more frequent and severe as COPD progresses, their incidence rates appear to have a distinct susceptibility phenotype, which is of great significance for developing treatments preventing COPD exacerbation and ameliorating the severity of various diseases.

The article by Jones PW published in 1992 (18), which was cited the most number of times in this field (2,167 times), provides a self-assessment scale for chronic airflow limitation health status, namely the St. George’s Respiratory Questionnaire (SGRQ), which is now well-known in the field. The questionnaire includes three aspects—symptoms, activities, and the impact on daily life—which form the foundation for research on the QOL of patients with COPD. Subsequently, in 2009, Jones PW published the COPD Assessment Test (19), cited 1,782 times, further promoting the development of the field.

Annual production output of core authors

As shown in Figure 2, the production output of core authors appears sustainable, with most conducting research in the early stages of this field. In addition, individuals such as Singh D from the University of Manchester in the United Kingdom and Holland AE from the University of Lethbridge in Australia, despite having only published their first articles in 2009, have many citations (Table 2). Indeed, Singh D and Holland AE are considered emerging talents. Singh D’s most cited papers include the systematic review of the leading causes of death of COPD nationwide in 2012 (20) and the international guidelines introducing the global strategy for COPD, published in 2017 (21), for which he was a contributor. Meanwhile, Holland AE’s 2010 article (22) identified the minimum clinically significant difference of the six-minute walk distance in patients with COPD as 25 m, providing a basis for clinical practice. Furthermore, his most cited paper proposed an updated definition of pulmonary rehabilitation (23).

Figure 2 The annual productivity of the core authors. N., number; TC, total citations.

Author collaboration network

As shown in Figure 3, the author collaboration network can be primarily segmented into five clusters, and the specific centrality analysis for each author in the author collaboration network can be found in Table 3. The ten authors ranked by betweenness centrality from high to low, respectively, were Casaburi R, Wouters EFM, Jones PW, Vestbo J, Make B, Maltais F, Troosters T, Spruit MA, Bourbeau J, and Agusti A. Meanwhile, the top ten authors ranked by closeness centrality, respectively, were Wouters EFM, Maltais F, Make B, Casaburi R, Troosters T, Vestbo J, Agusti A, Bourbeau J, Sciurba FC, and Jones PW. Finally, the top ten authors ranked by PageRank, respectively, were Wouters EFM, Martinez FJ, Criner GJ, Spruit MA, Vestbo J, Wedzicha JA, Casaburi R, Agusti A, Troosters T, and Anzueto A.

Figure 3 Diagram of the author collaboration network.

Wouters EFM was centrally located in the author collaboration network flow within the field. The network centrality evaluation metrics include betweenness centrality, closeness centrality, and PageRank. Betweenness centrality characterizes the influence of a node on information flow within the network, with higher betweenness values indicating a more significant impact and importance of the node. Closeness centrality measures a node’s ability to influence other nodes in the network through the network itself. A greater closeness centrality value indicates that the node is more centrally located within the network. PageRank indicates a node’s importance. Wouters EFM excelled in all three metrics, pointing to this author’s prominence in the author collaboration network.

Journal distribution

By analyzing the sources of journals, we discovered that the European Respiratory Journal, the International Journal of Chronic Obstructive Pulmonary Disease, and Respiratory Medicine had the highest number of published articles (Table 4).

The publication trends over the years can be observed in Figure 4. It is evident that in the past decade, the European Respiratory Journal and the International Journal of Chronic Obstructive Pulmonary Disease demonstrated a rapid increase in the number of related publications. On the other hand, other journals have shown a relatively stable growth rate in terms of publications.

Figure 4 Yearly journal publication statistics.

Geographic distribution

As can be seen in Figure 5, the country with the highest citation frequency was Bangladesh, followed by Iceland and then the United Kingdom, Denmark, and the Netherlands. According to the statistics on the number of publications by country (Figures 6,7), the United States had the highest number of publications and growth rate, followed by the United Kingdom, with China’s publication volume ranking third. In 2019, China ranked eighth, indicating that China’s publication growth rate has increased rapidly, and some international cooperation has been initiated. However, it is clear that China still lacks highly regarded research and has relatively few citations.

Figure 5 Citation rates of articles from various countries.

Figure 6 International collaboration diagram.

Figure 7 The number of articles published by various countries from 1992 to 2022.

Research focus emphasis on topic distribution

Regarding research direction and focus, the prominent themes in this field (Figure 8) were found to include pulmonary rehabilitation, dyspnea, mortality, health-related QOL, health status, and emphysema, among others. More recently emerging topics encompassed microbiome, particulate matter, home-based telerehabilitation, Tai Chi, blood eosinophils, frailty, and pharmaceutical care, among others.

Figure 8 Topic distribution chart. COPD, chronic obstructive pulmonary disease.

In the hierarchical clustering diagram in Figure 9, the keywords in this field are clustered into two major categories. One category (in red) is COPD and includes population, symptoms, prevalence, anxiety, and depression, among others; the other category (in blue) is related to COPD and includes clinical terms such as double-blind, efficacy, randomized controlled trial, tiotropium, obstructive pulmonary disease, patients with COPD, airflow limitation, exacerbations, exercise capacity, lung function, chronic bronchitis, airflow obstruction, and acute exacerbations; and disease-related terms including risk factors, health status, mortality, risk, quality of life, lung disease, association, validation, burden, health, diagnosis, validity, impact, questionnaire; and diagnosis-related terms such as therapy, trial, rehabilitation, quality of life, predictors, care, management, outcomes, physical activity, and survival.

Figure 9 Hierarchical clustering diagram of keywords. COPD, chronic obstructive pulmonary disease.

Discussion

This bibliometric analysis revealed several key insights into the research landscape on the QOL of patients with COPD over the past 31 years. From 1992 to 2022, research attention into the QOL of patients with COPD continuously increased, as did the number of publications, indicating a growing clinical importance placed on improving the QOL of COPD patients. This aligns with the recognition that QOL is a critical measure of the effectiveness of pulmonary rehabilitation and other COPD management strategies. As COPD is a debilitating and progressive disease, the sustained research interest underscores the need for more effective treatments to alleviate the symptoms and burden experienced by patients.

An analysis of the journals revealed that the European Respiratory Journal and the International Journal of Chronic Obstructive Pulmonary Disease had an exceptionally high number of publications and exhibited higher growth rates than the other journals, making them the top journals in this field. Their increasing publication volumes over the past decade likely reflect the field’s expansion and the journals’ status as preferred venues for disseminating cutting-edge findings.

The identification of key authors, such as Wedzicha JA, Jones PW, Singh D, Holland AE, and Wouters EFM, provides insights into the thought leaders driving research progress in this domain. Wedzicha JA and Jones PW, who have a long publication history and an extensive number of citations, were frequently cited by senior researchers. Moreover, Singh D and Holland AE began their research later but have garnered a significant number of citations and contributed substantially to clinical research, emerging as rising stars in the field. Network centrality analysis indicated Wouters EFM to be a core member of the industry collaboration network.

The geographic distribution analysis revealed the dominance of developed nations, particularly the United States and the United Kingdom, in terms of publication volume, citation rates, and international collaboration. This likely reflects these countries’ more significant research funding, infrastructure, and clinical expertise. Additionally, the rapid growth in publication output from China and other countries suggests an increasing global recognition of the importance of COPD QOL research. Strengthening international collaborations and knowledge exchange could further accelerate progress in this field.

The thematic analysis highlighted several areas of focus, including pulmonary rehabilitation, dyspnea, mortality, health-related QOL, and emphysema. These align with the clinical priorities for COPD management, where improving patients’ symptoms, functional status, and overall well-being are paramount. Emerging topics, such as microbiology, particulate matter, home-based rehabilitation, and Tai Chi, suggest potential future research directions that could yield novel therapeutic approaches.

The management of long-term health problems such as COPD has added a heavy burden to medical services. Self-management is underutilized in the current clinical care of COPD (24). However, through the analysis of key research topics, it can be seen that home rehabilitation, self-management, and Tai Chi exercise are better choices for daily care of COPD, which can not only improve the QOL of patients, reduce the economic and social burden of patients, but also reduce the pressure on the health system.

In addition, the anticipation of dyspnea itself can have a significant impact on the patient’s mood and behaviour (25), and psychological distress is prevalent in patients with COPD and is associated with a more severe course of the disease, which can also increase the burden on patients, caregivers, and the healthcare system when psychological problems are not treated (26). Therefore, more attention needs to be paid to the psychological changes caused by COPD and the impact on relatives and caregivers in the process of family rehabilitation and self-management.

Conclusions

This bibliometric analysis highlights the growing importance of QOL research in the field of COPD, which can inform clinicians, researchers, and policymakers to prioritize areas for future investigation in order to develop comprehensive, patient-centered strategies. At the same time, it is suggested that researchers should pay more attention to the core authors, strengthen international collaboration and team exchanges, actively explore characteristic clinical featured treatment measures such as Tai Chi and family rehabilitation, carry out clinical research on the integration of traditional Chinese and Western medicine and self-management, focus more on the QOL, mental health and economic and social burden of patients, and ultimately enhance the well-being of individuals with chronic respiratory diseases.

Acknowledgments

Funding: This work was supported by Lin He’s New Medicine and Clinical Translation Academician Workstation Research Fund (No. 17331208), the Programs of Administration of Traditional Chinese Medicine in Zhejiang (Nos. 2015ZB077 and 2018ZB080), the Second Special Fund for Clinical Research of the Second Affiliated Hospital of Wenzhou Medical University in 2018 (No. SAHoWMU-CR2018-01-105), the Beijing Kangmeng Charity Foundation-Medical Scientific Research Development Fund Project for Clinical and Basic Research (No. WS676F), and the Zhejiang Provincial Natural Science Foundation of China (No. LGJ21H100001).

Footnote

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-591/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-591/coif). The authors have no conflicts of interest to declare.

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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