Global trends and research hotspots in pulmonary rehabilitation for chronic obstructive pulmonary disease: a bibliometric analysis (2000–2024)

Introduction

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disorder characterized by persistent airflow limitation and progressive symptom deterioration, and it has become one of the leading causes of death and disability worldwide. According to the Global Burden of Disease study, COPD has consistently ranked among the top three causes of mortality globally, with continuously increasing healthcare utilization and socioeconomic burden (1). Beyond pulmonary function impairment, patients with COPD frequently experience reduced exercise tolerance, skeletal muscle dysfunction, and psychological comorbidities, which collectively impair quality of life and substantially increase the risks of acute exacerbations, hospitalization, and mortality (2).

In this context, pulmonary rehabilitation (PR), owing to its well-established efficacy in improving exercise capacity, alleviating dyspnea, and enhancing health-related quality of life (HRQoL), has been progressively recognized as a fundamental component of comprehensive COPD management (3). With the accumulation of evidence, COPD rehabilitation has evolved from traditional exercise-centered, single-dimensional interventions toward modern rehabilitation frameworks emphasizing multidimensional integration and individualized prescription (4). This paradigm shift reflects not only advances in the understanding of COPD pathophysiology but also the incorporation of multidisciplinary strategies, including behavioral modification, nutritional optimization, and psychological interventions, alongside the rapid development of digital health technologies (3,5).

Concurrently, the delivery settings of PR have expanded from conventional center-based programs to community, home-based, and remote environments (6,7). The coronavirus disease 2019 (COVID-19) pandemic has further accelerated the adoption of tele-rehabilitation, virtual training platforms, and wearable technologies, thereby facilitating the transformation and broader implementation of PR models (5,6,8,9). Against the backdrop of global population aging and the growing demand for chronic disease management, the strategic importance of PR in both clinical practice and public health has become increasingly evident, accompanied by a sustained growth in related research output.

Traditional narrative reviews, while valuable for synthesizing evidence, largely rely on manual screening and subjective interpretation and remain limited in their ability to systematically characterize the overall knowledge structure, collaborative networks, and thematic evolution of a research field. In recent years, bibliometric approaches have been applied to analyze PR or COPD-related research (10); however, most existing studies have focused on relatively short time spans or addressed PR as a broad concept, lacking a long-term, continuous, and disease-specific examination of COPD-related PR research.

Therefore, using the Web of Science Core Collection (WoSCC) as the data source, this study included publications on PR in COPD published between 2000 and 2024. By applying CiteSpace, VOSviewer, and R-bibliometrix, we comprehensively analyzed publication trends, author and institutional collaboration patterns, keyword clustering, and co-citation structures, thereby delineating the developmental trajectory of this field over the past two decades and elucidating the temporal evolution of major research themes. These findings provide a clearer understanding of the knowledge evolution in COPD PR research and offer valuable insights to inform future study design and clinical practice. We present this article in accordance with the BIBLIO reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2026-1-0191/rc).

Methods

Data sources

The data for this study were obtained from the WoSCC. The search covered the period from 1 January 2000 to 31 December 2024, encompassing nearly two decades of publications. Eligible document types were limited to original research articles and review papers, and the search was restricted to English-language publications to ensure coverage of mainstream international research. A topic-based retrieval strategy was employed using the following search terms: TS = (“chronic obstructive pulmonary disease*” OR “COPD*” OR “chronic airflow obstruction*” OR “chronic obstructive lung disease*”) AND TS = (“pulmonary rehabilitation*” OR “respiratory rehabilitation*” OR “pulmonary rehabilitation training*” OR “exercise training*” OR “rehabilitation program*” OR “physical therapy*” OR “respiratory exercise*” OR “breathing exercise*” OR “exercise therapy*” OR “endurance training*” OR “functional training*” OR “cardiopulmonary rehabilitation*”).

The search was conducted through the Web of Science platform, and all retrieved records were exported using the Plain Text format. The exported files contained the full bibliographic information and cited references for each publication, with each record saved as an individual .txt file.

Research methods

A multi-tool bibliometric analysis framework was employed in this study. CiteSpace 6.4.R1 was used to construct dynamic knowledge networks and perform temporal evolution analyses, including the detection of keyword bursts and the generation of timezone visualizations (11). VOSviewer 1.6.20 was applied for high-dimensional data visualization, primarily for co-authorship and institutional collaboration analyses, as well as document co-citation clustering (12). The R package bibliometrix (version 4.0) was used for end-to-end data processing and statistical validation, covering annual publication trend analysis, national and institutional contribution mapping, core journal identification based on Bradford’s law, and thematic evolution visualization (13). Excel 2024 was utilized for data cleaning and basic descriptive statistical analysis throughout the research process. Publication counts at the country, institutional, and author levels were aggregated from the metadata fields of the WoS exported records, with each entity counted when it appeared in a publication record and subsequently ranked accordingly. Institutional publication rankings were generated by aggregating the affiliation field (affiliation/organization) at the institutional level, whereby a publication was counted for an institution when that institution appeared in the author affiliation information, and institutions were ranked in descending order by publication counts (documents). To reduce bias introduced by institutional name changes over time, naming variations, and recording inconsistencies, institutional names were standardized by harmonizing capitalization and punctuation, removing redundant characters, and merging obvious synonyms or name variants. It should be noted that institutional statistics were performed based on database-recorded entities; therefore, affiliated hospitals or regional branch sites within the same university system may be indexed as separate names in the database and were counted as distinct entities, which reflects an inherent limitation of the affiliation field granularity.

Statistical analysis

Descriptive statistics were used to summarize publication counts, annual growth rate, citation indicators, authorship characteristics, collaboration indicators, and keyword and reference distributions. Annual publication trends were fitted using a polynomial regression model, and the coefficient of determination (R²) was used to assess model fit. Bibliometric indicators, including publication counts, total citations, H-index, G-index, M-index, number of publications, links, and total link strength, were calculated using bibliometrix, VOSviewer, CiteSpace, and Excel. All analyses were based on bibliographic metadata exported from the Web of Science Core Collection, and no inferential statistical tests involving human participants were performed.

Results

Literature screening and publication overview

To comprehensively summarize the research landscape of PR training in COPD over the past two decades, a topic-based search was conducted in the WoSCC for the period from 2000 to 2024. A total of 5,173 records were initially retrieved (Figure 1A). During the preliminary screening, data cleaning was performed according to predefined criteria for document type, language, and duplication. Specifically, 1,280 non-research documents (e.g., conference abstracts, editorials, and book chapters), 183 non-English publications, and 2 duplicate records were excluded. After multiple rounds of screening, 3,708 articles were retained for bibliometric analysis (Figure 1A).

Figure 1 An overview of literature selection and publication. (A) Flowchart illustrating the inclusion and exclusion criteria for literature selection. (B) A comprehensive overview of annual publication volumes from 2000 to 2024.

To further characterize the evolution and scholarly output of this field from 2000 to 2024, descriptive statistical analyses were conducted on the included literature (Figure 1B). The 3,708 articles were published across 566 journals, authored by a total of 14,353 individuals, incorporating 4,250 keywords and citing 70,241 references. The annual publication growth rate reached 7.88%, with 23.73% of the publications resulting from international collaboration. Most studies were co-authored, with only 122 single-authored publications. The mean publication age was 9.07 years, and the average citation count per article was 33.65, indicating substantial academic influence and sustained research activity within this field (Figure 1B).

Publication trends and geographical distribution

From 2000 to 2024, research on PR training for COPD showed a continuous upward trajectory (Figure 2A,2B), with a total of 3,708 publications retrieved. The field progressed from a period of relatively low and fluctuating output to a phase of steady and sustained growth. Annual publication counts increased from several dozen articles in the early years to approximately 250 articles per year since 2021, indicating a notable rise in scholarly attention and research activity in this domain (Figure 2A).

Figure 2 Publication trends and geographic distribution. (A) Temporal trajectory of annual publications within the field. (B) Fitted curve representing the progression of publication volumes over time. (C) The top ten countries ranked by publication output. (D) The leading ten institutions ranked by publication output.

To further delineate the developmental pattern of this field, a polynomial fitting curve was applied to annual publication data (y =0.0024x³ +0.519x² −1.4329x +14.048, R²=0.9292). The high coefficient of determination demonstrates strong explanatory power and a good fit between the model and observed trends (Figure 2B).

The geographical distribution of research output was also examined by identifying the top ten contributing countries over the past two decades (Figure 2C). The United States ranked first with approximately 650 publications, followed by England with around 550 publications, with both countries demonstrating a clear leading position. Australia (approximately 400 publications) and Canada (approximately 390 publications) also maintained relatively high and stable research outputs. The Netherlands (approximately 305 publications), China (approximately 300 publications), and Italy (approximately 290 publications) represented a moderate level of productivity. Brazil, Belgium, and France likewise contributed to varying extents. Overall, research output was predominantly concentrated in North America and Europe, exhibiting a pronounced core distribution pattern.

At the institutional level (Figure 2D), the top 10 institutions demonstrated a clear gradient distribution pattern, with European and Australian institutions dominating the core research output in this field. Maastricht University ranked first with approximately 175 publications, followed by the University of Leicester (approximately 160 publications), and the University of Toronto and the University of Sydney (both approximately 150 publications). Together, these four institutions constitute the principal research forces in COPD PR. Notably, both Maastricht University and CIRO are located in the Netherlands. When their outputs are considered collectively, the Netherlands demonstrates a particularly prominent research contribution at the global level, reflecting its longstanding and well-established academic foundation in the field of COPD PR. Detailed information on the top 50 institutions by publication count is provided in Table S1.

Keyword analysis

Keyword analysis systematically revealed the co-occurrence patterns, burst strength, clustering structure, and temporal evolution of research topics in COPD PR training over the past two decades.

The keyword co-occurrence network (Figure 3A) identified “PR” as the largest node, indicating its central position within the research field. It showed strong linkages with high-frequency keywords such as “physical activity”, “obstructive pulmonary disease”, and “dyspnea”, reflecting close thematic associations within the network. Clustering analysis divided the keywords into several relatively stable thematic modules. The red cluster mainly comprised exercise training and functional outcomes related to PR, including exercise capacity, endurance, strength, skeletal muscle, and performance. The blue cluster focused on patient-reported outcomes and efficacy evaluation, including quality of life, health status, HRQoL, exercise tolerance, and randomized controlled trial (RCT). The green cluster included psychological and clinical management factors, such as depression, anxiety, diagnosis, therapy, and prevalence. The purple cluster was associated with measurement properties and instrument evaluation, including reliability, validity, pulmonary disease, and chronic obstructive. The network presents a multi-theme structure centered on “PR”, with dense interconnections among nodes across clusters.

Figure 3 Keyword analysis. (A) Co-occurrence network of frequently cited keywords. (B) Top 15 keywords with the strongest citation bursts. (C) Clustering diagram of prominent keywords. (D) Temporal evolution of keywords depicted in a timeline.

The keyword burst analysis (Figure 3B) reveals the temporal progression and shifting research priorities in COPD PR from 2000 to 2024. The keywords with the highest burst strengths included “respiratory rehabilitation” (strength =28.95), “RCT” (strength =26.64), and “air flow limitation” (strength =22.38), with burst periods mainly concentrated in the early phase from 2000 to 2010. During this stage, research primarily focused on efficacy and underlying mechanisms. In addition, “exercise tolerance”, “chronic bronchitis”, “quality of life”, and “endurance” exhibited significant bursts between 2000 and 2011, indicating an emphasis on exercise capacity, symptom improvement, and quality-of-life-related outcomes. Between 2006 and 2017, keywords such as “tiotropium”, “shuttle walking test”, “primary care”, and “6-minute walk distance” demonstrated sustained bursts, reflecting a shift toward specific assessment tools, pharmacological adjuncts, and primary care settings, with PR becoming increasingly integrated into clinical practice. In recent years, “association” and “statement” have emerged as new burst keywords, suggesting growing attention to guideline development, consensus documents, and professional society statements, indicating a trend toward greater standardization and formalization within the field.

As shown in the keyword clustering map (Figure 3C), the network was partitioned into eight major clusters (#0–#7). The clustering exhibited a clear structure and a high degree of modularity (Q =0.7299, S =0.8714), indicating good cluster separability and internal consistency. These clusters can be summarized into three interrelated research directions. Clusters represented by exercise training (#5), skeletal muscle (#1), and breathing exercises (#7) form a theme related to rehabilitation interventions and underlying physiological mechanisms, highlighting the prominent roles of exercise prescription, muscle function, and breathing training techniques within the overall knowledge structure. Noninvasive ventilation (#0) and supplemental oxygen (#4) constitute another relatively concentrated module, reflecting the relevance of ventilatory support and oxygenation management in the PR process. Clusters centered on quality of life (#2), older adults (#3), and sedentary behavior (#6) place greater emphasis on patient-centered outcomes and specific population characteristics. Overall, the network displays a multi-theme parallel distribution, with cross-links among clusters but relatively well-defined thematic boundaries.

The timeline view (Figure 3D) provides an intuitive representation of the thematic evolution of COPD PR research from 2000 to 2024. Each horizontal line corresponds to a thematic cluster, with nodes indicating associated keywords; larger nodes represent higher frequencies, and their colors denote the year of first appearance. The diagram is organized chronologically from left to right and hierarchically by cluster from top to bottom.

In the early period (approximately 2000–2008), active keywords mainly related to disease physiology and basic outcomes, concentrating on lung function and airflow limitation, exacerbations and mortality, as well as assessment items such as exercise capacity and quality of life. The research focus during this period was largely on characterizing disease features and conducting initial evaluations of intervention effects. During the mid-period (approximately 2008–2016), keywords such as exercise training, 6-minute walk test, outpatient rehabilitation, and self-management appeared persistently along the timeline, indicating a phase in which PR became centered on exercise training while incorporating standardized functional measurements and management strategies. Over the same period, supportive-therapy themes, including noninvasive ventilation and supplemental oxygen, spanned a relatively long time range, reflecting the parallel development of ventilatory support strategies and rehabilitation interventions. In more recent years (approximately 2017–2024), research hotspots further extended toward behavioral management, population stratification, and standardization. Keywords such as sedentary behavior, older adults, and sarcopenia were positioned closer to the right end of the timeline, and newer terms such as long COVID and guideline emerged at the terminal period. This indicates an expansion of research attention from traditional functional improvement to lifestyle factors, comorbid conditions, and guideline updates.

Overall, the timeline depicts a three-phase trajectory, namely baseline evaluation, maturation of interventions and measurement systems, and refinement toward behavioral and population-focused standardization, while core topics, including exercise training, outcome assessment, and respiratory support, remained continuously active throughout the study period.

Collaboration among authors, countries, and institutions

Figure 4 presents the collaboration networks and related distribution structures at the author, country, and institutional levels. The collaboration networks were constructed based on co-authorship relationships; when a publication was jointly authored by different authors, countries, or institutions, a collaborative link was established between the corresponding entities. Node size represents publication output, and edge thickness reflects collaboration frequency; at the institutional level, collaboration intensity was further quantified using the number of links (links) and total link strength (TLS).

Figure 4 Collaborative networks of authors, countries, and institutions. (A) Network illustrating collaboration among authors. (B) Countries clustered by keyword co-occurrence. (C) Network of collaborative ties between countries. (D) Institutional collaboration network.

The co-authorship network reveals the major scholarly communities and the core researchers within the field (Figure 4A). The author collaboration network (Figure 4A) demonstrates the presence of several clearly defined collaborative clusters, exhibiting a pronounced cluster-based structure. Authors such as Spruit, Martijn A., Wouters, Emiel F.M., Holland, Anne E., and Singh, Sally J. appear as prominent nodes with dense connections, occupying central positions within the network. Multiple closely connected research groups are organized around these core authors, with strong intra-cluster linkages. In contrast, connections between different clusters are relatively limited and are primarily mediated by a small number of cross-cluster authors, indicating a collaboration pattern characterized by stable team structures alongside selective inter-team interactions.

Additionally, global top authors were ranked based on three bibliometric indicators, and the top ten researchers according to each metric are presented in Table 1.

The country distribution map based on keyword clustering (Figure 4B) shows a clear thematic grouping across countries. The “respiratory muscles” cluster (#0) is the largest, bringing together Canada, Brazil, Germany, Switzerland, and Italy, with research more concentrated on respiratory muscle function and training-related interventions. In contrast, the “telerehabilitation” cluster (#2) aggregates Australia, France, Belgium, Spain, Portugal, and Norway, where remote rehabilitation and digital delivery constitute shared focal topics. A relatively independent cluster labeled “exercise training” (#1) comprises several Asian and Middle Eastern countries, represented by Japan, Turkey, and Saudi Arabia. The “diaphragm” cluster (#3) mainly includes England, China, and Greece, with a stronger emphasis on diaphragm-related research, while Denmark, Scotland, and Sweden are more concentrated within the “physical training” cluster (#4). Overall, the clusters are spatially well separated, indicating a relatively specialized and stable pattern of thematic preferences among countries in COPD PR research.

The country-level collaboration network is presented in Figure 4C. The United States, England, and Australia occupy central positions in the network, characterized by larger node sizes and dense interconnections. European countries form a relatively compact regional collaboration cluster, with frequent links observed among England, the Netherlands, Italy, France, and Germany. Canada maintains connections with multiple countries in both North America and Europe, reflecting cross-regional collaboration patterns. Although China demonstrates a relatively high publication output, its international links are comparatively fewer, and its overall collaboration intensity appears lower than that of the core Western countries. Overall, the network exhibits a multi-core and regionally clustered structure, with high-output countries positioned more centrally within the global collaboration system.

Figure 4D presents the institutional collaboration network. The University of Toronto had the highest publication output (148 publications) and exhibited the largest number of collaborative links (links =317) as well as the highest TLS (TLS =715), occupying a central position in the network. The University of Sydney (documents =104, TLS =648), Monash University (documents =93, TLS =629), and Alfred Health (documents =77, TLS =580) also demonstrated relatively high collaboration intensity. The overall network displays a clustered structure, with collaborations concentrated around several highly connected institutions. Inter-cluster links are comparatively limited, and most institutions are indirectly connected through a small number of central nodes.

Multiple correspondence analysis (MCA) and co-citation network analysis

To explore the conceptual structure of the PR field, MCA was performed to identify thematic patterns among high-frequency keywords. The resulting conceptual structure map is shown in Figure 5A. The first two dimensions explained 57.98% and 23.44% of the total variance, respectively, indicating that the two-dimensional projection adequately represents the main thematic distribution of the dataset. Three relatively distinct clusters were identified. The largest cluster, located on the right side of the map, included core terms such as PR, COPD, physical activity, quality of life, exercise capacity, exercise tolerance, skeletal muscle, lung function, exacerbation, and hospitalization, forming the main framework of PR research. A second cluster, positioned in the lower-right quadrant, comprised terms including capacity, performance, strength, and endurance, representing a concentrated group focused on physical performance and muscular function indicators. A third cluster, located on the left side of the map, contained depression and anxiety, which were spatially separated from the main rehabilitation cluster. Rehabilitation and functional outcomes occupied the central position in the conceptual structure, whereas psychological factors constituted a relatively independent component within the field.

Figure 5 MCA and co-citation network analysis. (A) MCA. (B) Author co-citation network. (C) Journal co-citation network. (D) Document co-citation network. MCA, multiple correspondence analysis.

The author co-citation network (Figure 5B) exhibited a densely interconnected structure, with Spruit MA, Holland AE, and Singh SJ positioned at the core of the network and demonstrating high co-citation frequencies. These authors formed prominent citation clusters, indicating their central role within the intellectual structure of the field. Additional clusters centered on Troosters T, Ries AL, and Griffiths TL constituted relatively independent yet interconnected knowledge domains, resulting in a multi-centered co-citation pattern.

The journal co-citation network (Figure 5C) was primarily concentrated around leading respiratory and rehabilitation journals. European Respiratory Journal, American Journal of Respiratory and Critical Care Medicine, Thorax, and Chest occupied central positions with dense co-citation links. Respiratory Medicine and Journal of Cardiopulmonary Rehabilitation and Prevention formed a rehabilitation-oriented cluster, whereas general medical journals such as The Lancet, New England Journal of Medicine, and JAMA were located at the periphery but maintained consistent co-citation connections. Together, the core respiratory journals and highly co-cited authors delineate the principal intellectual framework of COPD PR research.

The document co-citation network (Figure 5D; Table 2) traces landmark publications that have shaped the developmental trajectory of COPD PR. Foundational works include Lacasse Y [2006] and Ries A.L. [2007]. Lacasse [2006], one of the earliest large-scale systematic reviews, established robust evidence that PR significantly improves exercise tolerance and quality of life, marking the starting point for evidence-based practice in the field. Ries [2007], published in Chest, defined core PR components—including exercise training, education, and psychosocial support, and remains a key clinical and educational reference. Its central position within the “red cluster” reflects its longstanding influence. The document co-citation network (Figure 6A) demonstrates a densely connected structure centered on several highly cited landmark publications. Spruit MA (2013, Am J Respir Crit Care Med) occupies the most prominent position in the network, consistent with its highest total citation count (2,645 citations; 203.46 citations per year; normalized citations =50.84) as shown in Table 2. Other highly cited studies include Pedersen BK (2006, Scand J Med Sci Sports; 1,617 citations), Cieza A (2020, Lancet; 1,519 citations), Pedersen BK (2015, Scand J Med Sci Sports; 1,491 citations), and McCarthy B (2015, Cochrane Database Syst Rev; 1,365 citations). Classic earlier works such as Ries AL (2007, Chest; 925 citations) and Lacasse Y (2006, Cochrane Database Syst Rev; 770 citations) remain strongly co-cited and are positioned within the main citation cluster. The co-citation map reveals two closely interconnected clusters, indicating that contemporary guideline statements and systematic reviews are co-cited alongside foundational clinical trials and meta-analyses. Overall, the most frequently co-cited references correspond to consensus documents, systematic reviews, and pivotal rehabilitation trials, forming the principal citation backbone of COPD PR research.

Figure 6 Trends in topic evolution. (A) Centrality map of research topics, reflecting their relative influence within the field. (B) Temporal trend graph of evolving research topics. (C) Sankey diagram depicting the dynamic transformation and amalgamation of research themes.

Building on this foundation, Spruit M.A. [2013] represents a major milestone of the 2010s. Published in American Journal of Respiratory and Critical Care Medicine, this work has accumulated 2,645 citations, averaging over 200 citations per year. As the most influential “hub” document, it links the green and red clusters in the co-citation network and provides the theoretical framework for modern PR programs.

The field then entered a phase emphasizing individualized and diversified rehabilitation approaches. Studies by McCarthy B. [2015] and Cieza A. [2020] exemplify this paradigm shift. Notably, Cieza [2020], despite its recent publication in Lancet, has already achieved exceptionally high citation rates (60.99 per year), second only to Spruit [2013], suggesting its critical role in driving contemporary transformations in COPD rehabilitation.

Highly co-cited literature primarily consists of consensus statements, systematic reviews, and key intervention studies, forming the essential citation foundation in the field of COPD PR.

Thematic evolution analysis

To examine the thematic structure and temporal distribution of the field, a thematic map, trend analysis, and structural association analysis were performed (Figure 6). In the thematic map (Figure 6A), PR, COPD, and exercise are located in the quadrant characterized by high centrality and high density, representing the principal research themes. Keywords such as quality of life, dyspnea, and exercise capacity appear in the area with high centrality but relatively lower density, corresponding to basic themes. In contrast, telemedicine, telerehabilitation, and COVID-19 are positioned in the region with lower centrality and higher density, indicating relatively specialized thematic clusters. The keyword trend analysis (Figure 6B) shows that early research attention focused on functional status and quality-of-life indicators, later expanding toward intervention-related themes such as exercise and rehabilitation, with increasing occurrences of telemedicine, telerehabilitation, and virtual reality (VR) in recent years. The Sankey diagram (Figure 6C) further illustrates the associations among keywords, authors, and countries, with research groups from the United Kingdom, the Netherlands, Canada, and Australia demonstrating substantial participation in the core themes.

Discussion

Interpretation of bibliometric findings

This study conducted a systematic bibliometric analysis of 3,708 publications on PR for COPD indexed in the WoSCC from 2000 to 2024. The field exhibited a sustained annual growth rate of 7.88%, reflecting the convergence of multiple driving forces: the escalating global burden of COPD has elevated PR as a strategic non-pharmacological intervention, while milestone documents, such as the 2013 American Thoracic Society/European Respiratory Society (ATS/ERS) statement, together with successive international guideline updates, have helped to formalize and consolidate the research agenda. From 2022 onward, annual output stabilized at approximately 250 papers. suggesting a transition from an exploratory phase toward a more mature stage of knowledge accumulation. Geographically, the United States and England together contributed more than 1,200 publications, underscoring their dominant roles, which likely reflect long-term investments in RCT infrastructure, strong support from professional societies, and access to large clinical cohorts. Notably, despite the concentration of COPD burden in low- and middle-income countries (LMICs), the top 10 most productive countries were overwhelmingly high-income, highlighting a geographic mismatch between research output and disease burden. This imbalance implies that effective PR implementation typically requires multidisciplinary teams, standardized assessment and follow-up systems, and sustained health financing; consequently, existing evidence may underrepresent resource-limited settings, thereby constraining real-world applicability. Future research should strengthen participation from low-income countries by broadening sample sources and data contributions, developing scalable, low-cost, culturally adapted rehabilitation models (e.g., community-based, home-based, tele-rehabilitation, and locally tailored exercise interventions), and reducing inequities in evidence generation through cross-regional collaboration. At the institutional level, Maastricht University and CIRO—both based in the Netherlands—show a pronounced global advantage when considered jointly. The Netherlands’ ability to produce such high-density output despite its relatively small national scale may be attributable to the early establishment of specialized PR centers, tightly integrated clinical–research workflows, and a strong culture of inter-institutional collaboration.

Keyword burst detection and timeline analyses indicated an evolution of research priorities from early validation of efficacy and core outcomes, to mid-stage expansion into assessment instruments and broader clinical contexts, and more recently toward standardized consensus and emerging delivery models. The thematic strategic map positioned “telemedicine” and “telerehabilitation” within a specialized zone characterized by relatively low centrality, suggesting that these topics have not yet entered the high-density core of the field; however, their rapidly increasing burst intensity indicates that remote PR is at a pivotal inflection point, transitioning from an emerging theme to a mainstream research direction. Given the structural disruption of conventional center-based PR during the COVID-19 pandemic and the continued maturation of digital technologies, the priority of digital rehabilitation research is likely to increase substantially over the coming years. Nevertheless, current evidence is derived predominantly from stable-phase patients with higher technology readiness; expanding eligibility while safeguarding patient safety and intervention fidelity remains a critical unresolved issue.

From the perspective of knowledge network structure, the hub role of Spruit [2013] in the author co-citation network, together with the central position of leading respiratory journals such as the European Respiratory Journal in the journal co-citation network, collectively underscores the concentrated nature of knowledge production in this domain. While such concentration may facilitate standardization and consolidation of the discipline, it may also reduce the academic visibility of contributions from resource-constrained regions and emerging research teams. Of particular note, Cieza (2020, The Lancet), despite its relatively recent publication date, has already achieved a high annual citation rate within this field, suggesting growing recognition of re-evaluating COPD PR outcomes through the lens of the International Classification of Functioning, Disability and Health (ICF). This trend implies that future outcome selection may gradually shift from a primary focus on lung function or exercise capacity toward a more comprehensive emphasis on overall functioning and patient-centered, real-world benefits.

PR strategies for patients with COPD across different clinical states

PR is a cornerstone non-pharmacological intervention in the management of COPD. Early international guidelines recommended PR primarily for patients with severe airflow limitation (14). However, with the accumulation of evidence, the 2023 ATS guideline has explicitly broadened the indication, recommending PR for all symptomatic patients with COPD regardless of the degree of lung function impairment (15). This expanded recommendation is supported by systematic reviews demonstrating that even patients with mild symptoms can derive clinically meaningful benefits from PR (16), and that the severity of spirometric impairment is not significantly associated with the magnitude of treatment response (17). Collectively, these findings underscore that the essence of PR lies in targeting symptom burden and identifiable, treatable patient characteristics rather than relying solely on spirometric indices (18). Accordingly, both the anticipated benefits and optimal delivery strategies of PR vary substantially according to clinical stability, physiological risk, and comorbidity burden (19).

PR management strategies for stable COPD

In stable COPD, PR is a central non-pharmacological strategy for long-term management. Beyond gains in exercise capacity and dyspnea relief, PR is increasingly framed around sustaining everyday physical activity, addressing peripheral muscle dysfunction, and building patients’ self-management skills (3,20). Most programs are anchored in aerobic and resistance training, with additional components—such as breathing or inspiratory muscle training, balance work, and flexibility exercises—selected and progressed according to individual tolerance and goals. PR is also more than “exercise”: education that supports self-management, together with nutritional input and psychological support, are commonly incorporated to strengthen overall effectiveness (15,21). Because adherence often determines whether benefits persist, a maintenance plan should be introduced early after the initial course to help preserve and stabilize achieved improvements (22).

PR during acute exacerbations of COPD (AECOPD) in adult patients

For patients with an AECOPD, hospitalization for an exacerbation is followed by a higher risk of readmission and death, and PR has therefore been proposed as an adjunctive strategy in the post-exacerbation period. At this stage, the clinical focus is on limiting exacerbation-related functional decline, supporting recovery of functional capacity, and reducing early readmission risk (23,24). Evidence in this area, however, is not uniform. Studies differ markedly in when PR is initiated and how programs are delivered, including variations in intervention components, duration, and training frequency, which has contributed to inconsistent estimates of benefit (25).

Despite this heterogeneity, several systematic reviews and large retrospective analyses point in the same direction: when PR is initiated within 3 weeks after an AECOPD hospitalization, it is associated with lower readmission rates and improvements in dyspnea and exercise capacity, without an obvious increase in adverse events (26). By contrast, when PR is started immediately during the acute inpatient phase (e.g., within 48 hours of admission), some studies have not shown sustained long-term benefit, and isolated findings have raised concern about a possible increase in mortality (25). From a pragmatic perspective that weighs scalability against longer-term outcomes, the post-discharge initiation window of approximately 1–3 weeks currently appears to be supported by more consistent evidence (27).

In routine practice, engagement with PR after AECOPD is often limited. Symptom fluctuation and fatigue-related physical constraints, anxiety, and the added burden of travel and distance are frequently reported barriers (28). Accordingly, although PR protocols used in stable COPD can generally be adapted after exacerbations—and may confer benefits across exercise tolerance, balance, lung function, and subsequent exacerbation risk—the intensity, pacing, and monitoring strategy should be tailored to the patient’s physiological reserve, symptom burden, and psychological status to protect safety and promote adherence (14).

PR for patients with COPD complicated by chronic respiratory failure

For patients with COPD complicated by chronic respiratory failure—particularly those with marked hypoxemia, chronic hypercapnia, or requiring long-term oxygen therapy and/or non-invasive ventilation—rehabilitation is often best delivered in settings with adequate supervision, given their higher risks of exercise-induced desaturation, limited ventilatory reserve, and cardiovascular events (29). When designing the program, progressive training should remain the organizing principle, with resistance and balance training advanced stepwise within the patient’s tolerance. In parallel, oxygen therapy management, breathing techniques, and ventilatory support when indicated should be incorporated to reduce symptom burden and improve the feasibility of training (30). From a safety perspective, potential risk factors—including falls risk, malnutrition, cardiovascular comorbidities, musculoskeletal limitations, and cognitive or adherence-related barriers—should be identified upfront and managed longitudinally with appropriate support (29). Together, these training and safety components constitute a set of identifiable, quantifiable, and modifiable key traits that should be systematically embedded within a treatable-traits–oriented rehabilitation pathway, thereby maximizing rehabilitation gains while maintaining safety.

Across different clinical states, COPD patients demonstrate marked inter-individual variability in their response to PR. Available evidence suggests that approximately 30–50% of patients may be classified as “non-responders” after completing a standard PR programme, with insufficient improvement particularly evident in muscle-strength outcomes such as quadriceps strength (31). Several factors may contribute to this phenomenon. On the patient side, baseline disease severity, the degree of deconditioning, comorbidity burden, and conditions such as malnutrition, frailty, or sarcopenia may reduce exercise tolerance and limit the achievable training dose (32,33). On the intervention side, programme design quality and variability in the prescription and implementation fidelity of training dose (intensity, frequency, and duration) can substantially influence overall effectiveness and the magnitude of benefit (34). In addition, heterogeneous patient adherence may lead to an insufficient or unstable “received” training stimulus, thereby attenuating clinical gains (35). Therefore, when developing PR programmes, beyond clearly defining indications, clinicians should concurrently evaluate an individual’s improvement potential and safety risks, and dynamically adjust prescriptions during follow-up based on observed responses (4). For patients with suboptimal outcomes, targeted intensification of resistance training may be considered, together with nutritional support, psychological interventions, and oxygen or ventilatory support when indicated, to improve overall intervention efficiency (32,36). Importantly, practical criteria for defining “non-responders” and implementable optimisation pathways should be established to ensure that a broader patient population derives meaningful benefit from PR (31).

PR models informed by risk and monitoring needs

The recent growth of research on non-institutional and alternative models of PR reflects continued efforts to improve access and broaden service coverage. PR can be implemented in different settings. These include center-based/outpatient programmes, community services, and home-based care. Connections across settings are increasingly supported by telerehabilitation and hybrid approaches (37). In practice, these models function as complementary options along a continuum of care. Clinicians should select the most appropriate model according to patients’ risk profiles, monitoring requirements, and local service availability (38).

Center-based or inpatient PR is typically reserved for patients with more severe disease who need closer supervision and multidisciplinary support. After hospitalization for a severe exacerbation, local service capacity often determines whether PR can be initiated. Patients receiving oxygen therapy and/or non-invasive ventilation also appear more likely to enter PR. This pattern suggests that center-based programmes frequently serve individuals with higher support and surveillance needs (39).

By contrast, home-based and telerehabilitation models may be suitable for patients who are relatively stable, at lower exercise-related risk, and transitioning into maintenance after completing an initial programme (40). These patients should have basic self-management capacity and be able to follow a prescribed training plan. They also need adequate equipment and internet access to receive regular feedback and timely adjustments to their rehabilitation prescriptions (41).

Tele-PR has become an important complement to center-based PR. It also offers a practical route to improving access. Delivered through web-based platforms and mobile applications (42), tele-PR extends exercise training, health education, and self-management support into home and community settings. This design enables more continuous intervention and follow-up (43). VR and motion-sensing exergames can further enhance enjoyment and engagement. In turn, these tools may strengthen adherence (44,45).

Beyond remote participation, many tele-PR programmes now integrate wearable and sensor-based monitoring. These systems capture digital endpoints such as step counts, activity intensity, heart rate, and oxygen saturation. Such data can support adherence tracking, early risk detection, and more timely adjustment of exercise prescriptions (46).

Current evidence suggests that in stable COPD, tele-PR can improve key outcomes, including 6-minute walk distance, HRQoL, and dyspnea. The magnitude of benefit appears broadly comparable to that achieved with conventional center-based programmes (47,48). A recent systematic review and meta-analysis also indicates that digital health interventions incorporating apps and wearable monitoring may improve patient-reported outcomes and functional capacity in COPD. However, substantial heterogeneity remains in the technologies used, supervision intensity, and outcome definitions (49).

Nevertheless, important limitations should be acknowledged. Studies differ markedly in platforms, supervision intensity, exercise prescription, feedback mechanisms, and dose/progression protocols. As a result, generalisability should be interpreted cautiously and in the context of programme characteristics and patient risk profiles (37,39). In addition, the current evidence base is still dominated by stable COPD populations. Data on the effectiveness and safety of tele-PR across different phases following AECOPD remain limited (38,50).

Therefore, available evidence does not support universal replacement of inpatient or center-based programmes. Further high-quality studies are needed to confirm effectiveness and safety across clinical phases (38).

These considerations highlight the need for standardized, reproducible, and adequately dosed PR protocols across inpatient, outpatient/center-based, and home/telehealth settings. Clear and operational procedures for safety monitoring and risk management are also essential (50,51). For tele-PR, minimum safety requirements should be specified explicitly. These include baseline risk assessment, symptom monitoring during training, oxygenation monitoring when indicated, and contingency plans for clinical deterioration (50). Hybrid models may offer a pragmatic compromise. For example, initial training and intensity calibration can be completed in a center-based setting, followed by home-based or telehealth maintenance (37). Such pathways may better balance safety with scalability in routine practice.

Overall, setting-appropriate eligibility criteria and stratified strategies can make PR services more precise, efficient, and sustainable across different clinical states. Remote and digital models should complement, rather than replace, traditional center-based services. When implemented within standardized protocols and robust quality-assurance frameworks, these models may improve access to PR and support sustained gains in function and HRQoL over time.

Treatable-traits-guided PR to advance precision management in COPD

Beyond persistent airflow obstruction and lung hyperinflation, patients with COPD frequently exhibit multi-system impairments—including skeletal muscle dysfunction, systemic inflammatory activation, anxiety and depression, malnutrition, social isolation, and low self-efficacy—that collectively reinforce a vicious cycle of disability and symptom burden (4,52,53). Evidence indicates that while exercise training alone can significantly improve 6-minute walk distance and HRQoL, its effects on extra-pulmonary manifestations—such as anxiety/depression, nutritional depletion, and long-term maintenance of physical activity—are often limited; moreover, follow-up studies have shown that the initialgains in function and symptoms are not consistently sustained after program completion in a subset of patients (20,52). Since 2020, international guidelines and consensus statements have explicitly defined PR as a comprehensive intervention process grounded in holistic patient assessment and comprising, but not limited to, exercise training, education, behavioral interventions, nutritional support, and psychological interventions, positioning PR as a core component of COPD management (4,53). Against this backdrop, the concept of “treatable traits” (TTs) has been increasingly incorporated into PR. TTs refer to clinically relevant characteristics that are identifiable, measurable, and modifiable, spanning pulmonary, extra-pulmonary, and behavioral/lifestyle domains; the central premise is to systematically profile an individual’s trait burden to enable precision intervention and truly individualized management (54-56). This approach has the potential not only to improve symptoms, exercise capacity, and quality of life, but also to reduce exacerbation risk and decrease healthcare utilization (57,58). Biomarker-informed profiling may further enhance treatable-traits–guided PR by supporting more robust stratification and monitoring beyond conventional functional outcomes. However, current evidence on biomarker responses to PR remains heterogeneous, underscoring the need for standardized assessment frameworks (59).

At the pulmonary level, although the structural changes underpinning airflow limitation are largely irreversible, aerobic exercise and breathing training have been shown to improve ventilatory efficiency, relieve dyspnea, and enhance exercise tolerance, with more pronounced effects after optimization of bronchodilator therapy (57). Evidence further indicates that, in patients with an eosinophil-high phenotype, adding anti-inflammatory therapy to standard bronchodilator treatment can further reduce the risk of moderate-to-severe exacerbations by approximately 30% (4,60). For individuals with chronic cough and mucus hypersecretion, combining airway clearance techniques—including postural drainage, oscillatory devices, and the active cycle of breathing technique—with nebulized therapy may facilitate mucus clearance and alleviate symptoms (55). Within this process, PR provides important synergistic support by strengthening adherence management, optimizing inhaler technique, and ensuring effective medication delivery (61,62).

Beyond pulmonary traits, extra-pulmonary manifestations are equally pivotal determinants of functional limitation and prognosis in COPD. These systemic abnormalities interact to accelerate functional decline and to shape responsiveness to rehabilitation. Skeletal muscle dysfunction—one of the most prevalent and modifiable TTs in COPD—is a major driver of exercise intolerance and disability; targeted intervention through individualized resistance and endurance training can improve muscle function and exercise capacity and is increasingly regarded as a key strategy for improving long-term outcomes (63). Nutritional derangements further influence prognosis by altering respiratory mechanics and metabolic demands. In the muscle-wasting/metabolic-abnormality phenotype, malnourished patients with COPD and concomitant muscle loss who receive nutritional supplementation in combination with standard PR show not only improved exercise performance and reduced dyspnea, but also significant gains in fat-free mass and quadriceps cross-sectional area (64). In addition to physiological factors, psychological comorbidities represent common extra-pulmonary TTs that substantially affect self-management capacity and engagement with rehabilitation. Integrating approaches such as cognitive behavioral therapy, uncertainty management, and telephone-based health coaching into PR can further improve anxiety, depression, and HRQoL, with benefits exceeding those of exercise training alone; severe cases should be referred for specialist care when indicated (52). Moreover, cardiovascular comorbidity markedly increases morbidity and mortality risk; cardiovascular risk assessment and multidisciplinary management should therefore be embedded within PR, including monitoring of blood pressure, lipids, and glycemic control, and tailoring exercise prescriptions within cardiovascular safety limits (65).

Behavioral and lifestyle traits represent a key dimension within the treatable-traits framework. By shaping self-management capacity and the maintenance of long-term health behaviors, these factors exert a sustained influence on COPD prognosis. Physical inactivity is closely linked to functional decline, whereas structured exercise training combined with self-management education can increase daily activity levels and interrupt the cycle of deconditioning (66). Smoking cessation interventions, adherence-focused education, and the strengthening of social support are also integral components of PR, helping to slow disease progression and to facilitate durable self-management (54).

Although a substantial body of evidence has demonstrated the clinical benefits of PR for patients with COPD, real-world referral and participation rates have remained persistently low, with only limited improvement in overall service accessibility (67). A nationwide retrospective cohort study based on electronic health records reported that fewer than 10% of eligible patients with COPD actually received a PR referral (68). This gap is driven by multiple interacting barriers. In LMICs, insufficient healthcare resources, infrastructure, and trained personnel constrain the delivery of PR at scale; moreover, clinicians often have limited familiarity with PR benefits, referral pathways, and eligibility criteria (69). At the patient level, individual factors—including age, comorbidity burden, and socioeconomic circumstances—can shape clinicians’ referral decisions and contribute to inequities in access to PR services (28). Collectively, these constraints impede the translation of research advances into service expansion and meaningful health policy change. The persistence of this implementation gap indicates that evidence generation alone is unlikely to shift routine practice; rather, effective translation will require coordinated efforts in policy support, workforce training, and health-system integration to narrow the divide between evidence and practice.

Future research may incorporate machine-learning approaches across the full COPD disease trajectory to construct multidimensional phenotypes and dynamic risk stratification, and to jointly leverage lung function, imaging features, daily physical activity, and biomarkers to further refine and adapt PR prescriptions (70,71). For exacerbation-related PR, additional work is needed to clarify the optimal initiation window and safety thresholds, and to better integrate care transitions from the inpatient setting to the early post-discharge period and into long-term maintenance, ensuring that intervention goals and outcome measures are aligned with each clinical phase (72,73). With more standardized assessment and follow-up, the focus of PR in COPD is also expected to evolve from a singular emphasis on survival extension toward more consistently achieving sustained improvements in function and HRQoL.

Limitations

Using data from the WoSCC, this study provides a comprehensive overview of research activity, highlights major themes, and identifies emerging trends in COPD PR. This approach improves our understanding of the field and helps define future research priorities. Nonetheless, several limitations should be acknowledged. First, although WoSCC is widely recognized for its quality and suitability for bibliometric analysis, reliance on a single database may result in the omission of relevant publications. Second, the analysis was restricted to English-language articles, which may introduce language bias; however, given the dominant role of English in academic publishing, this limitation is considered acceptable. Despite these constraints, the findings remain robust and provide valuable insights to inform future research directions in this domain.

Conclusions

Based on the WoSCC, this study conducted a systematic bibliometric analysis of COPD PR literature published between 2000 and 2024. By examining the knowledge structure, collaboration networks, and thematic evolution, we mapped the overall developmental trajectory of the field over the past 25 years. The results showed a sustained increase in publication output over the last two decades. Collaboration patterns indicated that research productivity and international collaboration are mainly concentrated in high-income countries, with a small number of core countries and highly connected institutions serving as hubs for knowledge production and cross-national partnerships; in contrast, research participation and evidence generation in resource-limited settings remain insufficient. Research priorities have shifted from early efficacy validation and mechanistic exploration toward the refinement of assessment frameworks and more diverse clinical application contexts, and more recently toward the establishment of standardized management pathways, ongoing updates of guidelines and consensus statements, and a more individualized, precision-oriented practice agenda. Future studies may adopt a treatable-traits–guided framework to optimize stratified prescriptions for different clinical states and high-risk populations, and to evaluate the real-world safety, feasibility, and long-term sustainability of remote and digital rehabilitation models through standardized assessment and follow-up systems, thereby improving access to PR and achieving more consistent long-term benefits.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the BIBLIO reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2026-1-0191/rc

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2026-1-0191/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2026-1-0191/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. This study is a secondary analysis based solely on bibliographic and citation data and does not involve human participants or identifiable personal information; therefore, institutional ethics review and informed consent were not required.

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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