A comprehensive literature search was conducted on the Web of Science Core Collection (WoSCC), a multidisciplinary database with an extensive citation network, for data pertinent to our field of study. The search strategy, as described in Supplementary material, combined subject terms and free-text keywords related to obstructive sleep apnea and medical imaging. The literature surveyed spanned from 2004 to 2023 and encompassed both original and review articles. The search terms included TS = (“obstructive sleep apnea,” “obstructive sleep apnea syndrome,” “obstructive sleep disorder,” “sleep apnea disorder,” “obesity hypoventilation syndrome”) and TS = (“magnetic resonance imaging” or “computed tomography” or “ultrasound imaging” or “imaging” or “tomography” or “medical imaging” or “medical imaging” or “radiology”). The final step entailed the exportation and storage of all retrieved documents in text format, thus facilitating subsequent bibliometric analyses. On May 15, 2024, two researchers independently executed the literature data search. The comprehensive search procedure is illustrated in Figure 1.

The data analysis and management were conducted using CiteSpace 6.1. R2, VOS viewer 1.6.17, and Microsoft Office Excel 2010. Microsoft Office Excel 2010 software is capable of data management, annual publication tallying, and the creation of related tables. CiteSpace 6.1. R2 creates a visual map of annual publications, showing data on publication count, country, institution, author, keywords, and highly cited articles. VOS viewer 1.6.17, on the other hand, provides a graphical depiction of highly co-cited literature along with the co-occurrence of authors. CiteSpace settings and results match those of previous versions (6), where nodes can represent countries and institutions.

As of 31 December 2023, a total of 2,000 articles related to Obstructive Sleep apnea syndrome have been published in the field of radiological imaging, comprising 1,783 research articles and 217 review articles. The number of annual publications can be employed as a means of gauging trends in a specific research area. The analysis demonstrates a year-on-year increase in the number of papers published in this field, rising from 26 articles in 2004 to a peak of 174 articles in 2020 and 2021 (Figure 2). This indicates an escalating interest from researchers in the field. Moreover, the growth trend depicted in Figure 2, with a coefficient of determination (R²) of 0.5375, exhibits a positive correlation between the publication year and the count of publications. This suggests a continuing upward trajectory in the annual publication volume within this field.

The articles were disseminated in 376 countries and regions worldwide. The 74 nodes and 369 links represented in Figure 3 illustrate the geographical distribution of countries and the nature of international collaboration. In the graph, the node size reflects the volume of publications a country has contributed to a specified research area. If the centrality surpasses 0.1, a purple circle will augment the corresponding node on the network map. Table 1 enumerates the top 10 countries based on their publication count and centrality. The United States leads in terms of the number of published papers, with 704 publications accounting for 35.2% of the total, followed by China with 382 publications (19.1%), and Turkey with 133 publications (6.65%). These countries are all at the forefront of research in obstructive sleep apnea syndrome and imaging. A positive correlation exists between the degree of international collaboration and centrality. The findings reveal that the United States (0.48), China (0.15), Turkey (0.14), Australia (0.14), and Japan (0.12) rank as the top five countries in terms of centrality.

A collective total of 7,202 institutions have contributed to this research field. Figure 4 delineates the collaborative networks among these institutions, embodying 473 nodes and 1,527 connections. Table 1 discloses that the top five universities in terms of publication count are the University of California System, with 97 publications (16.83%), and Harvard University, with 40 publications (13.86%). Capital Medical University (39 publications, 10.89%), University of Pennsylvania (38 publications, 9.90%), and University of California Los Angeles (38 publications, 8.91%). The five institutions exhibiting the highest centrality, indicative of the most extensive collaboration, encompass Harvard University (0.42), the University of California System (0.33), the University System of Ohio (0.20), Harvard Medical School (0.20), and Capital Medical University (0.16). These leading global universities and research institutions have significantly propelled progress in this field.

Figure 5 illustrates that 10,099 authors have published papers on the topic of obstructive sleep apnea and medical imaging. Table 1 enumerates the top five authors based on their respective counts of published articles. The four authors with the highest number of publications were Kumar R (38 publications, 8.91%), Harper RM (32 publications, 8.91%), Schwab RJ (26 publications, 8.91%), and Macey PM (26 publications, 8.91%). These were followed by Woo MA (24 publications, 15.79%). These five authors occupy significant positions within the field of obstructive sleep apnea and medical imaging research. The centrality of all authors is zero, suggesting a need for bolstering collaboration among authors.

Co-cited references are those collectively cited by researchers. By analyzing these, VOSviewer visualizes the interconnections, emphasizing shared research areas between obstructive sleep apnea and medical imaging. As per VOSviewer’s analysis, a total of 53,446 references were cited in this field of study. When the citation threshold is lowered to 20, this number reduces to 291 references. Figure 6 reveals that these co-cited references are categorized into three clusters, each denoted by a distinct color on the visualization graph. The red cluster primarily highlights the assessment, diagnosis, measurement, and health impacts of OSA, including updates to the rules for evaluating sleep apnea events (7), clinical practice guidelines for diagnosing adult OSA (8), factors influencing daytime sleepiness (9), gender differences in the prevalence of sleep apnea (10), and the impact of severe OSA on cardiovascular events in men (11). The blue cluster mainly focuses on basic research evaluating the effects of OSA on brain regions and neural structures using medical imaging techniques (12–15). The green cluster’s literature primarily addresses the impact of OSA on the upper airway and soft tissue structures (16–19). Table 2 lists the top 10 most cited references, most of which come from the world’s leading journals in sleep medicine, such as the “New England Journal of Medicine” and “SLEEP.” Therefore, research on OSA in the field of radiological imaging is a current hotspot and frontier in sleep medicine.

“Identification of upper airway anatomic risk factors for obstructive sleep apnea with volumetric magnetic resonance imaging” is the most cited paper published in the “American Journal of Respiratory and Critical Care Medicine” in the past 20 years (20). In this paper, Schwab et al. proposed that volumetric magnetic resonance imaging can be used to identify structural risk factors for obstructive sleep apnea. Furthermore, an examination of the top 10 most cited papers reveals that the majority originate from esteemed sleep medicine journals, such as the “New England Journal of Medicine” and “SLEEP.” This underscores the cutting-edge nature and innovation within this research field.

Furthermore, the cited literature over the past 20 years has focused on the impact of OSA on the anatomical structure of the upper airway and brain regions, as well as its health implications. Half of the top cited studies in the past 20 years are based on medical imaging analysis of the effects of OSA on the upper airway and brain regions. Schwab et al. found that volumetric magnetic resonance imaging can identify structural risk factors for obstructive sleep apnea, with the volume of the tongue and lateral pharyngeal walls being independent risk factors for OSA (19). Schwab et al.’s research also found that magnetic resonance imaging can visually show significant differences in upper airway size and surrounding soft tissue structures among apneic subjects, snorers, and normal subjects, but did not find a close relationship with parapharyngeal fat pads (19). Macey et al. observed that OSA leads to a reduction in gray matter volume in patients’ brains using high-resolution T1-weighted magnetic resonance imaging, with these gray matter loss areas occurring in regions involved in upper airway motor regulation and cognitive functions (13).

The co-occurrence of keywords provides insights into the topic and scope of the research field, as depicted in Figure 7. Table 3 displays the top 20 keywords based on their co-occurrence rate and centrality of obstructive sleep apnea and radiological imaging research from 2004 to 2023. “Obstructive sleep apnea” is the most frequently occurring keyword, followed by “upper airway” and “children.” More importantly, keywords such as “computed tomography,” “positive airway pressure,” “prevalence,” “magnetic resonance imaging,” “morphology,” “risk,” and “association” have been used more than 100 times, highlighting the current research hotspots and themes in this field. There is a positive correlation between centrality and the degree of linkage among keywords. In Table 3, “obstructive sleep apnea” is the most central keyword, followed by “computed tomography,” “magnetic resonance imaging,” “upper airway,” and “pharyngeal airway.” These keywords remain concentrated on the relationship between obstructive sleep apnea and the upper airway, as well as their connection with radiology.

To understand the research frontiers of obstructive sleep apnea syndrome in the field of radiological imaging since 2003, CiteSpace was used to cluster the keywords related to OSA and radiological imaging. Table 4, Figures 8, 9 show eight clusters. Generally, when the silhouette score is greater than 0.5, the clustering effect is considered reasonable. Cluster #0 is labeled “obstructive sleep apnea syndrome,” followed by Cluster #1 “male patient,” Cluster #2 “upper airway,” Cluster #3 “pediatric sleep-disordered breathing,” Cluster #4 “upper airway anatomy,” Cluster #5 “systematic review,” Cluster #6 “drug-induced sleep endoscopy,” and Cluster #7 “retinal nerve fiber layer thickness,” representing the research frontiers since 2003. Burst keywords encapsulate a sudden surge in research content over a specific period, potentially signaling future research trends. Figure 10 presents the top 25 items with the highest burst strength in this research topic. The red lines in the chart denote the duration of the keyword bursts. From this chart, we can discern that the keyword themes have progressively transitioned from “sleep apnea,” “size,” and “C-reactive protein” to more recent themes such as “structural changes,” “inflammation,” “diagnosis,” and “mechanisms.” This suggests that the correlation between obstructive sleep apnea syndrome and aspects such as maxillofacial changes, imaging diagnosis, and pathological mechanisms is the central focus of both current and anticipated future research in this field.

The objective of this study was to collate all pertinent WoSCC data to identify research areas of significance and emerging trends within the field. The number of publications has been increasing at a steady rate on an annual basis. The United States was the most prolific nation in terms of published articles, with a total of 704, followed by China and Turkey. The United States occupies a dominant position in this field due to its robust economic strength, favorable policies, and robust scientific support. Meanwhile, although China is a developing country, it has the highest number of patients with obstructive sleep apnea syndrome (OSAHS) in the world, at 176 million. In the context of specific research fields, bibliometrics can be employed to assess the extent of collaboration among authors, institutions, and countries (20). The concept of centrality is used to quantify the degree of collaboration. The countries with the highest centrality are the United States, China, Canada, Sweden, and Australia, indicating that these countries are actively engaged in collaborative research with a range of other nations.

The most closely collaborating institutions in obstructive sleep apnea (OSA) imaging research include the University of California system, Harvard University, the University System of Ohio, Capital Medical University, and Seoul National University (SNU). While these institutions demonstrate formal partnerships, author centrality metrics remain at 0, revealing fundamental collaboration deficits. Notably, influential contributors such as Kumar R., Harper RM., Schwab RJ., Macey PM., and Woo MA. exhibit minimal co-authorship patterns, suggesting systemic barriers to knowledge exchange rather than individual reluctance. Two major obstacles hinder global research synergies:

The fostering of collaboration among authors necessitates the existence of a supportive environment, characterized by cooperation across related research fields and the implementation of government policies conducive to such endeavors. We contend that close collaboration among countries, institutions, and authors will contribute to significant progress in this field.

Performing keyword analysis to summarize the themes and research directions of Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) within the field of medical imaging is crucial. Our research findings suggest that research topics related to the pathophysiological mechanisms and comorbidities of OSAHS have become increasingly concentrated and interconnected in recent years. This suggests that interest in this research field is becoming more convergent, and the relationships between different topics are becoming closer. Our keyword analysis underscores that the imaging assessment of upper airway structures in relation to Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) has emerged as a focal point of extensive discourse in the field. Polysomnography is the gold standard for diagnosing OSAHS and grading its severity8. However, due to limitations such as venue and personnel, only a few hospitals can conduct it, resulting in a high prevalence but low diagnosis rate of OSAHS. Imaging plays an important role in evaluating the repetitive collapse of the upper airway and studying the anatomical factors related to the pathogenesis of OSAHS. Different imaging modalities have different focuses on the diagnosis and treatment of OSA patients.

This investigation utilizes bibliometric techniques to scrutinize articles published over an approximately two-decade span (2004–2023), to discern global patterns and emergent research focal points in the domain of medical imaging for Obstructive Sleep Apnea Syndrome (OSA). The intention is to furnish insights that can guide future scientific inquiries. Nevertheless, it is crucial to acknowledge certain constraints of this study. First, the research is contingent on the Web of Science (WoS) core database, excluding other databases, which may inadvertently lead to the exclusion of pertinent literature, thereby introducing a degree of selection bias. Second, the study is confined to English language publications, potentially exacerbating language and publication bias. Lastly, while the study’s principal emphasis is on adult sleep apnea syndrome, offering a broad perspective of the field by evaluating countries, journals, institutions, authors, and keywords, it might neglect crucial, nuanced aspects of the developmental trends of pediatric obstructive sleep apnea syndrome in the realm of medical imaging. Given these limitations, future studies should aim to widen the study population, encompass a broader array of databases, incorporate non-English publications, and delve into more granular aspects of the imaging field for obstructive sleep apnea syndrome. This approach will facilitate a more comprehensive and precise comprehension of this field.