Chronic Respiratory Diseases: A Mediterranean View

INTRODUCTION

Chronic Respiratory Diseases (CRDs) encompass various lung-related illnesses primarily triggered by exposure to environmental inhalants, impacting individuals globally (James et al., 2018). CRDs pose a significant health burden in the Mediterranean region due to their high prevalence, severity, and financial burden, necessitating effective interventions and policies (Aït-Khaled et al., 2001). Despite their significant public health burden, CRDs receive less research funding and attention compared to other diseases like Alzheimer's, cancer, and heart disease (Fallahzadeh et al., 2022). Globally, CRDs have seen a significant rise in prevalence, particularly in high-income regions, with bronchial asthma and Chronic Obstructive Pulmonary Disease (COPD) being the most prevalent types (Soriano et al., 2020).

This increase emphasizes the need for intensified research and preventive measures, including vaccination campaigns and smoking cessation programs (Hellings et al., 2017). Moreover, lifestyle modifications, early diagnosis, and addressing environmental factors play a crucial role in managing these complex diseases, which often manifest from childhood and worsen with age.

The Mediterranean region, despite its diverse cultures and climates, suffers significantly from CRDs, making it a unique area for research. However, there's a lack of information on CRD prevalence, incidence, and burden in the Eastern Mediterranean region (Masjedi et al., 2018). Given the region's unique characteristics, a comprehensive review of the literature is necessary to identify research gaps. Thus, a bibliometric study is needed to assess the volume of research on CRDs, identify management trends, and pinpoint risk factors contributing to their rising prevalence.

Researchers in the Mediterranean region can collaborate through research networks identified via bibliometric analysis, fostering collaboration and joint research projects. Understanding these networks helps locate key scholars and institutions leading in the field, offering future cooperation opportunities. A bibliometric analysis of studies on CRDs in the Mediterranean region is urgently needed based on these points.

This work aims to assess research on CRDs in the Mediterranean region through a bibliometric analysis, revealing publication trends and key issues. The main goal is to map the current state of research on CRDs in the Mediterranean by offering an in-depth analysis of focus areas and collaboration patterns.

METHODOLOGY

This study focused on CRDs as the primary research field, utilizing SCOPUS and PubMed databases. Explicit criteria were set for search precision.

Keyword combinations like “Chronic Respiratory Diseases”, “Risk Factors”, and “Management”, along with Mediterranean countries, were used. Boolean operators like AND, OR, and NOT were applied to align curated studies with research objectives, excluding irrelevant ones.

A systematic search was conducted using PubMed and SCOPUS, focusing on original studies on risk factors and management strategies for CRDs, limited to clinical and epidemiological studies on human adults in Mediterranean countries. Reviews, systemic reviews, meta-analyses, studies on infectious diseases, pediatrics, trauma, cell cultures, in vitro experiments, and animal models were excluded.

Three reviewers examined publications from 1997 to 2023 to identify the country of origin and publication type. Data was confirmed by at least one other reviewer.

The ratio of CRD research in the Mediterranean region to global CRD research was calculated by dividing the number of Mediterranean references by the global references on CRDs.

VOSviewer software was used for bibliometric analysis to visualize bibliometric networks by creating clusters of related nodes (Van Eck and Waltman, 2014). In the authorship network, the top 30 authors contributing to Mediterranean CRD research were identified. The size of each node represented the number of articles published by an author, with larger nodes indicating higher publication counts. Additionally, two co-occurrence networks were created to reflect associations between keywords found in titles and abstracts. In these networks, nodes represented keyword frequency, while lines between nodes illustrated connections between keywords (Arruda et al., 2022).

RESULTS

Many authors published papers on chronic respiratory diseases across 22 Mediterranean countries. The top 30 authors, selected for having at least eight publications, are listed in Table 1 by the number of papers they've written. These authors are primarily from Spain, Italy, France, and Greece. The mean H-index among them is 60 (range: 19-119). The top five are Miravitlles, M; Roche, N; Soriano, JB; Garcia-Aymerich, H; and Gourgoulianis, KI. Professor Miravitlles leads with 33 papers, an H-index of 98, and a total link strength of 133. Garcia-Aymerich follows with 16 papers, an H-index of 67, and a link strength of 103. Despite having one of the highest H-indexes (119), Torres has only 11 papers and a link strength of 53. At the list's end, Plaza V has eight papers, an H-index of 40, and a link strength of 8. Figure 2 also highlights low collaboration levels among authors from different countries.

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To enhance visualization, 73 keywords appearing more than five times were selected using VOSviewer. The analysis focused on the total occurrences, with the visualization map shown in Figure 2. Tables 2a and 2b present the top 20 terms by occurrence and relevance. A keyword's relevance indicates its ability to provide valuable insights, while its occurrence shows its frequency. The five most frequent keywords are quality (46), life (43), diagnosis (27), smoker (24), and adult and COPD exacerbation (23). However, no clear pattern links occurrence to relevance, as some low-occurrence terms like COPD prevalence, stable COPD, air pollution, and idiopathic pulmonary fibrosis still hold high relevance in chronic respiratory disease research.

Title content

For better visualization of the search, title content with more than 5 appearances was selected via VOSviewer title and 73 keywords met this requirement. The visualization was based on the total number of occurrences, and the visualization map is presented in (Figure 3). In addition, Tables 2a and 2b were shown to analyze the occurrence and relevance of the 1^st 20 terms. The relevance of a keyword depends on its ability to convey valuable information or insights within a given context, while its occurrence indicates how frequently it appears within that context.

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The five most frequently used keywords were determined as quality (occurrences=46), life (occurrences=43), diagnosis (occurrences=27), smoker (occurrences=24), and adult and COPD exacerbation (occurrences=23). However, the pattern between occurrence and relevance is random, suggesting no discernible relationship as they appear to happen independently of each other. For example, COPD prevalence has an occurrence of 5 but it has the 2^nd highest relevance (2.5431) similarly to the keywords stable COPD, air pollution, and idiopathic pulmonary fibrosis that have low occurrence but are significant in relation to the research about chronic respiratory diseases.

In Figure 3, 73 keywords appearing over five times were grouped into seven clusters, with node size indicating frequency. Keywords in titles and abstracts reveal a paper's main ideas. From 352 keywords appearing over ten times, five clusters were identified (Figure 4). The blue and purple clusters mainly include chronic respiratory disease names like asthma and interstitial lung disease. The green cluster includes smoker, nitric oxide, and air pollution. The red and yellow clusters focus on CRD management, with terms like improvement and hospital admission, while depression appears in the red cluster, highlighting the importance of managing psychological symptoms.

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Tables 3a and 3b analyze the top 20 title and abstract keywords. The most frequent keywords are asthma (207 occurrences), mortality (180), quality (157), smoking (104), and hospitalization (98). However, the highest relevance scores are for HADS (4.2139), C-PAP (4.074), depression scale (3.8585), hospital anxiety (3.7507), and continuous positive airway pressure (3.4395), indicating that the most relevant research focuses on CRD management, including asthma, COPD, and idiopathic pulmonary disorder.

DISCUSSION

This bibliometric analysis of chronic respiratory disease research over 25 years in Scopus and PubMed offers valuable insights into the field's progress, challenges, and the Mediterranean region's significant contribution, driven by high disease prevalence. However, eight Arab nations within the region contribute far less than European countries like Spain, France, Italy, and Greece. Factors like wars, displacement of scholars, poor infrastructure, brain drain, and limited funding due to poverty and a lack of research culture have hindered Arab research output. The absence of high-income economies further exacerbates these challenges (Elsayed and Sabtan, 2019; World Bank, 2024).

The prominence of European authors in COPD research may be linked to higher COPD prevalence in Europe (12.4%) (Han et al., 2020) compared to the Middle East (3.6%) (Tageldin et al., 2012) influenced by lifestyle, smoking rates, and research infrastructure (Blanco et al., 2019). Low collaboration between Western European researchers highlights the need for more international partnerships, which could enhance global citations and scientific knowledge. Such collaborations also foster cultural maturity and inclusion, benefiting the global scientific community. Institutions, particularly in the MENA region, should seek cross-border collaborations to boost research impact and resource sharing (Alamah et al., 2023).

Keywords analysis reveals that terms like "quality," "smoking," "life," and "death" are research hotspots, reflecting the significant global impact of chronic respiratory diseases, which accounted for 7% of global deaths in 2017. Smoking and pollution are major risk factors, with tobacco smoke's toxins causing extensive damage throughout the respiratory system, leading to diseases like COPD. Prioritizing tobacco control and improving air quality are crucial to reducing CRD-related mortality (Gan et al., 2022; Laniado-Laborín, 2009).

The keyword "asthma" has the highest occurrence in the Title and Abstract (207 times), highlighting its significance as a common chronic respiratory disease in the Mediterranean region. According to the 2017 Global Burden of Disease Study, asthma's prevalence in the Middle East and North Africa was 4.95%, higher than COPD (3.13%) and interstitial lung disease (0.03%). Despite their low occurrence, terms like HADS, depression scale, and hospital anxiety have high relevance, reflecting the psychological distress often seen in chronic respiratory disease patients (Nowak et al., 2014). Up to 40% of these patients suffer from mood and anxiety disorders (Maurer et al., 2008), which are often underdiagnosed, impacting their daily lives and disease severity (Cafarella et al., 2012).

Preventable risk factors for CRDs, such as tobacco smoking, indoor pollution, and allergens, can be managed, but research on these topics is lacking (Bousquet et al., 2007). Notably, smoking, a significant keyword, is linked to worse outcomes in asthma patients, including more severe symptoms, higher healthcare costs, and reduced lung function (Polosa and Thomson, 2013). Despite the importance of allergens and pollution, they are absent from high-occurrence or relevance keyword tables, indicating insufficient research in these areas. This gap is concerning and suggests a need for more focused research on preventable CRD risk factors in the Mediterranean region.

STUDY LIMITATIONS

While the search strategy effectively covered many relevant publications on chronic respiratory diseases, it may not have been entirely comprehensive. Expanding keywords to include regional phrases or specific chronic respiratory disorders could capture more relevant literature, especially outside European countries. Although major databases like PubMed and Scopus were used, other studies, particularly those in regional languages such as Arabic, Turkish, Spanish, French, and Greek, may better represent the field. Including these languages could have yielded more results, highlighting studies not indexed in widely used global databases.

CONCLUSION

Chronic Respiratory Diseases (CRDs) pose a significant public health burden in the Mediterranean region. However, no such qualitative examination of the study environment, such as collaboration patterns and dominant thematic directions, has previously been done. This bibliometric analysis provides valuable insights into chronic respiratory disease research in the region and quantifies the Mediterranean area's high proportion (34.7%) of contribution to global research in CRDs. The findings show a significant contribution from this region, particularly from European countries, and emphasize the dedication of its researchers. The analysis identified key authors, leading universities, and potential collaboration areas, shedding light on major topics like risk factors and treatment strategies for CRDs in adults, with relative lack of concerns like allergens, air pollution, and psychological impact of CRDs. These insights can help identify research gaps, encourage collaboration, and support the development of effective CRD prevention and management strategies. Ongoing monitoring of research output in this region is essential to track progress, identify emerging trends, and inform evidence-based interventions and policies.