Mapping evidence on the impact of chronic respiratory diseases on cardiovascular diseases in sub-Saharan Africa: a protocol for a scoping review

Background Chronic respiratory diseases (CRD) account for 4.0 million deaths, with a prevalence of 454.6 million cases worldwide1 however, detailed data on morbidity and mortality due to CRD in sub-Saharan Africa are scarce. Among the main CRD are Chronic Obstructive Pulmonary Disease (COPD), asthma, interstitial lung diseases, including pulmonary sarcoidosis, occupational lung diseases1 and, in countries with a high burden of tuberculosis (TB) such as those in sub-Saharan Africa, post-tuberculosis lung disease.2,3 COPD is currently one of the most prevalent CRD and is the third leading cause of death worldwide, accounting for 6% of all deaths, behind only coronary heart disease and cerebrovascular disease.1 Epidemiological studies reveal that COPD-related mortality rates have been increasing in South Asia, Sub-Saharan Africa, and parts of Latin America, highlighting substantial regional disparities in the burden of the disease.1 There is a strong association between COPD and cardiovascular disease (CVD), leading to COPD being considered a major cardiovascular risk factor.4 Both conditions are related to the same risk factors such as smoking, aging, and physical inactivity and to pathophysiological mechanisms such as arterial stiffness, inflammation, and endothelial dysfunction.4 The presence of CVD is associated with a poor prognosis, particularly an increased risk of exacerbations, hospitalizations, and mortality.4,5 The authors of a systematic review and meta-analysis demonstrated that cardiac arrhythmias are common among patients hospitalized for acute exacerbations of COPD, with a pooled prevalence of 15%, and are significantly associated with increased in-hospital mortality.6 Therefore, early identification of high-risk patients through continuous electrocardiographic monitoring and multidisciplinary collaboration can improve short-term prognosis and long-term outcomes.6 Pulmonary hypertension (PH) affects approximately 1% of the world’s population, and more than 80% of those affected live in low- and middle-income countries (LMIC).7–9 Is defined as a mean pulmonary artery pressure greater than 20 mmHg at rest. There is evidence that a diagnosis of PH in patients with CRD is associated with increased morbidity and mortality, particularly among those who develop severe PH.10 Although PH generally occurs in the more advanced stages of respiratory disease, its onset is sometimes unrelated to the progression of lung function or structural impairment of the lung parenchyma.10 Furthermore, the severity and course of PH may vary depending on the underlying respiratory disease.11 For these reasons, early and individualized identification of PH in patients with CRD is crucial for better understanding the disease’s progression and evaluating the application of therapeutic measures aimed at its control.12,13 In countries with a high burden of TB, post-TB lung disease has been considered one of the most common causes of PH associated with lung disease and/or hypoxia, and despite the recognized clinical correlation between TB, post-TB lung disease, and PH, the magnitude of the burden of PH associated with TB is poorly defined.14 A systematic review reported a high prevalence of PH in individuals with post-TB lung disease, and estimates of the prevalence of TB-associated PH varied depending on the patient population, the severity of lung disease, and the clinical context.8 In resource-limited countries with a high burden of TB, the diagnosis of PH presents unique challenges, resulting in underdetection and underreporting of PH.9,14 Many risk factors for PH in Africa are known, yet the epidemiology of PH remains poorly described, and there is a lack of studies on the prevalence of PH on the continent.14,15 The high prevalence of risk factors for PH, specific genetic predisposition, and lifestyle factors, in addition to limited access to health care services, suggest that the epidemiology of PH in Africa may differ.15 Some systematic reviews6–8,16–18 have assessed the relationship between CRD and CVD however, very few of them included studies from sub-Saharan African countries. Therefore, the objective of this scoping review is to map the current evidence generated in sub-Saharan African countries regarding the impact of CRD on CVD. Methodology This protocol will be registered in the Open Science Framework (OSF). The review will be carried out in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Scoping Review (PRISMA-ScR),19 and will be conducted according to existing guidelines (Joanna Briggs Institute),20,21 with the following stages: identification of the research question, study identification, study selection, data extraction, data analysis and dissemination of results. Identifying the research question We identify the research questions using the acronym PCC (Population, Concept, Context). Table 1. PCC framework for eligibility of research question Criteria Determinants Population Adults with chronic respiratory diseases Concept Associated cardiovascular impact Context Sub-Saharan Africa Research questions Main research question What is the impact of chronic respiratory diseases (COPD, post-TB lung disease) on cardiovascular diseases (pulmonary hypertension, cor pulmonale and right heart failure) in populations in sub-Saharan Africa? Sub-research question 1. What is the association between CRD diseases and cardiovascular complications in adults in sub-Saharan Africa? 2. How do CRD influence morbidity, mortality, and cardiovascular complications in sub-Saharan Africa? 3. What are the clinical mechanisms and cardiovascular outcomes associated with COPD and post-tuberculosis lung disease in sub-Saharan Africa? Study identification Research strategy We will search the databases PubMed/Medline, Web of Science, Scopus, African Journals Online (AJOL), and African Index Medicus. The search dates will be from the start of a database, until April 2026. The references of all eligible studies will be reviewed to identify possible additional studies and if necessary, we will contact authors who have published in this field to request potentially additional studies. No language restrictions will be imposed, translations will be carried out if necessary. We developed a search strategy and used the following keywords: Chronic respiratory diseases, MeSH terms: ("Pulmonary Disease, Chronic Obstructive"; "Asthma"; "Tuberculosis"; "Lung Diseases"; "Bronchiectasis"; "Pulmonary Fibrosis"); Chronic respiratory diseases, synonyms/free terms: (COPD; chronic obstructive pulmonary disease; chronic respiratory disease*; chronic lung disease*; post-tuberculosis lung disease; post-TB lung disease; post TB; PTLD; post-tuberculous lung disease; tuberculous destroyed lung; destroyed lung; TB sequelae; pulmonary sequelae of tuberculosis; asthma*; bronchiecta*; chronic airflow obstruction); Cardiovascular diseases, MeSH terms: ("Hypertension, Pulmonary"; "Heart Failure"; "Cor Pulmonale"; "Cardiovascular Diseases"); Cardiovascular diseases, free terms: (pulmonary hypertension; pulmonary arterial hypertension; cor pulmonale; right heart failure; cardiac dysfunction; cardiovascular complication*; cardiovascular disease*; ventricular dysfunction); Geographic context, MeSH terms: ("Africa South of the Sahara"); Geographic context, free terms: (sub-Saharan Africa; Sub Saharan Africa; SSA; Africa south of the Sahara) Study selection We intend to include all cross-sectional studies, cohort studies, case-control studies, clinical trials, qualitative studies, relevant case series, carried out in sub-Saharan African countries. We will select all studies exploring the relationship between CRD and CVD in sub-Saharan African populations, that include adult participants (≥ 18 years), and that may also explore other risk factors, such as exposure to biomass, smoking, HIV co-infection, poverty, delayed diagnosis. Inclusion criteria Population: Adults (≥ 18 years) in sub-Saharan Africa; patients with COPD, post-TB lung disease, TB-related bronchiectasis, and asthma. Concept: Studies evaluating the association between CRD and CVD, PH, cor pulmonale, right heart failure, cardiovascular mortality, electrocardiographic abnormalities, prognostic impact. Context: Studies conducted in sub-Saharan African countries, in hospital, community, or outpatient settings. Exclusion criteria Population: Exclusively pediatric studies, studies on active TB without assessment of chronic pulmonary sequelae. Concept: Studies that do not assess cardiovascular outcomes, that focus solely on acute respiratory infections, or that address only congenital heart disease without pulmonary involvement. The following will also be excluded: publication types such as editorials, letters without original data, commentaries/opinions, conference abstracts, case reports, and review articles. While review articles, letters and editorials, will not be included, we will search through their reference lists to find additional observational studies. Data extraction and management The studies found in the databases will be exported to a reference management program (Rayyan QCRI)22 where further screening will be carried out. After duplicate removal, eligibility assessment will be conducted independently by two reviewers (HN and AA). Firstly, we will conduct a round of title and abstract screening, where all the obviously irrelevant articles will be excluded, considering the inclusion criteria. Secondly, we will conduct a full text assessment of all potentially eligible studies, also applying the inclusion criteria. Any disagreements will be resolved by discussion, with the reviewers (OS and MA) arbitrating in the event of unresolved discrepancies. Data from the selected studies will be transferred to an appropriate table in the Microsoft Excel© program, with each study given a reference code. If necessary, we will collect indirect data from figures and graphs, adapting their interpretation from two different authors by consensus, and authors of original articles will also be contacted to obtain more information and data. For all included studies, the following information will be recorded: country, author and their institutions/affiliations, year of publication, title and objective of the study, study design, diagnostic criteria for CRD, diagnostic criteria for CVD, number of participants, and their characteristics (age, gender, CRD, CVD, exposure to biomass, smoking) and the results of the study. Confounding factors such as HIV co-infection or other chronic inflammatory/infectious diseases, alcoholism, malnutrition, overcrowded houses, exposure to environmental pollution and access to healthcare will also be recorded if reported, as well as information about the extent of medical appointments and results of complementary exames in people with CRD and CVD. To ensure transparency, the selection process will be summarized using the PRISMA-ScR flow chart.19 Data synthesis A descriptive table of all the included studies will be drawn up in order to summarize the data. We will carry out a narrative synthesis of the data in which we will use text to describe the general findings of the studies, highlight their strengths and limitations, and make textual comparisons between the studies in this category in the light of the study question. The analysis will be based on the relationship between CRD and CVD, and will also assess other potential risk factors that may influence this association. If data are available, we will also provide a narrative description of the evolution and prognosis of patients, as well as the determinants that influence the prognosis, to answer our research questions. We will also analyze existing gaps related to CRD studies for future research in African countries. Ethics and data management plan Ethical approval is not required because the data to be collected and analyzed will be based only on published literature and therefore cannot be linked to specific participants. The selected data will be kept in a database which will have protected access and will only be used by the authors involved. However, anonymized data will be placed in an open repository. Patient and public engagement Since this will be a scoping review, there will be no direct involvement of patients or the public. Dissemination This scoping review will allow us to identify the available evidence on the relationship between CRD and CVD in sub-Saharan African populations. This is a highly relevant topic for sub-Saharan Africa because there is a significant epidemiological overlap between CRD and the growing burden of CVD. On the other hand, with this review, we will probably find gaps in studies related to associated factors, which will lead to the need for future research on CRD in African countries. Nevertheless, our dissemination strategy will involve presentations at scientific meetings, as well as the publication of articles in international, peer-reviewed, open-access journals. We also plan to organize meetings with researchers, physicians, and other health service providers, as well as with local communities to analyze and discuss our results and their potential implications. As strengths, we can mention that this is a scoping review to address the relationship between CRD and CVD in African countries. Our review involves a thorough search strategy using the main medical and public health databases and will ensure that relevant studies on the topic are identified. This review will follow the PRISMA-ScR guidelines,19 will have no language restrictions, will provide comprehensive information on the topic, and will allow for future research in the region involved. Limitations While we will search specifically in African Research Databases and we will include studies published in any of the Africa languages, it will not be feasible to search the gray literature. Therefore, we may not capture all the potentially eligible studies in the region. Conclusion We anticipate that the results of this scoping review will identify available evidence on the relationship between CRD and CVD, factors associated with this relationship, as well as identify the existence of gaps in this relationship in African countries. Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors. Conflicts of interest None declared.   References 1. Momtazmanesh S, Moghaddam SS, Ghamari SH, et al. Global burden of chronic respiratory diseases and risk factors, 1990–2019: an update from the Global Burden of Disease Study 2019. eClinicalMedicine. 2023;59(May). doi:10.1016/j.eclinm.2023.101936 2. Kherabi Y, Silva DR, Centis R, D’Ambrosio L, Migliori GB. Beyond a cure for TB : confronting the hidden burden of post-TB lung disease. Int J Tuberc Lung Dis. 2025;2(March):248-250. doi:10.5588/ijtldopen.25.0222 3. 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