African Populations Underrepresented in High-Impact Clinical Trials

The evidence gap in global clinical practice

Randomized controlled trials serve as the gold standard for clinical evidence, providing the rigorous data necessary to minimize bias and establish the safety of medical interventions [1]. These trials directly inform the development of international guidelines for managing prevalent conditions such as hypertension, atrial fibrillation, and hyperlipidemia [2, 3, 4]. However, the clinical utility of these guidelines depends on the external validity (the extent to which study results can be generalized to diverse patient populations) of the underlying data, as physiological responses to therapies can vary significantly across different ethnic and regional groups [5, 6]. Despite a high global prevalence of chronic kidney disease and a rising burden of cardiovascular pathology, research often fails to reflect the full diversity of patients seen in daily practice [7, 8]. A new systematic review now offers fresh insights into the geographic representation of diverse populations within the clinical evidence base used to treat patients [9].

Quantifying representation across top-tier journals

To evaluate the current state of geographic diversity in clinical evidence, researchers conducted a systematic review (CRD42024603157) quantifying African representation in randomized controlled trials published between 2019 and 2024. The analysis scrutinized eight of the most influential publications in global medicine, including five leading general medical journals: the British Medical Journal, the Journal of the American Medical Association, The Lancet, Nature Medicine, and the New England Journal of Medicine. Given the high global burden of heart disease, the researchers also specifically examined three leading cardiovascular journals: Circulation, the European Heart Journal, and the Journal of the American College of Cardiology. This selection represents the primary literature that shapes standard-of-care protocols for clinicians worldwide.

The systematic review utilized broad inclusion criteria for study designs to ensure a comprehensive overview of the evidence base available to clinicians. Eligible studies included traditional randomized controlled trials, pragmatic trials (which evaluate the effectiveness of interventions in real-world clinical settings rather than highly controlled environments), cluster randomized trials (where entire groups or clinics are randomized rather than individuals), and stepped-wedge randomized controlled trials (a design where clusters cross over from a control to an intervention state at different time points, eventually ensuring all participants receive the intervention). By including these diverse methodologies, the authors captured a wide spectrum of clinical research that informs modern practice standards, from strictly controlled efficacy studies to real-world effectiveness data.

To provide a detailed assessment of how African populations are integrated into high-impact research, the researchers evaluated several key metrics of representation. These included the trial scope, which distinguished between Africa-only studies and multicontinental trials that included at least one African site. The analysis further categorized data by specific country and regional participation, the disease category under investigation, and the presence of African authorship. By tracking these variables, the study aimed to identify not only where research is being conducted but also the extent to which local clinicians and researchers are leading the studies that define care for their own patient populations, a factor that often influences the clinical relevance of the research questions asked.

Disparities in cardiovascular and general medical literature

The systematic review of 2,138 randomized controlled trials published in leading general medical journals reveals a stark geographic imbalance in clinical evidence. Of these high-impact studies, only 83 trials (3.9%) were conducted exclusively in Africa, limiting the availability of data derived from local patient populations and healthcare infrastructures. Furthermore, the researchers found that 195 trials (9.1%) were multicontinental studies that included at least one African site. This limited inclusion suggests that even when African patients are represented in general medical literature, they are often part of larger, global cohorts where regional physiological or socioeconomic nuances may not be the primary focus of the analysis, potentially masking differences in drug metabolism or treatment adherence specific to the region.

The disparity is even more pronounced within specialized cardiovascular literature, where the evidence base for heart disease management appears largely decoupled from the African continent. Among the 334 randomized controlled trials published in the three leading cardiovascular journals, a mere 2 trials (0.6%) were conducted exclusively in Africa. This near-total absence of localized cardiovascular research is compounded by the fact that African sites were included in only 9 multicontinental cardiovascular trials (2.7%). For practicing clinicians, these figures indicate that the vast majority of the gold-standard evidence used to develop cardiovascular treatment protocols and medication dosages has not been validated within African clinical settings. This lack of validation raises concerns regarding the generalizability of global guidelines to these populations, particularly when managing conditions like hypertension where genetic polymorphisms can influence the efficacy of specific antihypertensive classes.

Regional concentration and disease focus

The geographic distribution of clinical research within the continent is heavily skewed, which limits the applicability of findings across diverse African populations. The researchers found that South Africa accounted for the majority of Africa-based randomized controlled trials across both general medical and cardiovascular journal categories. On a broader scale, southern Africa predominated in trial participation, while central Africa was minimally represented in the reviewed literature. This concentration of data in specific locales suggests that clinical evidence may not account for the regional variations in genetics, diet, and environmental factors that clinicians must consider when treating patients in understudied areas, such as the diverse populations of central Africa where healthcare infrastructure and disease prevalence may differ significantly from southern regions.

The thematic focus of these studies also reveals a significant misalignment with the shifting global burden of disease. Among the trials published in general medical journals that were conducted exclusively in Africa, the vast majority focused on infectious diseases, accounting for 63 trials or 75.9% of the total. In contrast, the researchers identified that only 3 trials conducted exclusively in Africa and published in these journals addressed cardiovascular disease. While infectious disease remains a critical concern, this research distribution does not reflect the rising prevalence of chronic conditions. Interestingly, the study noted that Africa-including multicontinental trials more frequently investigated noncommunicable diseases, including cardiovascular disease, compared to trials conducted solely within the continent. This suggests that while African patients are being included in global cardiovascular research, there is a lack of independent, continent-specific trials dedicated to these conditions, which are necessary to address unique local challenges in chronic disease management.

Authorship and the path toward equitable evidence

The researchers examined the distribution of leadership roles to understand the degree of local autonomy in clinical research, finding a significant disparity based on the scope of the study. The analysis revealed that African leadership, as measured by authorship, was common in randomized controlled trials conducted exclusively in Africa. This suggests that when research is localized within the continent, African investigators are frequently at the helm of study design and execution. For the clinician, this local leadership is a critical factor in ensuring that research questions are tailored to the specific healthcare needs, cultural contexts, and resource constraints of the populations being studied, ultimately leading to more actionable clinical data.

A stark contrast emerged when the researchers analyzed larger, international collaborations. The study found that African leadership was rare in multicontinental studies that included African sites, indicating that while African patients contribute data to global trials, African researchers are often excluded from primary leadership positions in these high-impact publications. This lack of representation at the leadership level can limit the applicability of trial findings to local practice, as the nuances of local clinical delivery may be overlooked during the study design phase. The authors conclude that addressing this imbalance requires expanding African participation in global trials, investing in local research capacity, and promoting equitable leadership to strengthen the relevance and validity of clinical evidence for African patient populations, ensuring that the global medical community can provide evidence-based care that is truly inclusive.

References

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