1. Introduction

Diabetes is now a major public health challenge in Africa, with particularly rapid growth over the past decade. It is increasing quickly in Africa, contributing to higher rates of major cardiovascular events (MACE). Chronic high blood sugar affects the body through several mechanisms, such as oxidative stress, endothelial dysfunction, persistent inflammation, and rapid atherosclerosis. According to recent African cohort and registry data, the prevalence of diabetes could have doubled in some sub-Saharan African countries between 2015 and 2025 [1,2,3,4].

The epidemiological transition, urbanization, sedentary lifestyles, and changes in eating habits, which encourage obesity and insulin resistance, increase this risk [3,5].

MACEs, defined as cardiovascular death, acute coronary syndromes, strokes (CVA), serious heart rhythm disorders, chronic kidney disease, chronic obstructive arterial disease, and hospitalization for heart failure, are the main cause of premature death in African diabetic patients [2,6]. Recent African literature also shows that unequal access to specialized care, the low availability of modern cardioprotective therapies (SGLT2i, GLP-1 RA), and

poor treatment adherence contribute to the ongoing high incidence of major cardiovascular events (MACE). Several recent studies show high incidences, especially in West, Central, and Southern Africa [6,7,8,910,11].

However, no consolidated summary covering the 2015–2025 period was available. This study aims to quantify the instantaneous incidence (incidence rate) of MACE and their types in African diabetic patients. The data from this study will be used to develop targeted prevention policies suited to our African context.

2. Methodology

This section goes over the protocol and selection criteria used for this study. We carried out a systematic review along with a meta-analysis, strictly following the guidelines laid out in the PRISMA 2020 protocol.

Regarding the inclusion criteria, we focused on publications about diabetic adults, whether type 1 or type 2, living in Africa. We limited our search to original studies, such as cohort studies, cross-sectional analyses, and clinical trials, published between January 2015 and March 2025. A key criterion for including a study was that it reported at least one major cardiovascular event, commonly referred to by the acronym MACE.

To identify these studies, we put together a thorough search strategy querying several key databases, namely PubMed, Scopus, African Journals Online, and Web of Science. The search terms we used included specific keywords like 'diabetes', 'major cardiovascular events', 'myocardial infarction', 'stroke', 'heart failure', 'obliterative arteropathy of the lower limbs', and 'Africa'. The MeSH keywords with the Boolean operators used were: ("Diabetes Mellitus" OR diabetes) AND ("Major Cardiovascular Events" OR MACE) AND ("Stroke" OR "Heart Failure" OR "Myocardial Infarction") AND (Africa OR Sub-Saharan Africa).

The studies were selected based on predefined inclusion and exclusion criteria. We included publications on diabetic adults (type 1 or type 2) living in Africa. Only original studies, such as cohort studies, cross-sectional analyses, and clinical trials, published between January 2015 and March 2025, were considered. An essential inclusion criterion was reporting at least one major cardiovascular event (MACE). Specific inclusion criteria were: adults aged ≥18 years, type 1 or type 2 diabetes, located in Africa, original studies (cohorts, cross-sectional studies, trials), and reporting MACE incidence.

The exclusion criteria included reviews, editorials, letters, case reports, animal studies, studies without usable data, and duplicates. The study selection process was carried out in several steps. Initially, 1,245 potential articles were identified. After removing duplicates, 1,010 articles were kept for an initial screening. Then, 120 full texts were assessed to check their compliance with our research criteria. Finally, 28 relevant studies were included in the final analysis. Figure 1 shows the PRISMA flow diagram illustrating the different stages of study selection, from initial identification to final inclusion. The review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) under registration number CRD420261432617.

The process of selecting and extracting data was organized in several steps. At first, we identified a total of 1,245 potential articles. After removing duplicates, 1,010 articles were kept for an initial review. Then, we assessed 120 full-texts to check if they fit our research criteria. In the end, this thorough process led to keeping 28 relevant studies for the final analysis.

The data was collected using a standardized form. The variables gathered included: the author, year of publication, country, population studied, sample size, average age of participants, gender, follow-up duration, type of diabetes, type of cardiovascular events, and their incidence.

Figure 1 shows the flowchart of the different steps in selecting studies, from the initial identification to the final inclusion. It shows that only the studies strictly meeting the methodological criteria were included in the meta-analysis.

Variables : country, sample size, average age, follow-up duration, number of cardiovascular events.

Risk of bias assessment :

The methodological quality of the included studies was independently assessed by two reviewers. Cohort studies were evaluated using the Newcastle–Ottawa Scale (NOS), which looks at three areas: participant selection, comparability of groups, and outcome assessment. Cross-sectional studies were evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Analytical Cross-Sectional Studies. Any differences between the reviewers were resolved through discussion and, if needed, with input from a third reviewer. The results of this assessment were taken into account when interpreting the meta-analysis findings.

Statistical analysis :

To estimate the overall incidence of MACE, a random-effects model was used, taking into account potential heterogeneity between studies. Heterogeneity was assessed using Cochrane's Q test and the I² index. An I² value above 50% was considered to indicate substantial heterogeneity. Publication bias was checked using a funnel plot and Egger's test. A p-value from Egger's test below 0.10 was considered significant for publication bias. Subgroup analyses were conducted for different types of MACE (heart failure, stroke, myocardial infarction). The results of each study, as well as the overall estimate, are presented in a forest plot.

1. Random effects model
2. Heterogeneity: Cochrane's Q test and I²
3. Publication bias: Funnel plot and Egger test

The forest plot shows the results of each study as well as the overall estimate. The combined incidence of MACE is around 15%, with significant variability between the studies. The meta-analysis shows a MACE incidence of about 14–15% according to a random-effects model, with substantial heterogeneity between the studies (high I²) (figure 2).

3. Results

• Characteristics of studies

28 studies covering 12 African countries, mostly prospective cohorts.

This meta-analysis included 28 studies from 12 African countries, totaling 94,512 participants. Most of these studies were prospective cohorts, providing longitudinal data on the incidence of major adverse cardiovascular events (MACE). Table 1, found at the end of the manuscript, shows the detailed characteristics of each study, including the country, sample size (N), follow-up duration in years, reported percentage of MACE, and study type. The reported cardiovascular events varied but mainly included heart failure, stroke, and myocardial infarction.

• Combined incidence (overall)

The overall combined incidence of MACE in African diabetic patients was estimated at 14.8% (95% confidence interval [CI]: 11.9–17.9%). This estimate was obtained using a random-effects model, given the significant heterogeneity observed between studies (I² = 82%). Figure 2, also at the end of the manuscript, shows the forest plot of cumulative MACE incidences in Africa, displaying the results of each individual study as well as the overall estimate.

1. Global MACE : 14,8 % (CI95 % : 11,9–17,9)
2. Hétérogénéity : I² = 82 %
3. Sub-analysis :

L'analyse des sous-groupes a révélé des incidences spécifiques pour les principaux types de MACE :

1. Heart failure : 13,7 %
2. Stroke (AVC) : 11,3 %
3. Myocardial infarction : 9,6 %

These figures show that heart failure and stroke are the most common cardiovascular events in this population, followed by heart attack.

1. Publication bias :
2. Funnel plot : moderate asymetry
3. Egger’s test : p=0,08

The funnel plot suggests the absence of major publication bias. The distribution of studies around the overall estimate remains relatively balanced, despite a slight asymmetry (figure 3).

Figure 3: Funnel plot of African studies on the incidence of MACE