Epidemiology of carotid atherosclerosis in Africa: a blind spot

In their meta-analysis1Song P Fang Z Wang H et al.Global and regional prevalence, burden, and risk factors for carotid atherosclerosis: a systematic review, meta-analysis, and modelling study.Lancet Glob Health. 2020; 8: e721-e729Summary Full Text Full Text PDF PubMed Scopus (39) Google Scholar of the global burden of carotid atherosclerosis, published in The Lancet Global Health, Peige Song and colleagues stated that “the African region had the smallest share of cases of increased carotid intima-media thickness (59·08 million [6·21%])”; however, we question the validity of this estimate. A study2Perret F Bovet P Shamlaye C Paccaud F Kappenberger L High prevalence of peripheral atherosclerosis in a rapidly developing country.Atherosclerosis. 2000; 153: 9-21Summary Full Text Full Text PDF PubMed Scopus (13) Google Scholar from the Seychelles, published in 2000 with 503 participants, was the sole source of data for the African region in Song and colleagues' analysis. We believe extrapolations from a study published 20 years ago are unlikely to reflect current trends, given the rapidly evolving prevalence of vascular risk factors driven by the epidemiological transition and air pollution.3Price AJ Crampin AC Amberbir A et al.Prevalence of obesity, hypertension, and diabetes, and cascade of care in sub-Saharan Africa: a cross-sectional, population-based study in rural and urban Malawi.Lancet Diabetes Endocrinol. 2018; 6: 208-222Summary Full Text Full Text PDF PubMed Scopus (99) Google Scholar, 4Feigin VL Roth GA Naghavi M et al.Global burden of stroke and risk factors in 188 countries, during 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013.Lancet Neurol. 2016; 15: 913-924Summary Full Text Full Text PDF PubMed Scopus (654) Google Scholar To date, a population study of the prevalence of carotid atherosclerosis in continental Africa has not been done. All existing studies of subclinical and clinical atherosclerosis were done on patients with rheumatoid arthritis, HIV infection, or stroke. Furthermore, all studies reporting on increased carotid intima-media thickness applied a cutoff of 1·0 mm to the average value obtained from both carotid arteries. Consequently, they inevitably underestimated the burden of subclinical atherosclerosis. According to the Mannheim consensus, age-specific cutoffs should be used to account for the normal ageing of the vessel wall,5Touboul PJ Hennerici MG Meairs S et al.Mannheim carotid intima-media thickness and plaque consensus (2004–2006–2011). An update on behalf of the advisory board of the 3rd, 4th and 5th watching the risk symposia, at the 13th, 15th and 20th European Stroke Conferences, Mannheim, Germany, 2004, Brussels, Belgium, 2006, and Hamburg, Germany, 2011.Cerebrovasc Dis. 2012; 34: 290-296Crossref PubMed Scopus (843) Google Scholar and carotid arteries should be considered individually because atherosclerosis is not a uniform symmetrical process. Such considerations increase the sensitivity of duplex ultrasound for the diagnosis of carotid atherosclerosis,6Kamtchum-Tatuene J Mwandumba HC Mwangalika Kachingwe G et al.A cross-sectional feasibility study of neurovascular ultrasound in Malawian adults with acute stroke-like syndrome.PLoS One. 2020; 15e0229033Crossref PubMed Scopus (3) Google Scholar especially in Africa, where intima-media thickening could be triggered at a younger age by HIV infection, which remains disproportionately prevalent on the continent.7Kamtchum-Tatuene J Mwandumba H Al-Bayati Z et al.HIV is associated with endothelial activation despite ART, in a sub-Saharan African setting.Neurol Neuroimmunol Neuroinflamm. 2019; 6: e531Crossref PubMed Scopus (10) Google Scholar There are two other specificities that Song and colleagues could not factor in their modelling work. First, the age structure of the population is highly variable across different world regions. Therefore, estimates of the number of Africans living with carotid atherosclerosis obtained by multiplying the age-specific prevalence and sex-specific prevalence by the corresponding world populations are inaccurate. Second, the influence of the genetic background of African populations on the susceptibility to and distribution of atherosclerotic lesions (ie, coronary, carotid, and intracranial) has not been studied, and it might not be appropriate to assume that the epidemiology of carotid atherosclerosis in Africa matches that of other continents where more data are available. In conclusion, the burden of carotid atherosclerosis in Africa remains an epidemiological blind spot, because adequate data to derive robust estimates are non-existent. High-quality population epidemiological studies are urgently needed to better understand the distribution, pathophysiology, risk factors, and consequences of carotid atherosclerosis in Africa to design tailored prevention and treatment strategies for the continent. I declare no competing interests. Global and regional prevalence, burden, and risk factors for carotid atherosclerosis: a systematic review, meta-analysis, and modelling studyA substantial global burden of carotid atherosclerosis exists. Effective strategies are needed for primary prevention and management of carotid atherosclerosis. High-quality epidemiological investigations on carotid atherosclerosis are needed to better address the global burden of carotid atherosclerosis at finer levels. Full-Text PDF Open Access

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