Systematic Reviews and Meta-analysesPrevalence of metabolic syndrome in sub-Saharan Africa: A systematic review and meta-analysis☆
Introduction
Metabolic syndrome (MS) is a clustering of insulin resistance, hyperglycaemia, hypertension, low HDL-cholesterol, raised triglycerides and central obesity [1]. When these metabolic abnormalities co-occur in one individual, they increase the risk of morbidity and mortality from cardiovascular diseases (CVD) and type 2 diabetes [1,2]. Individuals with MS are three times more likely to have a stroke or heart attack and two times more likely to die from these compared with individuals without the condition [2]. Furthermore, individuals affected with MS are five times more likely to develop type 2 diabetes compared to individuals without MS [2].
MS is thought to be a chronic state of low-grade inflammation caused by a complex interplay of both environmental and genetic factors [3]. The genetic component of MS is believed to be moderate to large with heritability estimates ranging from 10% to 30% [4]. There is evidence that genetic factors are shared between the components of MS [4]. Environmental factors comprise mostly of health-related behaviours such as physical inactivity, unhealthy diet, stress and tobacco smoking [1]. Knowledge regarding the factors driving the increasing prevalence of MS in different populations is needed to assist CVD and type 2 diabetes prevention efforts.
Currently, an epidemiological transition from predominantly communicable diseases and nutritional deficiencies to mainly non-communicable diseases (NCDs) is ongoing in low- and middle income countries (LMIC) including numerous Sub-Saharan African countries [5]. The transition can be attributed to the increased urbanization and the changing lifestyles. It is believed that advancing economies, lead to a population-wide atherogenic diets, reduced physical activity, increased tobacco smoking, increased use of alcohol and high levels of obesity [5]. This is reflected in the rising levels of NCDs in Sub-Saharan Africa (SSA). In 2004, 25% of the SSA population suffered from NCDs and this is expected to increase to 46% in 2030 [6]. Ischaemic heart diseases are already the first most common cause of death in men- and the second cause of death in women aged 60 years and older in Africa [7]. In addition, there are reports that stroke prevalence is higher in SSA than in many high-income countries; and that stroke affects more younger people in SSA than in high income countries although the rates are variable [5].
In light of the rising prevalence of CVDs and type 2 diabetes in the SSA region, it is likely that MS, a precursor of those conditions, is common in SSA. However, data on MS in SSA are limited and the available data have not yet been systematically assessed, except for some country-specific meta-analyses [8,9]. Insight into the extent of the burden and determinants of MS in SSA may guide efforts targeting populations at risk of CVDs and type 2 diabetes. The main aim of this systematic review and meta-analysis was to estimate the prevalence of MS in SSA and determine sub-populations that are most at risk.
Section snippets
Literature search
PubMed and Embase were systematically searched on the 9th of August 2019 and African Journal Online on the 24th of August 2019 for papers published reporting data on MS prevalence in the sub-Saharan African region. The search included terms on ‘prevalence’, ‘Metabolic Syndrome’ and ‘Sub-Sahara Africa’. The terms ‘prevalence’, ‘Metabolic Syndrome’ and ‘Sub-Sahara Africa’ were combined with ‘AND’. ‘Sub-Sahara Africa’ was divided in all the different Sub-Saharan countries using the term ‘OR’.
Study characteristics
The 65 included studies that reported the prevalence of MS in an adult SSA population are shown in Table 1. The studies were conducted in fourteen of the forty-eight SSA countries. Thirteen studies were conducted in Eastern Africa of which four were in both Kenya [[15], [16], [17], [18]], and Ethiopia [[19], [20], [21], [22]], three in Sudan [[23], [24], [25]] and two in Tanzania [26,27]. There were also fourteen articles conducted in Southern Africa of which twelve were in South-Africa [[28],
Discussion
This is, to the best of our knowledge, the first systematic review on the prevalence of MS in Sub-Saharan Africa. The overall pooled prevalence of MS in SSA ranged from 11.1 to 23.9% according to the various criteria used. The prevalence of MS in SSA was higher in women than in men. The prevalence of MS tended to be higher in semi-urban and urban areas than in rural areas. The MS prevalence was highest in the Southern African region followed by Eastern Africa, Western Africa and Central Africa.
Conclusions
This systematic review and meta-analysis show that MS is not rare in SSA, but not yet as common as in Europe or the US. The most at-risk population groups in SSA are the urban populations, populations living in Southern Africa and women. Our findings highlight the need to invest in efforts targeting the components of MS – i.e. insulin resistance, hyperglycaemia, hypertension, low HDL-cholesterol, raised triglycerides and central obesity - to prevent further increases in MS prevalence and
Financial disclosure
K.A.C.M. is supported by the Intramural Research Program of the National Institutes of Health in the Center for Research on Genomics and Global Health (CRGGH). The CRGGH is supported by the National Human Genome Research Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, the Center for Information Technology, and the Office of the Director at the National Institutes of Health (1ZIAHG200362).
Declaration of Competing Interest
The authors have declared that no competing interests exist.
Acknowledgements
None declared
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