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Diabetes in the Africa region: An update

  • Author Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Nasheeta Peer
    Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Affiliations
    Chronic Diseases of Lifestyle Research Unit, South African Medical Research Council, Durban, South Africa
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  • Author Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Andre-Pascal Kengne
    Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Affiliations
    Chronic Diseases of Lifestyle Research Unit, South African Medical Research Council, Cape Town, South Africa
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  • Author Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Ayesha A. Motala
    Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Affiliations
    Department of Diabetes and Endocrinology, Nelson R Mandela School of Medicine, University of KwaZulu – Natal, South Africa
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  • Author Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Jean Claude Mbanya
    Correspondence
    Corresponding author at: Department of Internal Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, BP 8046, Yaoundé, Cameroon. Tel.: +237 77607042.
    Footnotes
    1 On behalf of the Idf Diabetes Atlas.
    Affiliations
    Department of Internal Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Cameroon
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  • Author Footnotes
    1 On behalf of the Idf Diabetes Atlas.
Published:December 06, 2013DOI:https://doi.org/10.1016/j.diabres.2013.11.006

      Abstract

      The Africa Region (AFR), where diabetes was once rare, has witnessed a surge in the condition. Estimates for type 1 diabetes suggest that about 39,000 people suffer from the disease in 2013 with 6.4 new cases occurring per year per 100,000 people in children <14 years old. Type 2 diabetes prevalence among 20–79-year-olds is 4.9% with the majority of people with diabetes <60 years old; the highest proportion (43.2%) is in those aged 40–59 years. Figures are projected to increase with the numbers rising from 19.8 million in 2013 to 41.5 million in 2035, representing a 110% absolute increase. There is an apparent increase in diabetes prevalence with economic development in AFR with rates of 4.4% in low-income, 5.0% in lower-middle income and 7.0% in upper-middle income countries. In addition to development and increases in life-expectancy, the likely progression of people at high risk for the development of type 2 diabetes will drive the expected rise of the disease. This includes those with impaired glucose tolerance, the prevalence of which is 7.3% among 20–79-year-olds in 2013. Mortality attributable to diabetes in 2013 in AFR is expected to be over half a million with three-quarter of these deaths occurring in those <60 years old. The prevalence of undiagnosed diabetes remains unacceptably high at 50.7% and is much higher in low income (75.1%) compared to lower- and upper-middle income AFR countries (46.0%). This highlights the inadequate response of local health systems which need to provide accessible, affordable and optimal care for diabetes.

      Keywords

      1. Introduction

      The International Diabetes Federation Africa Region (AFR), comprised of countries in sub-Saharan Africa, has not been spared from the global diabetes epidemic. Indeed, diabetes has become a global public health challenge increasingly affecting the poor and posing serious threats to the economies of all countries [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Hu F.B.
      Globalization of diabetes: the role of diet, lifestyle, and genes.
      ,
      • Bruno G.
      • Landi A.
      Epidemiology and costs of diabetes.
      ]. AFR, where diabetes was restricted to anecdotic reports during the last century, has witnessed a surge in rates of the condition [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ]. Although infectious diseases outnumber diabetes and other non-communicable diseases (NCDs) as the predominant cause of mortality in the region [
      • World Health Organization
      World health statistics 2012.
      ], these are important contributors to the disease burden [
      • de-Graft Aikins A.
      • Unwin N.
      • Agyemang C.
      • Allotey P.
      • Campbell C.
      • Arhinful D.
      Tackling Africa's chronic disease burden: from the local to the global.
      ], and are projected to overtake infectious diseases as the leading cause of death in the region within the coming two decades. According to the World Health Organisation (WHO), in 2008 the age-standardised diabetes and cardiovascular disease (CVD) related mortality among 30–70-year-olds was 382 per 100,000 people in Africa, the highest in the world and more than double that of the WHO Region with the lowest rate (Region of the Americas: 169 per 100,000) [
      • World Health Organization
      World health statistics 2012.
      ].
      This discussion paper on diabetes in AFR describes the prevalence and distribution of diabetes and its risk factors, and examines the impact and management of the disease on the continent.

      2. Methodology and estimates

      The full description of the methodology and global estimates of diabetes prevalence for the International Diabetes Federation (IDF) Diabetes Atlas data has been described in detail elsewhere [
      • Guariguata L.
      • Beagley J.
      • Linnenkamp U.
      • Cho N.H.
      • Shaw J.
      • Whiting D.R.
      Global estimates of diabetes prevalence for 2013 and projections for 2035.
      ]. A list of the countries in the AFR Region is listed in the aforementioned paper.

      3. Prevalence and incidence of diabetes

      The common forms of diabetes include type 1 and type 2 diabetes as well as gestational diabetes. There are also less common secondary causes of diabetes including diseases of the exocrine pancreas, such as tumours or pancreatitis, endocrinopathies like Cushing's syndrome or phaeochromocytomas, drug-induced diabetes and infections, which are beyond the scope of this review. In AFR, the paucity of reliable epidemiological data on diabetes, including the absence of diabetes registries, limits the accurate estimation of the prevalence and incidence of the disease. However, there has been a recent increase in the number of studies describing the epidemiology of diabetes in the region.
      In many AFR countries, recent studies on the burden of diabetes have used the WHO STEPwise chronic disease risk factor surveillance tools (STEPS). Inconsistencies, with higher diabetes rates in some studies compared to other reports in indigenous African populations, may be related to differences in methodological approaches across studies. These may include differences in sampling strategy (for e.g. random vs. convenient sample) or methods for diagnosing diabetes (random blood samples, fasting specimens vs. oral glucose tolerance tests (OGTT)) [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ].

      3.1 Type 1 diabetes

      Estimates for type 1 diabetes suggest that about 39,000 people in AFR were suffering from the disease in 2013, and that 6.4 new cases were occurring per year per 100,000 people in those <14 years old (Table 1). Epidemiology data for type 1 diabetes are scarce with studies conducted two to three decades ago reporting prevalence of 0.33 per 1000 in 5–17year-old Nigerian and 0.95 per 1000 in 7–14 year-old Sudanese children [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Hu F.B.
      Globalization of diabetes: the role of diet, lifestyle, and genes.
      ]. Furthermore, the incidence of type 1 diabetes was reported to be 10.1 per 100,000 per year in Sudan in children <15 years old. In Tanzania, the incidence was lower at 1.5 per 100,000 per year with the peak age of presentation at 15–19 years compared to 10–14 years shown in developed regions [
      • Swai A.B.
      • Lutale J.
      • McLarty D.G.
      Diabetes in tropical Africa: a prospective study 1981-7. I. Characteristics of newly presenting patients in Dar es Salaam, Tanzania, 1981-7.
      ]. In South Africa, the peak age of onset in black Africans was at 22–23 years with an earlier peak from 14 to 17 years, whereas in Europids peak age for type 1 diabetes was 12–13 years [
      • Kalk W.J.
      • Huddle K.R.
      • Raal F.J.
      The age of onset and sex distribution of insulin-dependent diabetes mellitus in Africans in South Africa.
      ].
      Table 1Summary data for diabetes and impaired glucose tolerance (IGT) in 2013 and projections for 2035for the Africa Region.
      20132035
      Adult population (20–79 years, 1000s)407,853.47775,491.47
      Diabetes in adults (20–79 years)
      Regional prevalence (%)4.855.35
      Comparative prevalence (%)5.666.01
      Diabetes cases (1000s)19,784.5941,459.73
      Cases undiagnosed (1000s)12,446.47
      IGT in adults (20–79 years)
      Regional prevalence (%)7.288.51
      Comparative prevalence (%)8.279.33
      Number of people with IGT (1000s)29,704.9165,988.31
      Type 1 diabetes in youth (0–14 years)
      Number of children with type 1 diabetes (1000s)39.14
      Number of newly-diagnosed (per 100,000 per year)6.4
      Deaths due to diabetes in adults (20–79 years)
      Total deaths due to diabetes522,631.45
      % of deaths under 6076.4
      Health expenditure
      Health expenditure due to DM (billion USD)4.03

      3.2 Type 2 diabetes

      In 2013, the prevalence of type 2 diabetes, which accounts for 90–95% of all diabetes, was relatively low at 4.9% in AFR (Table 1). Diabetes figures in AFR are projected to increase with the number of individuals with the condition rising from 19.8 million in 2013 to 41.5 million in 2035, representing a 110% absolute increase. The prevalence of diabetes in AFR is not uniformly distributed with apparent increases with economic development. This ranged from 4.4% in low-income countries to 5.0% in lower-middle income and 7.0% in the upper-middle income countries (Table 2).
      Table 2Characteristics of individuals with diabetes in 2013 in the Africa Region.
      Among people (20–79 years) with diabetesProportion (%)
      Age distribution in years
       20–3938.7
       40–5942
       60–7919.2
      Gender
       Men49.5
       Women50.5
      Location
       Rural44.3
       Urban55.7
      Undiagnosed diabetes by income group:
       Low-income75.1
       Middle-income46
      Among adults (20–79 years)Crude prevalence (%)
       Low-income4.4
       Lower middle-income5.0
       Upper middle-income7.0
      All AFR countries with available diabetes prevalence greater than 10% appeared to be upper-middle income economies (Table 3). In absolute terms, however, low-income countries in the region such as Ethiopia, Tanzania and the Democratic Republic of Congo, by virtue of their large populations, featured among AFR countries with the largest number of people with diabetes (i.e. exceeding 1.5 million individuals) (Table 4).
      Table 3Countries and territories in the Africa Region with the highest prevalence (%) of diabetes, 2013.
      Country/TerritoryPrevalence (%), 2013
      1. Réunion15.4
      2. Seychelles12.1
      3. Gabon10.7
      4. Zimbabwe9.7
      5. South Africa9.3
      6. Western Sahara9.2
      7. United Republic of Tanzania9.0
      8. Comoros8.4
      9. Djibouti6.8
      10. Republic of Congo6.3
      Table 4Countries and territories in the Africa Region with the highest number of people with diabetes (20–79 years), 2013.
      Country/TerritoryPrevalence (in 1000s), 2013
      1. Nigeria3921.50
      2. South Africa2646.05
      3. Ethiopia1852.23
      4. United Republic of Tanzania1706.93
      5. Democratic Republic of the Congo1594.11
      6. Kenya749.248
      7. Uganda625.045
      8. Zimbabwe600.668
      9. Côte d’Ivoire501.529
      10. Cameroon497.976
      The expected increase in diabetes figures in AFR will be driven not only by development and increases in life-expectancy, but also by the likely progression of people at high risk for the development of type 2 diabetes. This comprises a sizable portion of the population and includes those with impaired glucose tolerance (IGT), the prevalence of which was 7.3% among 20–79-year-olds in 2013 (Table 1). Given the current level of development of the health system in many AFR countries, it is unlikely that the necessary interventions for the prevention of progression to diabetes for people at high risk are in place.

      4. Risk factors for type 2 diabetes

      Driven by rapid globalisation and urbanisation, with subsequent changes in diet and the adoption of sedentary lifestyles, the diabetes epidemic has expanded in line with the worldwide rise in overweight and obesity. In addition, diabetes is rising on a global level but particularly in AFR largely due to population ageing and rapid urbanisation [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ,
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ,
      • Mensah G.A.
      • Mokdad A.H.
      • Ford E.
      • Narayan K.M.
      • Giles W.H.
      • Vinicor F.
      • et al.
      Obesity, metabolic syndrome, and type 2 diabetes: emerging epidemics and their cardiovascular implications.
      ,
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ,
      • International Diabetes Federation
      IDF Diabetes Atlas.
      ].
      A complex gene-environment interaction of non-modifiable (genetics, age, gender, ethnicity and family history) and modifiable risk factors drives the development of diabetes [
      • Hu F.B.
      Globalization of diabetes: the role of diet, lifestyle, and genes.
      ,
      • Alberti K.G.
      • Zimmet P.
      • Shaw J.
      International Diabetes Federation: a consensus on Type 2 diabetes prevention.
      ,
      • Noble D.
      • Mathur R.
      • Dent T.
      • Meads C.
      • Greenhalgh T.
      Risk models and scores for type 2 diabetes: systematic review.
      ]. The significant modifiable risk factors include overweight, physical inactivity and sedentary behaviour, and dietary changes with increased total dietary fat and carbohydrate intake, and alcohol consumption [
      • Mensah G.A.
      • Mokdad A.H.
      • Ford E.
      • Narayan K.M.
      • Giles W.H.
      • Vinicor F.
      • et al.
      Obesity, metabolic syndrome, and type 2 diabetes: emerging epidemics and their cardiovascular implications.
      ,
      • Alberti K.G.
      • Zimmet P.
      • Shaw J.
      International Diabetes Federation: a consensus on Type 2 diabetes prevention.
      ,
      • Mollentze W.F.
      • Levitt N.S.
      Diabetes mellitus and impaired glucose tolerance in South Africa.
      ]. In addition, intra-uterine and early childhood influences as well as psychosocial stress may also play a role [
      • Hu F.B.
      Globalization of diabetes: the role of diet, lifestyle, and genes.
      ,
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ,
      • Alberti K.G.
      • Zimmet P.
      • Shaw J.
      International Diabetes Federation: a consensus on Type 2 diabetes prevention.
      ,
      • Mollentze W.F.
      • Levitt N.S.
      Diabetes mellitus and impaired glucose tolerance in South Africa.
      ].

      4.1 Non-modifiable risk factors

      4.1.1 Age, gender and family history

      Since the risk of developing diabetes increases with age, the global ageing of the population, including in AFR, is a major driver of the global rise in diabetes [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ,
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ,
      • International Diabetes Federation
      IDF Diabetes Atlas.
      ]. Improvements in public health and medical care, particularly for infectious diseases, are contributing to changes in demography with increases in average life expectancy in AFR. Therefore, by 2035, the diabetes peak in AFR is expected to be in the oldest individuals [
      • International Diabetes Federation
      IDF Diabetes Atlas.
      ].
      Currently, the majority of individuals with diabetes in AFR were reported to be less than 60 years of age with the highest proportion (43.2%) in people aged 40–59 years. Only 18.8% of diabetic individuals were 60–79 years of age, probably because of the relatively small proportion of people in this age group in AFR. The progression of the diabetes epidemic and the increase in modifiable risk factors such as obesity and physical inactivity at early ages will likely shift the age of onset to younger individuals [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ].
      The distribution of diabetes by gender varies widely in AFR and demonstrates no apparent trend [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. Some populations have a male or female preponderance while others report equal gender prevalence. Overall, diabetes was equally distributed among men and women in AFR in 2013.
      A positive family history of diabetes is an established risk factor for the development of the disease. AFR studies from Sudan and South Africa have confirmed this association [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Peer N.
      • Steyn K.
      • Lombard C.
      • Lambert E.V.
      • Vythilingum B.
      • Levitt N.S.
      Rising diabetes prevalence among urban-dwelling black South Africans.
      ,
      • Motala A.A.
      • Esterhuizen T.
      • Gouws E.
      • Pirie F.J.
      • Omar M.A.
      Diabetes and other disorders of glycemia in a rural South African community: prevalence and associated risk factors.
      ].

      4.1.2 Ethnicity

      In addition to black African populations, there are established Europid and Indian populations living in AFR. Also, in South Africa, the previously defined official population groups classified people of mixed ancestry as “coloured”. Although recent diabetes studies among minority population groups in AFR are lacking, studies conducted over two decades ago in Tanzania and South Africa reported lower diabetes prevalence in black African than Indian communities (South Africa: 5.3% vs. 13.0%; Tanzania: 1.1% vs. 9.1/7.1%, respectively [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ,
      • Motala A.A.
      • Omar M.A.
      • Pirie F.J.
      Diabetes in Africa epidemiology of type 1 and type 2 diabetes in Africa.
      ]. Black African populations also had lower diabetes prevalence compared to populations with mixed Egyptian ancestry in Sudan (3.4% vs. 10.4%) and the “coloured” population in South Africa (8.0% vs. 10.8%), respectively [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ]. The prevalence in Europid populations in AFR was relatively high (6–10%) and similar to those of their European counterparts [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. Studies conducted recently in 2008–2009 reported markedly higher age-adjusted diabetes prevalence in Cape Town in “coloureds” (26.3%) [
      • Erasmus R.T.
      • Soita D.J.
      • Hassan M.S.
      • Blanco-Blanco E.
      • Vergotine Z.
      • Kegne A.P.
      • et al.
      High prevalence of diabetes mellitus and metabolic syndrome in a South African coloured population: baseline data of a study in Bellville, Cape Town.
      ] compared to black Africans (13.1%) [
      • Peer N.
      • Steyn K.
      • Lombard C.
      • Lambert E.V.
      • Vythilingum B.
      • Levitt N.S.
      Rising diabetes prevalence among urban-dwelling black South Africans.
      ].
      The lower diabetes prevalence in black Africans compared to other population groups in AFR may be related to their different susceptibility as well as to being in an earlier phase of the epidemiological transition. Notably, black African populations living abroad may be experiencing a later stage of the epidemiological transition compared to those on the African continent. Cooper and colleagues reported higher age-adjusted diabetes prevalence in black African populations living in the Caribbean (9%), USA (11%) and UK (11%) compared to Nigeria (2%) [
      • Cooper R.S.
      • Rotimi C.N.
      • Kaufman J.S.
      • Owoaje E.E.
      • Fraser H.
      • Forrester T.
      • et al.
      Prevalence of NIDDM among populations of the African diaspora.
      ].

      4.1.3 Genetic susceptibility

      In African people, type 1 diabetes is associated with similar HLA susceptibility loci to Europid populations, particularly with HLADR3, HLA-DR4 and HLA-DR3/DR4 heterozygosity [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ]. For type 2 diabetes, the only reports are those from the Africa American Diabetes Mellitus study [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Chen G.
      • Adeyemo A.
      • Zhou J.
      • Chen Y.
      • Huang H.
      • Doumatey A.
      • et al.
      Genome-wide search for susceptibility genes to type 2 diabetes in West Africans: potential role of C-peptide.
      ,
      • Chen Y.
      • Kittles R.
      • Zhou J.
      • Chen G.
      • Adeyemo A.
      • Panguluri R.K.
      • et al.
      Calpain-10 gene polymorphisms and type 2 diabetes in West Africans: the Africa America Diabetes Mellitus (AADM) Study.
      ,
      • Rotimi C.N.
      • Chen G.
      • Adeyemo A.A.
      • Furbert-Harris P.
      • Parish-Gause D.
      • Zhou J.
      • et al.
      A genome-wide search for type 2 diabetes susceptibility genes in West Africans: the Africa America Diabetes Mellitus (AADM) Study.
      ]. Four major genetic loci (10q23, 4p15, 15q14 and 18p11) have been found to influence C-peptide concentrations in West Africans with type 2 diabetes.

      4.1.4 Intrauterine influences

      We have described above that urbanisation and increasing exposure to unhealthy lifestyles are driving the diabetes burden in AFR. But the continuing reality of poverty, hunger and under nutrition for many AFR people is an equally large threat. More than a third of people in AFR live below the poverty line with many women undernourished [
      • World Bank
      World development indicators, the World Bank coverage 1960–2012.
      ]. There are strong links between maternal malnutrition and the risk of diabetes in later life [
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ], especially in AFR countries where children may be undernourished but are increasingly exposed to unhealthy diets and over nutrition as they grow up.
      Intrauterine growth retardation and subsequent low birth weight therefore likely predispose individuals to metabolic disorders during adulthood. The high prevalence of stunting (20–40% in children <5 years old [
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ]) and malnutrition in AFR may considerably increase the development of diabetes [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. Additionally, stunting is associated with a two- to seven-fold risk for overweight [
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ].

      4.2 Modifiable risk factors

      4.2.1 Urbanisation

      In AFR studies, diabetes is more prevalent in urban compared to rural areas [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Motala A.
      • Omar M.A.
      • Pirie F.J.
      Epidemiology of diabetes in Africa.
      ,
      • Hall V.
      • Thomsen R.W.
      • Henriksen O.
      • Lohse N.
      Diabetes in Sub Saharan Africa 1999–2011: epidemiology and public health implications. A systematic review.
      ] with a two-to-fivefold increased risk for diabetes associated with urban residence [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ]. The higher diabetes prevalence in urban compared to rural settings is attributable to nutritional and lifestyle changes [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. Studies have found higher rates of diabetes risk factors, especially obesity, in urban compared to rural areas in AFR [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ].
      AFR is currently experiencing one of the most rapid increases in urbanisation and changes in lifestyle behaviours [
      • BeLue R.
      • Okoror T.A.
      • Iwelunmor J.
      • Taylor K.D.
      • Degboe A.N.
      • Agyemang C.
      • et al.
      An overview of cardiovascular risk factor burden in sub-Saharan African countries: a socio-cultural perspective.
      ]. The continent is undergoing urbanisation faster than other Regions with the urban population currently growing at an average annual rate of 4.5% [
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ,
      • Maher D.
      • Smeeth L.
      • Sekajugo J.
      Health transition in Africa: practical policy proposals for primary care.
      ]. The estimated explosion of the urban population in AFR to 697million by 2035[31]is likely to lead to a marked increase in the rates of diabetes and its risk factors. Already, driven by globalisation and urbanisation, the rural–urban gap for diabetes seems to be narrowing in AFR. A surprisingly high prevalence of dysglycaemia and obesity has been reported in rural Cameroon [
      • Napoli N.
      • Mottini G.
      • Arigliani M.
      • Creta A.
      • Giua R.
      • Incammisa A.
      • et al.
      Unexpectedly high rates of obesity and dysglycemia among villagers in Cameroon.
      ].
      In 2013, of the number of people with diabetes, a high proportion [44.3%] resided in rural areas (Table 2). This may be a reflection of larger rural compared to urban populations and/or is possibly suggestive of a rapid epidemiologic transition. The widespread uptake of the modifiable risk factors and the rapid economic and social development of rural Africa are likely the key driving force in the development of diabetes in rural AFR. The change in the food environment that began in urban AFR possibly spread to rural centres more rapidly [
      • Popkin B.M.
      Global nutrition dynamics: the world is shifting rapidly toward a diet linked with noncommunicable diseases.
      ].

      4.2.2 Adiposity

      Overweight and obesity have been central to the expansion of the diabetes epidemic. Several studies reported the independent association of raised adiposity with diabetes in AFR [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ,
      • Peer N.
      • Steyn K.
      • Lombard C.
      • Lambert E.V.
      • Vythilingum B.
      • Levitt N.S.
      Rising diabetes prevalence among urban-dwelling black South Africans.
      ,
      • Motala A.A.
      • Esterhuizen T.
      • Gouws E.
      • Pirie F.J.
      • Omar M.A.
      Diabetes and other disorders of glycemia in a rural South African community: prevalence and associated risk factors.
      ].
      Population-based studies in the last decade have reported a high variability in the prevalence of overweight and obesity in AFR. In men, reported obesity levels ranges from 2.0% in Ethiopia [
      • Tesfaye F.
      • Byass P.
      • Wall S.
      Population based prevalence of high blood pressure among adults in Addis Ababa: uncovering a silent epidemic.
      ] to 12.2% in the Democratic Republic of Congo [
      • Kasiam Lasi On’kin J.B.
      • Longo-Mbenza B.
      • Nge Okwe A.
      • Kangola Kabangu N.
      Survey of abdominal obesities in an adult urban population of Kinshasa, Democratic Republic of Congo.
      ] and 13.8% in Cameroon [
      • Fezeu L.K.
      • Assah F.K.
      • Balkau B.
      • Mbanya D.S.
      • Kengne A.P.
      • Awah P.K.
      • et al.
      Ten-year changes in central obesity and BMI in rural and urban Cameroon.
      ]. The prevalence of obesity among women in AFR was usually much higher than in men and ranged from 10.8% in Ethiopia [
      • Tesfaye F.
      • Byass P.
      • Wall S.
      Population based prevalence of high blood pressure among adults in Addis Ababa: uncovering a silent epidemic.
      ] to 34.7% in Ghana [
      • Hill A.G.
      • Darko R.
      • Seffah J.
      • Adanu R.M.
      • Anarfi J.K.
      • Duda R.B.
      Health of urban Ghanaian women as identified by the Women's Health Study of Accra.
      ]. Nonetheless, despite a lower prevalence in men, their susceptibility to the health consequences of obesity seems to be greater [
      • Abubakari A.R.
      • Lauder W.
      • Jones M.C.
      • Kirk A.
      • Agyemang C.
      • Bhopal R.S.
      Prevalence and time trends in diabetes and physical inactivity among adult West African populations: the epidemic has arrived.
      ]. In addition, insulin sensitivity in women may be similar to their leaner male counterparts even though their percentage of fat may be higher [
      • Abubakari A.R.
      • Lauder W.
      • Jones M.C.
      • Kirk A.
      • Agyemang C.
      • Bhopal R.S.
      Prevalence and time trends in diabetes and physical inactivity among adult West African populations: the epidemic has arrived.
      ].
      In addition to the contribution of rapid globalisation and urbanisation, a complex set of cultural, psychosocial and biological factors influence the maintenance of a healthy weight [
      • Popkin B.M.
      Global nutrition dynamics: the world is shifting rapidly toward a diet linked with noncommunicable diseases.
      ,
      • Haskell W.L.
      • Lee I.M.
      • Pate R.R.
      • Powell K.E.
      • Blair S.N.
      • Franklin B.A.
      • et al.
      Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association.
      ,
      • Scott A.
      • Ejikeme C.S.
      • Clottey E.N.
      • Thomas J.G.
      Obesity in sub-Saharan Africa: development of an ecological theoretical framework.
      ]. Particularly in AFR, where access to food remains a daily challenge, overweight and obesity is perceived to be a sign of affluence and good living, and is a deeply rooted status symbol conferring respect and influence [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ,
      • Prentice A.M.
      The emerging epidemic of obesity in developing countries.
      ]. Another important influence on the positive attitude to overweight and obesity is the association of thinness with HIV/AIDS, with overweight and obesity perceived as an absence of the disease and with being healthy [
      • Prentice A.M.
      The emerging epidemic of obesity in developing countries.
      ,
      • Haslam D.W.
      • James W.P.
      ].
      Globally, the emergence of overweight and obesity in children has increased the likelihood of type 2 diabetes developing in the paediatric population. Even in AFR, despite the high prevalence of stunting and malnutrition, overweight and obesity has increased in children under five from 4.0% in 1990 to 8.5% in 2010 and is projected to rise to 12.7% by 2020 [
      • de Onis M.
      • Blossner M.
      • Borghi E.
      Global prevalence and trends of overweight and obesity among preschool children.
      ]. Although little is currently known about the prevalence of type 2 diabetes in children in AFR, rising overweight and obesity will likely contribute to the spread of the disease in this population in the region.

      4.2.3 Physical activity

      The adoption of physically inactive lifestyles in AFR is high [
      • Abubakari A.R.
      • Lauder W.
      • Jones M.C.
      • Kirk A.
      • Agyemang C.
      • Bhopal R.S.
      Prevalence and time trends in diabetes and physical inactivity among adult West African populations: the epidemic has arrived.
      ] and increasing, and can be ascribed to rapid urbanisation and socio-economic transitions [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ,
      • Unwin N.
      • James P.
      • McLarty D.
      • Machybia H.
      • Nkulila P.
      • Tamin B.
      • et al.
      Rural to urban migration and changes in cardiovascular risk factors in Tanzania: a prospective cohort study.
      ]. According to the WHO, insufficient physical activity, defined as less than 150 minutes of moderate physical activity per week [or equivalent], was present in about a quarter of men and a third of women in AFR [
      • World Health Organization
      Global status report on noncommunicable diseases 2010.
      ]. High levels of physical inactivity increase the risk of developing diabetes [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. Studies from Cameroon [
      • Assah F.K.
      • Ekelund U.
      • Brage S.
      • Mbanya J.C.
      • Wareham N.J.
      Urbanization, physical activity, and metabolic health in sub-Saharan Africa.
      ] and Kenya [
      • Christensen D.L.
      • Friis H.
      • Mwaniki D.L.
      • Kilonzo B.
      • Tetens I.
      • Boit M.K.
      • et al.
      Prevalence of glucose intolerance and associated risk factors in rural and urban populations of different ethnic groups in Kenya.
      ], conducted in large samples and using objective measures of physical activity, have found higher physical activity levels to be inversely related to abnormal glucose tolerance.

      4.2.4 Diet and alcohol

      Processed foods have become easily available in AFR as a result of foreign direct investment from transnational food companies [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ,
      • Madu E.C.
      • Richardson K.D.
      • Ozigbo O.H.
      • Baugh D.S.
      Improving cardiovascular disease prevention and management in Africa: issues to consider for the 21st century.
      ]. Consequently, there has been a shift away from traditional diets towards the higher fat and more refined carbohydrate Western diet [
      • Popkin B.M.
      The nutrition transition and obesity in the developing world.
      ], particularly in urban areas. Intake of unhealthy diets that are richer in high-fat, high-energy foods contributes directly to increased energy imbalances, and subsequent obesity and diabetes. Nonetheless, in some settings, rural to urban migration is accompanied by access to more varied diets and greater consumption of fresh fruit and vegetables [
      • Unwin N.
      • James P.
      • McLarty D.
      • Machybia H.
      • Nkulila P.
      • Tamin B.
      • et al.
      Rural to urban migration and changes in cardiovascular risk factors in Tanzania: a prospective cohort study.
      ].
      Other evolving dietary patterns affected by globalisation, acculturation and urbanisation include alcohol consumption. Currently, the prevalence of non-drinkers is higher in AFR compared to Europe (men: 32% vs. 8%, women: 45% vs. 14%, respectively) [
      • Agyemang C.
      • Addo J.
      • Bhopal R.
      • Aikins Ade G.
      • Stronks K.
      Cardiovascular disease, diabetes and established risk factors among populations of sub-Saharan African descent in Europe: a literature review.
      ]. Alcohol consumption has been reported to moderately increase the risk of type 2 diabetes but remains to be studied in greater depth in AFR [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. However, a few studies have reported a link: in rural South Africa, alcohol use was independently related to diabetes [
      • Motala A.A.
      • Esterhuizen T.
      • Gouws E.
      • Pirie F.J.
      • Omar M.A.
      Diabetes and other disorders of glycemia in a rural South African community: prevalence and associated risk factors.
      ] and in Kenya, frequent alcohol intake in men was associated with glucose intolerance [
      • Christensen D.L.
      • Friis H.
      • Mwaniki D.L.
      • Kilonzo B.
      • Tetens I.
      • Boit M.K.
      • et al.
      Prevalence of glucose intolerance and associated risk factors in rural and urban populations of different ethnic groups in Kenya.
      ]. Therefore, rising levels of consumption may likely contribute to higher diabetes prevalence.

      4.3 Emerging risk factors

      4.3.1 Psychosocial stress

      Many studies have found an association between depression and diabetes [
      • Pouwer F.
      • Kupper N.
      • Adriaanse M.C.
      Does emotional stress cause type 2 diabetes mellitus? A review from the European Depression in Diabetes (EDID) Research Consortium.
      ,
      • Chida Y.
      • Hamer M.
      An association of adverse psychosocial factors with diabetes mellitus: a meta-analytic review of longitudinal cohort studies.
      ]. Analyses of the World Health Survey data found diabetes to be associated with a twofold increase in the prevalence of an episode of depressive symptoms globally [
      • Mommersteeg P.M.
      • Herr R.
      • Pouwer F.
      • Holt R.I.
      • Loerbroks A.
      The association between diabetes and an episode of depressive symptoms in the 2002 World Health Survey: an analysis of 231,797 individuals from 47 countries.
      ]. There is also growing evidence that other forms of psychosocial stress contribute to the development of diabetes [
      • Pouwer F.
      • Kupper N.
      • Adriaanse M.C.
      Does emotional stress cause type 2 diabetes mellitus? A review from the European Depression in Diabetes (EDID) Research Consortium.
      ]. In addition to these studies, a South African study reported the association of psychosocial stress with diabetes in women but not men [
      • Peer N.
      • Steyn K.
      • Lombard C.
      • Lambert E.V.
      • Vythilingum B.
      • Levitt N.S.
      Rising diabetes prevalence among urban-dwelling black South Africans.
      ]. Nonetheless, longitudinal studies, particularly in AFR, are required to determine the role of psychosocial stress in the development of diabetes.

      5. Impact of HIV/AIDS and tuberculosis on diabetes

      Two of the most common infectious diseases seen in Africa, tuberculosis (TB) and HIV/AIDS, not only co-exist but interact with diabetes, with one exacerbating the other [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ,
      • de-Graft Aikins A.
      • Unwin N.
      • Agyemang C.
      • Allotey P.
      • Campbell C.
      • Arhinful D.
      Tackling Africa's chronic disease burden: from the local to the global.
      ,
      • Hall V.
      • Thomsen R.W.
      • Henriksen O.
      • Lohse N.
      Diabetes in Sub Saharan Africa 1999–2011: epidemiology and public health implications. A systematic review.
      ,
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ,
      • Maher D.
      • Smeeth L.
      • Sekajugo J.
      Health transition in Africa: practical policy proposals for primary care.
      ]. Diabetes increases the risk of developing TB three-fold [
      • Hall V.
      • Thomsen R.W.
      • Henriksen O.
      • Lohse N.
      Diabetes in Sub Saharan Africa 1999–2011: epidemiology and public health implications. A systematic review.
      ,
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ] and it seems that TB may predispose a person to diabetes [
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ]. Rising diabetes prevalence may hamper TB control efforts by increasing the number of susceptible individuals in endemic areas. The co-morbid presentation of diabetes and TB is associated with poorer outcomes [
      • de-Graft Aikins A.
      • Unwin N.
      • Agyemang C.
      • Allotey P.
      • Campbell C.
      • Arhinful D.
      Tackling Africa's chronic disease burden: from the local to the global.
      ,
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ].
      HIV/AIDS and antiretroviral therapy (ART) are associated with an increased risk of developing diabetes [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ,
      • Hall V.
      • Thomsen R.W.
      • Henriksen O.
      • Lohse N.
      Diabetes in Sub Saharan Africa 1999–2011: epidemiology and public health implications. A systematic review.
      ,
      • Bischoff A.
      • Ekoe T.
      • Perone N.
      • Slama S.
      • Loutan L.
      Chronic disease management in Sub-Saharan Africa: whose business is it?.
      ]. Factors contributing to the development of diabetes in HIV disease include inflammation and viral factors, among other influences, while ART causes insulin resistance and decreased insulin secretion [
      • Kalra S.
      • Agrawal N.
      Diabetes and HIV: current understanding and future perspectives.
      ]. The implementation of ART programmes, key to the management of the HIV/AIDS epidemic, is likely to lead to a rise in individuals with adverse metabolic consequences [
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ]. Considering the high burden of TB and HIV/AIDS in AFR, the impact of these co-morbidities is likely to be great.

      6. Morbidity and mortality

      Hyperglycaemia and diabetes contribute significantly to morbidity and premature mortality worldwide [
      • International Diabetes Federation
      IDF Diabetes Atlas.
      ]. In AFR, diabetes is responsible for a considerable amount of morbidity, mainly attributable to micro-vascular complications [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ,
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ,
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ,
      • Motala A.
      • Omar M.A.
      • Pirie F.J.
      Epidemiology of diabetes in Africa.
      ,
      • Young F.
      • Critchley J.A.
      • Johnstone L.K.
      • Unwin N.C.
      A review of co-morbidity between infectious and chronic disease in Sub Saharan Africa: TB and diabetes mellitus HIV and metabolic syndrome, and the impact of globalization.
      ,
      • Azevedo M.
      • Alla S.
      Diabetes in sub-Saharan Africa: Kenya, Mali, Mozambique, Nigeria, South Africa and Zambia.
      ] and due to poor glycaemic and blood pressure (BP) control [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. The prevalence varies widely across the continent which is likely due to the heterogeneity of the populations studied in terms of the type and duration of diabetes, glycaemic control, and accompanying risk factors such as hypertension or smoking, among other variables [
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ,
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. A systematic review found that the prevalence of diabetic retinopathy in diabetes clinic-based studies ranged from 7.0 to 62.4% [
      • Burgess P.I.
      • MacCormick I.J.
      • Harding S.P.
      • Bastawrous A.
      • Beare N.A.
      • Garner P.
      Epidemiology of diabetic retinopathy and maculopathy in Africa: a systematic review.
      ]. Owing to the frequent delayed diagnosis of diabetes, retinopathy is present in 21–25% of patients with type 2 diabetes at initial diagnosis [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ]. Type 1 and type 2 patients with long-standing diabetes (>10 years) who attended a diabetes clinic in South Africa had retinopathy rates of 53.2 and 64.5%, respectively [
      • Motala A.A.
      • Pirie F.J.
      • Gouws E.
      • Amod A.
      • Omar M.A.
      Microvascular complications in South African patients with long-duration diabetes mellitus.
      ]. In the same study, persistent proteinuria was present in 23.4 and 25.0% of type 1 and type 2 diabetic patients, respectively. In AFR, neuropathy affected 6–47% of diabetic individuals [
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ].
      In contrast, macro-vascular complications are low compared to other regions, probably because of the lower rates of traditional risk factors, except for hypertension, or the shorter disease duration [
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ]. Ischaemic heart disease affects 5–8% of diabetic patients [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ], while up to 5% of diabetic patients present with stroke symptoms at diagnosis [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. The prevalence of peripheral vascular disease ranges from 4 to 28% depending on the method of detection used [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Levitt N.S.
      Diabetes in Africa: epidemiology, management and healthcare challenges.
      ].
      Although diabetes-related mortality in AFR is unacceptably high with rates of 8–41% of all-cause mortality, poor documentation of underlying cause of death in vital statistics lead to significant uncertainty in estimates for the region [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. In 2013, mortality attributable to diabetes is expected to be over half a million with three-quarter of these deaths occurring in those <60 years old (Table 1). Mortality in the region is primarily due to acute metabolic complications and infections [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ,
      • Motala A.
      • Omar M.A.
      • Pirie F.J.
      Epidemiology of diabetes in Africa.
      ]. These include diabetic ketoacidosis caused by insulin deficiency or delayed diagnosis, and hyperosmolar non-ketotic coma [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ]. However, a changing pattern has been reported in some studies, with findings similar to that reported in Western literature i.e. the emergence of chronic complications as a major cause of mortality. In a 20-year outcome study of type 1 diabetic patients in South Africa, the most frequent cause of mortality was renal failure accounting for >40% of all deaths [
      • Gill G.V.
      • Huddle K.R.
      • Monkoe G.
      Long-term (20 years) outcome and mortality of Type 1 diabetic patients in Soweto, South Africa.
      ].

      7. Economic and socio-economic burden of diabetes

      The majority (76.4%) of diabetes mortality in the region occurred in people younger than 60 years old compared to the global proportion of 49% [
      • International Diabetes Federation
      IDF Diabetes Atlas.
      ]. The high burden of diabetes in the working age population has a critical impact on the health of the workforce with far-reaching economic repercussions [
      • Madu E.C.
      • Richardson K.D.
      • Ozigbo O.H.
      • Baugh D.S.
      Improving cardiovascular disease prevention and management in Africa: issues to consider for the 21st century.
      ]. In addition to undermining productivity and adversely affecting national economies, the socioeconomic costs of diabetes are devastating as the region simultaneously grapples with poverty-related diseases and poor healthcare facilities. In addition to compromised quality and duration of life in people with diabetes, the loss of wage-earners can drive families into poverty.
      Exacerbating the situation is the need for prolonged and expensive treatment associated with diabetes complications, the cost of which is often borne by the patient and depletes family resources [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ,
      • Gill G.V.
      • Mbanya J.C.
      • Ramaiya K.L.
      • Tesfaye S.
      A sub-Saharan African perspective of diabetes.
      ,
      • Hall V.
      • Thomsen R.W.
      • Henriksen O.
      • Lohse N.
      Diabetes in Sub Saharan Africa 1999–2011: epidemiology and public health implications. A systematic review.
      ,
      • Beran D.
      • Yudkin J.S.
      Diabetes care in sub-Saharan Africa.
      ]. Insulin, for example, is a relatively expensive drug that is unaffordable to the poor, particularly in resource-limited settings and often not available on an uninterrupted basis [
      • Hall V.
      • Thomsen R.W.
      • Henriksen O.
      • Lohse N.
      Diabetes in Sub Saharan Africa 1999–2011: epidemiology and public health implications. A systematic review.
      ,
      • Beran D.
      • Yudkin J.S.
      Diabetes care in sub-Saharan Africa.
      ].
      In 2000, diabetes was responsible for a total economic loss of 25.5 billion international dollars, that is, 3633 dollars per patient with diabetes [
      • Kirigia J.M.
      • Sambo H.B.
      • Sambo L.G.
      • Barry S.P.
      Economic burden of diabetes mellitus in the WHO African region.
      ]. Costs included direct costs related to healthcare for diabetes and indirect costs associated with loss of productivity caused by the disease.

      8. Diabetes management

      8.1 Healthcare expenditure and treatment of diabetes

      The healthcare expenditure on diabetes in AFR in 2013 was 4.0 billion USD (Table 1) representing less than 1% of the total global healthcare expenditure allocated to diabetes. Spending on diabetes care in the region is woefully inadequate given the substantial projected rise in cases and the overwhelming burden of premature mortality.
      About 90% of health ministries in Africa have a dedicated unit or department responsible for NCDs with 61% funded for treatment and control [
      • Kengne A.P.
      • Sobngwi E.
      • Echouffo-Tcheugui J.B.
      • Mbanya J.C.
      New insights on diabetes mellitus and obesity in Africa-Part 2: prevention, screening and economic burden.
      ]. However, only 26% had an operational diabetes programme highlighting that most AFR countries were ill-prepared to tackle the management of this disease. Notably, Diabcare Africa study found that diabetes care was sub-optimal with less than half (47%) of diabetic patients having had HbA1C measurements conducted in the previous year [
      • Sobngwi E.
      • Ndour-Mbaye M.
      • Boateng K.A.
      • Ramaiya K.L.
      • Njenga E.W.
      • Diop S.N.
      • et al.
      Type 2 diabetes control and complications in specialised diabetes care centres of six sub-Saharan African countries: the Diabcare Africa study.
      ]. Furthermore, the same study found that blood glucose treatment targets were achieved only in 29% of those who had an HbA1C measurement.

      8.2 Detection of undiagnosed diabetes

      The prevalence of undiagnosed diabetes in AFR in 2013 remained unacceptably high at 50.7% (Table 2). These levels were much higher in low income (75.1%) compared to lower- and upper-middle income AFR countries (46.0%). The high proportion of unknown diabetes reflects poorly on local health systems; strained economic resources and ill-equipped healthcare systems are mainly responsible for the inadequate detection and management of diabetes. The condition is usually only diagnosed once patients are overtly symptomatic or present with complications [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ].
      The high proportion of undiagnosed diabetes demonstrates the inadequate response in AFR to this growing threat, which will compound the continuing health burden. Early diagnosis and treatment of diabetes is essential to mitigate the serious and fatal consequences associated with the development of complications [
      • Mbanya J.C.
      • Motala A.A.
      • Sobngwi E.
      • Assah F.K.
      • Enoru S.T.
      Diabetes in sub-Saharan Africa.
      ].
      The detection of undiagnosed diabetes requires an appropriate biochemical test that is reliable, high performance, convenient and low-cost [
      • Narayan K.M.
      • Chan J.
      • Mohan V.
      Early identification of type 2 diabetes: policy should be aligned with health systems strengthening.
      ]. Oral glucose tolerance tests (OGTT) are cumbersome and inconvenient. HbA1C tests, while convenient as these can be performed in the non-fasting state, and much less time consuming, are expensive [
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ,
      • World Health Organization
      Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus.
      ]. Also, the discordant diagnosis of diabetes with HbA1C and the glucose criteria used are of concern [
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ]. Numerous studies have demonstrated a lower prevalence of undiagnosed diabetes using HbA1C compared to OGTT criteria. This may be related to several factors that influence the HbA1c result such as anaemia, haemoglobinopathies, pregnancy and uraemia [
      • World Health Organization, International Diabetes Federation
      Definition and diagnosis of diabetes mellitus and intermediate hyperglycemia: report of a WHO/IDF consultation.
      ]. The HbA1C criteria have high specificity (>90%) but lower and great variability in sensitivity in diagnosing diabetes when compared to OGTT. The sensitivity ranges from 17% in Australians to 78% in Asian Indians for HbA1C ≥ 6.5%. The use of alternative HbA1C cut-points as well as ethnic-specific cut-points has been proposed [
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ]. Additionally, the wide adoption of HbA1C as a diagnostic criterion would inevitably result in different prevalence estimates to that found with OGTT. The use of different methodologies to diagnose diabetes would therefore impact considerably on the ability to compare inter- and intra-population differences or changes in dysglycaemia [
      • Chen L.
      • Magliano D.J.
      • Zimmet P.Z.
      The worldwide epidemiology of type 2 diabetes mellitus – present and future perspectives.
      ]. Both OGTT andHbA1C tests require skilled healthcare personnel and laboratory facilities for sample analyses, a major challenge in resource-constrained AFR countries [
      • Narayan K.M.
      • Chan J.
      • Mohan V.
      Early identification of type 2 diabetes: policy should be aligned with health systems strengthening.
      ].
      The gold standard for diagnosing diabetes, advocated by the WHO, is the OGTT [
      • World Health Organization, International Diabetes Federation
      Definition and diagnosis of diabetes mellitus and intermediate hyperglycemia: report of a WHO/IDF consultation.
      ]. However, in light of the practical difficulties associated with testing, a pragmatic and cost-effective solution may be to initially identify high-risk individuals through questionnaires or non-laboratory risk scoring systems [
      • Echouffo-Tcheugui J.B.
      • Mayige M.
      • Ogbera A.O.
      • Sobngwi E.
      • Kengne A.P.
      Screening for hyperglycemia in the developing world: rationale, challenges and opportunities.
      ]. This may be accompanied by point-of-care capillary glucose testing to aid detection of individuals requiring further biochemical evaluation. Nonetheless, the introduction of diabetes screening programmes in already overburdened AFR healthcare systems which are delivering sub-optimal care is not a priority before providing care to those already diagnosed. Additional resources would be required or, more likely, a redirection of existing resources from other activities [
      • Echouffo-Tcheugui J.B.
      • Mayige M.
      • Ogbera A.O.
      • Sobngwi E.
      • Kengne A.P.
      Screening for hyperglycemia in the developing world: rationale, challenges and opportunities.
      ].

      8.3 Perspectives

      The UN High-level meeting on NCDs in New York in September 2011 raised international awareness on the magnitude, and socioeconomic and developmental impacts of diabetes and other NCDs [
      • Echouffo-Tcheugui J.B.
      • Kengne A.P.
      A United Nation high level meeting on chronic non-communicable diseases: utility for Africa?.
      ]. These conditions were positioned resolutely as a development, and not only a health, issue [
      • Beaglehole R.
      • Bonita R.
      • Alleyne G.
      • Horton R.
      NCDs: celebrating success, moving forward.
      ]. Therefore, governments in AFR need to recognise their primary role and responsibility to respond to the challenges of diabetes.
      However, national policies for the control of diabetes are absent in most AFR countries. Also, primary healthcare systems have not adapted to cope with the new additional challenges and many lack the most basic equipment [
      • Ibrahim M.M.
      • Damasceno A.
      Hypertension in developing countries.
      ]. There needs to be a sustained response and political commitment to the prevention, detection and control of diabetes. The IDF Africa Action Plan advocated harnessing political will for governments to develop national action plans for the adequate delivery of diabetes care and to promote community awareness of the disease as well as introduce school and workplace health programmes, among other initiatives [
      • International Diabetes Federation
      IDF Africa action plan summary.
      ].
      The rising number of individuals with diabetes has important implications for healthcare provision of care for people with diabetes [
      • Mbanya J.C.
      • Ramaiya K.
      Diabetes mellitus.
      ]. AFR countries with already burdened healthcare budgets cannot afford to ignore the opportunity to address this major problem. Limited resources must be prioritised efficiently using cost-effective strategies. The emphasis on early treatment and prevention of diabetes is an excellent, cost-saving economic investment as well as an established way to improve outcomes [
      • Noble D.
      • Mathur R.
      • Dent T.
      • Meads C.
      • Greenhalgh T.
      Risk models and scores for type 2 diabetes: systematic review.
      ,
      • World Health Organization
      Noncommunicable diseases. Fact sheet No. 355.
      ]. Programmes must be developed for health systems in AFR which align with this evidence.
      Feasible and cost-effective interventions in people with diabetes that improve health include tight glucose and BP control, and foot care for individuals with a high risk of ulcers [
      • World Health Organization
      Global status report on noncommunicable diseases 2010.
      ]. BP control in people with diabetes is very effective in reducing micro- and macrovascular complications. In resource-poor regions, measures for BP control are estimated to be one of the most feasible and cost-effective interventions for people with diabetes [
      • World Health Organization
      Global status report on noncommunicable diseases 2010.
      ].
      It is estimated that about 80% of type 2 diabetes can be delayed or prevented through early management and lifestyle modification [
      • Habib S.
      • Saha S.
      Burden of non-communicable disease: global overview.
      ,
      • Unwin N.
      • Alberti K.G.
      Chronic non-communicable diseases.
      ]. Therefore, equally important for successful management, is the need for health education and increased public awareness of diabetes and its risk factors [
      • Mbanya J.C.
      • Ramaiya K.
      Diabetes mellitus.
      ]. Poor patient and provider education are among the challenges to achieving optimal diabetes care in AFR [
      • Tuei V.C.
      • Maiyoh G.K.
      • Ha C.E.
      Type 2 diabetes mellitus and obesity in sub-Saharan Africa.
      ].

      9. Conclusions

      The prevalence of diabetes in AFR is rising and of particular concern is the high burden of undiagnosed diabetes. There is considerable variance in the prevalence of diabetes and its risk factors among AFR countries as well as by urban-rural location and sub-populations which is likely a reflection of the varying pace at which communities are developing. The challenges of diabetes in AFR include the need to stem the rising burden of type 2 diabetes, exacerbated by urbanisation and obesity, and to provide accessible, affordable and optimal care for the management of the disease [
      • Beran D.
      • Yudkin J.S.
      Diabetes care in sub-Saharan Africa.
      ]. This is compounded by the weakest health systems and workforces as well as the lowest per capita income globally [
      • Madu E.C.
      • Richardson K.D.
      • Ozigbo O.H.
      • Baugh D.S.
      Improving cardiovascular disease prevention and management in Africa: issues to consider for the 21st century.
      ,
      • Bischoff A.
      • Ekoe T.
      • Perone N.
      • Slama S.
      • Loutan L.
      Chronic disease management in Sub-Saharan Africa: whose business is it?.
      ]. Nonetheless, if the battle against diabetes is to succeed, it must be a public health priority on the continent. Further research is required to build the evidence base, design and implement an optimal strategy for early diagnosis and treatment, and to identify appropriate population-based prevention programmes. A concerted effort is required to change the course of the rising diabetes burden in AFR; the price of inaction will otherwise be devastating.

      Conflict of interest

      The authors have no conflicts to disclose.

      Acknowledgements

      The 6th edition of the IDF Diabetes Atlas was supported by the following sponsors: Lilly Diabetes, Merck and Co, Inc. , Novo Nordisk A/S supported through an unrestricted grant by the Novo Nordisk Changing Diabetes® initiative, Pfizer, Inc., and Sanofi Diabetes .

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