CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 4, July/August 2022 212 AFRICA Diabetes The most recent International Diabetes Federation Atlas (9th edn) has reported an estimated global diabetes prevalence of 9.3%, which is predicted to rise to 10.2% in 2030 and 10.9% in 2045.161 Of the 436 million people with diabetes, 19 million live in sub-Saharan Africa, 60% of whom do not know they have diabetes. The global prevalence is higher in urban compared to rural communities, with 67% of people with diabetes living in urban areas.161 Globally, between the ages of 45 and 65 years, there is a higher prevalence of diabetes in men compared to women, with the prevalence increasing in both genders between these ages. The latest Global Burden of Disease data (2019) shows that diabetes is one of only three conditions (the other two being HIV/AIDS and musculoskeletal disorders) that have shown large increases in age-standardised DALY rates since 1990, with an increase of 24.4% (95% UI: 18.5–29.7).162 While being the fifth leading cause of global DALYs in 1990 in people between the ages of 50 and 74 years, this has increased to being the third leading cause in 2019.162 The WHO global NCD target has set out to halt the rise in diabetes by 2025, while the diabetes goal outlined in South Africa’s Strategic Plan for the Prevention and Control of NCDs 2013–2017 is to increase the percentage of people controlled for diabetes by 30% by 2020.4 In South Africa, type 2 diabetes was the leading cause of death in 2016 in women (7.2% of deaths).163 SANHANES data published as part of a 12-country study reported the prevalence of diabetes as 14% in men and 17% in women between 40 and 54 years of age, and 23% in men and 30% in women in the 55- to 64-year-old age group.164 The 2016 SADHS, which used adjusted haemoglobin A1c (HbA1c) from dried blood-spot specimens in a sub-sample of nationally representative households, reported a similar prevalence of 12 and 21% in 45- to 54-year-old men and women, respectively, and 23 and 29% for 55- to 64-year-old men and women, respectively.9 Of the 42 articles that were selected based on title and abstract screening, only 19 met the inclusion criteria for this narrative.26,28,63,76,122,123,151,152,155,165-173 Twenty-three articles were excluded and the reasons for exclusion included no diabetesspecific data (n = 8), out of age range (n = 9), only included continuous glucose data (n = 2), only included impaired fasting glucose prevalence (n =1) or diabetes was a correlate with no prevalence data available (n = 1). One reference was a conference abstract and one was a conference poster. Comparisons between the studies is sometimes difficult as various methods and cut-off points are used to define diabetes [self-report, random blood glucose (RBG), HbA1c, fasting blood glucose (FBG)], and the study samples used in the various studies are often self-selected so do not represent a population. The diabetes prevalence reported by regional studies ranges from 2% in a study by Senekal et al. (n = 517; mean age of 45 years; RBG > 11.1 mmol/l) to 21.4% in 58- to 67-year-old men and women using self-report.122,155 Primary healthcare screening of adults in the Eastern Cape (n = 17 359, over 18 years, 50% older than 45 years) identified 14% of people over the age of 55 years with a RBG ≥ 7.8 mmol/l.165 Bailey et al. (2016), using RBG ≥ 11.1 and self-reported diabetes in a sample of 12 496 individuals from the Western Cape, reported a diabetes prevalence of 11.5% in adults between 40 and 49 years of age, and 18.1% between 50 and 59 years of age.166 The Bellville South study includes of a self-reported coloured population (n =1 294; mean age 47.8 years) and reported a 7.3% prevalence using WHO criteria,152 while another cohort study in South Africa, the HAALSI cohort, reported a 12% prevalence in their sample over the age of 40 years.151 A small study of commercial taxi drivers (98.8% men, mean age 43.3 years) reported a 16% prevalence of diabetes defined as a FBG ≥ 7.0 mmol/l or self-report.167 It is clear from national data as well as regional studies that the prevalence of diabetes increases with age and BMI. This is well illustrated by Shen et al. (2016), who include data from the CRIBSA study as part of amulti-site study, and reported a diabetes prevalence of 13.8% in the whole sample (25–74 years) but a clear increase in prevalence with age and BMI.76 Hird et al. (2016) compared the prevalence of diabetes using the WHO diagnostic criteria for FBG (≥ 7.0 mmol/l), two-hour plasma glucose level from an oral glucose tolerance test [two-hour postprandial glucose (PG) ≥ 11.1 mmol/l] and HbA1c ≥ 6.5%. 168 In men between 45 and 54 years, the prevalence was 9.3, 7.0 and 11.6% for FBG, two-hour PG and HbA1c, respectively, and for women of the same age, these were 23.2, 17.2 and 27.2%, respectively. In slightly older adults (55–64 years) these increased to 25.8, 25.8 and 29% for FBG, two-hour PG and HbA1c, respectively, in men, and 34.5, 30.1 and 32.7%, respectively, in women. Ethnic differences in the prevalence of diabetes have been reported in several regional studies.123,169 Peer et al. (2018) in a sample of 7 711 adults (mean age 47.6 years in men and 48.6 years in women) who attended a screening campaign, compared the prevalence of diabetes between self-identified white, coloured, black and Indian men and women. They showed that compared with self-identified white men and women, selfidentified black men (OR: 2.66, 95% CI: 1.70–4.16) and women (OR: 2.10, 95% CI: 1.49–2.96), self-identified coloured men (OR: 2.28, 95% CI: 1.44–3.60) and women (OR: 2.15, 95% CI: 1.52– 3.05) and self-identified Indian men (OR: 4.38, 95% CI: 2.65–7.26) and women (OR: 3.64, 95% CI: 2.50–5.32) were more likely to have diabetes.123 The prevalence of diabetes was highest in self-identified Indian men and women (26.2 and 26.8%, respectively), followed by self-identified coloured adults (men 12.6 and women 12.2%), then by self-identified black men and women (9.6 and 9.7%, respectively) and then by self-identified white adults (men 9.5% and women 6.8%). A smaller study (n = 317, age 45 ± 9 years) by Malan et al. (2013), reported an HbA1c ≥ 5.7% in 68.8% in self-identified black men, 47.3% in self-identified black women, 44.1% in self-identified white men and 20.7% in self-identified white women.169 Few studies have compared prevalence data between urban and rural populations, with only data from the WHO-SAGE study (n = 3 280; > 50 years of age) reporting a prevalence of self-reported diabetes of 11.1% in urban and 5.6% in rural samples.170 Data from the same study but including adults over 18 years of age (although 95.1% were over 40 years of age), reported a risk ratio for diabetes of 3.36 (1.92–5.74) in urban compared to a rural population.63 The same study also compared a migrant population group to a rural group and found no significant differences in diabetes risk. Using self-reported diabetes data from the Quality of Life Survey from the Gauteng province (n = 280 087; over 18 years of age), Motlhale et al. (2019) showed that being a migrant (internal or external) was associated with a
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