Introduction and the Literature review
1.3 The Literature Review
1.3.3 Cardiovascular risk in South Africans
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16 and low prioritisation of prevention strategies (Stewart et al., 2011) for CVD. However, it appears that the overburdened and underfunded Healthcare system still struggles to cope even with HIV/AIDs and poverty-related diseases, and is cause for concern as mortality rates amongst South Africans for DM and CVD are also on the rise (Mayosi et al., 2009). Since it is well established that CVD is largely preventable (Pearson et al., 2003) if population-wide interventions are initiated, it is logical that attempts to investigate the prevalence of CVD in these high-risk populations should be renewed, with a view to implement strategies that will stem the tide of the CVD epidemic.
Several studies have been done in South Africa, looking at the CV risk factor profile of Blacks and Caucasians, where a general trend of increasing prevalence of obesity has been documented (Mbanya et al., 2010; Mayosi et al., 2009; Puoane et al., 2002). A study by Kalke & Joffe (2007) showed that the prevalence of CAD in Africans was 4%, attributed to the contribution of low total cholesterol and the effects of insulin resistance, as compared to 23% prevalence in the White population. They projected that this prevalence was on the increasing trend, as the effects of urbanisation and a sedentary lifestyle translated into high-cholesterol diets and insulin resistance. This was also evident in an urban community in Mamre, near Cape Town, where subjects were reported to be at a high probability of suffering a CVD event in the next 10 years (Steyn et al., 2004).
Although the Asian Indian population is known to be high-risk for CVD, there is very limited data available on community-based evaluations of traditional CVD risk factors.
17 1.3.3.1 CARDIOVASCULAR RISK IN SOUTH AFRICAN ASIAN INDIANS
There are approximately 1.2 million Asian Indians currently living in South Africa (Stats SA P0302, 2011), who make up approximately 2.5 % of the total population. It has been established that the leading causes of morbidity and mortality in the Asian Indian community is related to CAD and other CV complications (Seedat et al., 1990). This community-based survey in the Durban metropolitan area documented the prevalence of CV risk factors in 778 subjects between 15 and 69 years of age, and found that the prominent risk factors were hypercholesterolemia, hypertriglyceridemia, DM, and smoking in men. A later study by Motala et al. (1993) reported that there was a high risk for the progression of impaired glucose tolerance to overt DM in Indian subjects in South Africa. The high prevalence of risk factors and the severe nature of coronary heart disease (CHD) in the South African Indian population lead these researchers to recommend an immediate and intensive primary prevention programme of CHD risk factors. To date, as far as we are aware, no such programme has been initiated.
The initial epidemiological study on hypertension in the South African Indian community was performed in 1978 by Seedat et al., who reported a prevalence of 19% (higher in females than males). A later study in 1988 by Omar et al. documented the prevalence of hypertension as 14.2% and DM as 9%. In yet a later study, these researchers documented an increase in the prevalence of DM in the South African Indian community (11%), with glucose intolerance found in 5.8% of the sample in Chatsworth, Durban (Omar et al., 1993). These two risk factors (hypertension and DM), coupled with urban
18 lifestyle patterns and sedentary habits, have consequently been suggested as the reasons for the excess in coronary heart disease in the South African Indian community (Seedat, 1994), although Sewdarsen et al. (1987) found that dyslipidaemia and obesity were also major contributory factors. This large study by Sewdarsen et al. (1987) compared fasting serum lipid and lipoprotein levels in 620 consecutive male survivors of myocardial infarction with those of 524 healthy male volunteer controls. Hypercholesterolemia was reported as the most common abnormality (25%), with obesity being significantly more common in patients with hypertriglyceridemia. Type 2 Diabetes Mellitus and hypertension were observed more commonly in patients with combined hypercholesterolemia and hypertriglyceridemia, illustrating a pattern of clustered risk factors. Later studies of subjects in this population group identified smoking and a positive family history for CAD (Ranjith et al., 2002) as common risk factors for CAD. More recent evidence from Ranjith et al. (2008) suggests that genetic polymorphisms may have an impact on the phenotypic expression of the metabolic syndrome in young Asian Indian males presenting with acute myocardial infarction. Since the interplay between genetic abnormalities and the response to environmental factors could not be clearly established, the study authors strongly recommended further studies of other genes involved in lipid metabolism and insulin resistance. Since then, further evaluations have not been performed on community subjects in the Asian Indian population in Durban.
The high prevalence of hypertension and DM, coupled with their comorbid complications in all the communities in South Africa places a high burden on the resources of the public
19 health sector. In fact, risk factor clustering has been reported to increase an individual’s risk for the development of CVD, and is becoming a frequent clinical finding as the young and ageing population becomes exposed to the effects of the socio-economic transition.