A time bomb of cardiovascular risk factors in South Africa: Results from the Heart of Soweto Study “Heart Awareness Days”

Abstract

Background

There is strong anecdotal evidence that many urban communities in Sub-Saharan Africa are in epidemiologic transition with the subsequent emergence of more affluent causes of heart disease. However, data to describe the risk factor profile of affected communities is limited.

Methods

During 9 community screening days undertaken in the predominantly Black African community of Soweto, South Africa (population 1 to 1.5 million) in 2006–2007, we examined the cardiovascular risk factor profile of volunteers. Screening comprised a combination of self-reported history and a clinical assessment that included calculation of body mass index (BMI), blood pressure and random blood glucose and total cholesterol levels.

Results

In total, we screened a total of 1691 subjects (representing almost 0.2% of the total population). The majority (99%) were Black African, there were more women (65%) than men and the mean age was 46 ± 14 years. Overall, 78% of subjects were found to have ≥ 1 major risk factor for heart disease. By far the most prevalent risk factor overall was obesity (43%) with significantly more obese women than men (23% versus 55%: OR 1.76 95% CI 1.62 to 1.91: p < 0.001). A further 33% of subjects had high blood pressures (systolic or diastolic) and 13% an elevated (non-fasting) total blood cholesterol level: no statistically significant differences between the sexes were found. There was a positive correlation between increasing BMI and other risk factors including elevated systolic (r² = 0.046, p < 0.001) and diastolic blood pressure (r² = 0.032, p < 0.001) with overweight subjects three times more likely to have concurrent hypercholesterolemia (OR 3.3, 95% CI 2.1 to 5.3: p < 0.01).

Conclusions

These unique pilot data strongly suggest a high prevalence of related risk factors for heart disease in this urban black African population in epidemiologic transition. Further research is needed to confirm our findings and to determine their true causes and potential consequences.

Introduction

In Africa, cardiovascular disease (CVD) and its most common form in the western world (heart disease) is traditionally caused by non-ischaemic pathology; led primarily by cardiomyopathy, rheumatic heart disease, and less so by tuberculous pericarditis and pulmonary heart disease.[1] However, there is emerging evidence in sub-Saharan Africa, both in respect to mortality [2] and morbidity [3], [4] rates, that CVD is both an increasing and evolving public health issue in the region. For example, the incidence of coronary heart disease (the most common form of CVD in the developed world) appears to be increasing [5] and hypertension has become a common cause of heart failure [5], [6].

Traditionally in Africa [7] and across the world, obesity was observed in the minority affluent groups who could afford sedentary lifestyles with high dietary sugar intake [8]. As late as the 1940s, hypertension was almost non-existent in non-Western populations [8]. Since then, introduction of Western culture and diet accounts for the greatest relative increase in hypertension, obesity, and diabetes observed in groups of lower socioeconomic support [8]. While considerable research in African-Americans implicates uricaemia (from increased fructose ingestion or low birth weight) as well as higher socioeconomic stress levels in the early pathogenesis of the high incidence of hypertension, obesity, and diabetes [8], very little such comparable data exists for Black Africans. It is known that hypertension in Black Africans occurs at a younger age, being more severe, and leading to earlier damage to vital organs [8], [9]. Moreover, there is a strong possibility that Black Africans differ in their therapeutic response to anti-hypertensive therapy predominantly tested and proven in Caucasian cohorts [10]. However, systematic studies of heart disease and other forms of CVD (most notably the THUSA Study) and its antecedents have been largely confined to rural communities. [11], [12], [13], [14], [15], [16], [17]

It is within this context that the “Heart of Soweto” Study (the purpose and methods of which have been previously described [18]), was initiated to establish the baseline profile of heart disease and its antecedents in the population of Soweto. Soweto is the largest urban residential area of predominantly Black Africans in South Africa. A major sub-study of this large project was “Heart Awareness Days”. In addition to visibly engaging the local community and raising awareness of heart disease in the process, the principle objective of our voluntary community-based screening program was to estimate the underlying prevalence of the most common risk factors of heart disease (e.g. hypertension, potential metabolic syndrome and lipid abnormalities) within the local population.