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Population Screening for Heart Disease inVulnerable Populations: Lessons from

the Heart of Soweto StudySimon Stewart ∗

Baker IDI Heart and Diabetes Institute, PO Box 6492, St Kilda Road Central, Victoria 8008, Australia

This article reviews the progress of the largest study of heart disease in Africa to date – the Heart of Soweto Study.Moreover, it discusses the relevance of this study in respect to population screening in vulnerable populations. Thisincludes Indigenous Australians living in communities that are remote from mainstream health care services.

(Heart, Lung and Circulation 2009;18:104–106)© 2009 Published by Elsevier Inc on behalf of Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac

Society of Australia and New Zealand.

Keywords. Heart disease; Population screening; Africa and Indigenous Australia

Background

Tpresented data that suggest that heart disease repre-

he causes and consequences of an epidemic of car-diovascular disease (CVD) and its major component,

heart disease, in the Western world are well known.In contrast, there is a paucity of data to describe the

emergence and impact of CVD in low to middle-incomecountries to pose a triple threat alongside the traditionalkillers of malnourishment and infectious disease. This isparticularly true in vulnerable populations where modifi-able risk factors have been previously rare and health careresources already over-burdened. The potential impact ofdifferent stages of epidemiologic transition is particularlyevident in South Africa. Although there is a sustained epi-demic of HIV/AIDS epidemic responsible for 41% and 64%of the causes of death for men and women aged 15–44years, coronary artery disease (CAD), hypertensive heartdisease and stroke already account for more than a thirdof deaths in those aged >65 years [1].

It is within this context that we established the Heartof Soweto Study to monitor, describe and respond to theevolving burden of heart disease in one of Africa’s largesturban concentrations of Black Africans [2]. The establish-ment of a rigorous program of research in this setting has,perhaps surprisingly, important lessons for the parallel

sents an emerging epidemic in urban South Africa dueto economic changes leading to increased susceptibility tonon-communicable forms of cardiovascular disease. Thisoutcome is consistent with the overall mission of this pro-gram of research:

The primary goal of the “Heart of Soweto Study” is tosystematically examine and respond to the epidemiologictransition in risk behaviours and clinical presentations ofheart disease in the internationally renowned and cele-brated community of Soweto, South Africa [2]

Key Findings

Thus far, we have generated key findings from two mainareas of activity. Firstly, a community screening program inSoweto (2006/2007) and secondly via the establishment ofa clinical registry at the 3500 bed Chris Hani BaragwanathHospital involving systematic screening with echocardio-graphy (2006 to date).

In a series of Heart of Soweto Awareness Days weundertook community screening of voluntary participants(>2000 subjects) and found that only 22% of participantshad no risk factor for CVD. Moreover, awareness rates of

development of research in disadvantaged and resourcepoor, Indigenous communities in Australia.

heart disease and its risk factors were extremely low. Mostparticipants (99%) were Black African, there were morewomen (65%) than men and the mean age was 46 ± 14

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Mission Statement

In a series of preliminary reports from what is nowregarded as a seminal study in the field [3], we have

Available online 27 February 2009

∗ Tel.: +61 8 8532 1111; fax: +61 8 8532 1100.E-mail address: simon.stewart@bakeridi.edu.au.

© 2009 Published by Elsevier Inc on behalf of Australasian SSurgeons and the Cardiac Society of Australia and New Z

years. Overall, 78% of subjects had ≥1 major risk factorfor heart disease: the most common risk factor was obe-sity (43%) with significantly more obese women than men(23% versus 55%: OR 1.76, 95% CI 1.62–1.91: p < 0.001). Afurther 33% of subjects had high blood pressures and 13%an elevated (non-fasting) total blood cholesterol level [4].

Since 2006, the Heart of Soweto Clinical Registry hascaptured detailed clinical data on more than 5000 de novo

ty of Cardiac and Thoracicnd.

1443-9506/04/$36.00doi:10.1016/j.hlc.2009.01.003

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Heart, Lung and Circulation Stewart 1052009;18:104–106 CVD in vulnerable population

presentations of heart disease. In 2006, for example, weidentified a total of 1593 newly diagnosed cases (38% oftotal case load in 2006) with a broad range of cardiovascu-lar disease states: predominantly advanced heart disease.Overall, Black Africans (85%) and women predominated(60%). Unlike high-income countries, women were slightlyyounger than men (mean age 53 ± 16 versus 55 ± 15 years:p = 0.031) with almost a quarter of cases aged <40 years old.Heart failure (HF) was the most common primary diagno-sis by far (44% of total cases)–see below. Black Africanswere far more likely to be diagnosed with heart failure(OR 2.36, 95% CI 1.74–3.21: p < 0.0001) but far less likely tobe diagnosed with coronary artery disease (OR 0.10, 95%CI 0.07–0.14: p < 0.0001). Consistent with our communityscreening data, the prevalence of modifiable cardiovascu-lar risk factors was very high with 56% of cases diagnosedwith hypertension (47% of which were also obese): only13% of cases had no identifiable risk factors while almosttwo thirds had multiple risk factors [5].

The predominance of advanced forms of heart disease isencapsulated by the contribution of HF. In 2006, there werea total of 1960 cases of HF and related cardiomyopathies(CMO) and 844 of these were de novo presentations (43%).Mean age was 55 ± 16 years while women (479 [57%]) andBlack Africans (739 [88%]) predominated. Most (761 [90%])had ≥1 cardiovascular risk. Mean left ventricular ejec-tion fraction was 45 ± 18%. Overall, 180 (23%) patients hadigrtalbOa(

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Figure 1. Key achievements in the Heart of Soweto Study.

ing to responding). This plan is summarised by Fig. 1.For example, we have recently commenced an African-specific trial of HF management to improve outcomes inpatients presenting to the hospital with advanced formsof the syndrome. We have also undertaken detailed stud-ies of the nexus between HIV infection, its treatment andacute coronary syndromes.

The Future

Extending community surveillance beyond our initialapproach is highly problematic relative to high-incomecountries due to a lack of basic infrastructure andresources. Pending future plans to establish a populationcohort study to definitively study the natural history ofheart disease, a logical and prospectively planned compo-nent of the Heart of Soweto Study is the establishment of aclinical registry in primary care to monitor the spectrum,burden and management of CV risk factors and milderforms of heart disease in the community setting. Fig. 2shows our progressive efforts to fill-in the “gaps” in ourknowledge about the spectrum of heart disease in thissetting.

Implications for Indigenous Research

A key question, of course, is whether our efforts to betteruoSsT

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solated diastolic dysfunction, 234 (28%) tricuspid regur-itation, 121 (14%) isolated right HF and 100 (12%) mitralegurgitation. The most common diagnoses were hyper-ensive HF (281 [33%]), idiopathic dilated CMO (237 [28%])nd, surprisingly, right HF (225 [27%]). Black Africans hadess ischaemic CMO (adjusted OR 0.12, 95% CI 0.07–0.20)ut more idiopathic and other causes of CMO (adjustedR 4.80, 95% CI 2.57–8.93). Concurrent renal dysfunction,

naemia and atrial fibrillation were found in 172 (25%), 7210%) and 53 (6.3%) cases, respectively [6].

These data have highlighted a broad spectrum of pre-ominantly advanced forms of heart disease not usuallyssociated with African communities. The phenomenonf epidemiologic transition is clearly playing a key role

n changing the overall burden and spectrum of non-ommunicable forms of heart disease in Soweto andotentially other parts of sub-Saharan Africa.

utting Heart of Soweto in Perspective

n order to study and understand the evolving problemf heart disease in Soweto, we have developed a strategiclan to steadily document and respond to this problem viaparallel program of capacity building (both in terms ofeople and facilities) and research studies (from count-

igure 2. Progressive understanding of heart disease in Soweto.

nderstand the evolution of heart disease in Soweto andther parts of Africa (as part of the future Heart of Africatudy) has any relevance to our efforts to better under-tand heart disease within our Indigenous communities.he parallels are, in fact, quite striking. These include:

A background of infectious disease and communicableforms of heart disease.

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• Development of early more aggressive forms of heartdisease.

• Late detection and treatment.• A need to “act” and develop health care resources rather

than just “count” and measure the problem.• Considerable capacity development required to address

a historical lack of local clinical researchers.

Overall, both settings require a unique perspectiveand solutions rather than relying upon clinical solutionsdesigned for mainstream populations in high-income,urban areas.

Clearly, the parallels are not complete, given thatSoweto represents a “time machine” that reflects the evo-lution of heart disease in previously virgin territory, whileour Indigenous communities have been exposed to theantecedents for heart disease for quite some time. Never-theless, any successful strategies developed at either endof the Southern Hemisphere are likely to have importantlessons for the other. The relative potency of underlyinginfectious disease/inflammation and genetic susceptibil-ity to relatively “new” insults to the cardiovascular systemmay well bring the research undertaken in these two com-munities closer together in the future.

References

[1] In Steyn K, Fourie J, Temple N, editors. Chronic diseases oflifestyle in South Africa: 1995–2005. Medical Research Council-technical report. Cape Town: South African Medical ResearchCouncil; 2006. p. 1–266.

[2] Stewart S, Wilkinson D, Becker A, Askew D, Ntyintyane L,McMurray JJ, Sliwa K. Mapping the emergence of heart dis-ease in a black, urban population in Africa: The Heart of SowetoStudy. Int J Cardiol 2006;108:101–8.

[3] White HD, Dalby AJ. Heart disease in Soweto: facing a triplethreat. The Lancet 2008;371:876–7.

[4] Tibazarwa K, Ntyintyane L, Sliwa K, Gerntholtz T, CarringtonM, Wilkinson D, Stewart S. A time bomb of cardiovascular riskfactors in South Africa: results from the Heart of Soweto Study“Heart Awareness Days”. Int J Cardiol 2009;132:233–9.

[5] Sliwa K, Wilkinson D, Hansen C, Ntyinyane L, Tibazarwa K,Becker A, Stewart S. A broad spectrum of heart disease andrisk factors in a black urban population in South Africa: resultsfrom The Heart of Soweto Study Clinical Registry. The Lancet2008;371:915–22.

[6] Stewart S, Wilkinson D, Hansen C, Vaghela V, Mvungi R,McMurray J, Sliwa K. A predominance of heart failure in theHeart of Soweto Study cohort: emerging challenges for urbanAfrican communities. Circulation 2008;118:2360–7.