Simon Stewart
Australian Catholic University, Melbourne, Victoria, Australia
It is now well established that urban communities in sub-Saharan Africa, unlike rural populations in whom traditional lifestyles are more often preserved, are undergoing various epidemiologic transitions [1–3] with the emergence of noncommunicable forms of heart disease (see Chapter 6) [4–6]. As described in Section 4, this has meant a relative decline in communicable forms of heart disease. The central paradox around the phenomenon of epidemiological transition is that despite increasing longevity, there is increased exposure to potentially devastating chronic disease in those who have escaped the traditional killers such as malnutrition and infectious disease; sometimes there is a legacy effect (e.g., late-stage RHD [7]—see Chapter 7) that leaves an individual more prone to develop chronic, noncommunicable disease later in life [8]. Unlike high-income countries in whom aging populations have already been exposed to a high burden of antecedent risk for decades, with peak (age-adjusted) rates of heart disease long passed [9–11], it appears sub-Saharan Africa is only just entering into a new era of noncommunicable disease where heart disease will play a major role. However, it would be a mistake to assume that this diverse and populous region will follow the exact same pathway. We already know that younger generations in high-income countries are exposed to different patterns of antecedent risk (i.e., obesity and metabolic disorders including type 2 diabetes [12]) due to changing lifestyles (including sedentary behaviors [13]). We also know that older generations are exposed to a more compressed phase of debilitating chronic disease (including CHF [14,15] and AF [16,17]). Consequently, successful strategies (and even treatments such as the polypill with a strong focus on lipid-lowering therapy [18]) from the past and/or applied to high-income populations and patient cohorts to prevent and treat heart disease do not readily apply in the sub-Saharan Africa context.
From a primary prevention perspective, a simple truism holds true—before you develop cost-effective, primary prevention strategies you must understand the prevalence of underlying risk in the target population. This includes understanding the “intensity” of risk not only in terms of numbers affected but the spectrum and complexity of risk values and coexisting risk factors. Beyond a “Westernized” perspective of risk (i.e., the all-encompassing Framingham Study [19]) it is important to accept that different populations may well have different pathways to heart disease; this alternative perspective is never more striking than considering the case of heart disease in Africa [20].
In this section of the Heart of Africa, we highlight a number of studies that have, over a relatively short period of time, highlighted the contemporary burden of underlying risk of noncommunicable forms of CVD in the region and the evolving spectrum of disease that has now emerged in a number of representative communities. As noted in the preface, we do not purport to provide the reader of this book with a definitive review of a healthy growth in the African literature (that will perhaps come with future editions of the book), representing an increasing area of research activity. Rather, we highlight key studies that have contributed to our current knowledge in this regard, noting the importance of previous and ongoing studies such as the sub-Saharan Africa Survey of Heart Failure (THESUS-HF) [21], the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) Study [22–24], the Transition and Health during Urbanisation of South Africans (THUSA) Study [20,25,26], and the Cardiovascular Risk in Black South Africans (CRIBSA) Study [27–29].
In Chapter 4 we summarize risk surveillance data from the community of Soweto in South Africa in addition to Abia State in Nigeria, providing important insights into the likely increase in noncommunicable forms of heart disease throughout sub-Saharan Africa. In Chapter 5, we present the results of one of the most important studies undertaken from a pan-African perspective (the African INTERHEART study), demonstrating common pathways to AMI from a global to African-specific basis. Last, Chapter 6 summarizes the multiple facets of the Heart of Soweto Study based at the Baragwanath Hospital in Soweto, outlining the broad spectrum of communicable versus noncommunicable forms of heart disease now evident in the urban African context.
Section 3 of this book sees a return to Soweto, South Africa, in Chapters 4 and 6 (see Section 1 for snapshots of South Africa and Soweto). Chapter 4 also familiarizes us with Nigeria, various regions of which will feature again in Section 6. In Chapter 5, eight diverse African countries are represented in the multisite INTERHEART study.
Nigeria, located in West Africa, is the continent’s most populous country, with 181,562,056 inhabitants and an annual population growth rate of 2.45% [30]. It is home to more than 250 ethnic groups, the most populous and politically influential being the Hausa, Fulani, Yoruba, and Igbo, which together account for almost 70% of the population [30]. English, Hausa, Yoruba, Igbo, and Fulani are thus the most common languages, with over 500 additional indigenous languages also in use. Urbanization is occurring rapidly in Nigeria, with 47.8% of the population currently identified as urban and a 4.66% rate of change per annum [30]. Although the last official poverty statistics (2010) estimated that 46% of Nigerians live below the poverty line, a recent update by the World Bank suggested that this figure might have improved to 33% [31]. However, individual poverty, shortages of heath personnel, and inadequate pharmaceutical and medical supplies continue to impede access to timely and quality health care despite this economic growth [32]. Life expectancy remains low at 53 years, and Nigeria has the world’s tenth-highest rate of infant mortality at almost 74 deaths per 1000 live births [30].
Abia State, the specific Nigerian setting of Chapter 4, is situated in the southeastern portion of Nigeria. Segmented into urban and rural sections, the state has a population of more than 3 million inhabitants, 70% of whom are concentrated in the rural regions [33] and 60% of whom are estimated to live below the poverty line [34]. Difficulties at the system level and a critical lack of resources continue to affect the availability and quality of health services and supplies in Abia State [33].