Cardiovascular disease prevention in the slums of Kenya

ISBN: 978-94-6169-753-0

Cover design: Nico Richter
Cover photograph: above overview of Korogocho and below testing pilot at Ngomongo with background of Dandora dumpsite. APHRC/Steven van de Vijver

Copyright: Steven van de Vijver, 2015.
All rights reserved. No part of this publication may be reproduced, stored or transmitted in any forms or by any means, without written permission of the author.

Voor Joep

Abbreviations

AIDS

Acquired Immune Deficiency Syndrome

AIGHD

Amsterdam Institute for Global Health and Development

AMC

Academic Medical Center

APHRC

African Population and Health Research Center

AU

African Union

BMI

Body Mass Index

BP

Blood Pressure

CHW

Community Health Worker

CI

Confidence Interval

CVD

Cardiovascular Disease

DALY

Disability Adjusted Life Year

DBP

Diastolic Blood Pressure

DM

Diabetes Mellitus

DSA

Demographic Surveillance Area

ID

Identity

LMIC

Low and Middle Income Country

LSM

Lifestyle Modification

NCD

Non-Communicable Disease

NGO

Non-Governmental Organization

NUHDSS

Nairobi Urban Health Demographic Surveillance System

OR

Odds Ratio

PHC

Primary Health Care

QALY

Quality Adjusted Life Year

RBS

Random Blood Sugar

SD

Standard Deviation

SMS

Short Message Service

SSA

Sub-Saharan Africa

UN

United Nations

USD

United States Dollar

WHA

World Health Assembly

WHO

World Health Organization

WHS

World Health Survey

Chapter 1

General introduction

CARDIOVASCULAR DISEASE: GLOBALLY, IN LOW AND MIDDLE INCOME COUNTRIES, AND IN AFRICA

Cardiovascular diseases (CVD) are the leading cause of death worldwide. In 1990 more than 25% of all global death was attributed to CVD, and this has grown in the last decades to more than 30% in 2013 [1]. It is estimated that in 2030 more than 23 million people will die on a yearly basis due to CVD, which includes ischemic heart disease, stroke, hypertensive heart disease, cardiomyopathy, rheumatic heart disease, aortic aneurysms, atrial fibrillation, congenital heart disease, endocarditis, and peripheral artery disease, among others [2].

There are several risk factors identified for developing CVD which includes: high blood pressure, diabetes, obesity, smoking, insufficient physical exercise and unhealthy diet. The burden of most CVD risk factors has increased significantly on a global scale in the last few decades [3]. For example the burden of high blood pressure, otherwise known as hypertension, has increased 27% in the period between 1990 and 2010, leading to close to one million casualties. The growth was even stronger for other risk factors like diabetes or high glucose levels being 58%, and overweight or obesity even reaching 82% [3].

Until recently, CVD was mainly associated with more affluent regions of the world. However, more than 80% of the overall burden of CVD is situated in low and middle-income countries (LMICs)[4, 5]. Mortality of CVD is decreasing in high income countries, like for example Denmark, Israel, Norway, UK and South Korea where death due to ischaemic heart disease reduced by more than 65%. However CVD is rising in almost every LMIC, where health resources are scarce and stretched by a high burden of infectious diseases such as HIV, malaria and tuberculosis [4].

Traditionally in Africa, communicable diseases and maternal, perinatal and nutritional conditions accounted for the greatest burden of morbidity and mortality [6]. This burden is fast shifting towards non- communicable diseases (NCDs), particularly CVDs. This phenomenon is what is being termed as a “double burden of disease”[7]. Between 1990 and 2013 the mortality burden of CVD in SSA has increased 81% [8]. While in other continents ischaemic heart disease is the main contributor to CVD deaths, stroke is causing most deaths in SSA. This is mainly due to hypertension and its related complications [9, 10], of which the population in SSA is more at risk partly due to their (epi) genetic background [11].

Whereas high blood pressure was estimated to be almost non-existent in African societies in the first half of the twentieth century [12], studies now show that in some settings in Africa close to 40 percent of adults have hypertension [13]. Similar trends are seen with other cardiovascular risk factors. As the continent has always been associated with hunger and malnutrition, the percentages of adults being underweight are now heavily outnumbered by Africans with overweight or obesity [14]. In some settings this has even led to populations where the majority is overweight or obese, especially among women [15]. Diabetes shows an identical situation where prevalence rates in some regions have even reached 12%, and the total amount of people with diabetes on the continent is expected to increase from 12.1 million in 2010, towards 23.9 million in 2030 [16].

EPIDEMIOLOGICAL TRANSITION

Health and disease patterns change over time in societies depending on the population structure and the rate of economic development, to result in the so-called epidemiological transition [17]. As societies develop, although communicable diseases such as tuberculosis prevail, NCDs become more prevalent. This is a result of changes in environmental and behavioral determinants such as increasing tobacco use, increasing fat and calorie consumption, and decreasing physical activity and longer periods of exposure to these determinants because of longer life expectancy. Whereas European and North American populations experienced similar changes in demography, determinants, and disease rates over the course of a century, African populations are passing through similar transitions in just a few decades [18].

While the rates of morbidity and mortality vary considerably across the African continent, at least one clear pattern is emerging that holds across most of Africa: a steady rise in NCDs, and more specifically CVD, in the presence of significant, long-standing infectious disease prevalence. The epidemiological transition is related as well to the urbanization with acculturation and modernization of lifestyle and therefore increasing CVD risk factors like hypertension as observed in Kenyan studies [19].

URBANIZATION IN AFRICA

In 2007 it was the first time that the majority of the global population was living in cities. This trend of urbanization will continue in the nearby future as 95% of the projected increase of 1,9 billion in the world population by 2025, will be living in cities [20]. Urbanization is happening on a global scale, with Africa having the highest rate of all continents [21]. The African urban population is expected to triple from 395 million in 2009 to 1.23 billion in 2050. Some African capitals like Nairobi, Kampala and Niamey will grow around 50% in the current decade, with exceptions like Ouagadougou’s projected 81% increase from 1.9 million in 2010 to 3.4 million in 2020 [21].

Globally the amount of people living in slums is estimated to be close to one billion [22], with a relatively high contribution from the African continent where currently between 60-70% of the urban population is living in slums [23]. The proportion of slum dwellers on the continent might even get higher than the currently estimated as the slum growth rate is higher than the overall urban rate [21]. The living conditions in poor urban settlements have a major impact on health and health care [24]. Besides changes in diet and physical activity there are also the psychosocial constraints of violence, insecurity and stress which leads to an increased risk of cardiovascular disease [25, 26]. The levels of risk factors like hypertension are higher in urban than in rural settings on the African continent [27, 28] mainly because of earlier mentioned contextual and behavioral factors associated with urban environments. However there is not much research on the health problems and cardiovascular risk in the slum settings [29]. As Africa becomes more urbanized, likewise the burden of CVD will increase, and the need for effective interventions.

PREVENTION AND INTERVENTION PROGRAMS

For a long time, the priority in most African health care systems has been the prevention and control of communicable diseases. With the earlier mentioned shift in disease burden, the attention has begun to shift to the control and prevention of NCDs like CVD. Within the context of limited resources due to double burden of disease, the greatest gains in controlling the CVD epidemic lie in its prevention, or at least early detection and adequate control of relevant risk factors. For most countries in the region the major obstacle to the control and management of CVD and related risk factors is the absence of appropriate services at the primary health care levels of the health service delivery system. One of the solutions might be placed in the community based approach and its community health workers (CHWs) who are well represented on the continent and are showing some encouraging results already [30].

The Institute of Medicine Report on cardiovascular health in the developing world stresses the need for evidence and best practices for cost-effective and sustainable community based strategies for prevention and control of cardiovascular risk factors [31]. Although several documents have been published on recommendations and advices for cardiovascular prevention in LMICs ([32, 33], they have often lacked practical real-life application, specifically for the growing slum settings in Africa. Therefore it is essential to develop, implement and evaluate effective strategies for prevention of CVD for the urban poor on the continent. We hoped to address this knowledge gap with our SCALE UP Study (Sustainable model for Cardiovascular health by Adjusting Lifestyle and treatment with Economic perspective in settings of Urban Poverty). This is a collaborative study of the Amsterdam Institute for Global Health and Development (AIGHD) and the African Population and Health Research Center (APHRC).

RESEARCH SETTING AND STUDY POPULATION

The SCALE UP study took place in two slum communities in Nairobi, the capital of Kenya. Both slums, Korogocho and Viwandani are located on the eastern side of town. Korogocho is situated more in the north-eastern part of Nairobi with a distance of 12 kilometers of the city center, whereas Viwandani is in the south-eastern region of town with a distance of 7 kilometers from the city center.

Korogocho covers an area of less than 1 square kilometer but has a population of around 35,000 inhabitants which makes it one of the most densely populated slums in Nairobi. Korogocho has a stable population and majority of its residents have lived in the area for many years. Viwandani is slightly smaller than Korogocho with approximately 30,000 residents of whom most of them are young and highly mobile, working or seeking jobs within the nearby industrial area.

As most other slums in Nairobi, the two communities are characterized by lack of social amenities, relatively high crime rates, high unemployment rates and extreme poverty. Most inhabitants in Korogocho and Viwandani are dependent on private health care facilities, which are unregulated and often run by unqualified personnel, as public health facilities are rare [34]. Access to private health facilities in turn increases patient’s out of pocket expenditures since 90% of the slum population do not have health insurance cover [35].

Both communities are situated within the Nairobi Urban Health and Demographic Surveillance System (NUHDSS), which was founded by the APHRC almost fifteen years ago. It was set up as the first urban-based longitudinal health and demographic surveillance platform in Africa [36]. The NUHDSS was set up to provide a platform to investigate the inter-linkages between urban poverty and health, monitor and evaluation of intervention programs implemented within the study communities and provide a sampling frame for nested studies.

RESEARCH OBJECTIVES

The aim of this thesis was to study the burden of cardiovascular risk factors in the urban slums, and the development and implementation of an intervention for prevention of CVD.

The research objectives of the thesis were:

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To assess the burden of cardiovascular risk factors like hypertension, diabetes, obesity among others in the urban slums of Nairobi

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To define and design a sustainable and cost-effective community-based intervention for prevention of CVD in the urban slums

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To implement and evaluate the newly designed CVD intervention in the urban slums

OUTLINE OF THE THESIS

The thesis comprises three parts that include a background of studies on the burden of CVD risk factors (Part I), the development of the intervention (Part II) and the implementation and evaluation of the intervention (Part III).

Part I Background

The first part of the thesis describes the burden of CVD risk factors on the African continent and more specifically the urban slums of Nairobi, in four chapters. We start in Chapter 2 with an overview of the definition, prevalence and management of hypertension and other related risk factors like diabetes, obesity among others in Africa. In Chapter 3 we focus on the slums of Nairobi and assess the prevalence, awareness, treatment and control of hypertension among the population. Subsequently in Chapter 4 we study the prevalence of diabetes and its association with obesity in the same settings. In Chapter 5 we assess the situation of overweight and obesity and its relationship with the perception of body image in the slums of Nairobi.

Part II Intervention

The second part focuses on the development of a sustainable and cost-effective CVD intervention in urban slums. In Chapter 6 we review a variety of community-based interventions for prevention of CVD in LMICs. Chapter 7 describes the development of our multi-component community-based intervention through the integration of a public health and private-sector approach. In Chapter 8 we describe the study protocol of our study in which we aim to evaluate the impact of our intervention. Part III Implementation and evaluation

The third part expands on the implementation and evaluation of the intervention for prevention of CVD in the urban slums. In Chapter 9 we discuss the challenges with health programs in urban slums, with some specific examples from our intervention. In Chapter 10 we present the outcomes of the process evaluation including the costs of the CVD intervention. We report in Chapter 11 the outcomes of our impact evaluation of the intervention on hypertension and other CVD risk factors among slum dwellers. We demonstrate in Chapter 12 how our intervention designed for the urban slums in Nairobi might of use for migrants in Amsterdam.

Finally, Chapter 13 is a summary and general discussion of the main research findings of this thesis, followed by concluding remarks.

REFERENCES

1. GBD. Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet. 2015; 385 (9963):117-71.

2. WHO. Global Atlas on cardiovascular disease prevention and control. Geneva: WHO; 2011.

3. Lim SS, Vos T, Flaxman AD, Danaei G, Shibuya K, Adair-Rohani H, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990?2010: a systematic analysis for the Global Burden of Disease Study 2010. The Lancet. 2012; 380 (9859):2224-60.

4. Ibrahim MM, Damasceno A. Hypertension in developing countries. Lancet. 2012; 380 (9841):611-9.

5. Fuentes R, Ilmaniemi N, Laurakainen E, Tuomilehto J, Nissinen A. Hypertension in developing economies: A review of population-based studies carried out from 1980 to 1998. Journal of hypertension. 2000; 18:521-9.

6. Lopez A, Mathers C, Ezzati M, al e. Global burden of disease and risk factors. Washington, DC: Oxford University Press and World Bank; 2006.

7. Bygbjerg IC. Double burden of noncommunicable and infectious diseases in developing countries. Science (New York, NY). 2012; 337 (6101):1499-501.

8. Mensah GA, Roth GA, Sampson UK, Moran AE, Feigin VL, Forouzanfar MH, et al. Mortality from cardiovascular diseases in sub-Saharan Africa, 1990-2013: a systematic analysis of data from the Global Burden of Disease Study 2013. Cardiovascular journal of Africa. 2015; 26 (2 Suppl 1):S6-S10.

9. Walker RW, McLarty DG, Kitange HM, Whiting D, Masuki G, Mtasiwa DM. Stroke mortality in urban and rural Tanzania. Adult morbidity and mortality project. Lancet. 2000; 355:1684-7.

10. Mensah AG. Epidemiology of stroke and high blood pressure in Africa. Heart. 2008; 94:697-705.

11. Ding K, Kullo IJ. Geographic differences in allele frequencies of susceptibility SNPs for cardiovascular disease. BMC medical genetics. 2011; 12:55.

12. Donnison C. Blood pressure in the African natives: its bearing upon aetiology of hyperpiesa and arteriosclerosis. Lancet. 1929; 1:6-7.

13. Addo J, Smeeth L, Leon DA. Hypertension in sub-saharan Africa: a systematic review. Hypertension. 2007; 50 (6):1012-8.

14. Jones-Smith JC, Gordon-Larsen P, Siddiqi A, Popkin BM. Is the burden of overweight shifting to the poor across the globe? Time trends among women in 39 low- and middle-income countries (1991-2008). International journal of obesity (2005). 2012; 36 (8):1114-20.

15. Peer N, Lombard C, Steyn K, Gwebushe N, Levitt N. Differing patterns of overweight and obesity among black men and women in Cape Town: the CRIBSA study. PloS one. 2014; 9 (9):e107471.

16. Hall V, Thomsen RW, Henriksen O, Lohse N. Diabetes in Sub Saharan Africa 1999-2011: epidemiology and public health implications. A systematic review. BMC Public Health. 2011; 11:564.

17. Omran A. The Epidemiologic Transition: A Theory of the Epidemiology of Population Change. The Milbank Memorial Fund Quarterly. 1971; 49 (4):509-38.

18. The continuing epidemiological transition in sub-Saharan Africa: A workshop summary. In: Thomas JP, Kinsella K, editors.; 2012; Washington DC: The national academies press; 2012.

19. Poulter NR, Khaw KT, Hopwood BE. The Kenyan Luo migration study: Observations on the initiation of a rise in blood pressure. BMJ. 1990; 300:967-72.

20. Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat. World Population Prospects: The 2010 Revision and World Urbanization Prospects: The 2011 Revision. In: Nations U, editor.; 2011.

21. UN-Habitat. The State of African Cities 2010: Governance, Inequalities and Urban Land Markets. Nairobi: UN-Habitat; 2010.

22. UN-Habitat. Urban World: Ten years into the Millenium. Nairobi: UN-Habitat; 2010.

23. UN-Habitat. UN-Habitat and the Kenya Slum Upgrading Programme. Nairobi: UN-Habitat; 2008.

24. Ross CE, Mirowsky J. Neighborhood disadvantage, disorder, and health. Journal of health and social behavior. 2001; 42 (3):258-76.

25. Chambers EC, Duarte CS, Yang FM. Household instability, area poverty, and obesity in urban mothers and their children. J Health Care Poor Underserved. 2009; 20 (1):122-33.

26. Pawar AB, Mohan PV, Bansal RK. Social determinants, suboptimal health behavior, and morbidity in urban slum population: an Indian perspective. J Urban Health. 2008; 85 (4):607-18.

27. Damasceno A, Azevedo A, Silva-Matos C, Prista A, Diogo D, Lunet N. Hypertension prevalence, awareness, treatment, and control in mozambique: urban/rural gap during epidemiological transition. Hypertension. 2009; 54 (1):77-83.

28. Agyemang C. Rural and urban differences in blood pressure and hypertension in Ghana, West Africa. Public health. 2006; 120 (6):525-33.

29. Riley LW, Ko AI, Unger A, Reis MG. Slum health: diseases of neglected populations. BMC Int Health Hum Rights. 2007; 7:2.

30. Gaziano TA, Bertram M, Tollman SM, Hofman KJ. Hypertension education and adherence in South Africa: a cost-effectiveness analysis of community health workers. BMC Public Health. 2014; 14:240.

31. Institute of Medicine. Promoting Cardiovascular Health in the Developing World. Washington: The National Academies Press; 2001.

32. WHO. Cardiovascular diseases in the African region: current situation and perspectives. 2005.

33. Beaglehole R, Epping-Jordan J, Patel V, Chopra M, Ebrahim S, Kidd M, et al. Improving the prevention and management of chronic disease in low-income and middle income countries: A priority for primary health care. Lancet. 2008; 372:940-9.

34. Zulu EM, Beguy D, Ezeh AC, Bocquier P, Madise NJ, Cleland J, et al. Overview of migration, poverty and health dynamics in Nairobi City’s slum settlements. J Urban Health. 2011; 88 Suppl 2:S185-99.

35. Kimani JK, Ettarh R, Kyobutungi C, Mberu B, Muindi K. Determinants for participation in a public health insurance program among residents of urban slums in Nairobi, Kenya: results from a cross-sectional survey. BMC Health Serv Res. 2012; 12:66.

36. Emina J, Beguy D, Zulu EM, Ezeh AC, Muindi K, Elung’ata P, et al. Monitoring of health and demographic outcomes in poor urban settlements: evidence from the Nairobi Urban Health and Demographic Surveillance System. J Urban Health. 2011; 88 Suppl 2:S200-18.

PART I

BACKGROUND

Chapter 2

Status Report on hypertension in Africa: Consultative review for the 6th Session of the African Union Conference of Ministers of Health on NCD’s

Steven van de Vijver, Hilda Akinyi, Samuel Oti, Ademola Olajide,
Charles Agyemang, Isabella Aboderin, Catherine Kyobutungi

Pan African Medical Journal. 2013; Oct 5;16:38

Abstract

Background

Hypertension has always been regarded as a disease of affluence but this has changed drastically in the last two decades with average blood pressures now higher in Africa than in Europe and USA and the prevalence increasing among poor sections of society.

Methods

We have conducted a literature search on PubMed on a broad range of topics regarding hypertension in Africa, including data collection from related documents from World Health Organization and other relevant organizations that are available in this field. We have shared the initial results and drafts with international specialists in the context of hypertension in Africa and incorporated their feedback.

Results

Hypertension is the number one risk factor for CVD in Africa. Consequently, cardiovascular disease (CVD) has taken over as number one cause of death in Africa and the total numbers will further increase in the next decades reflecting on the growing urbanization and related lifestyle changes. The new epidemic of hypertension and CVD is an important public health problem in all African countries, with its prevalence of risk factors varying between different settings.

Conclusion

It is essential to develop and share best practices for affordable and effective community-based programs in screening and treatment of hypertension. In order to prevent and control hypertension in the population, Africa needs policies developed and implemented through a multi-sectoral approach involving the Ministries of Health and other sectors including education, agriculture, transport, finance among others.

BACKGROUND

Hypertension, otherwise known as high blood pressure, is a leading cause of cardiovascular disease (CVD) worldwide [1]. The proportion of the global burden of disease attributable to hypertension has significantly increased from about 4.5 percent (nearly1 billion adults) in 2000 [2], to 7 percent in 2010 [3]. This makes hypertension the single most important cause of morbidity and mortality globally and highlights the urgent need of action to address the problem [4]. Until recently, hypertension was mainly associated with more affluent regions of the world. However, the condition is increasingly emerging in low and middle-income countries (LMICs) [5] where health resources are scarce and stretched by a high burden of infectious diseases such as HIV, malaria and tuberculosis, and where awareness and treatment levels on hypertension control are still very low [6]. Currently, the worldwide burden of hypertension is greatest in LMICs where it affects about 1 in every 5 of the adult population and this is projected to increase [7]. By 2025, almost 3 out of every 4 people with hypertension will be living in LMICs where more than 80 percent of the world population lives. The absolute numbers affected by hypertension in LMICs are therefore considerably higher and are likely to increase as globalization and economic advancement usher in urbanization and longer life expectancy in these countries [8]. The prevalence of hypertension on the African continent has increased significantly over the past two to three decades [9]. There were approximately 80 million adults with hypertension in sub-Saharan Africa in 2000 and projections based on current epidemiological data suggest that this figure will rise to 150 million by 2025 [8]. Further, there is evidence that indicates that related complications of hypertension, and in particular stroke and heart failure are also becoming increasingly more common in this region [10, 11]. These trends have been strongly linked with changes in individual and societal lifestyle such as an increase in tobacco use, excessive alcohol consumption, reduced physical activity and adoption of ‘Western’ diets that are high in salt, refined sugar and unhealthy fats and oils.

PREVALENCE OF HYPERTENSION IN AFRICA

Hypertension prevalence data are crucial for understanding the magnitude of the problem, identifying groups at high risk for CVD, and evaluating the effects of interventions in policy and practice [12]. An increase in hypertension prevalence will invariably lead to dramatic rises in the incidence of CVDs and their consequences, which has the potential to overwhelm health care systems [13, 14]. It will also have financial implications for national and local treatment plans because there is increasing evidence that the majority of patients with hypertension will require two or more drugs to achieve blood pressure control [15].

Available data on hypertension prevalence are from a wide range of studies [7, 16], and this limits the opportunity for reliable comparison between different settings. There is heterogeneity in the studies including differences in sampling methods and study settings (predominance of health facility- based studies), the study population, measurement of blood pressure and definition of hypertension as well as the study time periods. Reliable, large-scale, population based data on hypertension in Africa are scarce [17]. In this section we describe the prevalence of hypertension and the determinants for high blood pressure in various settings in Africa garnered from the available published studies and from some nationally representative surveys.

The WHO STEPS survey conducted between 2003 and 2009 in 20 African countries reported high rates of hypertension in most countries, particularly among men (Figure 2). The prevalence ranges from 19.3% in Eritrea to 39.6% in Seychelles (32). The prevalence is for the adult population aged 18 years and above. For more country specific estimates see Figure 1. The prevalence is for the adult population aged 18 years and above. In Africa, hypertension is usually more pronounced in males than in females (11). However, in a few countries there were higher levels of prevalence in women than men such as in Algeria 31.6 percent vs. 25.7 percent in 2003, Botswana 37.0 percent vs. 28.8 percent in 2006 and Mali 25.8 percent vs. 16.6 percent in 2007, for women and men, respectively (see Figure 2).

Figure 1- Prevalence of Hypertension in Selected African Countries that Participated in the WHO-STEPS Surveys (2003 to 2009)

Figure 2- Prevalence of Hypertension by Sex in Selected African Countries that Participated in the WHO-STEPS Surveys (2003 to 2009)

Apart from sex differences in the prevalence of hypertension, there are also large differences based on residence. In all countries where data are available from the World Health Study (WHS), the urban population has a higher prevalence of hypertension than the rural population (see Figure 3). We used data from the WHS because those from the STEPS surveys are not disaggregated by area of residence.

Figure 3- Prevalence of Hypertension by Rural-urban Residence in Selected African Countries participated in the World Health Survey (2003)

In South Africa and Democratic Republic Congo, the urban has almost 10 percentage points higher prevalence than the rural population. This is in comparison to countries like Ethiopia and Tanzania where the prevalence is only a bit more than 5 percent higher. It is noteworthy that since countries are at different stages of the epidemiological transitions, there are some rural populations in some countries whose prevalence is higher than some urban populations in other countries. For instance, rural populations in Ghana, South Africa, and DRC have a higher prevalence than the urban populations in Ethiopia and Tanzania.

It is well known that urban averages mask great intra-urban disparities largely due to the presence of large populations in poor slum settlements that characterize most urban centers in Africa. Data from Nairobi collected from the adult population in two slum settlements [18] show a high prevalence of hypertension (overall of 19%) with large sex and age-specific differences (see Figure 4). The data also dispel the notion that hypertension is a disease of affluence since the majority of residents surveyed are poor. The data also show a reversal of the general trend of males having higher prevalence than females shown in Figure 2. There is no comparable data from the more affluent urban parts of the country.

Figure 4- Prevalence of Hypertension by Age and Sex in an Urban Poor Population in Kenya

RISK FACTORS FOR HYPERTENSION IN AFRICA

Hypertension is mainly associated with environmental and lifestyle factors rather than with genetics and has a stronger association and causal link with five particular behaviors: tobacco use, excessive use of alcohol, physical inactivity, unhealthy diet (high salt intake and, insufficient fruit and vegetable consumption) and obesity. Risk factors leading to hypertension can be reversible (modifiable), irreversible (non- modifiable), or associated with other predisposing disorders (List 1).

This section describes the distributions of these main modifiable risk factors for hypertension in Africa. Analysis is based on findings in African countries from the 2003 World Health Survey (WHS) and the WHO STEPS survey (2003-2009) on chronic disease risk factors. Data for the described modifiable risk factors are presented at the end of this section.

List 1: Risk factors for hypertension

Non-modifiable factors
Modifiable factors (environmental or lifestyle)

• Age • Gender (male sex) • Family history of cardiovascular events and genetic predisposition
• High Sodium consumption (in salt sensitivity cases) • Smoking • Excess alcohol • Overweight and obesity • Inadequate physical activity • Low Potassium intake • Unhealthy diet, particularly excess calories, fats, and fructose • Sedentary lifestyle • Psychological stress • Urban living • Vitamin D deficiency • Low Folic-acid intake

Other factors

• Dyslipidemia (altered blood lipid profile) • Increased triglycerides • Hyperuricaemia (high levels of uric acid) • Increased arterial stiffness • Systemic pro-inflammatory state • Under nutrition in childhood • Sleep deprivation • Prescription drugs (e.g. non-steroidal anti-inflammatory drugs) • Long-term exposure to noise

modifiable risk factors for hypertension

Tobacco Use

Tobacco smoking is known to increase the risk of developing hypertension and cardiovascular diseases like stroke, thrombosis and heart attack. Smoking causes an immediate increase in blood pressure resulting in higher ambulatory blood pressure levels for smokers than for non-smokers. Smoking cessation is known to reduce the overall risk of cardiovascular diseases [19]. In order to reduce smoking at the population level, it is important to implement multi-sectoral interventions like increasing taxes on tobacco products, banning of tobacco advertisements and banning smoking in public spaces [20].

The prevalence of tobacco smoking varied widely in the 2003 WHS. In all countries, men smoked more than women, with the largest disparities observed in Central and Western Africa. Among men, the prevalence of smoking was highest in Southern Africa followed by Eastern Africa. Remarkably, smoking was more prevalent in rural than in urban areas in most countries. Only in Kenya, Mauritania, Senegal and South Africa, were smoking levels higher among the urban population than their rural counterparts. A similar trend is observed in results from the STEPS survey. Daily smokers represented a greater proportion of actual smokers and were disproportionately male. Smoking was more likely in the island nations of Seychelles (22.2 percent), Madagascar (19.6 percent) and Mauritania (19.0 percent) and less pronounced in Western and Eastern African countries. For example, Ethiopia reported prevalence at 4.6 percent in 2006 and Benin was slightly lower at 3.8 percent in 2007.

Alcohol Consumption

Alcohol consumption is relatively frequent in Africa [21]. There is a direct effect between high levels and specific patterns of alcohol consumption (such as binge drinking) and rising risk of hypertension. The influence of heavy drinking, on increasing blood pressure levels has been described in Nigeria [22]. Interventions to limit alcohol use should be introduced in a multi-sectoral manner and adapted to the local situation. Such interventions, like in reducing tobacco use, include increasing taxes on alcohol, and banning alcohol advertising especially to young people [20].

In both the STEPS and the World Heath Survey (WHS), prevalence of alcohol consumption did not vary significantly between rural and urban populations. This implies an increase in prevalence rates in the rural, to levels similar to those previously only found in urban areas. Men show higher prevalence of alcohol consumption in terms of current and daily drinkers and are more likely to be frequent drinkers (defined as having more than four standard drinks/day on average on most days of the week) than women.

Inadequate Physical Activity

Adequate physical activity has been shown to have many health-promoting effects and has a direct, independent role in reducing hypertension [23, 24]. Traditionally, it has been thought that a high level of physical activity could in part explain the low levels of chronic diseases found in most of Africa. However, the amounts of physical activity have been decreasing as a result of the high rate of urbanization that has been occurring across the continent[25]. Few studies on the physical activity patterns of African populations have been published.

From the STEPS survey, adequate physical activity, defined as more than 150 minutes per week walking/moderate activity/vigorous activity, reported by males was markedly higher than that of females. In the WHS, women also reported lower levels of physical activity than men, probably because of their traditionally defined roles, such as caregiving, that require less physical strain. Adequate physical activity is more prevalent in rural than urban regions of Africa, which partly explains the high prevalence of obesity in urban areas.

High Salt Intake

A high intake of sodium is common, in Africa mostly from salt used to preserve food or to make it tastier [26]. Also, salt is added to already-prepared food by the consumer, as processed food is rare. Decreased salt intake not only reduces blood pressure and related CVD risk, but has other beneficial cardiovascular effects that are independent of and additive to its effect on blood pressure [27]. It has been reported to have a direct effect on reducing stroke, left ventricular hypertrophy, aortic stiffness, and chronic kidney disease and proteinuria [20]. For that reason, it is reasonable to infer that the total impact of reducing salt intake on cardiovascular outcomes could be greater than those expected from blood pressure reduction only.

Few intervention studies have been conducted to show that a reduction in salt intake and an increase in potassium improve the blood pressure in African populations. A study done in Tanzania indicated that a low sodium diet leading to a low urinary excretion level of 52 mmols per day, reduced blood pressure in normotensive people significantly within four to five days [28]. A study in Kenya reported that supplementation with potassium in newly diagnosed patients with hypertension reduced the blood pressure to a level similar to that found in patients treated with a diuretic [29]. These studies provide evidence of the impact of community- based and context specific salt – reduction programs in Africa where most salt is still discretionary rather than from processed foods as is the case in developed countries.

Insufficient Fruit and Vegetable Consumption

Fruit and vegetable consumption is one element of a healthy diet and varies considerably among countries, reflecting economic, cultural and agricultural production environments [30]. Most of the benefits of fruits and vegetables come from reduction in CVD and risk factors, particularly hypertension. In addition to a high salt intake, many people in Africa often eat insufficient fruits and vegetables, resulting in low potassium intake. This in turn is associated with higher blood pressure in some patients; a potassium intake of 90 mmol/day is recommended [31].

The STEPS surveys reported sufficient fruits and vegetables intake, defined as five or more servings of fruits or vegetables per one typical day, as being very low across all countries. There were slight gender variations in mean servings of fruit and vegetables reported with women more likely to consume the recommended number of servings than men. This finding was mirrored in the WHS where also, rural people were more likely to consume insufficient amounts of fruits and vegetables compared to their urban counterparts.

Obesity

The World Health Organization (WHO) defines obesity as a condition in which excess body fat has accumulated to such an extent that health may be adversely affected. The degree of body weight is usually expressed as BMI; this is the ratio of weight in kilograms to the square of height in meters. The BMI is used to classify a person’s body weight as underweight (BMI less than 18.5), normal weight (BMI 18.5–24.9), overweight (BMI 25-29.9), or obese (BMI greater than 30). Obesity greatly increases the risk for hypertension and has also been shown to be associated with coronary artery disease and some cancers, and to reduce life expectancy [32]. As obesity is rapidly rising in different countries, it will be important to share best practices to reduce this trend[25].

STEPS findings show that there is a high prevalence of overweight and obesity in many African countries particularly among urban women. The mean BMI was significantly higher for women compared to men across all countries as was the standardized prevalence of overweight (BMI> 25Kg/m²) and obesity (BMI>30Kg/m²). Presumably, the lower male prevalence relates, in part, to the much higher rate of heavy manual labor commonly reported in men while the higher prevalence rates among women may be explained by the physiological changes related to pregnancy and childbirth, and cultures that put a high premium on overweight and obesity among women.

In Table 1, we show the prevalence of five key risk factors for hypertension in selected countries based on data from the nationally representative STEPS surveys.

Table 1: Prevalence of Risk Factors for Hypertension in Selected Countries from the WHO STEPwise Surveys (2003-2009)

Country
Tobacco smoking*
Alcohol intake**
Inadequate physical activity
Insufficient fruit/vegetable intake
Obesity

Algeria (2003)
15.1
-
37.1
87.1
16.6

Cameroon (2003)
8.2
-
26.6
-
22.3

Congo (2004)
11.1
-
-
-
8.6

Seychelles (2004)
22.2
87.3
42.2
78.8
25.1

Eritrea (2004)
8.7
28.3
33.7
97.6
4.0

Côte d’Ivoire (2005)
14.4
34.0
24.3
83.5
8.5

DRC(2005)
7.6
-
23.1
86.5
8.2

Madagascar (2005)
19.6
31.7
46.5
72.6
2.2

Mozambique (2005)
18.7
45.2
85.3
95.0
7.5

Ethiopia (2006)
4.6
45.7
42.1
98.9
7.1

Mauritania (2006)
19.0
-
10.3
94.3
24.7

Botswana (2006)
19.7
18.7
43.4
96.6
15.6

Benin (2007)
3.8
36.9
66.2
94.7
21.6

Cape Verde (2007)
9.9
40.3
60.3
86.1
10.5

Mali (2007)
15.8
3.8
23.4
80.2
17.9

Niger (2007)
5.0
0.2
56.1
96.3
3.2

Swaziland (2007)
7.1
11.8
53.3
87.4
24.3

Benin (2008)
8.8
48.8
80.8
78.5
9.4

Chad (2008)
11.2
17.0
41.1
84.8
13.7

Sao Tome (2009)
5.5
84.5
65.9
83.3
11.7

*Current smoker

** Current user i.e. has consumed an alcoholic drink in the last seven days before the survey

AWARENESS, TREATMENT AND CONTROL OF HYPERTENSION IN AFRICA

The low rates of awareness, treatment and control of hypertension in Africa are a major public health concern as the population in this region is growing [33]. The low levels of all these indicators imply that there will be significantly large populations of hypertensive patients unaware of their increased risk of hypertension-related complications in the coming years. Studies in Africa have shown that many people with hypertension are unaware of their condition, many of those who are aware are not on treatment, and many of those treated are not well controlled [34]. A possible contributory factor would be the affordability of the cost of health care, which remains a major barrier in the African setting as out-of-pocket spending is the main source of funding for health care costs [35].

Another common occurrence is the non-adherence to treatment and follow-up for hypertension. In one intervention study in Cameroon, for instance, just about half of the participants were still in the program at one-year follow-up [36]. Indeed, patients are expected to be treated and controlled only if they can access appropriate health services, receive adequate advice and prescriptions and subsequently afford and adhere to those prescriptions. Increasing awareness, treatment and control rates of hypertension will have a huge impact on CVD prevention in Africa [37]. For instance, data from the national health and nutrition examination survey (NHANES) showed that the age-adjusted percentage of adults with hypertension whose blood pressure was controlled increased from 48.4% in 2007–2008 to 53.3% in 2009–2010, whereas in Africa only 5 to 10 percent is controlled at a blood pressure of less than 140/90 mmHg [38-40].

Studies in Tunisia, Cameroon and Kenya assessed the levels of awareness, treatment, and control (Figure 5). All levels of awareness, treatment and control were found to be significantly lower for men than women, lower in rural than urban areas and to be higher among older age groups (see Figure 5).

Figure 5: Rates of Hypertension Awareness, Treatment and Control in Selected African Countries by Sex

CARE AND MANAGEMENT OF HYPERTENSION

Management of hypertension involves lifestyle changes as well as drug treatment. Lifestyle measures are useful both in the control of high blood pressure and in risk factor management. They include weight reduction, increase in physical activity, reduction in salt intake, moderation of alcohol intake and cessation of smoking. As regards drug treatment, several classes of drugs are recommended for the treatment of hypertension and this is dependent on co-existing disease conditions and on the presence or absence of complications. Often, more than one drug is necessary to achieve control. In Africa, providing medication is considered an important and cost effective way to reduce hypertension [41], but accessibility to and cost of the treatment are very often forgotten. Currently, African countries are 80 percent below the global average for pharmacological spending and 20 percent below the global average of behavioral risk factors for hypertension[42]. There is a lot of opportunity for hypertension control through improving availability of medication as has been widely reported in the literature.

The efficacy of blood pressure lowering medications is well demonstrated and treatment of high-risk individuals has been advocated as a major strategy for CVD prevention in all regions, including Africa [4]. However, managing hypertension -or elevated total CVD risk- is challenging in Africa for a variety of reasons, including lack of availability of drugs, high treatment costs, as well as inadequacy of health services for identification and management of CVD and its risk factors [43]. Moreover, health systems in most LMICs are already stretched by the high burden of infectious diseases such as HIV, TB and malaria. Furthermore, individuals who struggle with a broad range of day-to-day problems may discount the benefit of long-term treatment for silent and painless conditions that do not immediately jeopardize their health.

There is also evidence that Africa is undergoing very rapid transitions characterized by increasing urbanization, including the adoption of unhealthy lifestyles. These transitions are paralleled by changes in the profile of chronic disease risk factors including blood pressure.

Recently, there has been increasing awareness of the threat that the looming non-communicable diseases epidemic poses to the health of the population in the region at different levels. This increasing awareness has catalyzed initiatives aimed at improving access to detection and care of chronic diseases including hypertension in many countries of the region. The pace of the above developments suggests that data on the burden of hypertension must be updated regularly, in order to provide the reliability needed in drawing up effective health service and policy solutions.

Historically, hypertension guidelines focused on blood pressure values as the only or main variables determining the need and the type of treatment. The current approach emphasizes that diagnosis and management of hypertension should be related to quantification of total (or global) CVD risk.

HYPERTENSION PREVENTION AND CONTROL INITIATIVES

Hypertension is the most important modifiable risk factor for CVD, yet the control of this condition in Africa is far from adequate. Available data from a few countries in Africa have highlighted the increasing importance of CVD and other chronic non-communicable diseases in this region, and some of these countries have taken steps to develop relevant policies and programs to address this issue [44]. For this, an integrated approach to the prevention and management of non-communicable diseases, irrespective of cause, is needed in primary health care (PHC) settings [12]. It is likely that hypertension is particularly poorly detected and treated in PHC settings in many African countries given the low levels of awareness, treatment and control as described above. Countries in the region should therefore be encouraged to establish country-specific recommendations for the prevention and management of hypertension, as already recommended by the World Health Assembly (WHA) and the WHO Regional Committee for Africa. Chronic disease interventions selected for use in PHC must lead to productive changes in risk status and outcomes, be cost effective, and be financially and logistically feasible, to be available for implementation across a range of resource settings.

Strategies and Interventions to Prevent/control Hypertension

The commonality of many risk factors for hypertension and other CVD justifies an integrated approach to prevention and control. This requires tackling at several levels (a) Primordial prevention i.e. the reduction of the risk factors of hypertension in the general population and thereby decreasing the risk of developing hypertension in future (b) Primary prevention i.e. prevention of the condition in those who have prehypertension (c) Secondary prevention i.e. prevention of complications in those who have already developed hypertension, and (d) Tertiary Prevention i.e. preventing progression to end stage complications in those who have already developed some associated complications (see Figure 6).

Figure 6: Strategies for the Prevention and Control of Hypertension

Primordial Prevention