EDITORIAL
Editorial
Population Health Studies – What Do They Tell Us? Patricia M. Davidson, PhD ∗ and Cheryl Dennison- Himmelfarb, PhD Centre for Cardiovascular and Chronic Care, University of Technology Sydney, St. Vincent’s Hospital Sydney, Sydney, Australia School of Nursing, Johns Hopkins University, Baltimore, USA
T
he burden of cardiovascular disease (CVD) is a global concern [1]. People living in resource-limited settings are affected disproportionately, with more than 80% of CVD deaths occurring in low and middle-income countries. Although inflammatory and rheumatic heart diseases remain common in these countries atherosclerosis is becoming a critical concern [2,3]. In sub-Saharan Africa, there is an evolving disease profile from infectious diseases and nutritional deficiencies to non-communicable chronic diseases [4]. CVD will become the leading cause of death in low-income countries in Africa, contributing 13.4% of total deaths, in spite of the spread of HIV/acquired immune deficiency syndrome [5]. Transformation in the profile of infectious to noncommunicable disease is attributed to lifestyle changes including rising rates of smoking, urbanisation and westernisation of the diet and increases in sedentary behaviour. Moreover, inflammatory changes including the exposure to infectious disease, particularly HIV, increases the vulnerability to CVD [5]. Population studies investigating a group of individuals taken from the general population who share a common characteristic, such as age, sex, or health condition are useful in identifying patterns and are also important in health services planning. These studies quantify the burden and pattern of disease as well as generating hypotheses for testing causal associations. A recent review of population studies in sub- Saharan Africa has identified heterogeneity in studies and the need for robust, prospective studies [6]. The prevalence of hypertension in sub-Saharan Africa is estimated to be 30% and is likely to drive a considerable burden of disease [7]. This prevalence is attributable to multiple causative factors including life-style and genetic factors such as the underweight phenotype [8]. A number of studies have been undertaken to examine risk factors for CVD. In the INTERHEART Africa study, case–control study recruited 578 cases of first-time myocardial infarction and 785 controls from nine subSaharan African countries [9]. Although risk factors were consistent with the overall INTERHEART study findings, Received 27 August 2013; available online 7 September 2013 ∗
Corresponding author. Tel.: +61 2 9514 4822; fax: +61 2 9514 4474. E-mail address: [email protected] (P.M. Davidson).
risk factor patterns and the risk of acute myocardial infarction suggest that this population is at a different stage of the epidemiological transition [9]. As a consequence, although the cardiovascular risk factors in Africa are similar to those identified in other regions of the world, there are likely factors that are unique to this area and require specific investigation. The Sympathetic Activity and Ambulatory Blood Pressure in Africans, SABPA Study was a longitudinal study of approximately 100 black female, 100 white female, 100 black male and 100 white male South African school teachers and has sought to determine the relationship between increased sympathetic nervous system activity and cardiovascular activity, stress hormones, metabolic syndrome indicators and the renin-angiotensin-aldosterone system in urban Caucasians and Africans. In this edition of Heart Lung & Circulation, two analyses from the SABPA Study provide insight into the mechanisms of hypertension and cardiovascular risk [10,11]. van der Walt and colleagues assessed the association between elevated ambulatory blood pressure, inflammation and the potential additive effect of left ventricular hypertrophy (LVH) identified on electrocardiogram (ECG) in sub-Saharan African men. The main finding in this study was the strong association between ECG LVH, systolic blood pressure (SBP) and pulse pressure in African men. Uys et al. investigated possible associations between norepinephrine metabolite, 3-methoxy-4hydroxyphenylglycol (MHPG), nocturnal blood pressure and carotid intima-media thickness (CIMT) in urban African and Caucasian men [11]. Despite higher usage of anti-hypertensive medications, the nocturnal SBP, diastolic blood pressure (DBP) and heart rate of the African men were higher. In this study no associations were identified between MHPG as sympathetic activity marker and CIMT or, between MHPG and nocturnal blood pressure [11]. Each of these studies adds to the increasing literature on the burden of cardiovascular risk in Africa. A single population study or analysis is unlikely to provide the answer to the complex issues contributing to CVD. But each of these studies provides a piece of the puzzle and adds to our understanding of the problem and possible solutions. Though screening and identifying increased risk and vulnerability are important, we must advance to the next level, intervening to decrease the burden of
© 2013 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier Inc. All rights reserved.
1443-9506/04/$36.00 http://dx.doi.org/10.1016/j.hlc.2013.08.014
886
Davidson and Himmelfarb Population Health Studies – What Do They Tell Us?
EDITORIAL
CVD. This will require collaboration and additional or re-allocated resourcing and most importantly addressing social determinants of health [12,13]. A critical part of the solution to decreasing the burden of CVD is developing culturally appropriate and accessible interventions to decrease risk [14]. The earlier the signs of cardiovascular dysfunction are identified the earlier intervention can occur. But most importantly preventing these changes is likely to leverage maximal benefit. In particular it is important to address the high numbers of individuals with hypertension and reduce rates of smoking [15,16]. Although many studies have focused on identifying physiological explanations for the increased CVD risk in Africa, the potential impact of addressing health disparities through improving access to care and implementing strategies to increase health promotion and support lifestyle changes cannot be ignored. Moreover, strategies to foster treatment adherence, particularly for hypertension, are critical in decreasing the burden of CVD [17]. Interventions at health care system, health care provider and the individual and communities levels will be essential in addressing the looming crisis of CVD in Africa. Well-designed prospective cohort studies are needed to inform and update our knowledge regarding the epidemiology CVDs and their interactions with known risk factors in the context of common infectious diseases in this region [6]. Ongoing population surveillance is required to monitor cardiovascular risk factors and identify opportunities for intervention. However, as a global community we need to move from screening to intervening in order to improve health outcomes [18]. This will require complex and multifaceted interventions and partnerships across the globe but most importantly engagement and dialogue with local communities. The rallying of the global response to CVD will require a similar effort, energy and resources that have been applied to addressing the scourge of the HIV/acquired immune deficiency syndrome in Africa. This tragedy has united the world in a global focus similar approaches are required for non-communicable diseases, particularly CVD. Most importantly many population health studies have told us about the problems – now we need to shift to solutions.
References [1] Labarthe DR, Dunbar SB. Global cardiovascular health promotion and disease prevention 2011 and beyond. Circulation 2012;125:2667–76.
Heart, Lung and Circulation 2013;22:885–886
[2] Celermajer DS, Chow CK, Marijon E, Anstey NM, Woo KS. Cardiovascular disease in the developing world: prevalences, patterns, and the potential of early disease detection. J Am Coll Cardiol 2012;60:1207–16. [3] Opie LH, Mayosi BM. Cardiovascular disease in sub-Saharan Africa. Circulation 2005;112:3536–40. [4] Naghavi M, Forouzanfar MH. Burden of non-communicable diseases in sub-Saharan Africa in 1990 and 2010: global burden of diseases, injuries, and risk factors study 2010. The Lancet 2013;381:S95. [5] Deeks SG. HIV infection, inflammation, immunosenescence, and aging. Annu Rev Med 2011;62:141–55. [6] Kengne AP, Ntyintyane LM, Mayosi BM. A systematic overview of prospective cohort studies of cardiovascular disease in sub-Saharan Africa. Cardiovasc J Afr 2012;23:103. [7] Sliwa K, Mayosi BM. Recent advances in the epidemiology, pathogenesis and prognosis of acute heart failure and cardiomyopathy in Africa. Heart 2013, http://dx.doi.org/10.1136/heartjnl-2013-303592. [8] Opie LH, Seedat YK. Hypertension in sub-Saharan African populations. Circulation 2005;112:3562–8. [9] Steyn K, Sliwa K, Hawken S, Commerford P, Onen C, Damasceno A, et al. Risk factors associated with myocardial infarction in Africa the INTERHEART Africa study. Circulation 2005;112:3554–61. [10] van der Walt C, Malan L, Uys AS, Malan NT. Low grade inflammation and ECG left ventricular hypertrophy in urban African males: the SABPA study. Heart Lung Circ 2013. [11] Uys AS, Malan L, van Rooyen JM, Steyn HS, Ziemssen T, Reimann M. Nocturnal blood pressure, 3-methoxy-4hydroxyphenylglycol and carotid intima-media thickness: the SABPA study. Heart Lung Circ 2013. [12] Marmot M. Social determinants of health inequalities. The Lancet 2005;365:1099–100. [13] Harper S, Lynch J, Smith GD. Social determinants and the decline of cardiovascular diseases: understanding the links. Annu Rev Public Health 2011;32:39–69. [14] Farley JE, Tudor C, Dennison CR. Progress in prevention: improving cardiovascular risk management among human immunodeficiency virus–positive individuals. J Cardiovasc Nurs 2010;25:259. [15] Dennison CR, Peer N, Steyn K, Levitt NS, Hill MN. Determinants of hypertension care and control among peri-urban black South Africans: the hihi study. Ethn Dis 2007;17:484–91. [16] Sheridan J, Collins A. Adult lung cancer in southern Africa: epidemiology and aetiology. Afr J Respir Med 2013;8. [17] Bakris G, Hill M, Mancia G, Steyn K, Black H, Pickering T, et al. Achieving blood pressure goals globally: five core actions for health-care professionals. A worldwide call to action. J Hum Hypertens 2007;22:63–70. [18] Leeder S. Developing a global agenda for action on cardiovascular diseases. Med J Aust 2013;199:145–6.
Editorial
Population Health Studies – What Do They Tell Us? Patricia M. Davidson, PhD ∗ and Cheryl Dennison- Himmelfarb, PhD Centre for Cardiovascular and Chronic Care, University of Technology Sydney, St. Vincent’s Hospital Sydney, Sydney, Australia School of Nursing, Johns Hopkins University, Baltimore, USA
T
he burden of cardiovascular disease (CVD) is a global concern [1]. People living in resource-limited settings are affected disproportionately, with more than 80% of CVD deaths occurring in low and middle-income countries. Although inflammatory and rheumatic heart diseases remain common in these countries atherosclerosis is becoming a critical concern [2,3]. In sub-Saharan Africa, there is an evolving disease profile from infectious diseases and nutritional deficiencies to non-communicable chronic diseases [4]. CVD will become the leading cause of death in low-income countries in Africa, contributing 13.4% of total deaths, in spite of the spread of HIV/acquired immune deficiency syndrome [5]. Transformation in the profile of infectious to noncommunicable disease is attributed to lifestyle changes including rising rates of smoking, urbanisation and westernisation of the diet and increases in sedentary behaviour. Moreover, inflammatory changes including the exposure to infectious disease, particularly HIV, increases the vulnerability to CVD [5]. Population studies investigating a group of individuals taken from the general population who share a common characteristic, such as age, sex, or health condition are useful in identifying patterns and are also important in health services planning. These studies quantify the burden and pattern of disease as well as generating hypotheses for testing causal associations. A recent review of population studies in sub- Saharan Africa has identified heterogeneity in studies and the need for robust, prospective studies [6]. The prevalence of hypertension in sub-Saharan Africa is estimated to be 30% and is likely to drive a considerable burden of disease [7]. This prevalence is attributable to multiple causative factors including life-style and genetic factors such as the underweight phenotype [8]. A number of studies have been undertaken to examine risk factors for CVD. In the INTERHEART Africa study, case–control study recruited 578 cases of first-time myocardial infarction and 785 controls from nine subSaharan African countries [9]. Although risk factors were consistent with the overall INTERHEART study findings, Received 27 August 2013; available online 7 September 2013 ∗
Corresponding author. Tel.: +61 2 9514 4822; fax: +61 2 9514 4474. E-mail address: [email protected] (P.M. Davidson).
risk factor patterns and the risk of acute myocardial infarction suggest that this population is at a different stage of the epidemiological transition [9]. As a consequence, although the cardiovascular risk factors in Africa are similar to those identified in other regions of the world, there are likely factors that are unique to this area and require specific investigation. The Sympathetic Activity and Ambulatory Blood Pressure in Africans, SABPA Study was a longitudinal study of approximately 100 black female, 100 white female, 100 black male and 100 white male South African school teachers and has sought to determine the relationship between increased sympathetic nervous system activity and cardiovascular activity, stress hormones, metabolic syndrome indicators and the renin-angiotensin-aldosterone system in urban Caucasians and Africans. In this edition of Heart Lung & Circulation, two analyses from the SABPA Study provide insight into the mechanisms of hypertension and cardiovascular risk [10,11]. van der Walt and colleagues assessed the association between elevated ambulatory blood pressure, inflammation and the potential additive effect of left ventricular hypertrophy (LVH) identified on electrocardiogram (ECG) in sub-Saharan African men. The main finding in this study was the strong association between ECG LVH, systolic blood pressure (SBP) and pulse pressure in African men. Uys et al. investigated possible associations between norepinephrine metabolite, 3-methoxy-4hydroxyphenylglycol (MHPG), nocturnal blood pressure and carotid intima-media thickness (CIMT) in urban African and Caucasian men [11]. Despite higher usage of anti-hypertensive medications, the nocturnal SBP, diastolic blood pressure (DBP) and heart rate of the African men were higher. In this study no associations were identified between MHPG as sympathetic activity marker and CIMT or, between MHPG and nocturnal blood pressure [11]. Each of these studies adds to the increasing literature on the burden of cardiovascular risk in Africa. A single population study or analysis is unlikely to provide the answer to the complex issues contributing to CVD. But each of these studies provides a piece of the puzzle and adds to our understanding of the problem and possible solutions. Though screening and identifying increased risk and vulnerability are important, we must advance to the next level, intervening to decrease the burden of
© 2013 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier Inc. All rights reserved.
1443-9506/04/$36.00 http://dx.doi.org/10.1016/j.hlc.2013.08.014
886
Davidson and Himmelfarb Population Health Studies – What Do They Tell Us?
EDITORIAL
CVD. This will require collaboration and additional or re-allocated resourcing and most importantly addressing social determinants of health [12,13]. A critical part of the solution to decreasing the burden of CVD is developing culturally appropriate and accessible interventions to decrease risk [14]. The earlier the signs of cardiovascular dysfunction are identified the earlier intervention can occur. But most importantly preventing these changes is likely to leverage maximal benefit. In particular it is important to address the high numbers of individuals with hypertension and reduce rates of smoking [15,16]. Although many studies have focused on identifying physiological explanations for the increased CVD risk in Africa, the potential impact of addressing health disparities through improving access to care and implementing strategies to increase health promotion and support lifestyle changes cannot be ignored. Moreover, strategies to foster treatment adherence, particularly for hypertension, are critical in decreasing the burden of CVD [17]. Interventions at health care system, health care provider and the individual and communities levels will be essential in addressing the looming crisis of CVD in Africa. Well-designed prospective cohort studies are needed to inform and update our knowledge regarding the epidemiology CVDs and their interactions with known risk factors in the context of common infectious diseases in this region [6]. Ongoing population surveillance is required to monitor cardiovascular risk factors and identify opportunities for intervention. However, as a global community we need to move from screening to intervening in order to improve health outcomes [18]. This will require complex and multifaceted interventions and partnerships across the globe but most importantly engagement and dialogue with local communities. The rallying of the global response to CVD will require a similar effort, energy and resources that have been applied to addressing the scourge of the HIV/acquired immune deficiency syndrome in Africa. This tragedy has united the world in a global focus similar approaches are required for non-communicable diseases, particularly CVD. Most importantly many population health studies have told us about the problems – now we need to shift to solutions.
References [1] Labarthe DR, Dunbar SB. Global cardiovascular health promotion and disease prevention 2011 and beyond. Circulation 2012;125:2667–76.
Heart, Lung and Circulation 2013;22:885–886
[2] Celermajer DS, Chow CK, Marijon E, Anstey NM, Woo KS. Cardiovascular disease in the developing world: prevalences, patterns, and the potential of early disease detection. J Am Coll Cardiol 2012;60:1207–16. [3] Opie LH, Mayosi BM. Cardiovascular disease in sub-Saharan Africa. Circulation 2005;112:3536–40. [4] Naghavi M, Forouzanfar MH. Burden of non-communicable diseases in sub-Saharan Africa in 1990 and 2010: global burden of diseases, injuries, and risk factors study 2010. The Lancet 2013;381:S95. [5] Deeks SG. HIV infection, inflammation, immunosenescence, and aging. Annu Rev Med 2011;62:141–55. [6] Kengne AP, Ntyintyane LM, Mayosi BM. A systematic overview of prospective cohort studies of cardiovascular disease in sub-Saharan Africa. Cardiovasc J Afr 2012;23:103. [7] Sliwa K, Mayosi BM. Recent advances in the epidemiology, pathogenesis and prognosis of acute heart failure and cardiomyopathy in Africa. Heart 2013, http://dx.doi.org/10.1136/heartjnl-2013-303592. [8] Opie LH, Seedat YK. Hypertension in sub-Saharan African populations. Circulation 2005;112:3562–8. [9] Steyn K, Sliwa K, Hawken S, Commerford P, Onen C, Damasceno A, et al. Risk factors associated with myocardial infarction in Africa the INTERHEART Africa study. Circulation 2005;112:3554–61. [10] van der Walt C, Malan L, Uys AS, Malan NT. Low grade inflammation and ECG left ventricular hypertrophy in urban African males: the SABPA study. Heart Lung Circ 2013. [11] Uys AS, Malan L, van Rooyen JM, Steyn HS, Ziemssen T, Reimann M. Nocturnal blood pressure, 3-methoxy-4hydroxyphenylglycol and carotid intima-media thickness: the SABPA study. Heart Lung Circ 2013. [12] Marmot M. Social determinants of health inequalities. The Lancet 2005;365:1099–100. [13] Harper S, Lynch J, Smith GD. Social determinants and the decline of cardiovascular diseases: understanding the links. Annu Rev Public Health 2011;32:39–69. [14] Farley JE, Tudor C, Dennison CR. Progress in prevention: improving cardiovascular risk management among human immunodeficiency virus–positive individuals. J Cardiovasc Nurs 2010;25:259. [15] Dennison CR, Peer N, Steyn K, Levitt NS, Hill MN. Determinants of hypertension care and control among peri-urban black South Africans: the hihi study. Ethn Dis 2007;17:484–91. [16] Sheridan J, Collins A. Adult lung cancer in southern Africa: epidemiology and aetiology. Afr J Respir Med 2013;8. [17] Bakris G, Hill M, Mancia G, Steyn K, Black H, Pickering T, et al. Achieving blood pressure goals globally: five core actions for health-care professionals. A worldwide call to action. J Hum Hypertens 2007;22:63–70. [18] Leeder S. Developing a global agenda for action on cardiovascular diseases. Med J Aust 2013;199:145–6.
