Managing the global burden of cardiovascular disease

Transcription

1 European Heart Journal Supplements (2002) 4 (Supplement F), F2 F6 Managing the global burden of cardiovascular disease B. Neal, N. Chapman and A. Patel Institute for International Health, Sydney, New South Wales, Australia There is a large and increasing global burden of cardiovascular disease. Approximately 14 million individuals died of cardiovascular disease in 1990, and this is projected to rise to about 25 million by In large part, this increase can be explained on the basis of major ongoing sociodemographic changes in developing countries, and associated effects on the numbers of individuals at risk and the levels of cardiovascular risk factors. Developing countries now experience a much greater burden of cardiovascular disease than do developed countries. In addition, developing countries are expected to experience the greatest rise in cardiovascular disease burden over the next few years. Cardiovascular disease prevention programmes designed and implemented primarily in developed countries have most likely averted much premature cardiovascular disease in those Introduction In 1990 there were an estimated 50 million deaths worldwide, of which approximately 14 million (28%) were due to cardiovascular disease (Fig. 1) [1]. The majority of cardiovascular deaths were due to either ischaemic heart disease (6 2 million) or stroke (4 3 million) the first and second leading causes of death, respectively. In addition to death, cardiovascular diseases also caused many serious non-fatal events and in 1990 they were major causes of disability-adjusted life years (DALYs) a measure of the total burden of disease caused by premature deaths and nonfatal events combined. At this time, ischaemic heart disease and stroke were ranked as the fifth and sixth leading causes of DALYs, respectively (Table 1). By 2020 the global burden of fatal and non-fatal cardiovascular disease is anticipated to grow in importance in both relative and absolute terms [1]. At this time it is projected that there will be approximately 68 million deaths worldwide from all causes, of which about 25 million (37%) deaths worldwide will be due to cardiovascular causes. Correspondence: Bruce Neal, Institute for International Health, University of Sydney, PO Box 576, Newtown, Sydney, NSW 2042, Australia X/02/0F $35.00/0 countries over the past few decades. However, cardiovascular disease prevention programmes designed for developed countries are unlikely to be directly transferable to developing countries. Reliable information to inform the design and implementation of cardiovascular disease prevention programmes, tailored to the socioeconomic circumstances of developing countries, is now required. Such programmes have great potential to impact on the current and projected global epidemic of cardiovascular disease. (Eur Heart J Supplements 2002; 4 (Suppl F): F2 F6) 2002 The European Society of Cardiology Key Words: Cardiovascular disease burden, global. Ischaemic heart disease and stroke are anticipated to remain the first and second leading causes of death, being responsible for about 11 1 million and 7 7 million deaths, respectively [2]. The total number of DALYs due to all causes in 2020 is expected to be approximately the same as that in 1990 (approximately 1 4 billion). However, the number of DALYs attributable to cardiovascular disease is expected to rise from 134 million in 1990 (10% of all DALYs) to about 204 million (15% of all DALYs) in Ischaemic heart disease is expected to be the leading cause of DALYs worldwide in 2020 (82 million DALYs). Burden of cardiovascular disease in developing countries For much of the 20th century the majority of cardiovascular disease occurred in industrialized, higher income countries [1]. For the past few decades, however, the absolute burden of cardiovascular disease has been greater in developing countries, and it is these countries that will bear the greatest burden of cardiovascular disease in the 21st century [1,3]. It is estimated that in 1990 there were already almost twice as many deaths and more than three times as many DALYs attributable to cardiovascular diseases in 2002 The European Society of Cardiology

2 Managing the global burden of cardiovascular disease F3 60 Chronic diseases and injuries Millions of deaths CVD 14 million 1990 CVD 25 million 2020 Figure 1 Changing patterns of death worldwide. Actual (1990) and projected (2020) numbers of deaths [1]. CVD=cardiovascular disease. developing countries (9 1 million deaths, 101 million DALYs) than there were in developed countries (5 2 million deaths, 33 million DALYs). By 2020, it is anticipated that the difference in cardiovascular disease burden between higher income and lower income countries will have expanded still further. At this time it is estimated that there will be about 6 million deaths and 35 million DALYs annually from cardiovascular causes in higher income countries and about 19 million deaths and 170 million DALYs annually from cardiovascular causes in lower income countries. The projected large increase in DALYs attributable to cardiovascular diseases in developing countries is due not just to an anticipated greater number of individuals suffering cardiovascular events, but also to the occurrence of these events at younger ages [1]. Infectious, maternal, perinatal and nutritional conditions Table 1 Ten leading actual (1990) and projected (2020) causes of global burden of death and disability in rank order [1] Rank Cause % Rank Cause % 1 Lower respiratory infections Ischaemic heart disease Diarrhoeal disease Major depression Perinatal conditions Road traffic accidents Major depression Cerebrovascular disease Ischaemic heart disease COPD Cerebrovascular disease Lower respiratory infections Tuberculosis Tuberculosis Measles War Road traffic accidents Diarrhoeal diseases Congenital abnormalities HIV 2 6 Ischaemic heart disease and stroke (emboldened) are currently ranked as the fifth and sixth leading causes of disability-adjusted life years (DALYs), respectively. By 2020 they are anticipated to rise in ranking to first and fourth leading causes, respectively. % Indicates proportion of all DALYs caused [1]. COPD=chronic obstructive pulmonary disease; HIV=human immunodeficiency virus. Changing sociodemographic characteristics of developing countries The differences in the current and projected burden of cardiovascular disease between developed and developing countries are closely associated with the current and projected sociodemographic characteristics of each [4]. In particular, the absolute burden of cardiovascular disease in these countries is associated with the size of the population, the age structure of the population [5] and the proportion of the population living in an urban environment [6]. At present, approximately 5 billion individuals live in developing countries and 1 billion individuals live in developed countries. By 2050 the world population is

3 F4 B. Neal et al. expected to have reached approximately 9 billion, with almost all of the 3 billion population increase expected to occur in developing countries [2]. A marked feature of developed populations is the number of individuals who live in urban environments [6]. In the U.S.A. about three quarters of the population live in urban areas, and in many European countries the proportion is higher (up to 90% in some) [7]. Ongoing large-scale urbanization of the population has been a feature of many developing countries over the past few decades and is anticipated to continue apace. The proportion of the global population living in urban areas has risen from about 40% in 1975 to 50% in 2000, with a projected increase to about 60% in 2025 [6]. By 2025, about 90% of the world s urban population will reside in cities in developing countries, and more than 80 of the world s 100 largest cities are expected to be in developing countries (an increase from about 40 in 1950). Over the same time period, in addition to expanding in size and shifting from a rural to urban setting, the global population is also projected to age considerably [1]. In 1999 there were approximately 600 million individuals in the world aged 60 years or over (10% of the world population) and by 2050 this figure is expected to rise to about 2 billion (approximately 22% of the world population). The greatest changes in age structure will be in developing countries, in which currently only about 8% of the population are older than 60 years. In 50 years time the proportion aged 60 years or over in developing countries is anticipated to have almost tripled, to 21%. Although the proportion aged 60 years or older will be greater (approximately 32%) in developed countries in 2050, the relative change will be smaller (less than a doubling, from 19% aged 60 years or above in 2000). In 2050, for the first time there will be more individuals in the world aged 60 years or over than individuals aged 14 years or younger, with substantial implications not just for health care provision, but also for the global economy as a whole [6]. Cardiovascular risk factors in developing countries Reliable data from developing countries on current levels of cardiovascular risk factors and on recent changes in the levels of cardiovascular risk factors are few. In general, however, the data that are available suggest that levels of cardiovascular risk factors are deteriorating in developing countries [8]. These observations are consistent with the effects anticipated to follow from sociodemographic change (particularly ageing and urbanization) [9]. For example, blood pressure levels typically rise progressively with age [10,11], and mean cholesterol levels and mean body mass index are typically higher in urban than rural populations [12,13]. Similarly, an increased prevalence of diabetes is associated with both increasing age and a higher proportion of the population living in an urban environment [14]. Of particular importance in determining the current and future global burden of cardiovascular disease is tobacco consumption [15]. Although tobacco consumption has stabilized in many developed countries, and is even decreasing in some, increasing rates of cigarette smoking are a feature of many developing countries. Overall, in the 20 years from 1971 to 1991 average tobacco consumption per capita in developing countries rose from around 800 to 1400 cigarettes per year [16]. In 1990, the total number of deaths attributed to tobacco consumption (of which cardiovascular deaths constituted a substantial proportion) was 3 0 million, but this is anticipated to rise to 8 4 million in 2020 [17]. The greatest numbers of new deaths attributable to tobacco consumption will be in China ( , from 0 8 to 2 2 million) and India ( , from 0 1 to 1 5 million) [1]. Levels of cardiovascular risk factors and secular trends in cardiovascular risk factors are in many cases very different in lower income countries as compared with developed countries [17]. However, the associations of established cardiovascular risk factors with the risks for cardiovascular events appear to be broadly similar in both developing and developed regions [18,19]. For example, long-term tobacco consumption leads to a doubling of risk for ischaemic heart disease among residents of both the U.K. [20] and China [21], and a 10-mmHg increment in systolic blood pressure is associated with an approximate one-third increase in the risk for stroke among both Eastern [19] and Western populations [18]. Because homogeneity, rather than heterogeneity, is a feature of most data comparing the associations of exposures with risks for cardiovascular disease in developing and developed countries, the current and projected distributions of cardiovascular disease can be broadly understood in terms of the same traditional risk factors. However, although the relative associations of risk factors with disease appear to be broadly consistent, differences in the absolute levels of risk factors between countries may result in substantial variation in the numbers of different types of cardiovascular events [1]. For example, the ratio of stroke deaths to ischaemic heart disease deaths is high in China and low in the U.K. [1], perhaps in part reflecting higher levels of blood pressure in China, and greater prevalence of diabetes and obesity in the U.K. Strategies for managing the global burden of cardiovascular disease During the second half of the past century much research was conducted into strategies for treatment and prevention of cardiovascular diseases. Subsequent widely implemented intervention programmes have most likely resulted in the prevention of many premature strokes and heart attacks over the past few decades [5,22]. It has been estimated that, in parts of Western Europe, Australia, Canada, the U.S.A. and Japan, premature cardiovascular mortality has decreased by 25 60% [23]. Although the proportion of such effects directly attributable to prevention projects is uncertain, many extremely effective treatments have been discovered [24 26]. Ongoing projects continue to address many persisting uncertainties regarding the management of cardiovascular disease in developed countries [27] and are likely to result in

4 Managing the global burden of cardiovascular disease F5 further modification to cardiovascular disease management strategies in those countries over the next few years. In direct contrast, data on the effectiveness of programmes for the prevention of cardiovascular disease in populations in developing countries are very limited, and there are few ongoing projects addressing that issue. Furthermore, it is uncertain whether the findings from intervention studies conducted in developed countries can be generalized to developing countries. In particular, the different social, demographic and economic conditions in developing countries make it unlikely that the findings of intervention studies conducted in developed countries will be directly transferable. The lack of reliable information on strategies for cardiovascular disease management in developing countries has been recognized by a number of bodies [8,28,29], and recommendations for research into strategies for control of cardiovascular disease in developing countries have been made. In brief, these recommendations relate to research that will provide reliable information on the burden of cardiovascular disease, the levels of cardiovascular risk factors and effective strategies for the prevention of cardiovascular diseases in developing countries. The feasibility of obtaining information on the burden of cardiovascular disease [30] and the levels of cardiovascular risk factors [19] in developing countries has already been proven. However, models for the identification of effective cardiovascular disease management strategies in developing countries are not well established. Despite a large and increasing disease burden, the resources available for cardiovascular disease management programmes in developing countries are likely to be few in comparison with those typically available in developed countries [6]. As a consequence, the costs associated with disease management programmes are likely to be of even greater importance in developing countries than they are in developed countries. In developed countries, among the most cost-effective strategies have been preventive therapies that target individuals at high risk, such as those with a history of diabetes or prior vascular disease [31]. Similar strategies focused primarily on secondary prevention are likely to be the most cost-effective approaches in developing countries. Fortunately, there are a number of low-cost treatments of proven efficacy that might form the basis for such programmes. For example, aspirin reduces the risk for vascular events by between one-fifth and onesixth among individuals who have experienced a prior stroke or heart attack [24] and costs very little. Similarly, diuretics, beta-blockers and generic angiotensin-converting enzyme inhibitors might be provided to appropriately selected high-risk individuals at very low cost, with an expectation of substantial benefit [32]. Although the rationale for clinical strategies targeting high-risk individuals is reasonably clear, the potential for community-based interventions in developing countries is less certain. Experience in higher income countries indicates that large changes in population levels of cardiovascular risk factors are difficult to achieve with community-based interventions [33 37], but circumstances in developing countries might improve the chances of success. For example, in situations where there is little awareness of issues concerning cardiovascular disease and few or no organized programmes in place for the care of individuals who are at high risk, even simple, inexpensive intervention programmes, if targeted appropriately, might result in large changes in knowledge, practices and risk factor levels [28]. Furthermore, by focusing on high-risk individuals, community-based interventions may be able to maximize the participation of those who are most likely to benefit [38]. Conclusion There is a large and increasing global burden of cardiovascular disease that can in large part be explained on the basis of sociodemographic changes and associated effects on the levels of cardiovascular risk factors in developing countries. The greatest current burden of cardiovascular disease and the greatest projected increase in the burden of cardiovascular disease are in developing countries. Cardiovascular disease prevention programmes have most likely averted much premature cardiovascular disease over the past few decades, although almost all of the available data regarding such programmes come from developed countries. Reliable information to inform the development and implementation of cardiovascular disease prevention programmes in developing countries is now required. Such programmes have great potential to impact on the current and projected epidemic of cardiovascular disease in those countries. References [1] Murray C, Lopez A. The Global Burden of Disease. Cambridge, Harvard University Press, [2] Murray C, Lopez A. Global patterns of cause of death and burden of disease in 1990, with projections to In: Investing in Health Research and Development. Report of the Ad Hoc Committee on Health Research Relating to Future Intervention Options. Geneva, World Health Organization, [3] Yao C, Wu Z, Wu Y. The changing pattern of cardiovascular diseases in China. 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