Cardiovascular Disease Trends: United States and Worldwide
Abstract & Commentary
Synopsis: The developing world is experiencing an epidemic of CAD "which expects to continue to increase in the foreseeable future."
Sources: Ergin, et al. Am J Med. 2004;117:219-227.; Arciero, et al. Am J Med. 2004;117:228-233.; Okrainec, et al. Am Heart J. 2004;148:7-15.; Yusuf, et al. Am Heart J. 2004;148:7-15.
Three recent publications have focused on the worldwide state of cardiovascular disease (CVD), including coronary disease and stroke. Two articles assess the United States experience, while the third focuses on multiple countries around the world. Ergin and colleagues analyzed the National Health and Nutrition Examination Survey Epidemiologic Follow-up Study (NHANES) which compared 2 cohorts, 1971-1982 and 1982-1992.1 The data were based on medical history questionnaires and follow-up interviews, as well as hospital records and death certificate documentation. Other surveys estimate a 60% decrease in coronary disease (CAD) and stroke between 1970 and 2000. The NHANES analysis suggests an estimated 31% decline in CVD mortality, a 33% decrease in CAD mortality, and a 37% decrease in myocardial infarction (MI) mortality. Stroke mortality declined by 38%. All of these reductions were highly, statistically significant. CAD incidence declined only in whites. Acute MI decreased a little, and actually increased 21% in white women. The incidence of stroke declined overall except in black males. One month hospital fatality rates fell by 27-38% for all end points, particularly striking in black subjects. Ergin et al conclude that the decline in CV disease mortality was associated with a 3% decrease in CV disease incidence, as well as improvements in both short term and long term survival. The data suggest "that the decrease in mortality from cardiovascular disease was likely due to a combination of primary prevention, which reduced cardiovascular disease incidence, and secondary prevention and treatment, which reduced short- and long-term case fatality rates." There was a robust fall in age adjusted mortality from CAD and MI, but the incidence of MI remained stable among white and black men and women, but was increased somewhat in white women. This was also true for recurrent MI. In spite of relatively stable rates of MI incidence, 1 month and long term survival improved significantly. Ergin et al point out that their analysis is consonant with other community surveillance studies and national vital statistics. Ergin et al attribute the ". . . substantial decline in stroke incidence" to "a large reduction in mean blood pressure levels and improvement in detection, treatment, and control of hypertension." However, no data to confirm this are provided. Analysis of both the earlier and later cohort surveys indicates a narrowing of the difference in CV mortality rates between blacks and whites. Ergin et al conclude that the decrease in CV mortality from the 1970s to the mid 1990s "can be explained by a decline in both cardiovascular disease incidence and case fatality rates." They emphasize that while CV disease remains the U.S. leading cause of death, vigorous primary and secondary prevention efforts, as well as improved treatment must continue to be emphasized.
In a similar article assessing the Olmsted County, Minnesota, population between 1979-1998, Arciero and colleagues confirmed a modest decline in coronary disease incidence and conclude CV mortality decreases are explained both by primary and secondary prevention.2 Arciero et al emphasized the rate of increasingly early detection of CAD. In the Olmstead County data, CAD incidence was relativity stable but mortality decreased, as in other data bases. This study, part of the Rochester Epidemiologic Project, determined trends and incidence of several CAD manifestations. Because of the stable population in Olmstead County (the site of the Mayo Clinics and a relatively white population isolated from urban centers), these data are felt to be valid. Arciero et al analyzed incident CAD events, including MI, sudden death, and angiographic CAD. The latter is not felt to be a reliable method of examining trends, as there was an enormous increase in coronary angiography beginning in the 1980s. Arciero et al found that the overall incidence of CAD declined modestly. Sudden death decreased. MI rates were somewhat lower between 1979 and 1998. Documentation of CAD was considerably more common than the incidence of MI and sudden death. There was a 9% decrease in CAD incidence between 1988 and 1998. Overall, the incidence of combined hospitalized MI and sudden death decreased by 17% over the 20 years. MI rates were little changed, concordant with other studies. As in the NHANES analysis, MI rates in women, and in this study, older individuals, actually increased. Arciero et al stress the early detection of CAD in this population, in part related to the widespread use of coronary angiography, and note the discrepancy between the increasing burden of CAD, as documented by angiography and the decline in CVD incidence. The age and sex related trends for all CAD parameters were comparable. Arciero et al conclude that overall, "trends in the age- adjusted incidence in coronary disease in the 1990s paralleled the trends in myocardial infarction and sudden death." They note that in Olmsted County, there has been relative shift of CAD burden to women and older persons. Arciero et al cite both primary and secondary prevention improvements to explain the modest decrease in CV mortality during the study interval. They call for an increase in prevention efforts in the aging population; the decreases in CAD incidence in younger individuals, particularly males, was noteworthy. In conjunction with the Ergin et al, Arciero et al believe that "declining CAD mortality is multifactorial, explained in part by primary prevention and secondary prevention and mediated by earlier detection."
The last study is an assessment of CAD in the developing world.3 This is a sobering overview of CAD in multiple countries derived from an extensive review of Medline database articles from 1990 to 2002 regarding CAD prevalence in developing countries. Okrainec and colleagues conclude that there is relatively sparse, reliable data regarding CAD in the developing world, but it is clear that overall, CAD mortality rates are increasing, and are projected to double between 1990 and 2002 , almost all attributable to the developing world countries.
Multiple factors, including increasing exposure to CAD risk factors (diabetes, hypercholesteremia, hypertension, smoking) and a "relative lack of prevention and control measures to decrease exposure to these risk factors in developing countries, are contributing to what appears to be a projected epidemic." Furthermore, there has been a major decline in infectious disease mortality. Thus, this "epidemiologic transition" is in part due to increased longevity, with greater exposure for CAD to manifest developing as individuals live longer due to the decline in communicable diseases. Furthermore, globalization of dietary habits and urbanization are major factors in developing countries that increase the risk of CAD by exposure to risk factors. Dietary practices, with enhanced consumption of sugar and fat and increased sedentary lifestyles are also more common than in the past. Diabetes incidence and prevalence is increasing worldwide, much attributed to the atherogenic "western diet." They note that almost half of the world’s diabetic population is found in China. Smoking has increased in Africa by 40% over the past 2 decades. Higher socioeconomic class appears related to a higher prevalence of CAD in developing populations. This may relate to increased diabetes and obesity. Okrainec et al discuss prevention and control approaches, which are highly variable from region to region. The WHO global study of risk factors called INTER-HEART is evaluating risk factors for acute MI in 46 countries, so that risk factors may be isolated as to their contribution to CAD in different populations. They conclude that the developing world is experiencing an epidemic of CAD "which expects to continue to increase in the foreseeable future." Adverse dietary practices, high rates of tobacco use, urbanization, and sedentary lifestyle are all major factors. Okrainec et al estimate that current statistics underestimate the extent of the CAD epidemic, and they call for immediate prevention and control measures from the developing world, such that CAD prevalence and mortality can be reduced by primary and secondary prevention. "Thus, an opportunity before the international community to intervene in the growing threat of CAD worldwide."
Comment by Jonathan Abrams, MD
These articles represent somewhat difficult reading for the non-epidemiologist or sophisticated expert. Nevertheless, the first 2 reflect what has been happening in the United States, which contrasts markedly to the developing world. In our country, CAD prevalence has declined somewhat, as well as myocardial infarction, but this is not as dramatic as predicted several decades ago. Clearly, the prevalence of CAD in the United States, is in part related to the aging of our population, providing far more individuals the likelihood of developing vascular disease. One conclusion that can be drawn from these data are that western countries, and in particular the United States, have benefited remarkably from policies of early detection, appropriate treatment, and prevention. The armamentarium available to physicians today is remarkable, with respect to CAD prevention and treatment, compared to just 20 years ago. As our therapies keep patients with CVD alive longer, and the population ages, there clearly will be plenty of vascular disease for American physicians to deal with for decades. The flipside is the very disturbing statistics and predications relating to CVD in developing countries. New data confirms that emotional stress is an important risk factor not adequately appreciated. An editorial by Yusuf et al4 lays out a worldwide plan for dealing with the challenge of cardiovascular disease in developing countries. However, as with the current war against HIV/AIDS, there are profound obstacles to implementation of these proposals, and it is difficult to have much optimism that the dire developing country analysis can be significantly and favorably impacted with the modern day detection and prevention strategies so available to the Western world.
Dr. Abrams, Professor of Medicine, Division of Cardiology, University of New Mexico, Albuquerque, is on the Editorial Board of Clinical Cardiology Alert.
The developing world is experiencing an epidemic of CAD which expects to continue to increase in the foreseeable future.
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