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The Prevention Of Cardiovascular Disease: Have We Really Made Progress?
Despite reductions in cardiovascular disease (CVD) mortality, current evidence suggests that CVD is not being prevented but, rather, is being made less lethal. Evidence-based guidelines have been developed for secondary, primary, and community-based prevention. To improve compliance with secondary prevention guidelines, programs must better organize and monitor care. Primary prevention requires assessment of risk in asymptomatic people, to yield cost-effective benefits. CVD prevention at the societal level should target deleterious behavior in community settings, using effective public health interventions. Policy options that involve multiple preventive approaches offer the best opportunity to minimize the economic and social burdens of CVD.
CARDIOVASCULAR DISEASE (CVD) is largely preventable, based on several lines of evidence. First, heart disease and stroke mortality rates vary greatly among countries.1 Second, several studies of people without established CVD risk factors (cigarette smoking, diabetes mellitus, elevated blood pressure, elevated blood cholesterol, and so forth) demonstrate exceptionally low rates of CVD incidence.2 Third, studies of people without deleterious health behavior (tobacco use, sedentary lifestyle, high saturated fat and cholesterol in the diet, and excess body weight) suggest that a large proportion of CVD incidence could be prevented by lifestyle modifications alone.3 Therefore, nihilistic assumptions of the inevitability of CVD development in individuals or societies are unwarranted. The intent of this paper is to describe the various approaches to CVD prevention, examine the extent to which they have been implemented, and examine policy approaches to improving that implementation.
The reductions in mortality from CVD have been appropriately lauded as one of the major health accomplishments of the twentieth century. However, these promising results have been tempered by the large annual reductions in age-adjusted CVD mortality rates slowing to 1.5 percent per year and stroke mortality not declining altogether.4 To understand mortality rates, one must know two parameters: the incidence (rate of new cases) and their case-fatality rates (percentage of cases dying of the disease). Dramatic declines in case-fatality rates have been documented over the past thirty-five years. However, at least two well-designed, population-based studies found no change in the incidence of acute myocardial infarction (AMI)—in Worchester, Massachusetts, and in Olmstead County, Minnesota—from 1990 onward.5 The recent decline in mortality has been mostly attributed to improvements in acute cardiac care and secondary prevention after CVD onset.6 In this case, policy development has been impaired by limited surveillance data, which highlights the need for improved systems of surveillance for incidence and prevalence of CVD. A stable incidence in the setting of an improving case-fatality rate can translate into only one thing: an increasing prevalence, as people previously succumbing to CVD now survive the acute presentation of the disease. These people then return to their communities as CVD cases. In 2000 the American College of Cardiology (ACC) estimated that the population of 12.5 million Americans with the diagnosis of heart disease in that year would double in size by 2050, on the basis of the aging of the population.7 Continued case-fatality reductions would further accelerate this rise in prevalence. The implications for health care costs and for public health are enormous. Some of these survivors will have sequelae of their disease—namely, disability and reduced quality of life. Almost all will require numerous medications, increased care by medical specialists, recurrent testing, and, for some, recurrent hospitalizations and invasive procedures.
Definitions of types of prevention. Secondary prevention has been classically defined as the prevention of disease recurrence and death after the onset of symptomatic disease. Because the strongest predictor for death or a recurrent CVD event is having a history of CVD, patients with such a history are all considered to be at very high risk. Primary prevention traditionally has been the prevention of the onset of symptomatic disease through the treatment of risk factors for CVD, such as treating hypertension to prevent stroke. Primordial prevention describes efforts to reduce the onset of the risk factors known to predispose people to CVD. For example, lifestyle modifications to maintain ideal body weight and to limit sodium consumption are means of preventing the development of high blood pressure. Blurring of distinctions between types of prevention. The secondary, primary, and primordial prevention distinctions are of decreasing usefulness. The advent of a variety of imaging and noninvasive testing modalities have demonstrated the ability to identify asymptomatic people with apparently established CVD.8 Tests such as exercise electrocardiography, coronary calcium scoring using computed tomography (CT) scans, ankle-brachial blood pressure indexes, and so forth provide evidence for the asymptomatic presence of atherosclerotic disease. Whether this early identification of disease will lead to prevention of symptoms is not frequently investigated, which makes it difficult for policymakers to accept or prioritize the use of these new technologies. Epidemiologic studies such as the Framingham Heart Study have provided support for the identification of high-risk people using risk-factor profiles.9 In the instance of diabetes mellitus, history of a stroke, or symptomatic peripheral arterial disease, the risk is considered so high that these patients are considered to have a "coronary heart disease equivalent," with a risk similar to a myocardial infarction (MI) survivor.10 In addition, the Framingham study developed equations to estimate absolute risk, on the basis of the level and number of risk factors, to quantify individuals’ risks over the next ten years for death from MI or coronary disease.11 Using these tools, today’s approach is to stratify people on the basis of risk. This may be viewed from a cost-effectiveness perspective, in which the total cost of a prevention program would be minimized by limiting costly and side effect–prone treatments to people at high enough risk to prevent adequate numbers of CVD cases to balance treatment costs. Several interventions have attractive cost-effectiveness ratios of $50,000–$70,000 per year of life saved.12 A small (but growing) number of people would be at high risk (arbitrarily defined as more than 20 percent risk per ten years), demanding aggressive risk-factor management, prophylactic medications, and treatment of symptoms of CVD.13 A larger group would be considered to be at moderate risk (10–20 percent risk), benefiting from risk-factor management with less costly drugs and devices. Finally, low-risk people (less than 10 percent risk) would benefit from health education, modification of harmful health behavior, and a healthier environment, at little direct personal cost.
Risk-factor paradigm in CVD prevention.
Fundamental to any prevention of CVD is the role of risk factors in the etiology of CVD and in their modification to reduce CVD risk. Risk factors may be classified into three groups (Exhibit 1
Need for a combined approach to CVD risk reduction. The risk-factor paradigm in Exhibit 1  identifies at least three opportunities for intervention to reduce CVD mortality: treatment of the symptomatic patient; treatment of behavioral and physiologic risk factors to reduce risk of disease onset or progression in individuals; and modification of deleterious risk behavior at the population level to prevent the onset of risk factors themselves. In reality, a balance of the three is required, with priorities set by the efficacy and cost-effectiveness of the interventions. Treatment of symptomatic disease does not inhibit the atherosclerotic disease process, which, left unimpeded, will reemerge with symptomatic disease from new lesions in other arterial beds. Treatment of risk factors has excellent efficacy and cost-effectiveness as part of the long-term therapy for CVD.15 Perhaps the best evidence for the merits of a balance of primordial, primary, and secondary prevention approaches is illustrated by Lee Goldman and Francis Cook, who analyzed factors explaining the reduction in U.S. mortality from coronary heart disease between 1968 and 1978.16 They concluded that only a small part of the decline could not be explained. Populationwide changes in blood cholesterol (presumably from changes in the U.S. diet) and reductions in cigarette smoking accounted for 54 percent of the decline. Changes in health care, including treatment of hypertension, emergency coronary care, and revascularization, accounted for another 39.5 percent. This illustrates the contribution of a broad and balanced CVD prevention effort, rather than one focused on a single risk factor or stage of disease.
American Heart Association (AHA)/ACC guidelines: 2006 update. The enormous evidence base regarding intervention to prevent vascular disease recurrence and death was first distilled into secondary prevention guidelines, with the most recent in 2006.17 These guidelines set down goals for risk behavior, physiologic risk factors, and prophylactic interventions in CVD patients (Exhibit 2  ).
Policy issues in secondary prevention. Unresolved scientific issues. The secondary prevention guidelines of the AHA/ACC have not met with much controversy, given the depth of evidence supporting them. One unresolved issue is the low-density lipoprotein cholesterol (LDL-C) goal in CVD patients. Several clinical trials have suggested that patients whose LDL-C levels are lowered below 100 mg/dl have fewer events than those just reaching that LDL-C goal.18 A lowering to less than 70 mg/dl is considered reasonable. This degree of reduction often requires multiple cholesterol-lowering drugs with implications for drug costs, side effects, and the need to engage a lipid specialist. The lowering of the LDL-C goal is likely less of an efficacy issue and more of a cost-effectiveness issue. Second, interventions on other lipid fractions (for example, high-density lipoprotein cholesterol [HDL-C], triglycerides) might provide a better opportunity than interventions to lower LDL-C levels even further. A third issue is the need for combinations of prophylactic drugs. The guidelines currently recommend aspirin, clopidogrel (for twelve months), beta-blockers, angiotensin-converting enzyme (ACE) inhibitors for poor left ventricular function, and usually a cholesterol-lowering drug such as a statin. The evidence supporting the efficacy of each of these drugs is derived from placebo-controlled, single-drug trials. As each intervention reduces risk and improves survival, the residual risk becomes less and less, with less cost-effectiveness. Recent proposals for combination of generic drugs into a single pill, so named the Polypill, are attractive because of very low drug costs with improvements in compliance and safety.19 Health care provider compliance. A "treatment gap" persists in the implementation of the guidelines. For example, use of aspirin, lipid-lowering drugs, and smoking intervention counseling varies considerably from one hospital to the next. Two initiatives have helped reduce this variability. First, secondary prevention guidelines were included in the earliest quality-of-care indicators. Thus, numerous third-party payers, governmental organizations, and other entities scrutinize and value the attainment of secondary prevention goals. Second, professional societies and voluntary health agencies have developed hospital-based programs to improve and maintain compliance with the guidelines, including the AHA’s Get with the Guidelines Program and the ACC’s Guidelines Applied to Practice Program.20 Such programs should be extended to ambulatory care settings. Patient compliance. Many studies demonstrate high rates of noncompliance with secondary prevention guidelines. For example, the HMG-CoA reductase inhibitors (statins) need six to twelve months of use to cause a measurable reduction in CVD events. Yet compliance studies have frequently documented 50 percent or less compliance with these agents after six to twelve months.21 Cost of the multiple drugs required in secondary prevention is often cited as a barrier to compliance, yet even 81 mg of aspirin, available without prescription for pennies per day, has a 10 percent or greater noncompliance rate. A variety of programs have been developed to improve providers’ and patients’ adherence to the guidelines. Sporadic contact (such as every six months) with a health care provider is often inadequate to maintain and reinforce complicated lifestyle modifications and pharmacologic regimens.22 Many services for lifestyle modification or more frequent follow-up care are not reimbursed. Solutions to problems encountered in the long-term management of CVD risk have been addressed by the Chronic Care Model.23 This model proposes the integration of at least six policy elements: a shift in emphasis in CVD management from hospital-based to ambulatory care; the redesign of the health care delivery system from an acute to a chronic care system; development of decision-support systems and specialty care programs; clinical information systems with reminders for long-term follow-up of patients; the involvement of community resources to support the patient; and the development and use of patient and family self-management support tools, including monitoring devices, risk behavior–modification aids, medication adherence reminders, over-the-counter (OTC) drugs, and support groups. The Chronic Care Model provides an example for better organizing efforts to comply with secondary prevention guidelines and a platform for effective risk-factor management. Implementation of its six elements would be reasonable considerations for resource allocation by policymakers.
AHA guidelines: 2002 update. The AHA Primary Prevention Guidelines contain identical recommendations to the secondary prevention guidelines for smoking, blood pressure, physical activity, weight management, and diabetes management.24 The detection and treatment of atrial fibrillation is added for the primary prevention of stroke. One important difference in the guidelines is the need to assess risk through risk-factor screening and global-risk estimation. In primary prevention, patients with a wide range of risks are encountered. The guidelines recommend that risk factors be assessed beginning at age twenty. The calculation of a global risk for coronary disease using the Framingham risk equations should be performed for all adults age forty and older using age, sex, smoking status, systolic blood pressure, total cholesterol, and HDL cholesterol levels to calculate ten-year risk. A variety of tools (for example, software programs for handheld devices, worksheets, and color-coded tables) are available for quick reference. People are then stratified into low (less than 10 percent), moderate (10–20 percent) and high (more than 20 percent) risk groups.25 Primary prevention guidelines for both aspirin use and treatment of lipid disorders are based on levels of absolute risk. The U.S. Preventive Services Task Force recommendations for aspirin use in primary prevention illustrates the usefulness of risk stratification for optimal risk-benefit ratios in primary prevention.26 Aspirin use, 75–162 mg per day, causes a small but measurable risk of hemorrhagic stroke and major gastrointestinal bleeding. On the other hand, there is substantial evidence that aspirin reduces the risk of coronary disease by 25–32 percent. The solution to this conundrum is to limit aspirin use to those with sufficient risk for CVD to assure that the coronary disease events prevented outweigh the adverse events caused. At low baseline risk (for example, 1 percent risk over five years), aspirin has a poor benefit-to-risk ratio, while at moderate risk (for example, 5 percent risk over five years), aspirin has a clear benefit in excess of risk. Absolute risk assessment then becomes a useful tool to select patients for primary preventive interventions. Policy issues in primary prevention. Lack of risk-factor screening and absolute risk assessment. Despite the recommendations that adults age twenty and older have their risk factors measured, many Americans do not know their blood pressure or cholesterol levels. The 1999–2000 National Health and Nutrition Examination Survey (NHANES) screened approximately 4,000 U.S. adults for their serum cholesterol.27 Of those with high cholesterol (240 mg/dl), only 40 percent were assessed and aware of their levels. The lack of risk-factor awareness is therefore a barrier to diagnosis and treatment. Nonetheless, some specialty societies and third-party payers do not support recommendations for risk-factor assessment in early adulthood (under age forty). Their stated rationale is that cholesterol-lowering pharmacotherapy would not be initiated in young, low-risk people, so that risk-factor screening can be delayed until the fourth or fifth decade of life or the onset of symptoms. The counterargument is that an increased awareness of a risk factor motivates lifestyle changes independent of pharmacotherapy and encourages monitoring of the risk factor so that pharmacotherapy can be initiated at the appropriate time.28 Indeed, population surveys of U.S. adults identify more than half of men age fifty and older to be at moderate to high risk, as defined by the global risk score.29 The entire idea of matching the intensity of risk-factor modification to the hazard for CVD is based on identifying those moderate-to-high-risk subjects prior to the onset of disease. Use of additional tests to further stratify risk. A variety of additional tests have been proposed to more precisely define risk, including biomarkers such as high-sensitivity c-reactive protein, imaging modalities such as coronary calcium scoring with chest CT, and functional testing such as exercise electrocardiography or ankle-brachial blood pressure ratios.30 Many of these tests are expensive, carry potential risks (such as radiation exposure), or could lead to additional testing in false-positive cases.31 Few of these risk-assessment tools have been studied in randomized controlled trials to quantify whether they really alter outcomes or justify the costs of the tests. Policies advocating their widespread implementation should await the results of these trials. Compliance with risk-reduction interventions. Only a small proportion of people aware of their risk factors are treated, and an even smaller proportion have those risk factors controlled. For example, in the 1999–2000 NHANES survey of adults with hypercholesterolemia, only 14.5 percent were using cholesterol-lowering drugs, and only 6.8 percent had total cholesterol levels less than the goal of 200 mg/dl.32 Noncompliance with weight management regimens, diets, and exercise programs all represent challenges to the office-based practitioner. The practitioner can often provide only brief, episodic advice with poor long-term results, whereas structured, longitudinal programs for lifestyle modifications, such as Phase III cardiac rehabilitation, are typically not reimbursed by third-party payers, despite their evidence for long-term efficacy.33 Self-management strategies. The Chronic Care Model advocates for the development of tools that patients can use for risk-factor control.34 Risk-factor monitoring devices, such as blood pressure, glucose, and cholesterol-measuring instruments; waist-girth measures; and pedometers to assess physical activity can be effectively integrated into a self-monitoring program. Skill- and confidence-building programs could include, for example, nutrition and exercise classes, support groups, and tobacco quit lines. Access to drug therapies might also be limited by the availability and cost of visits to primary care providers. This has led to the use of OTC medications, including aspirin, nicotine replacement drugs, cholesterol-lowering margarines, and fiber supplements. OTC availability of statins has been proposed as safe and effective. The trade-off is the increased availability of agents to safely reduce risk in the informed consumer, versus the use of pharmaceuticals without integration of their use with their overall health care by their provider. As the costs of agents such as statins decline, their cost-effectiveness is likely to improve, and policies encouraging self-management could become a strategy to expand risk reduction to a wider spectrum of the population.
AHA "Guide for Improving Cardiovascular Health at the Community Level." These guidelines are directed at the social and physical environment, rather than the medical care system or even public health agencies.35 Indeed, the targets for these guidelines are policymakers, community leaders, employers, teachers, and social service agencies. The origins of the targeted behavior are within society; therefore, the solutions for removing these risks are likely to be social and economic. The clear distinction between primordial and primary prevention relates to primordial prevention activities lying outside the doctor-patient relationship and the medical model. The social/ecologic model moreover carries economic and social benefits outside the health arena, as well as extending cost reduction to diseases other than CVD. The International Heart Health Network has issued a series of declarations that provide a policy framework for such societally oriented approaches.36 The AHA community guide organizes these efforts along three dimensions: (1) behavior targeted for change; (2) community settings in which intervention might be implemented; and (3) interventions themselves, usually organized along the lines of essential public health services. Some behavior needs to be targeted, including diet, sedentary lifestyle, tobacco use, behavior dealing with seeking screening and treatment for blood pressure and cholesterol, as well as the early recognition of symptoms of heart attack and stroke. The evidence base has tested interventions in specific community settings (such as schools, health care settings, worksites, and religious organizations). The essential public health services specifically deal with interventions at the community level, including assessment of burden of disease (surveillance), public health education involving mass media, the organization and mobilization of communities, the assurance of essential health services, and environmental change through legislation and policy change. The resulting three-dimensional matrix identifies discrete opportunities for intervention by behavior, community setting, and public health strategy. Policy issues in primordial prevention. Is a community approach needed in the presence of clinical programs for primary and secondary prevention? Risk-factor trends over the past fifteen years provide a strong rationale for a population approach, even in the setting of large expenditures for primary and specialty cardiovascular care. The National Conference on CVD Prevention documented difficulty in reducing national rates of tobacco use below 25 percent; no change in physical activity, with 40 percent of U.S. adults being sedentary; and dietary increases in carbohydrates and calories.37 These are population health issues as well as clinical ones. Policies to encourage healthy lifestyles. The AHA community guide contains fifty-nine recommendations to attain nineteen goals for policy change. For example, policy recommendations for changes in one risk behavior (physical activity) with the use of one essential public health service (environmental change) include five recommendations for improving access to physical-activity opportunities in schools, worksites, and whole communities. One area with major success from policy formulation has been the reduced initiation of tobacco use by adolescents and young adults. Policies related to taxation, elimination of tobacco advertising to young people, and restriction of tobacco sales to minors are examples of policies that have successfully targeted risk behavior. Adequate reimbursement for clinical preventive and rehabilitative services. Advocacy positions must emphasize the empirical evidence supportive of primary and secondary prevention services, including behavior modification programs, nutritional counseling, tobacco-use cessation, physical activity regimens, and cardiac rehabilitation. The current reimbursement for diabetic counseling services but not for other CVD risk factors appears inconsistent with the overall goals of the program—namely, the reduction in disease progression leading to disability, poor quality of life, and additional health care spending. Such reimbursement needs to be extended universally for control of all established CVD risk factors. FURTHER REDUCTIONS IN CVD MORTALITY will likely need to involve the entire range of opportunities to prevent CVD. Secondary prevention programs have driven case-fatality rates to extremely low levels, which suggests that there are relatively limited opportunities to make inroads on mortality through this approach alone. However, persistent treatment gaps should be removed. Primary prevention will require expansion of risk-factor assessments and global-risk scoring, with prioritization of cost-effective interventions in moderate- and high-risk people. The best opportunity to reduce CVD may be at the community and societal levels, where improvements in diet, exercise, and tobacco use have recently been elusive and where an obesity epidemic threatens to overwhelm progress made on the clinical treatment of individual risk factors. A balanced, integrated approach by policymakers should create a comprehensive program across the risk spectrum, rather than focusing on one risk factor, one segment of risk, or one type of intervention.
Thomas Pearson (thomas_pearson{at}urmc.rochester.edu) is the Albert D. Kaiser Professor and Chair, Department of Community and Preventive Medicine, and senior associate dean for clinical research at the University of Rochester School of Medicine and Dentistry in New York. He currently directs the Rochester Prevention Research Center and the Cardiology Clinic at the University of Rochester Medical Center. The author thanks Maureen Marcello and Christina McCoy for their assistance in manuscript preparation.
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