33RD BETHESDA CONFERENCE: TASK FORCE
Task Force #1—magnitude of the prevention problem: opportunities and challenges
Emelia J. Benjamin, MD, ScM, FACC, Co-Chair,
Sidney C. Smith, Jr, MD, FACC, Co-Chair,
Richard S. Cooper, MD, FACC,
Martha N. Hill, RN, PhD, FAAN and
Russell V. Luepker, MD, MS, FACC
Cardiovascular disease (CVD) is the leading cause of death and disability in most Western industrialized countries including the U.S., cutting across all ethnic, racial, and gender groups. Despite the tremendous body of research to support the efficacy and cost-effectiveness of CVD prevention, interventions to prevent CVD are universally underutilized. This section describes what is known about the epidemiology of CVD, the distribution of CVD risk factors, and the impact of treating CVD risk factors. The following is a broad overview of the barriers to achieving CVD risk-factor reduction and the measures that must be pursued to enhance risk-factor reduction and CVD prevention. Research, funding, and policy recommendations that would improve CVD prevention, if embraced, will be provided.
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Epidemiology of CVD
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Global burden.
Cardiovascular disease includes common conditions, such as coronary heart disease (CHD), stroke, hypertension, and heart failure (HF), and those less common, such as congenital heart disease, cardiomyopathy, and peripheral vascular disease (1). Cardiovascular disease is increasing in prevalence in many regions of the world, particularly in developing countries and in formerly socialist countries (2). Worldwide, it is estimated that death from CHD will increase 100% in men and 80% in women from 1990 to 2020, with the majority of that increase coming from Asia, Africa, and Latin America (2). Similarly, disability-adjusted life-years lost will increase 107% in men and 74% in women worldwide (2).
The reasons for this epidemic are easily identifiable. The 20th century saw dramatic economic improvement, with declines in major infectious diseases and malnutrition in industrialized countries. Associated with a longer life span and affluence has been the emergence of chronic diseases that occur among those living past middle age. Changes that were seen in the 20th century in industrialized countries are now increasingly observed in the developing world. Technology and the expanding control over the environment have resulted in abundant food supplies in many nations. Industrialization of everyday life with laborsaving devices and motor transportation results in a loss of regular physical activity and the assumption of a sedentary lifestyle. The combination of inactivity and surplus calories (particularly from animal products) contributes to abnormal blood lipids and elevated blood pressure (BP) and results in widespread obesity, diabetes, and excessive risk of CVD. Inexpensive machine-made cigarettes and the social acceptance of tobacco smoking result in widespread nicotine addiction and the many chronic illnesses associated with tobacco. These dramatic changes in the social and economic environment, which are unparalleled in human history, are resulting in massive elevations in both the risk and expression of CVD (3).
Genetic influences.
The transformation of the social environment, coupled with increased longevity, have unmasked a genetic susceptibility to a number of chronic diseases. Although it is very unlikely that evolution would result in genes that promote lethal diseases, it is hypothesized that so-called "thrifty genes" were adaptive in a primitive world of deprivation and danger. The retention of sodium, storing of food calories, and preparation for severe stress were protective of humankind’s existence (3). However, in an aging society of affluence, such genes may promote high BP, obesity, and maladaptive responses to stress. The effect of the environment on genetic susceptibility is best exemplified in evaluative studies of individuals from low-risk, low-CVD cultures who migrate to Western cultures, such as Japanese from Japan to California. The low-risk Japanese become like their white neighbors in disease-risk factors and expression when they assume their high-risk environment and behaviors (4).
Gender.
Cardiovascular diseases are manifest earlier in the lives of men, and much of the focus of research has been on this group. Although women manifest CVD 10 to 15 years later than men, the overall morbidity and mortality over a lifetime is similar in men and women (1). Many Americans do not realize that CVD mortality for both men and women is higher than mortality from all cancers combined. Women are now appropriately recognized as frequent victims of CVD; thus, programs oriented to the diagnosis and treatment of CVD in women as well as men increasingly are being emphasized in the U.S.
Racial and socioeconomic disparities.
In a period of epidemiological transition, chronic disease epidemics usually emerge first among economically advantaged segments of society, and the burden is subsequently shifted to the working class and minority populations (5,6). Cardiovascular disease represents one of the most dramatic examples of this process. Not only has the overall rate of CVD changed dramatically in the U.S. over the last 50 years, the distribution of disease burden among sociodemographic subgroups has changed as well. Although virtually every U.S. subpopulation has experienced a decline in mortality from CHD, the rate of decline has been much steeper among those of higher socioeconomic status. National data by social class are limited, because the required information was not collected on death certificates until the 1990s. However, trends by geographic and racial/ethnic categories confirm these growing disparities in CVD (7). Income inequality is correlated with CVD incidence and may partially account for these worsening trends (8). Black Americans now experience the highest age-adjusted rates of heart disease, in addition to the highest rates of stroke, as has been noted for many years (7). Native Americans, Asians, and Hispanics, on the other hand, currently have rates of both CHD and stroke that are substantially lower than among the white majority population (9), although the limited data that are available suggest relative increases in rates of CVD among Native Americans. Economically disadvantaged neighborhoods (10) and regions of the country (e.g., Appalachia and the South) experience higher rates of CVD (7). One of the most extreme examples can be found among blacks in Mississippi, in whom CHD rates are still rising in absolute terms, and a very large gap has emerged in comparison to the majority population. This heterogeneity in trends requires a broadening of the definition of "high-risk." Whereas the term previously referred to individuals whose coronary profile put them at increased risk of CVD, high-risk population subgroups can now be identified on the basis of sociodemographic profiles.
Temporal trends.
Perhaps the most striking disease trend in the U.S. during the 20th century was the rise of age-adjusted CVD to a peak in the 1960s and a subsequent decline. Similar, although somewhat delayed, patterns were observed in much of Western Europe. In many of the former socialist countries and the developing world, increasing rates of CVD continued in the last part of the 20th century (1,11).
There are other trends in CVD not readily apparent in the overall age-adjusted data. For example, although age-adjusted rates have declined steadily, absolute mortality (i.e., the total number of deaths) has changed little in the past two decades (12,13). Cardiovascular diseases are still highly prevalent but have been pushed into older age groups, a trend obscured by age adjustment.
Also apparent in the mortality trend is the wide difference between in-hospital and out-of-hospital mortality. Out-of-hospital mortality accounts for approximately two-thirds of all deaths from CHD (14). Whereas in the 1970s and early 1980s, in-hospital and out-of-hospital mortality fell in a parallel fashion, more recent data from the late 1980s and 1990s found in-hospital mortality falling more rapidly. Sudden, out-of-hospital death comprises an increasing proportion of the mortality burden. This pattern, combined with increasing rates of HF mortality and a gradual leveling of stroke mortality, finds overall age-adjusted CVD mortality still falling, but more slowly than during the period from 1970 to 1990 (Fig. 1) (13). Finally, these trends are not equally manifest in all ethnic groups, with the poor and ethnic minorities manifesting less positive changes, as noted earlier.
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Figure 1 CHD mortality trends by race and gender, U.S. 1979–1998. CHD = ICD-9 410–914, 429.2. Data source: CDC Wonder.
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Many factors have been invoked to explain these trends. In earlier years, better detection and treatment of hypertension contributed to declines in CHD, stroke, and HF mortality. Similarly, falling levels of blood cholesterol associated with improved dietary patterns influenced the atherosclerotic diseases. Finally, cigarette smoking decreased, dramatically influencing many diseases (15). However, in the 1990s, risk factors did not decline at the same rate. In fact, obesity and diabetes are increasing in the U.S. population, and physical inactivity is common and is not improving. At the same time, medical care has advanced considerably leading to improved survival (reduced case fatality) in acute myocardial infarction (MI). While enhanced medical care reduces mortality and prolongs survival, it adds to the number of prevalent cases in need of secondary prevention.
These contrasting trends lead to both optimistic and pessimistic inferences. On the one hand, the highly dynamic nature of the trends demonstrates that broad interventions aimed at CVD control can be highly effective. On the other hand, the moderating decline and the fact that current approaches apparently lack efficacy for many segments of our society suggest that "more of the same" may not be successful and that new interventions and implementation strategies will be required.
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Cardiovascular risk factors: distribution and impact of treatment
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Relationship of risk factors to major CVDs.
Atherosclerosis and hypertension are lifelong processes that result in diseased arterial vessels that ultimately restrict blood flow, reaching the clinical spectrum in late middle age. This pathology is manifest as MI, stroke, congestive HF, peripheral vascular disease, and other conditions (Fig. 2). The scientific understanding of the origins of this lifelong illness and its etiologic mechanisms is substantial. To the classical risk factors of hypertension, hypercholesterolemia, and cigarette smoking are added diabetes, obesity, and sedentary lifestyle. Genetic factors play an important role in the development of these risk factors (e.g., familial hypercholesterolemia) and susceptibility to the progression to CVD. A second level of risk factors associated with the atherosclerotic lesions, more recently described, may play an important role in combination with classic risk factors. Such factors include inflammation, endothelial dysfunction, hypercoagulability, insulin resistance, and others. Finally, acute risk factors may precipitate atherosclerotic plaque rupture and be crucial in sudden out-of-hospital cardiac death, acute MI, and stroke. Such factors include heavy physical exertion, sexual activity, emotional stress, and nicotine (16). Knowledge about the detection, treatment, and control of risk factors provides the impetus and rationale for CVD prevention.
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Figure 2 Risk factors. LVH = left ventricular hypertrophy; MI = myocardial infarction; PVD = peripheral vascular disease.
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Global distribution of risk factors.
The distribution of risk factors in different parts of the world varies considerably, resulting in high- and low-risk cultures. Key observations that led to the identification of classical CVD risk factors have come from international comparisons such as the Seven Countries Study (17). This study demonstrated that differences in disease rates among the U.S., various nations in Europe, and Japan were directly related to BP, eating patterns, blood cholesterol, and cigarette smoking. More recent comparisons with similar findings were found in the Monitoring Trends and Determinants in Cardiovascular Disease (MONICA) Study, which principally included centers not only in Europe but also in North America, Australia, and Asia (18).
Just as the global burden of CVD is great, the burden of risk factors within geographic areas closely matches those disease patterns. In addition to the substantial continuing burden of CVD risk factors in Western industrialized countries, there is an increasing burden of risk in other parts of the world. Rich diets, obesity, sedentary lifestyle, cigarette smoking, hypertension, elevated blood lipids, and diabetes, common in the U.S., are increasingly observed in developing nations. These observations underlie the concerns about a coming global epidemic (3).
Age.
The major CVDs are conditions associated with gains in life span (e.g., atherosclerotic lesions increase with advancing age). While 19% of all deaths in the 35- to 44-year-old age category are due to CVD , 53% of deaths are CVD-related by age 85 years (13). This age–disease relationship is consistent across genders and ethnic groups in the U.S. (1). The prevalence of classic risk factors of blood cholesterol and cigarette smoking in the population declines with age. For example, smoking rates are under 10% for those over age 84 (19). The decline in smoking with advancing age is partially due to smoking cessation in the elderly and to selective attrition as those at highest risk succumb to the disease. Systolic BP climbs with age, presumably as a result of increasingly noncompliant blood vessels, and continues to carry increased risk. Although the average prevalence and relative risk of risk factors are lower in the older adult group, blood lipids, cigarette smoking, and hypertension remain predictive of mortal and morbid outcomes, and the absolute risk of these risk factors is greater, resulting in an enormous burden in the older adult population (20).
The crucial importance of aging as a risk factor for CVD relates in part to the aging of the population. In 2000, the U.S. life expectancy at birth achieved a new high of 76.9 years (21), up almost 30 years from 1900, when life expectancy was 47 years. It is estimated that currently one in every eight Americans is age 65 years or older; a number expected to increase to one in five by 2030 (22). Because the incidence of CVD, such as HF, MI, atrial fibrillation, and stroke, increases dramatically with advancing age, CVD will place an increasing burden on the health care system in the new millennium.
Gender.
Cardiovascular (CV) risk factors differ by gender, as does their treatment. Mean blood cholesterol levels are higher in men than in women until the sixth decade, and higher in women after that (14). Women are less likely to be treated for elevated blood cholesterol than men (23). Blood pressure and the prevalence of hypertension are higher in men than in women across the age spectrum, though the differences narrow in the elderly. However, high BP is more likely to be detected, treated, and controlled among women (24). Rates of smoking in the U.S. and most Western industrialized nations were higher in men than in women for many years, but women have lagged behind men in the decline in smoking prevalence. Hence, the gap between male and female smoking rates has narrowed (25). Although there are differences, other major risk factors, including obesity and diabetes, are high and increasing for men and women.
Ethnicity and socioeconomic status.
As is well known, a fundamental racial/ethnic differential for BP is found in the U.S., with twofold excess of hypertension among black Americans. Mean blood pressures are approximately 5 mm Hg higher in the adult black population; treatment and control rates are currently somewhat better for whites than blacks (26). As in the past, this differential accounts for some of the excessive CVD mortality. Among Mexican Americans, hypertension rates are similar to whites; however, the rate of detection, treatment, and control is low. Among men in this ethnic group, for example, only 11% of those with hypertension are controlled, compared with a national average of 28% (27).
Racial and economic disparities in cigarette smoking also have been observed. Native Americans have the highest rates of cigarette use, whereas Asian and Hispanic women have the lowest. Tobacco use declined through the early 1990s and appears to have leveled at 25% of the population (7). Further declines appear to have slowed for all ethnic groups. The greatest declines have been among persons with a college education.
White and black Americans have similar levels of total serum cholesterol, although blacks—particularly black men—have higher levels of high-density lipoprotein cholesterol and lower triglycerides (28). Other U.S. ethnic groups have usually been found to have lower cholesterol. A positive social class gradient (i.e., lowest levels among persons with the least educational or occupational attainment) was observed in surveys in the 1960s; however, by 1990 that gradient had been reversed.
Among the most important emerging differentials in CVD risk is that observed for obesity and diabetes (26). A sharp social class gradient exists for obesity, especially among women, and is associated with a similar pattern for type II diabetes. All the major ethnic subpopulations in the U.S., with the exception of Chinese and Japanese, have twofold greater prevalence of diabetes than do whites.
Temporal trends: risk factors are changing in the U.S. population.
Risk factors in the U.S. population continue to change in a complex pattern. Currently, within the U.S., elevated risk factors are quite common, with hypertension affecting 25%, hypercholesterolemia 20% to 50%, and cigarette smoking 25% of the adult population. The classic risk factors consistently improved through the 1970s and 1980s. Perhaps the most outstanding success story is that of cigarette smoking. Cigarette consumption per capita for individuals age 18 years and older rose steadily from 1900 through the late 1960s. Since that time, it has steadily declined, though in recent years that decline has been slower (29). The National Health Interview Survey found that 37.6% of adult men smoked in 1980 and 28.4% in 1990. Similar declines were noted among women. However, there is significant variability by region of the country. In 1999, the percentage of adults who smoked ranged from a high of 29.7% in Kentucky to a low of 13.9% in Utah (30). In states such as California and Massachusetts, where increased taxes have been used for tobacco education and research, some of the lowest smoking rates (18.7% and 19.4%, respectively) have been observed.
Similar to cigarette smoking, there was a consistent fall in elevated blood cholesterol and hypertension between the Second National Health and Nutrition Examination Survey (NHANES II) (1976 to 1980) and the Third National Health and Nutrition Examination Survey (NHANES III) (1988 to 1991) studies. Between NHANES II and NHANES III, the prevalence of hypertension fell 42.5% in men and 38.9% in women (31). These data, while somewhat inaccurate because of differing measurement methodologies, are observed in other population studies (32). In addition, blood cholesterol above 240 mg/dl (greater or equal to 6.2 mmol/L) dropped 28.9% in men and 27.6% among women, and the mean cholesterol in adults decreased from 220 mg/dl to 205 mg/dl in the same period. This striking difference results largely from dietary changes in the population, as few individuals during this period were under treatment with cholesterol-lowering medications (14). However, more recent data suggest that despite the availability of more effective pharmacologic treatment methods, blood cholesterol in the population is no longer falling (23).
Likewise, leisure time physical inactivity has not declined in recent years (33). Approximately 25% of Americans age 18 and older report no leisure-time physical activity, and only 23% of American adults report vigorous sustained physical activity of any intensity lasting 30 min or more five times a week. The majority of Americans fail to reach the recommended amount of physical activity. Inactivity is more prevalent among women than men, among blacks and Hispanics than whites, and among older than younger adults (34). Physical inactivity is closely related to obesity, hypertension, and unfavorable lipid levels.
Finally, other risk factors are moving in the opposite, unhealthy direction. The population is gaining weight at an alarming rate. The prevalence of obesity (body mass index greater than 30 kg/m2) increased 61.8% in men and 50.9% in women between NHANES II and NHANES III (35). Increasing obesity affects both genders and all race groups but is particularly marked in black women (26). Associated with increasing obesity is type II diabetes, which is also increasing in the population (1). Diabetics also frequently have hypertension, hyperlipidemia, and other conditions that add to their risk of CVD. The Framingham Study found that diabetics have double the age-adjusted CVD risk in men and triple in women compared with non-diabetics (1,36).
In summary, the prevalence of CV risk factors is changing. Although some of these changes are in a favorable direction, such as cigarette smoking, cholesterol, and BP, the majority of other risk factors in the 21st century are not showing similar trends. The loss of momentum is a cause for concern.
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CVD prevention
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Primordial prevention with health promotion.
Considerable progress in the primary and secondary prevention of CVD has occurred in the past 30 years. Risk factors are identified and treated in those not yet ill (primary prevention) and among those with established CVD to prevent recurrent events (secondary prevention). It is time to consider whether elevated risk factors are, in fact, necessary and inevitable. Should we consider primordial prevention (i.e., the prevention of risk factors) in the first place? This may be the only viable strategy if ultimately we are to eliminate these diseases and expand the achievements of primary and secondary prevention (Fig. 3).
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Figure 3 Cardiovascular disease prevention opportunities. ACE-I = angiotensin converting enzyme inhibitor; ASA = aspirin.
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The predominant focus on the manifest-disease end of the spectrum of risk factors may have inadvertently robbed the community of opportunities for prevention. Although the development of risk-factor thresholds (e.g., hypertension being defined as a BP greater than 140/90 mm Hg, systolic and diastolic, respectively) has helped patients and clinicians focus on treatment objectives, such cut points have obscured the continuum of risk. Normal levels are inappropriately assumed to be desirable. For instance, BP levels considered by most clinicians and patients to be "normal" (systolic pressure of 130 to 139 mm Hg, or diastolic pressure of 85 to 89 mm Hg, or both) are associated with a risk-factors-adjusted hazard for CVD of 2.5 in women and 1.6 in men (37).
If studies of individuals at the healthiest end of the risk-factor spectrum are examined, successful primordial prevention would shift the population distribution to a higher prevalence of individuals with optimal risk factors. Such a shift would end the CVD epidemic and would significantly extend life expectancy (38–41). The definition of "optimal" or "low risk" varies somewhat from study to study but generally includes a combination of having low cholesterol (less than 200 mg/dl), low BP (less than or equal to 120/80 mm Hg), desirable body weight (body mass index is less than 25 kg/m2), no current smoking, and an absence of diabetes and prior CVD. Currently, the percentage of individuals in the U.S. and Europe with low risk-factor profiles is low, on the order of 3% to 10%. (38,39). Of note, individuals with low-risk profiles have markedly better prognoses, with an 80 to 90% decrease in coronary events and CVD mortality (38,39) and an estimated gain in life span of 6 to 10 years (38).
Progress toward the goal of primordial prevention has achieved mixed results. For most risk factors (e.g., high cholesterol) a basis for action exists, effective results have been demonstrated in trials, and reductions in cholesterol have been observed in the population. The Dietary Approaches to Stop Hypertension study has demonstrated that nutritional intervention reduces high-normal BP and cholesterol in adults (42). Observational data from the Nurses’ Health Study suggests that 91% of cases of diabetes were associated with unhealthy behaviors and habits (43). A recent trial from Finland testing the efficacy of moderate weight loss and exercise (44), and data from the larger Diabetes Prevention Program clinical trial examining diet and exercise, demonstrate that diet and exercise significantly lower the risk of diabetes (45). Hence, the available evidence supports recommendations for exercise and for healthy eating patterns (low sodium, low saturated fat, low cholesterol, and high intake of fruits and vegetables), to prevent a number of chronic diseases.
Is primordial prevention feasible? A primordial prevention strategy will require a very different approach from the current high-risk strategies. The campaign will need to confront many of the social, cultural, and community aspects of elevated risk. Primordial prevention will require a focus on youth and a particular emphasis on exercise and diet (minimizing fat, calories, and sodium) (46). There are data on the positive effects of programs beginning in youth, though further research is clearly needed (47–49). Healthy communities and healthy societies should be the goal. While risk factors in the U.S. track from childhood, there are many societies in the world that do not have a progressive elevation of BP with age and do not increase their lipids after adolescence. In these societies, physical activity and healthy diets are the norm, and CVD does not occur at epidemic levels. Such is the hope, promise, and challenge of primordial prevention of CVD.
Primary prevention.
The undeniable health and survival benefits of optimizing of CVD risk factors have been documented by numerous observational and randomized controlled trials and have been incorporated into widely disseminated guidelines (50,51). Meta-analyses and cost–benefit analyses (reviewed in depth in Task Force 2) of BP reduction (52), cholesterol lowering (53,54), increased physical activity (55), glucose control in diabetics (56), weight loss among obese individuals (57), and smoking cessation (58,59) reveal significant reductions in a wide variety of CVD end points (including MI and stroke), health care expenditures, and death.
Evaluating the individual’s global risk is essential in gauging the intensity of intervention, as has been highlighted by a previous Bethesda Conference (60). Until recently, practitioners and professional societies have focused on treating individual risk factors in treatment plans and practice guidelines. However, risk factors frequently cluster in the individual, and risk escalates dramatically with the accumulation of risk factors (61). This is particularly true of patients affected by the metabolic syndrome, wherein insulin resistance is accompanied by obesity, hypertension, and an unfavorable lipid profile (62). The presence of diabetes is now understood to confer equivalent risk on established CVD (63), and hence recent guidelines emphasize that subjects with diabetes are appropriately treated with secondary prevention thresholds developed for patients with prior CVD events (64). Despite the rapid growth in scientific knowledge, as previously described, evidence suggests that the decline in most risk factors seen from 1970 to the 1990s has either slowed or stopped. A number of factors may be responsible. The segments of the population that are most willing to adopt preventive recommendations have been reached. Remaining obstacles are often deeply embedded in the structure of our society—for example, the high salt content of processed food and the lack of opportunity to maintain an active lifestyle in many communities. Regaining the momentum in primary prevention will require widespread policy changes and education.
Primary prevention encompasses strategies to prevent clinical events after the development of risk factors that require drug treatment. Unless we effectively implement primordial prevention, 21st century public health may have to incorporate lifelong "pill taking" among those at high risk. As we develop new policy directions in primary prevention, the magnitude of the challenge to control risk factors in those who have already developed them is becoming better recognized. In the U.S. the prevalence of hypertension is 25%, and 18% of the population meets the new criteria for drug treatment of hypercholesterolemia (65). To reach this large a segment of the population, new approaches to detection, drug distribution, and strategies to maintain adherence will be required.
Secondary prevention.
The implementation of preventive therapies after a clinical event or manifestation of an underlying atherosclerotic process, termed "secondary prevention," has received increased attention and emphasis during the past decade. This emphasis on secondary prevention has been attributable largely to the increase in survival resulting from an improved treatment of patients presenting with acute coronary syndromes and the emergence of several landmark studies demonstrating the efficacy of preventive interventions in reducing subsequent mortality and morbidity in this patient population.
Patients with established CVD are at high risk for future events and therefore merit the implementation of aggressive secondary prevention therapies (65,66). Sudden death is 4 to 6 times more frequent among survivors of MI than in the normal population. Patients who survive MI until discharge have a one-year mortality rate as high as 26% to 36% if they have moderate or severely decreased left ventricular systolic dysfunction and clinical or radiographic signs of HF during hospitalization (67). Increasing numbers of patients are being diagnosed and hospitalized with CHD. From 1979 to 1998, hospital discharges for CHD increased 24.5% for men and 26.4% for women (1).
The American Heart Association (AHA), American College of Cardiology (ACC), and other professional and governmental organizations have endorsed secondary prevention interventions through the formulation of guidelines, which should be widely used for the secondary prevention of atherosclerotic CVD (66,68). These recommendations generally include: 1) smoking cessation; 2) BP control to a goal of less than 140/90 mm Hg (or lower with co-morbidity); 3) management of dyslipidemia to a target low-density lipoprotein cholesterol level less than 100 mg/dl using dietary measures and lipid-lowering therapy; 4) regular exercise; 5) weight management; 6) diabetes management; 7) angiotensin-converting enzyme inhibitor therapy (ACE-I), especially for those with depressed ventricular function; 8) antiplatelet therapy; and 9) beta-blocker therapy. Similar guidelines for the treatment of HF have also been developed (69). The evidence-based support for these recommendations is compelling. Most of the interventions are associated with reductions of 20% to 30% in total mortality, similar reductions in recurrent CV events including stroke, and the need for revascularization procedures (70). Adherence to the treatment guidelines is also associated with improved quality of life (71).
Unfortunately, secondary prevention therapies are not fully implemented. Studies from the Health Care Financing Agency (now called Centers for Medicare and Medicaid Services) and several large registries indicate that on average, among ideal candidates, appropriate treatment is received by less than 25% for lipid-lowering therapy, less than 25% for smoking cessation, and less than 65% for ACE-I and beta-blockers (72–74). A recently published study from the NHANES III database suggests that among survivors of stroke or MI almost half of the subjects with hypertension, hypercholesterolemia, and diabetes have inadequate risk-factor control (75). There is significant regional variation in the U.S. in the use of secondary prevention therapies; with the greatest implementation generally in the Northeast and the lowest in the Southeast. There is also reported lower use of secondary prevention therapies among the elderly (73,76) and certain ethnic groups, particularly black Americans (75). Of concern is the low utilization of cardiac rehabilitation programs nationwide, estimated to be less than 20%, which offer the potential for support of secondary prevention therapies. Similar to other preventive modalities, cardiac rehabilitation programs are disproportionately underutilized by the elderly, women, minorities, and those living in the southern U.S. (77). It is important to recognize that lack of insurance coverage may contribute to underutilization of cardiac rehabilitation.
Studies using hospital-based secondary prevention treatments have been initiated by several groups including the AHA and the ACC. The initial results from these programs suggest that significant improvement in treatment rates, which are associated with reductions in one-year mortality, can be achieved (78,79). In addition, analyses of the economic benefits suggest that the implementation of secondary prevention treatments would be cost-effective compared with standard high-technology approaches (see Task Force #2) (80,81).
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Barriers to achieving risk-factor reduction
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Community and societal barriers to the prevention of CVD.
The fundamental contribution of lifestyle behaviors to the prevention and reduction of risk factors, and the high prevalence of risk factors in most population groups, mandate a public health approach to preventing CVD. Community-wide as well as clinical strategies must be employed in an effort to reduce both individual and population risk.
As reviewed in depth by Task Force #3, research has demonstrated that interventions to date have increased knowledge, changed lifestyle behaviors, and improved risk factors. However, CVD morbidity and mortality in the intervention communities did not exceed the gains observed in control communities (82). Only one of the six community CVD Prevention studies (83–89), the Franklin Cardiovascular Health Program, has demonstrated a reduction in mortality. It is possible that secular trends were shifting the population distribution of risk factors during these years. Confounding changes, such as the rise in obesity, may have blunted the effect of the interventions. Furthermore, none of these studies had the statistical power necessary to examine subgroup differences that might illustrate significant effects of the interventions. It may be that study designs other than clinical trials, which evaluate the effects of more intensive interventions or interventions delivered over longer periods of time, would result in more encouraging results.
Despite the difficulties of effective intervention, the importance of community, socioeconomic, and environmental barriers to risk reduction has been demonstrated by numerous studies (90). In Harlem, a survey was conducted to examine the prevalence and social correlates of CVD (91). A high prevalence of major risk factors and the presence of multiple risk factors were observed. Income and education were inversely related to hypertension, smoking, and physical inactivity. Having three or more risk factors was associated with low income, low education, and a history of unstable work or homelessness.
Recently, the National Heart, Lung, and Blood Institute (NHLBI) as part of a Request for Application (RFA) targeting underserved minorities, funded several studies examining community-based hypertension programs and the extent to which they are linked to clinical care. A clinical trial in Seattle assessed the effectiveness of enhanced tracking and follow-up services provided by community health workers in promoting medical follow-up of persons whose elevated BP was detected at community sites. The enhanced community health worker intervention increased medical follow-up by 39% (92). Ward et al. (93) in Los Angeles are conducting a clinic- and community-based study of hypertension control focusing on environmental and psychological factors related to treatment adherence. The investigators are examining the effects of three interventions: individualized counseling sessions, home visits/discussion groups, and a computerized appointment-tracking system to evaluate how to most effectively enhance adherence to hypertension treatment. Studies of this nature will provide valuable insights into patient adherence.
Community-based studies have contributed to our understanding of the importance of the environmental, social, and cultural context of individuals’ CV risk. Environmental stressors and accepted cultural "norms" may be barriers to achieving CV risk reduction and must therefore be identified and addressed to realize the reductions. Similarly, an understanding of changes in cultural norms (e.g., increased hours and pace of work, decreasing leisure time, and increased consumption of fast food) will inform community-level strategies to reduce risk. The variation in the composition of subgroups of individuals who respond to various aspects of community CVD interventions illustrates the necessity for the development and evaluation of interventions that are targeted to specific age, socioeconomic, and cultural subgroups.
Numerous studies in community settings, such as the work site, show that it is possible to increase access, convenience, and continuity of care and to reduce the cost of preventive health care for eligible individuals. However, over time, even in fully insured health workers receiving free medication, BP control rates averaged only 12% (94). As Alderman (95) suggested, "Blood pressure treatment is preventive medicine and it may not mix well with sick care, which is what the American medical care system is about."
Inequities in health status have long been associated with education, poverty, inadequate housing, unemployment, lack of health insurance, racism, and gender barriers (96). The gap in income in the U.S. between those well above and well below the poverty line continues to widen, and the disproportionate prevalence of risk factors and receipt of medical services among racial and ethnic groups across the income continuum persists (97). Health providers’ lack of understanding, stereotypical perceptions, and insensitive communication pose major challenges in practice and research among our increasingly diverse population (98). Social, economic, and environmental risk factors, as well as individual differences in risk factors, and community participation in the design and conduct of studies need to be major foci of community-based research.
Medical setting barriers.
There is a disappointing discrepancy between the efficacy of treatments in randomized trials and their effectiveness in clinical practice (99). For many years, the onus for the gap between the expectations for CVD prevention and the reality of practice was placed on the patient’s "failing to follow doctor’s orders" (100). However, virtually every study of preventive therapies, including hypertension control, smoking cessation and cholesterol lowering, has demonstrated that physicians have not pursued the goals of prevention outlined in widely disseminated guidelines. It is tempting to blame individual physicians as lacking the knowledge or the motivation to effectively implement preventive practices. However, marked gaps between risk-factor reduction goals and achieved results have been documented in a broad range of medical settings throughout the developed world, including nations with national health care systems (101,102). Thus, increasingly, experts have looked to the health care system to explain the lack of adherence to prevention guidelines. The systemic barriers include a complex weave of attitudinal, knowledge, and systemic limitations (Fig. 4) (103).
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Figure 4 Practice guidelines—barriers to adherence. Modified with permission from Cabana MD, et al. Why don’t physicians follow clinical practice guidelines? A framework for improvement. JAMA 1999;282:1458–65.
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The attitudinal barriers in the medical system involve both priorities and beliefs (as reviewed in depth by Task Force #5). The emphasis in medical school and training is on diagnosing and treating acute illness. Physicians receive very little education in prevention and the management of chronic conditions (104). Cardiologists, in particular, often view their role as managing the acute event; they frequently defer long-term prevention issues to primary care providers. But the lack of specialist attention reinforces the perception on the part of primary care providers and patients that the treatment of chronic risk factors and lifestyle modification are discretionary practices (104,105). Another barrier for physicians is their perception of their role as teachers rather than as facilitators of medical treatments. The difference in responsibilities is captured in the very language we use to describe the failure of patients to follow advice and take medications. The term "compliance" implies a passive role for patients, rather than more contemporary terms such as concordance or adherence, which emphasize interactive problem solving between patients and doctors to achieve the desired end—risk-factor modification (adherence is also reviewed in the Task Force #4 report) (106,107). Still another belief, referred to as "poor outcome expectancy," that acts as a barrier to improving risk factors in the public is the ubiquitous perception that counseling about lifestyle modification, such as smoking, is ineffective (108), despite published studies to the contrary (109).
Part of the gap in risk-factor reduction may be the result of knowledge deficits. The quantity of accumulated observational and randomized studies linking a multitude of risk factors to CVD is staggering; it is increasingly difficult for the busy clinician to "keep up" with the literature in any area of medicine. Professional societies and experts have looked to guidelines to summarize the existing literature and provide the clinician with direction in best practices. Unfortunately, there is an extensive literature on the failure of guidelines to live up to expectations, highlighting attitudes, knowledge, and behavior as barriers to implementation (103). Attitudinal barriers, alluded to earlier, include a lack of outcome expectancy, lack of self-efficacy, and lack of motivation (103). Many physicians resent the rigidity of guidelines and the attendant loss in autonomy (110) because they misunderstand the concept of guidelines. Guidelines are not intended as rigid rules but rather as an evidence-based framework within which clinicians should exercise their judgment. Others have raised concerns about the scientific rigor and independence of guidelines (111). A lack of knowledge of the content of guidelines constitutes another barrier to their implementation. In one study, 41% of physicians were unaware of or unfamiliar with, the Joint National Committee Guidelines on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, and this lack of familiarity translated into less adherence to the Guidelines’ recommendations (112). The lack of familiarity with a specific set of guidelines is not surprising, as it has been estimated that general practitioners have as many as 25 guidelines to follow on a wide range of medical conditions (113). Disagreement among guidelines, which sometimes conflict in their assessment of risk and their recommendations, has also been a deterrent to their implementation (114,115).
The plethora of available guidelines—which have focused on the relative risk of specific risk factors rather than on absolute risk of CHD given the presence of several risk factors in an individual patient—has also contributed to confusion (116). The physician and patient may feel overwhelmed as to how to prioritize risk factor reduction in a realistic and cost-effective manner. Health care providers need to understand and be able to communicate what the anticipated absolute benefit of a given risk-factor reduction strategy is in a specific patient. Recognizing the importance of these barriers, the ACC and the AHA have endorsed consensus guideline statements for the primary and secondary prevention of atherosclerotic CVD. As discussed later in this report, the secondary prevention guidelines have been successfully incorporated into the ACC Guidelines Applied in Practice project (www.acc.org/home_links/gap.htm) (117) and the AHA Get with the Guidelines program. Health care provider compliance with, and utilization of, secondary prevention therapies has risen dramatically in hospitals where these programs have been implemented.
The other major knowledge deficit for most providers is in techniques for enhancing adherence to medication and lifestyle changes. Although 95% of medical schools currently instruct students in communication skills (118), these skills are rarely reinforced in postgraduate training and continuing medical education programs. There is a large body of literature in health social psychology that provides insights into effective health counseling techniques (106). However, most physicians have little exposure to current theories in health psychology and effective counseling in health behavior change, such as the 4As (ask about the problem, advise with clear recommendations about desired behavior change, assist in problem solving to overcome barriers to behavior change, arrange follow-up) (118). Hence, most physicians lack confidence in their ability to enhance their patients’ adherence to medication and behavior-change regimens (100).
Finally, there are profound systemic and organizational barriers to the optimal implementation of risk-factor modification in clinical practice. The lack of clinician knowledge in effective adherence techniques stems in part from a lack of research on the subject. There has been an emphasis on technology and treatment, with comparatively little attention to factors that enhance adherence to recommended treatments. For instance, there have been few randomized controlled trials with adherence as the outcome—and even fewer that have focused on techniques to increase long-term adherence (119,120). Reviews of treatment-adherence studies reveal that many are methodologically flawed, prohibiting firm recommendations on how to improve adherence (121). Fortunately, recent grants from the NHLBI are beginning to address the deficits in research on physician compliance with guidelines, by researching minority and low socioeconomic status patients’ adherence to risk-factor intervention (e.g., http://grants.nih.gov/grants/guide/rfa-files/RFA-HL-01-005.html).
Fundamentally, preventive services and risk-factor modification have not been given high priority by health care organizations and third-party payors, either public or private. For instance, Medicare and many insurance companies do not reimburse for preventive screening, medications, or cardiac rehabilitation (e.g., for patients with HF or coronary artery disease not immediately post-MI). Individual physicians are offered little incentive and organizational support to pursue prevention in their practices. Preventive services require time and effective communication, which often is not reimbursed, and which competes with addressing the immediate problems of patients (119).
Patient-related barriers to CVD prevention.
The risk status of individuals without CVD varies greatly, and this variability mandates a range in the type, frequency, and intensity of intervention (60). The Framingham Heart Study and other studies have demonstrated that the major risk factors for CVD are multiplicative in predictive power, and many epidemiologic studies have identified a high prevalence of multiple risk factors within individuals (62,122). Cardiovascular disease intervention programs increasingly target multiple risk factors. Successful risk-factor reduction requires a targeted approach, with consideration given to individual barriers to modifying major independent risk factors prevalent in both symptomatic and asymptomatic individuals.
A recent review of the hypertension literature revealed numerous patient barriers, including deficient knowledge about the severity and controllability of risk factors, a lack of health insurance or a primary care provider, economic constraints to cover the cost of medication, and challenges to adhering to a complex lifestyle and medication regimen (100). These and other barriers, such as lack of confidence in one’s ability to control risk factors, perceptions that the benefits of risk reduction do not exceed the risks associated with control of the risk factors, and competing priorities in patients’ lives, make it difficult for some patients to commit to achieving risk-factor control and to actively engage in care.
The National Council on Aging conducted a national survey in January 2000 comprising 1,500 persons age 50 and older. The Council reported the following findings from telephone interviews: 46% believed that a stressful life causes high BP; 51% did not recognize kidney failure as a consequence of untreated hypertension; nearly half (45%) did not know their recent BP numbers, yet 80% had had their BP checked within the past four months; and surprisingly, 69% of the men and women surveyed had not discussed the health consequences of high BP with their health care providers in the past year (http://www.ncoa.org/news/hypertension/hypertension.html). The results of this study highlight the prevalence of inadequate knowledge about risk factors.
One potential explanation for the lack of information about the assessment of patient barriers, other than lack of knowledge and insurance, is the inattention to myths about coronary artery disease. Jan Breslow, MD, PhD, highlighted these myths, during his 1996 to 1997 presidency of the American Heart Association as follows: 1) heart disease is going away; 2) living with heart disease is not so bad; 3) heart disease is a good way to die; 4) only older people have strokes; 5) women do not get heart disease; and 6) no more research is needed. Little is known about the extent to which myths such as these influence patients’ prevention-related to behavior. The influence of myths on patient behavior and the effect of dispelling myths are important areas for study.
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Approaches to barriers in CVD prevention
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A number of approaches to the barriers outlined in this report have been identified and will be reviewed in depth by Task Forces #3, #4, and #5. While there is overlap, the proposed solutions can be analyzed as addressing knowledge, attitudes, and structural barriers in the community, in the medical setting, and at the patient level.
In the case of preventive CV medicine, advances in knowledge have been incorporated into guidelines. Critiques of guidelines have emphasized that guidelines must be straightforward, concise, multidisciplinary, and evidence-based. The goal is to develop guidelines that provide clinicians with a rapid understanding of the strength of the research supporting the guideline, the desired treatment goal, and the relevance and anticipated benefit of risk-factor treatment to the specific patient (111,113,123). To this end, computerized risk-factor assessment tools have been developed (including a Personal Digital Assistant version available at http://www.statcoder.com/cardiac.htm) (122,124). Similarly, the consolidation of primary and secondary prevention guidelines for multiple cardiac risk factors into one guideline by the AHA and the ACC is useful (50,66,68). There is a great deal known about specific risk factors and efficacious treatment, but research must address the major scientific deficits in our understanding of how to improve both provider and patient long-term adherence to preventive treatments and lifestyle modifications.
To change provider attitudes about prevention, organizations have pursued strategies of increasing incentives for risk-factor achievement, in part by using professional societies and opinion leaders to promulgate the prevention message, and in part through quality improvement activities. The National Committee for Quality Assurance is a voluntary accreditation program with participation of 48% of the nation’s 650 medical care organizations. The Health Plan Employer and Data Information Set (HEDIS) has begun to require health plans to report the percentage of hypertensive patients who achieve BP levels less than 140/90 mm Hg and the percentage of patients who achieve low-density lipoprotein cholesterol levels less than 130 mg/dl within one year after CV events (http://www.ncqa.org/Programs/HEDIS/) (125). Twenty-seven U.S. medical care organizations have developed a CHD outcomes management program that follows the quality improvement model of assessing the baseline condition and strategizing for improvement (phase 1), intervening (phase 2), and subsequent follow-up assessment and modification (phase 3). As noted by the investigators, these programs provide several incentives to medical care organizations—the potential to reduce case management costs, improve patient care, and enhance perceived value to potential plan purchasers (125). Similar primary and secondary prevention projects following the quality improvement model have been pursued in Texas. The model of empowering site-specific problem solving for quality improvement has been demonstrated to improve adherence to guidelines (126,127).
There have been several organizational interventions designed to enhance the adherence of medical organizations to risk-factor modification. To overcome barriers to adherence will require adequate reimbursement for preventive activities as well as modification of practice settings to implement technological and health care team approaches to enhancing risk-factor control. Examples of an organizational approach to improving risk-factor modification, involving quality improvement activities that provide direct feedback on preventive medicine outcomes to plans and providers, are the HEDIS and Texas projects described earlier. In addition, there is increasing evidence that computer software can enhance clinical performance in assessing CV risk and implementing preventive care by providing accurate assessments of risks and reminders of desired treatment goals (128,129). Critical pathways (management algorithms that specify the sequence and timing of optimal treatment) (130) and initiation of preventive treatment before hospital discharge for an acute coronary event can also improve the utilization of preventive therapy. Acknowledging the importance of critical pathways and hospital initiation of treatment, the AHA has launched a national program with web-based resources (http://www.americanheart.org/getwiththeguidelines/) to encourage acute care hospitals to "Get with the Guidelines" for secondary prevention. Case management systems integrating the services of a variety of CV specialists, including physicians, nurses, and nutritionists, have also improved adherence to preventive treatments (131). Yet another structural mechanism for improving the delivery of preventive cardiology is achieved by ensuring that patients have adequate benefit coverage and that providers receive appropriate remuneration for preventive cardiology activities (132).
As noted throughout this report, despite the proliferation of guidelines, the wealth of medications, and the increase in knowledge about the benefits of risk-factor reduction, studies have demonstrated a leveling off, and in some instances an increase in CV risk factors in the U.S. A tremendous amount of money and effort continues to be devoted to finding increasingly effective drugs. However, at least one analysis of hypertension drugs suggested that improving treatment compliance would create the highest gain in cost-effectiveness and efficiency (133). Some have suggested a departure from standard approaches to prevention. Experts have provocatively suggested that the same marketing strategies aggressively and strategically employed by tobacco, pharmaceutical, and advertising companies be used in medical education for professionals and to educate our patients and the public (106,134).
Patient factors influencing CV health have been conceptualized as predisposing, enabling, and reinforcing by Green and Kreuter (135) (Fig. 5). This approach integrates health education, behavioral change and maintenance principles, culturally sensitive strategies, social action, and social learning theory. This conceptual approach also allows for the incorporation of economic, psychosocial, and behavioral factors as antecedents to behavior change. Patients’ knowledge, beliefs, values, and attitudes provide the rationale or motivation for the healthy behavior. Enabling factors allow a predisposition to be translated into behavior, such as accessing health care resources or acquiring appropriate skills. Reinforcing factors—such as family, peer, or health care provider support—and supportive social services provide continuing support, reward, or incentives, reinforcing maintenance of healthy behaviors.
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Figure 5 CVD prevention–conceptual framework. CVD = cardiovascular disease. Modified with permission from Green LW, et al. Health promotion planning: an educational and environmental approach. 2nd ed. Mountain View, CA: Mayfield Publishing Company, 1991:150.
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Further research is needed to better understand the extent to which patient beliefs, expectations, and preferences influence provider–patient communication, shared decision making, greater achievement of risk-factor reduction, and prevention of CVD. This is particularly needed in underserved minority groups that suffer a disproportionate CV risk burden. For many patients, perhaps particularly for those living in poverty with social, environmental, and behavioral burdens, daily burdens are of greater priority than preventive CV health care and are obstacles to health improvement. Consideration of an individual’s environmental, social, and cultural context is paramount in addressing and overcoming individual barriers to risk reduction.
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Summary
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At the beginning of the 21st century, the record in the fight against CVD has been mixed. Tremendous gains have been seen in our understanding of the etiology, treatment, and prevention of CVD. There has been modest success in implementing preventive risk-reduction therapies. For instance, the prevalence of smoking has declined, and significant gains have been made in the development and the implementation of effective secondary prevention measures. However, in the face of these successes, disturbing trends have emerged. Obesity and diabetes mellitus are increasing in epidemic proportions, and gains in smoking cessation and physical activity appear to be stagnating. Furthermore, as affluent Americans are receiving increasingly better CV care and enjoying a longer life span free of CVD, the ethnic and economic disparities are widening. In addition, in all economic strata, ethnicities, and regions, the gap between primordial, primary, and secondary CVD prevention goals and the reality of implementation is enormous.
Despite the emergence of these new challenges, unprecedented opportunities exist for CVD prevention. Given the breadth and richness of the accumulated knowledge base, society is now in a position to envision the ultimate control of CVD. The fundamental causes of atherosclerosis, hypertension, and diabetes are increasingly understood; highly effective preventive interventions are known; and many therapeutic modalities are available to treat patients with established disease. Based on an examination of the last four decades, when overall CVD death rates in the U.S. have declined an average of 2.5% per year, a future date can be projected when mortality from CVD will be markedly lower assuming that the current rate of decline continues (Table 1). Furthermore, based on accumulated epidemiological experience worldwide, a population lifestyle can be specified that would be associated with very low or absent rates of atherosclerosis. Thus, eliminating smoking, reducing total fat to less than 25% to 30% of calories and saturated fat to less than 7%, reducing dietary salt to less than 3 g/day, eliminating obesity, encouraging moderate daily physical activity, and treating high BP and high cholesterol with available drugs can confidently be predicted to reduce CHD rates to very low levels, perhaps less than 10% to 15% of all deaths. That level of mortality should qualify as an achievable goal over the next 20 years. Achieving a lifestyle that promotes that level of CV health for all members of society remains an enormous practical challenge in political terms, requiring fundamental changes in food production and marketing, community design, work routines, and patterns of care delivery. Nonetheless, attempts should continue to communicate more forcefully the enormous success of the scientific enterprise in its evolution of the position that CVD would now be controlled if existing knowledge were put into practice.
The cardiology community thus has a unique obligation to promote CV health, particularly in the medical setting. The cardiology community must partner with others to remove obstacles to disease prevention in the health care environment, including the community, the medical setting, and patients. To achieve significant reductions in CVD will require the following: 1) intensive research into the attitudinal, knowledge, and organizational barriers that decrease adherence to known efficacious preventive strategies; 2) the funding of commitments to research and to the delivery of preventive services; 3) policy changes to guarantee access to care by all members of society, to promote healthy lifestyles and environments in the community, and to facilitate a shift in emphasis toward prevention by health care providers; and 4) changes in clinical practice to emphasize prevention.
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References
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Epidemiology of CVD
Cardiovascular risk factors:...