A Public Health Action Plan to Prevent Heart Disease and Stroke

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Section 1. Heart Disease and Stroke Prevention: Time for Action

The Knowledge Base for Intervention

The CVD epidemic in the United States and other Western industrialized countries was first recognized around the middle of the twentieth century.³ In response, extensive research programs involving laboratory, clinical, and population–based investigations were undertaken to identify the causes and the means of preventing coronary heart disease and stroke. The result of this research has been a major growth in knowledge and understanding of the causes of CVD, especially because of the work of NIH and the American Heart Association. 

Statistical research has shown that death rates from heart disease and stroke vary among populations and over only a few years' time in ways that cannot be explained by differences or changes in genetic factors. Such findings demonstrate clearly that environmental factors, in the broadest sense, play a major role in the occurrence of heart disease and stroke and can do so over a relatively short term. Thus, controlling these factors offers opportunities for prevention. Major epidemiologic studies revealed that incidence rates (measures of the occurrence of new cases of CVD, whether fatal or not) could be predicted by blood cholesterol level, blood pressure level, smoking, diabetes, and certain other potentially modifiable characteristics. These characteristics, recognized as "risk factors" since the 1960s, were ultimately established as the major causes of CVD. 

How do these factors cause CVD? The principal pathway to a heart attack or stroke is through the gradual, years–long development of atherosclerosis and high blood pressure. Atherosclerosis is a disease of the medium–sized and larger arteries, such as those that supply the heart (the coronary arteries), the brain (the carotid and cerebral arteries), and the lower extremities (the peripheral arteries), as well as the aorta. Atherosclerosis consists of concentrated areas of mushy material (atheromas) within the arterial wall that are often encrusted or hardened (sclerosed) by deposited calcium. The resulting abnormality is a plaque that weakens the arterial wall and may intrude into the lumen or channel of the artery to limit blood flow or obstruct it completely. A plaque may suddenly rupture, leading to blockage of the artery and precipitating a heart attack or stroke. 

High blood pressure (or hypertension) also can cause heart disease or stroke by exacerbating the effects of other risk factors in accelerating progression of atherosclerosis by placing a continuous, excess workload on the heart (hypertensive heart disease). It can also cause a cerebral artery to rupture (cerebral hemorrhage). 

Atherosclerosis begins to develop in childhood and progresses into the adult years, under strong influence of the risk factors noted previously. Autopsy studies of young American men who died in the Korean War and in Vietnam confirmed that people in their 20s can have moderate and sometimes severe atherosclerosis despite a lack of any medical history to suggest it.^18,19 More recent studies of children, adolescents, and young adults (younger than 35) have demonstrated the close link of blood cholesterol level, blood pressure level, smoking, and obesity with the extent and severity of atherosclerosis among people well below age 20.^20,21 High blood pressure also develops progressively throughout life, undergoing major increases in adolescence and late adulthood. These findings underscore the opportunities for preventing CVD during childhood and adolescence, as well as the lifelong importance of prevention. 

Establishing a way to prevent risk factors requires knowledge about the risk factors themselves. That is, can they be changed? Can heart attacks and strokes be prevented as a result? How prevalent are these risk factors? If their frequency is reduced in the population as a whole, what will the impact be on rates of heart disease and stroke nationwide? An impressive body of evidence amassed over the last 30 years has established that blood cholesterol levels, blood pressure levels, and smoking habits can be modified and that diabetes can be prevented and controlled by behavioral change as well as by medication, all with favorable impact on CVD risk. Population studies have monitored the continuing high prevalence of these risk factors in the United States since the early 1960s. 

In the mid–1980s, researchers projected how the CVD burden would be affected if the major risk factors were reduced.²² These projections suggested that CVD death rates could be reduced by 70% by reducing the population's mean level of blood cholesterol to 190 mg/dl and the mean level of diastolic blood pressure to 80 mm Hg. Because this estimate did not consider the added impact of reducing the prevalence of smoking, it probably underestimated how much CVD death rates could be reduced. Current estimates indicate that these major risk factors account for 75% of the difference in risk for CHD within populations.²³ If these projections were systematically updated, we could estimate how much the CVD burden might be reduced over the next two decades. This estimate might be substantially greater than the Healthy People 2010 target of reducing heart disease and stroke deaths by 20%. As indicated previously, a greater reduction is needed if the projected increase in CVD burden is to be offset. 

Finland’s experiences during 1970–1990 are a good example of the healthy changes that can be achieved by reducing major risk factors for heart disease.²⁴ Improvements in blood cholesterol levels, blood pressure levels, and smoking rates for both women and men closely predicted the actual declines in heart disease deaths that were observed over 20 years. Deaths declined more than 60% for women and more than 50% for men. Although community intervention studies in the United States also have demonstrated positive changes, these interventions have generally lacked the intensity and duration (i.e., the "preventive dose") needed to demonstrate that they actually reduced CVD deaths beyond the influence of favorable changes taking place in society at large.²⁵ 

What knowledge constitutes a sufficient basis for public health action? Both formal research and relevant practical experience are important. Like evidence–based medicine, evidence–based public health needs established criteria for systematically evaluating available evidence. Continuous evaluation can guide current and future programs and advance policies as new knowledge is acquired.

In contrast to evidence–based medicine, evidence–based public health depends on different types of evidence. For example, randomized controlled trials are considered essential to evidence–based medicine but are often lacking in the public health arena. On the other hand, population–based observations that are often unavailable in clinical decision making are included in the evidence base for public health decisions. The context of public health practice is the world at large, where many influences on health are continually at play. Therefore, the central question for evidence–based public health is not whether to take a particular action or no action, but whether the status quo, with its prevailing influences on the population's health, is best. By asking what evidence supports the status quo, as well as what supports a proposed alternative policy or program, evidence–based public health can help establish the relative merits of proposed interventions. 

Clearly, the CVD burden of this nation will not improve under the status quo. We have the knowledge needed to launch a comprehensive public health strategy to change this situation. In fact, only by putting current knowledge into action now can we strengthen the body of knowledge substantially, as new and expanded programs and policy frameworks are implemented and rigorously evaluated.

Next Section: Evolution of Prevention Policy

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Date last reviewed: 05/12/2006
Content source: Division for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion