Lowering Blood Cholesterol To Prevent Heart Disease

Introduction

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Coronary heart disease is responsible for more than 550,000 deaths in the United States each year. It is responsible for more deaths than all forms of cancer combined. There are over 5.4 million Americans with symptomatic coronary heart disease and a large number of others with undiagnosed coronary disease, many of them young and highly productive. It has been estimated that coronary heart disease costs the United States over $60 billion a year in direct and indirect costs.

Coronary heart disease is due to atherosclerosis, a slowly progressive disease of the large arteries that begins early in life but rarely produces symptoms until middle age. Often the disease goes undetected until the time of the first heart attack, and this first heart attack is often fatal. Modern methods of treatment have improved greatly the outlook for patients having heart attacks, but major progress in our battle against this number one killer must rest on finding preventive measures.

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A number of risk factors have been identified as strongly associated with coronary heart disease. Cigarette smoking, high blood pressure, and high blood cholesterol are the most clearly established of these factors. Risk is greater in men, increases with age, and has a strong genetic component. Obesity, diabetes mellitus, physical inactivity, and behavior pattern are also risk factors.

A large body of evidence of many kinds links elevated blood cholesterol levels to coronary heart disease. However, some doubt remains about the strength of the evidence for a cause-and-effect relationship. Questions remain regarding the exact relationship between blood cholesterol and heart attacks and the steps that should be taken to diagnose and treat elevated blood cholesterol levels.

To resolve some of these questions, the National Heart, Lung, and Blood Institute and the NIH Office of Medical Applications of Research convened a
Consensus Development Conference on Lowering Blood Cholesterol to Prevent Heart Disease on December 10-12, 1984. After hearing a series of expert presentations and reviewing all of the available data, a consensus panel of lipoprotein experts, cardiologists, primary care physicians, epidemiologists, biomedical scientists, biostatisticians, experts in preventive medicine, and lay representatives considered the evidence and agreed on answers to the following questions:

• Is the relationship between blood cholesterol levels and coronary heart disease causal?
• Will reduction of blood cholesterol levels help prevent coronary heart disease?
• Under what circumstances and at what level of blood cholesterol should dietary or drug treatment be started?
• Should an attempt be made to reduce the blood cholesterol levels of the general population?
• What research directions should be pursued on the relationship between blood cholesterol and coronary heart disease?

Panel's Conclusions

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Elevated blood cholesterol level is a major cause of coronary artery disease. It has been established beyond a reasonable doubt that lowering definitely elevated blood cholesterol levels (specifically blood levels of low-density lipoprotein cholesterol) will reduce the risk of heart attacks due to coronary heart disease. This has been demonstrated most conclusively in men with elevated blood cholesterol levels, but much evidence justifies the conclusion that similar protection will be afforded in women with elevated levels. After careful review of genetic, experimental, epidemiologic, and clinical trial evidence, we recommend treatment of individuals with blood cholesterol levels above the 75th percentile (upper 25 percent of values). Further, we are persuaded that the blood cholesterol level of most Americans is undesirably high, in large part because of our high dietary intake of calories, saturated fat, and cholesterol. In countries with diets lower in these constituents, blood cholesterol levels are lower, and coronary heart disease is less common. There is no doubt that appropriate changes in our diet will reduce blood cholesterol levels. Epidemiologic data and over a dozen clinical trials allow us to predict with reasonable assurance that such a measure will afford significant protection against coronary heart disease.

For these reasons we recommend that:

1. Individuals with high-risk blood cholesterol levels (values above the 90th percentile) be treated intensively by dietary means under the guidance of a physician, dietitian, or other health professional; if response to diet is inadequate, appropriate drugs should be added to the treatment regimen. Guidelines for children are somewhat different, as discussed below.
2. Adults with moderate-risk blood cholesterol levels (values between the 75th and 90th percentiles) be treated intensively by dietary means, especially if additional risk factors are present. Only a small proportion should require drug treatment.
3. All Americans (except children under 2 years of age) be advised to adopt a diet that reduces total dietary fat intake from the current level of about 40 percent of total calories to 30 percent of total calories, reduces saturated fat intake to less than 10 percent of total calories, increases polyunsaturated fat intake but to no more than 10 percent of total calories, and reduces daily cholesterol intake to 250 to 300 mg or less.
4. Intake of total calories be reduced, if necessary, to correct obesity and adjusted to maintain ideal body weight. A program of regular moderate-level exercise will be helpful in this connection.
5. In individuals with elevated blood cholesterol, special attention be given to the management of other risk factors (hypertension, cigarette smoking, diabetes, and physical inactivity).

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These dietary recommendations are similar to those of the American Heart Association and the Inter-Society Commission for Heart Disease Resources.

We further recommend that:

6. 6.New and expanded programs be planned and initiated soon to educate physicians, other health professionals, and the public to the significance of elevated blood cholesterol and the importance of treating it. We recommend that the National Heart, Lung, and Blood Institute provide the focus for development of plans for a National Cholesterol Education Program that would enlist participation by and contributions from all interested organizations at national, state, and local levels.
7. The food industry be encouraged to continue and intensify efforts to develop and market foods that will make it easier for individuals to adhere to the recommended diets and that school food services and restaurants serve meals consistent with these dietary recommendations.
8. Food labeling should include the specific source or sources of fat, total fat, saturated and polyunsaturated fat, and cholesterol content as well as other nutritional information. The public should be educated on how to use this information to achieve dietary aims.
9. All physicians be encouraged to include whenever possible a blood cholesterol measurement on every adult patient when that patient is first seen; to ensure reliability of data, we recommend steps to improve and standardize methods for cholesterol measurement in clinical laboratories.
10. Further research be encouraged to compare the effectiveness and safety of currently recommended diets with that of alternative diets; to study human behavior as it relates to food choices and adherence to diets; to develop more effective, better tolerated, safer, and more economical drugs for lowering blood cholesterol levels; to assess the effectiveness of medical and surgical treatment of high blood cholesterol levels in patients with established clinical coronary artery disease; to develop more precise and sensitive noninvasive artery imaging methods; to apply basic cell and molecular biology to increase our understanding of lipoprotein metabolism (particularly the role of HDL as a protective factor) and artery wall metabolism as they relate to coronary heart disease.
11. Plans be developed that will permit assessment of the impact of the changes recommended here as implementation proceeds and provide the basis for changes when and where appropriate.