The Prevention Of Cardiovascular Disease: Have We Really Made Progress?

Thomas A. Pearson

Disclosures

Health Affairs. 2007;26(1):49-60. 

In This Article

Primary Prevention For Adult Patients Without Coronary Or Other Atherosclerotic Vascular Disease

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.

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