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Atherosclerosis Arises When .
Fat, cholesterol, and other substances accumulate along artery walls and form a sticky buildup known as plaque. Left untreated, atherosclerosis can lead to atherosclerotic cardiovascular disease (ASCVD), which includes coronary heart disease, stroke, and peripheral arterial disease.
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Lifestyle changes—such as quitting smoking, following a healthy diet, and being physically active—can help prevent or delay cardiovascular disease.
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Medicines such as statins, which decrease low-density lipoprotein (LDL) cholesterol, may be prescribed if lifestyle changes aren’t enough.
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In 2013, the American College of Cardiology and American Heart Association, in collaboration with NIH’s National Heart, Lung, and Blood Institute (NHLBI), released new clinical practice guidelines on cholesterol treatment to reduce ASCVD risk. Among the recommendations was that people 40 to 75 years of age without clinical ASCVD and diabetes should take statins if they have an LDL cholesterol level of 70 to 189 mg/dL and an estimated 10-year ASCVD risk of 7.5% or more.
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The guidelines also included methods for making this risk estimate.
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The threshold of 7.5% or higher seemed a low threshold to many experts. Two research teams supported by NHLBI recently examined this aspect of the guidelines. Their findings were published in 2 papers on July 14, 2015, in The Journal of the American Medical Association.
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A group led by Dr. Udo Hoffmann at Massachusetts General Hospital and Harvard Medical School studied whether the new guidelines improved the efficiency and accuracy of the previous ones. The group drew on data from nearly 2,500 adults in the Framingham Heart Study. Participants underwent testing to detect coronary artery calcification—an early sign of coronary artery disease—and were followed for a median of 9.4 years to assess cardiovascular disease.
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About 39% of the participants were eligible to receive statins under the ACC/AHA guidelines, compared to 14% under the previous 2004 guidelines. The new guidelines proved more accurate and efficient at identifying people at increased risk of both cardiovascular disease and subclinical coronary artery disease. The findings were consistent for men and women. They were particularly important for people at intermediate risk, for whom deciding when to begin statin therapy is challenging. The researchers estimated that between 41,000 and 63,000 cardiovascular events would be prevented over a 10-year period by adopting the ACC/AHA guidelines compared to the previous guidelines.
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Another group led by Drs. Ankur Pandya and Thomas A. Gaziano at the Harvard T.H. Chan School of Public Health developed a computer model to project the lifetime health outcomes and cardiovascular disease–related costs of 1 million hypothetical U.S. adults. They used data from the nationally representative National Health and Nutrition Examination Survey (NHANES) and several other published sources.
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The team found that the health benefits conferred by the current ASCVD risk threshold of 7.5% or higher were worth the incremental costs,
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according to commonly accepted “willingness-to-pay” public health standards. Lowering the threshold for statin treatment to 3% or 4% could avert another 125,000 and 160,000 cardiovascular events, respectively. Depending on assumptions about benefits and risks, these risk thresholds might also be considered cost-effective options. These estimates can help inform future decisions about balancing costs with quality years of life.
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“The new cholesterol treatment guidelines have been controversial, so our goal for this study was to use the best available evidence to quantify the tradeoffs in health benefits, risks, and costs of expanding statin treatment. We found that the new guidelines represent good value for money spent on health care, and that more lenient treatment thresholds might be justifiable on cost-effectiveness grounds even accounting for side effects such as diabetes and myalgia,” Pandya says.