For millions of people who take statins to prevent the onset of cardiovascular disease, the potential harms of the cholesterol-lowering medication may outweigh the benefits.

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Statins may be ‘significantly overprescribed’ for the primary prevention of cardiovascular disease, suggests a new study.

So concludes a recent modeling study from the University of Zurich in Switzerland that questions whether statins are “significantly overprescribed.”

The research, which features in the Annals of Internal Medicine, concerns the use of statins for the “primary prevention” of cardiovascular disease in people with no history of the disease.

A primary prevention measure is one that intervenes to prevent a condition before it can impact health. Vaccinations, for example, are primary prevention measures.

Statins are some of the most prescribed classes of drugs worldwide. They work by blocking an enzyme called HMG-CoA reductase that helps the liver to make cholesterol.

Most medical guidelines recommend the use of statins for people with no history of symptoms when their expected risk of developing cardiovascular disease over the next 10 years is 7.5–10 percent.

Such a 10-year risk threshold places around 3 out of every 10 adults worldwide as eligible for treatment.

However, the authors note that “whether and how guideline developers weighed harms against benefits is often unclear.”

In 2013, the American College of Cardiology (ACC) and the American Heart Association (AHA) updated the recommendations that guide doctors in the treatment of cholesterol and use of statins.

One reason for the update was the argument that high blood cholesterol is one of the “most prevalent” of alterable cardiovascular risk factors.

Another argument was that there is evidence that treating cholesterol reduces numbers of people who develop cardiovascular diseases and who die of them.

The update caused controversy. This was mainly because it lowered the thresholds that doctors should use to help them decide whether to prescribe statins for primary cardiovascular disease prevention.

This recommended that doctors should consider adults with no history of heart problems as eligible for primary prevention if their risk of developing cardiovascular disease in the next 10 years is 7.5 percent or higher.

Also, the revision expanded the target of prevention to include not just coronary heart disease, but also atherosclerosis, stroke, and peripheral arterial disease.

Experts predicted at the time that full implementation of the guidelines would identify around 13 million people in the United States as “newly eligible for consideration” for treatment with statins.

The University of Zurich researchers used a computer model to assess the 10-year risk for cardiovascular disease “at which statins provide at least a 60 percent probability of net benefit.”

They adjusted the results to take out any effects from “competing risk” of death that was not due to cardiovascular disease, as well as “baseline risk, frequencies of and preferences for statin benefits and harms.”

The harms that they included in their calculations were “adverse events,” such as myopathy (muscle weakness), liver dysfunction, and onset of diabetes.

The results showed that the 10-year cardiovascular risk thresholds at which benefits of statin use exceed the harms are consistently higher than those recommended in the guidelines.

For instance, in the case of men aged 70–75 years with no history of symptoms, the harms of taking statins were greater than the benefits until the risk of developing cardiovascular disease over 10 years was over 21 percent.

For women aged 70–75 years, the 10-year risk required for benefit to outweigh harms was 22 percent.

For those aged 40–44, the benefits outweighed harms at 14 percent 10-year cardiovascular risk for men and 17 percent for women.

Atorvastatin and rosuvastatin provided net benefit at lower 10-year risks than simvastatin and pravastatin,” note the authors.

In an editorial linked to the findings, Drs. Ilana B. Richman and Joseph S. Ross of Yale University School of Medicine in New Haven, CT, note some concerns about the updated thresholds, particularly in relation to older adults.

They also comment that the guidelines have “largely dismissed” many of the side effects included in the study.

The recommendation raised important questions about the ‘right’ risk threshold at which to start statin therapy for primary prevention, particularly because many older adults exceed this threshold on the basis of age alone.”

Drs. Ilana B. Richman and Joseph S. Ross