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Protein Power: The Role of CRP in Heart Disease

People with normal cholesterol levels may feel like heart disease is not a condition they need to worry about. But new research suggests that, when figuring out their risk for heart attack, people also need to consider their levels of a substance called C-reactive protein (CRP).

In 2005 two studies, published in the New England Journal of Medicine, show that lowering blood levels of CRP, a marker of inflammation in the body, may help prevent heart attacks and heart-related deaths in people with heart disease.

"This gives us evidence for the first time that CRP is not a bystander." says Dr. Steven E. Nissen, a Cleveland Clinic Foundation cardiologist who led one of the studies. "CRP is not just associated with the disease, there appears to be a cause-and-effect relationship."

The study led by Nissen and his colleagues revealed that low CRP levels slowed the progression of artheroscerolosis, the build-up of plaque in the arteries that can cause to a heart attack. In the study, high doses of cholesterol-lowering statin drugs reduced both CRP and cholesterol levels, helping researchers conclude that intensive statin therapy has an anti-inflammatory effect.

The second study, led by researchers at the Brigham and Women’s Hospital in Boston, found that people with severe heart disease who had low CRP levels after statin therapy had fewer heart attacks. Additionally, they were less likely to die of heart disease than those with higher levels of CRP, whether or not they had low levels of the so-called "bad" LDL cholesterol.

While the studies were conducted in people with heart disease, the findings have some experts suggesting that certain people at risk for heart disease, as well as those with heart disease, should have regular blood tests to measure CRP levels. According to the American Heart Association (AHA), a CRP level of less than 1 mg per liter is considered low risk; average risk is between 1 and 3 mg per liter; and a CRP of more than 3 mg per liter is high risk.

For some, the studies indicate that CRP level can help doctors and patients make treatment decisions.

"There are a lot of individuals who fall just below the cholesterol guidelines levels of risk that requires them to be treated." Nissen says. "If their CRP levels are elevated, that would push me to try a statin drug. It also tells me if I have a patient with borderline cholesterol who has a CRP of 0.5, maybe I shouldn’t treat them."

Cardiologist Dr. Richard Stein, a professor of clinical medicine at Albert Einstein College of Medicine in New York and a spokesperson for the AHA, cautions that it is too early to base treatment guidelines on this finding.

"It would seem intuitive that reducing CRP is an important goal, but the questions are ’Does one go on a statin to do that?’, ’What are the risks?’ and ’In whom are the risks worthwhile?’" he says. According to Stein, high doses of statins have been linked to muscle breakdown, kidney failure and, in rare circumstances, death. As a result, the risks and benefits of high-dose statin therapy—which is needed to have an anti-inflammatory effect—should be carefully evaluated.

"If I was faced with a patient with a low LDL but a CRP that was still high, I would probably go up a notch with the statin." Stein continues. "Cardiac risk is a global issue, so it is the sum of all risk factors and not a single risk factor that affects heart attack risk." Other risk factors for heart disease include smoking and levels of HDL cholesterol, the "good" cholesterol.

While the CRP’s precise role in heart disease is still being figured out, an awareness of it may help certain people avoid heart attacks.