What is C-reactive protein (CRP)?
C-reactive protein (CRP) is a blood test marker for inflammation in the body. CRP is produced in the liver and its level is measured by testing the blood. CRP is classified as an acute phase reactant, which means that its levels will rise in response to inflammation.
Is there a link between C-reactive protein (CRP) and cardiovascular disease risk?
The elevation of CRP has also been linked to atherosclerosis and heart disease. Atherosclerosis, or cholesterol plaguing of the arteries, is known to have an inflammatory component that is thought to cause the rise in CRP levels in the blood. Atherosclerosis is also felt to be affected by age and other cardiovascular risk factors including diabetes, high cholesterol, high blood pressure and cigarette smoking.
In atherosclerosis, the blood vessel wall becomes injured. This injury acts as a focus of inflammation and leads to the formation of plaques in the blood vessel walls. The plaques typically contain blood cells of inflammation, cholesterol deposits, and debris from the injured cells in the blood vessel lining. The accumulation of these elements leads to narrowing of the wall of the blood vessel. The blood vessel narrowing can hinder the blood flow and the plaque can rupture and flake off of the blood vessel wall causing blockage and leading to strokes and heart attacks.
The burden of plaques in the body can be proportional to the degree of CRP elevation in persons with atherosclerosis. Atherosclerotic plaques can exist in different stages throughout the body.
Because of the inflammatory component of atherosclerosis, elevated CRP level has been linked with cardiovascular disease. However, based on the current available data it cannot be considered an independent risk factor for cardiovascular disease.
The traditional risk factors for cardiovascular disease, including high blood pressure (hypertension), diabetes, elevated cholesterol, age, cigarette smoking, obesity and family history of heart disease may correlate with an elevated CRP level. According to recent studies, after adjusting for these traditional risk factors, an elevated CRP level alone is unlikely to be a cause of cardiovascular disease.
Nevertheless, CRP levels may be used as a predictor of cardiovascular disease based on its correlation with the other known cardiac risk factors and their role in the formation of atherosclerosis. In individuals with some or all of these traditional risk factors, the elevated CRP levels have been detected. Some data even suggest a trend of higher CRP elevation in the presence of higher numbers of risk factors.
According to the American Heart Association (AHA) and the Center for Disease Control (CDC), the following guidelines are recommended for the assessment of cardiovascular risk in regards to CRP levels:
Low risk for cardiovascular disease if CRP is 1 milligram (mg) per liter or less
Moderate risk for cardiovascular disease if CRP is between 1 and 3 mg per liter
High risk for cardiovascular disease if CRP greater than 3 mg per liter
A CRP level of greater than 10 mg per liter may be seen in an acute plaque rupture such as, a heart attack or stroke, provided there is no other explanation for the elevated level (other inflammatory or infectious process).
The treatment of an elevated CRP in the context of cardiovascular disease, in and of itself, may be meaningless. Instead, appropriate treatment and prevention of the underlying risks and conditions need to be the primary focus of cardiovascular risk reduction.
The most effective and reliable ways to reduce many cardiac factors are regular exercise, balanced diet and cigarette smoking cessation. In individuals with elevated cholesterol levels who do not reach their target cholesterol level with diet modification and proper exercise, cholesterol lowering medication may be advised by their treating physicians.
Reduction of CRP levels has also been noted in individuals with known cardiovascular disease who begin aspirin therapy. In those without known cardiovascular disease or significant risk factors for it, aspirin use is not generally recommended.
The overall outlook for those with an elevated CRP level largely depends on the cause. More specifically, as a risk assessment tool for cardiovascular disease, the elevation of CRP correlates with the presence of the traditional cardiac risk factors including, hypertension (high blood pressure), high cholesterol, diabetes mellitus, obesity, advanced age, cigarette smoking, and strong family history of cardiac disease. Diet, exercise, smoking cessation, and appropriate medical management of these risk factors in hopes of preventing future cardiovascular disease cannot be overemphasize.
Following the principles of the Mediterranean Diet has shown to prevent or reduce the risks of heart disease, stroke, diabetes and obesity. The Mediterranean diet incorporates the basics of healthy eating — plus a splash of flavorful olive oil and perhaps a glass of red wine — among other components characterizing the traditional cooking style of countries bordering the Mediterranean Sea.
Key ingredients of Mediterranean cuisine include olive oil, fresh fruits and vegetables, protein-rich legumes, fish and whole grains with moderate amounts of wine and red meat. The flavors are rich, and the health benefits for people choosing a Mediterranean diet are hard to ignore. They are less likely to develop high blood pressure, high cholesterol or become obese. If you’re trying to eat foods that are better for your heart, start with these nine healthy ingredients; the staples of Mediterranean cooking.
John Danesh, M.B., Ch.B., D.Phil., Jeremy G. Wheeler, M.Sc., Gideon M. Hirschfield, M.R.C.P., Shinichi Eda, Ph.D., Gudny Eiriksdottir, M.Sc., Ann Rumley, Ph.D., Gordon D.O. Lowe, M.D., F.R.C.P., Mark B. Pepys, M.D., Ph.D., and Vilmundur Gudnason, M.D., Ph.D. C-Reactive Protein and Other Circulating Markers of Inflammation in the Prediction of Coronary Heart Disease. N Engl J Med 2004; 350:1387-1397, April 1, 2004.
Lloyd-Jones DM, Liu K, Tian L, Greenland P (June 2006). “Narrative review: assessment of C-reactive protein in risk prediction for cardiovascular disease”. Ann Intern Med 145 (1): 35–42. PMID 16818927.
Blake, Gavin J. MD, MPH, et al. Blood Pressure, C-Reactive Protein, and Risk of Future Cardiovascular Events. Circulation 2003.