By Debra Wein, MS, RD
CRP and Cardiovascular Disease
racking your total cholesterol level is a good way to assess your risk of coronary heart disease. But is it enough? Despite progress in the prevention of cardiovascular disease, a significant number of first cardiovascular events occur among individuals without traditional risk factors, such as total cholesterol above 200 or LDL cholesterol above 130 (Morrow & Ridker 2000). According to accumulating research, high-sensitivity C-reactive protein (CRP) concentrations can indicate relative cardiovascular risk, even when other traditional high-risk indicators are absent. In fact, over the past five years, researchers have accumulated data documenting an association between mild elevation of CRP and cardiovascular risk among those without known vascular disease, as well as those who are trying to prevent cardiovascular recurrences.
CRP Overview CRP, an acute-phase reactant, is a nonspecific marker of systemic inflammation (Ford & Giles 2000). CRP concentrations are very low in healthy people,
but can rise in response to a wide variety of stimuli. Its exact role remains unclear, but it can stimulate mononuclear cells to release tissue factor, which initiates coagulations and can play a role in acute myocardial infarction (heart attack). As the contribution of inflammation to atherogenesis--thickening of artery walls--has received increased recognition, researchers have focused on key markers of the inflammatory process, including CRP. Inflammatory processes occur at every stage of atherothrombosis, including the initiation of the fatty streak, maturation of the advanced atherosclerotic lesion, thinning of the fibrous cap with plaque compromise, and platelet aggregation and thrombosis. Thus, a mild elevation of CRP may indicate future cardiovascular risk (Morrow & Ridker 2000). Until recently, however, high-sensitivity assays for CRP were not available and, therefore, detection of mild elevation within the normal range was not possible.
Recent Investigations Study: Ford, E. S., & Giles, W. H. 2000. Serum C-reactive protein and self-
RISK FACTORS FOR CARDIOVASCULAR DISEASE
C-reactive protein concentrations Systolic blood pressure Diastolic blood pressure Total cholesterol HDL cholesterol LDL cholesterol Body mass index 0.55 milligrams per deciliter 140 millimeters of mercury (mm Hg) 90 mm Hg 200 millimoles per liter (mmol/L) 35 mmol/L 160 mmol/L 30
reported stroke. Arteriosclerosis, Thrombosis, and Vascular Biology, 20 (4), 1052. Purpose: To determine if a high CRP level is associated with a higher risk for stroke in the U.S. population. Methods: In a cross-sectional study, 414 white, African-American and Mexican-American subjects from the National Health and Nutrition Examination Survey study participated. Each responded "yes" to the following question: Has a doctor ever told you that you had a stroke? All participants were between the ages of 40 and 70. Results: Subjects who reported having a stroke were older, less educated, had higher systolic blood pressure, had higher total cholesterol and lower HDL cholesterol levels, were less active, and were more likely to have diabetes than were persons who had not had a stroke. After adjusting for age, sex, race, ethnicity, education, smoking status, systolic blood pressure, total cholesterol, HDL cholesterol, diabetes, body mass index and physical activity, the results showed that participants with a high CRP level were 1.7 times more likely to have a stroke than those with lower levels. In addition, the mean concentration for CRP was 41 percent higher for those who had had a stroke than those who had not. A significant positive association was found between CRP and self-reported past history of stroke among men and women and among whites, African Americans and Mexican Americans. Because the study was cross-sectional, a direct cause and effect association cannot be clearly established.
Study: Ridker, P. M., et al. 2000.
Inactivity History of diabetes Smoker
Ford, E. S., & Giles, W. H. 2000. Serum C-reactive protein and self-reported stroke. Arteriosclerosis, Thrombosis, and Vascular Biology, 20 (4), 1052.
C-reactive protein and other markers of inflammation in their prediction of cardiovascular disease in women. New England Journal of Medicine, 342, 836-43. Purpose: To determine if a marker of inflammation exists that can provide
IDEA PERSONAL TRAINER SEPTEMBER 2001
an improved prediction of the risk for cardiovascular events in apparently healthy women. Methods: Researchers conducted a prospective, nested case-control study with 28,263 apparently healthy postmenopausal women, with no history of cardiovascular disease or cancer. The subjects were observed for three years. Results: CRP was the highest predictor of risk, even in women with LDL cholesterol less than 130 (as recommended by the National Cholesterol Education Program). Thus, women who might otherwise have been listed as low risk actually experienced a greater level of cardiovascular events than suggested by their LDL levels. Of the 12 markers measured, including HDL cholesterol, LDL cholesterol, total cholesterol and the ratio of total cholesterol to HDL, CRP was the strongest predictor of the risk of cardiovascular events.
Bottom Line A measurement of inflammatory markers, such as CRP, may provide a novel method for detecting individuals at high risk of plaque rupture. Several large-scale, prospective studies demonstrate that CRP is a strong independent predictor of future myocardial infarction and stroke among apparently healthy men and women. The addition of CRP to standard lipid screening may improve global risk prediction among those with high as well as low cholesterol levels (Ford & Giles 2000; Ridker et al. 2000; Ridker 2001). Inexpensive commercial assays for CRP are currently available to health professionals to allow screening for high CRP levels.
Debra Wein, MS, RD, is president of The Sensible Nutrition Connection Inc., and an adjunct faculty member at Simmons College, The Boston Conservatory and
the University of Massachusetts. Register at www.sensiblenutrition.com to receive her free e-mail newsletter, SNaC Bytes.
Ford, E. S., & Giles, W. H. 2000. Serum C-reactive protein and self-reported stroke. Arteriosclerosis, Thrombosis, and Vascular Biology, 20 (4), 1052. Morrow, D. A., & Ridker, P. M. 2000. C-Reactive protein, inflammation, and coronary risk. Medical Clinics of North America, 84 (1), 149-61. Ridker, P. M. 2001. High-sensitivity C-reactive protein. Circulation, 103, 1813-8. Ridker, P. M., et al. 1997. Inflammation, aspirin, and the risk of cardiovascular disease in apparently healthy men. New England Journal of Medicine, 336 (14), 973-9. Ridker, P. M., et al. 1999. Long-term effects of pravastatin on plasma concentration of C-reactive protein. Circulation, 100, 230-5. Ridker, P. M., et al. 2000. C-reactive protein and other markers of inflammation in the prediction of cardiovascular disease in women. New England Journal of Medicine, 342, 836-43. Ridker, P. M., Glynn, R. J., & Hennekens, C. H. 1998. C-reactive protein adds to the predictive value of total and HDL cholesterol in determining risk of first myocardial infarction. Circulation, 97, 2007-11.
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