The connection between elevated levels of C-reactive protein (CRP) and coronary heart disease has long been acknowledged in the scientific community. Stirring up a storm among heart professionals however, is the recent finding by Dr. Paul Ridker and colleagues that CRP levels are actually superior to LDL cholesterol in predicting cardiovascular events. Moreover, the two factors seem to be unrelated, meaning there may be a whole new way to control the risk of heart disease.The Ridker study consisted of approximately 28,000 apparently healthy women, who were monitored during an average of eight years for myocardial infarction, ischemic stroke, coronary revascularization, or death from cardiovascular causes. The women’s CRP and LDL cholesterol levels were determined at the start of the study, and factors such as age, smoking status, diabetes mellitus, blood pressure, and hormone replacement therapy were taken into account. The results indicated a strong, direct correlation between each individual indicator and the occurrence of cardiovascular events. Specifically, the women who were among the top 20% in CRP levels were 2.3 times more likely than those in the bottom 20% to experience coronary heart disease. Comparatively, the women who were among the top 20% in LDL cholesterol had only 1.5 times the risk of their bottom 20% counterparts.
The identification of CRP as such an important predictor of cardiovascular events could potentially explain why as many as half of all heart attacks occur in individuals with normal cholesterol levels. In Ridker’s investigation, for example, 77% of adverse events struck subjects with LDL levels below 160 mg/dL, while 46% had levels even below 130 mg/dL. As a point of reference, the American Heart Association considers LDL levels of less than 100 mg/dL “optimal,” while only levels above 160 mg/dL are believed “high.”
Although the CRP findings will doubtless impact the future of preventative heart disease treatments, the old LDL standards will by no means be abandoned. Indeed, as Ridker writes, “C-reactive protein and LDL cholesterol measurements tended to identify different high-risk groups, [and] screening for both… provided better prognostic information than screening for either alone.”
So what exactly is this new diagnostic weapon? CRP is secreted by the liver in response to inflammatory events throughout the human body. It is believed likely that CRP plays a role in coronary heart disease because many cardiovascular problems, such as atherosclerosis (where fatty deposits accumulate in artery linings), have a significant inflammatory component. In fact, an earlier 1997 Ridker publication revealed that the reduction in risk of a first myocardial infarction associated with aspirin was directly related to CRP levels. Such results may indicate a possible role for anti-inflammatory drugs in preventing cardiovascular disease. Other studies have further indicated that statins, which are commonly used to lower LDL levels, have the additional and independent effect of reducing coronary heart disease risk in people with high CRP.
It is difficult to estimate the full future impact of this development for cardiovascular medicine. In addition, the effects are unlikely to be contained to one field, as results indicating that CRP levels are elevated from hormone replacement therapy, for example, gain new significance. The American Heart Association and Centers for Disease Control and Prevention plan to publish recommendations regarding whether physicians should routinely include CRP tests to monitor heart disease risk. For certain, it is clear that C-reactive protein has permanently joined the ranks of LDL, HDL, blood pressure and others as an important health standard.
Sources:
• New England Journal of Medicine 2002 Nov 14;347(20):1557-65
• http://www.nhlbi.nih.gov/about/framingham/riskabs.htm
• http://www.health.harvard.edu/fhg/Darchive/diseases.701.shtml
• New England Journal of Medicine 1997 Apr 3;336(14):973-9
• Journal of American Medical Association 2002 Aug 28;288(8):980-7
