Does C-reactive protein predict cardiovascular events in women better than LDL?
The Journal of Family Practice. 2003 March;52(3):183-200
March 1, 2003|The Journal of Family Practice
Author and Disclosure Information
- BACKGROUND: A growing body of evidence suggests an important role for inflammation in cardiovascular disease. Nested case-control studies have shown a consistent association between CRP and cardiovascular events such as stroke or myocardial infarction (MI). People in the Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/ TexCAPS) were most likely to have benefit from lovastatin if they had elevated CRP.2
- POPULATION STUDIED: The subjects were women enrolled in the Women’s Health Study, an ongoing trial evaluating aspirin and vitamin E for the primary prevention of MI. These women were all older than 45 when enrolled from 1992 to 1995. There were 28,345 women who had blood drawn at the onset of the trial, but only 27,939 women (with a mean age of 54.7 years) had samples that could be evaluated. Forty percent were using hormone replacement therapy (HRT), 25% had hypertension, 12% were smokers, and 2.5% were diabetic.
- STUDY DESIGN AND VALIDITY: This prospective cohort study followed the women for a mean of 8 years. Cholesterol and CRP levels from the more than 15,000 women not on HRT were used to create the population-based distributions. The researchers found the crude and risk-adjusted hazard ratio for each quintile of CRP levels compared with the lowest quintile value. They also evaluated the additive predictive properties of CRP, as well as LDL cholesterol, and measured the effect of adjusting the Framingham 10-year cardiovascular risk score with CRP levels.
- OUTCOMES MEASURED: The primary outcome was the ability to predict the occurrence of a first cardiovascular event, defined as nonfatal MI, nonfatal ischemic stroke, coronary revascularization procedures, or death from a cardiovascular disease. Standard definitions were used to determine whether patients had these events. They also analyzed the risks for developing each type of event individually.
- RESULTS: The median CRP level was 1.52 mg/L and the median LDL was 123.7 mg/dL. The risk for a first cardiovascular event was linearly associated with increasing CRP levels. The adjusted relative risk of first cardiovascular event for increasing quintiles of CRP was 1.0 (the lowest quintile serves as the reference), 1.4, 1.6, 2.0, and 2.3. The adjusted risk for increasing quintiles of LDL was 1.0 (reference), 0.9, 1.1, 1.3 and 1.5. These findings are consistent with each type of event (stroke, MI, etc) as well as being independent of HRT usage.
PRACTICE RECOMMENDATIONS
C-reactive protein (CRP) is an independent predictor of a first cardiovascular event in women and appears to be a stronger predictor than low-density lipoprotein (LDL) cholesterol levels.
Unfortunately, this information does not lead directly to a therapeutic intervention. As an accompanying editorial stated, low carotenoid levels also predict cardiovascular events, but supplementation with beta carotene does not reduce an individual’s risk.1
This study does not clarify whether CRP is a causative agent, a marker, or a result of cardiovascular disease. Our focus should remain on identifying and treating conventional risk factors until we better understand the exact role CRP has in therapeutic decisions regarding cardiovascular disease.
