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C-reactive protein, cardiovascular risk factors and the association with myocardial infarction in men
C J Doggen1, R J Berckmans, A Sturk
1Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
Insights
High C-reactive protein levels are linked to myocardial infarction risk in men. However, this association is largely explained by other cardiovascular risk factors, suggesting it may not be causal.
Area of Science:
- Cardiology
- Biomarkers
- Epidemiology
Background:
- C-reactive protein (CRP) is an inflammatory marker.
- Elevated CRP levels have been observed in patients with cardiovascular disease.
Purpose of the Study:
- To investigate the association between C-reactive protein levels and myocardial infarction (MI) in men.
- To examine the relationship between CRP and cardiovascular risk factors.
- To adjust MI risk for these associated factors.
Main Methods:
- A case-control study was conducted.
- Included 560 male patients with a first myocardial infarction and 646 control subjects.
Main Results:
- Patients with MI had significantly higher CRP levels than controls (2.2 vs. 1.7 mg L-1).
- The highest CRP quintile showed an unadjusted 1.9-fold increased risk of MI.
- After adjusting for cardiovascular risk factors (lipids, blood pressure, etc.), the MI risk for the highest CRP quintile decreased to 1.3-fold.
Conclusions:
- CRP levels predict MI risk in men, confirming previous findings.
- The observed association between CRP and MI risk is substantially attenuated when adjusted for other cardiovascular risk factors.
- The increased risk of MI associated with CRP is likely not causal but mediated by other established risk factors.
Objectives:
This study had three objectives: first, to investigate the association of C-reactive protein levels and myocardial infarction amongst men; secondly, to study the associations of C-reactive protein levels with cardiovascular risk factors; and thirdly, to adjust the risk of myocardial infarction for such factors.
Design And Subjects:
A case-control study including 560 patients with a first myocardial infarction who had survived at least 6 months, plus 646 control subjects.
Results:
Patients had significantly higher levels of C-reactive protein (mean 2.2 mg L-1) than control subjects (mean 1.7 mg L-1; P < 0.001). Persons in the highest quintile of C-reactive protein had an unadjusted 1.9-fold increased risk of myocardial infarction compared with persons in the lowest quintile (odds ratio 1.9, 95% CI: 1.3-2.7). C-reactive protein was, in addition to smoking, associated with several cardiovascular risk factors: age, obesity, diabetes, blood pressure, triglycerides and inversely associated to HDL cholesterol. Adjustment for these variables, especially for total cholesterol, HDL cholesterol and triglycerides, substantially decreased the risk of myocardial infarction for persons in the highest quintile of C-reactive protein, compared to those in the lowest quintile, to 1.3 (95% CI: 0.9-1.9).
Conclusions:
Our findings confirm previous reports that C-reactive protein predicts the risk of myocardial infarction. However, this association does not appear to be causal, since the increase in risk can to a large extent be explained by the presence of other cardiovascular risk factors.