Background: The role of C-reactive protein (CRP) as a novel plasma marker of atherothrombotic disease is currently under investigation. Previous studies have mostly related CRP to coronary heart disease, were often restricted to a case-control design, and failed to include pertinent risk factors to evaluate the joint and net effect of CRP on the outcome. We related plasma CRP levels to incidence of first ischemic stroke or transient ischemic attack (TIA) in the Framingham Study original cohort.
Methods: There were 591 men and 871 women free of stroke/TIA during their 1980 to 1982 clinic examinations, when their mean age was 69.7 years. CRP levels were measured by using an enzyme immunoassay on previously frozen serum samples. Analyses were based on sex-specific CRP quartiles. Risk ratios (RRs) were derived, and series of trend analyses were performed.
Results: During 12 to 14 years of follow-up, 196 ischemic strokes and TIAs occurred. Independent of age, men in the highest CRP quartile had 2 times the risk of ischemic stroke/TIA (RR=2.0, P=0.027), and women had almost 3 times the risk (RR=2.7, P=0.0003) compared with those in the lowest quartile. Assessment of the trend in risk across quartiles showed unadjusted risk increase for men (RR=1.347, P=0.0025) and women (RR=1.441, P=0.0001). After adjustment for smoking, total/HDL cholesterol, systolic blood pressure, and diabetes, the increase in risk across CRP quartiles remained statistically significant for both men (P=0.0365) and women (P=0.0084).
Conclusions: Independent of other cardiovascular risk factors, elevated plasma CRP levels significantly predict the risk of future ischemic stroke and TIA in the elderly.