NEW YORK, April 02 (Reuters) -- High levels of C-reactive protein, a marker of inflammation, predict a person's risk for heart attack and stroke, a new study suggests.
Using an inexpensive, widely used laboratory test, researchers at Harvard's Brigham and Women's Hospital in Boston, Massachusetts, measured levels of the protein in 1,086 healthy male participants in the ongoing Physicians' Health Study. These men were then followed over an eight-year period for first heart attack, stroke, or blood clot in a vein.
"Everyone in our study had normal levels," says cardiologist Dr. Paul Ridker, the Harvard assistant professor of medicine who led the study. "And what we found was that even among these individuals, those with the highest (C-reactive protein) levels had roughly a three-fold increase in having a future heart attack and roughly a two-fold increase of having a stroke over the next eight years of their lives."
But the researchers found no link between levels of C-reactive protein in the blood and the risk for developing blood clots in the veins, "suggesting that the relation of inflammation to vascular risk may be limited to the arterial circulation."
Writing in this week's issue of The New England Journal of Medicine, Ridker and his colleagues note that the increased risks for heart attack and stroke were independent of other, traditional risk factors including high cholesterol, smoking, high blood pressure, and obesity.
Ridker says the findings support the hypothesis that atherosclerosis (fatty blockages in the coronary arteries) is, in part, an inflammatory disease, and that such a measurement of the body's response to injury may provide new means of preventing heart attack and stroke.
In addition to measuring C-reactive protein, Physicians' Health Study researchers had previously assigned study participants at random to take an aspirin or a look-alike placebo every other day. As previously reported, aspirin reduced the risk of a first heart attack by 44%.
But in this new study, researchers observed that the degree of benefit from aspirin seemed to vary depending on the baseline, or initially measured level of C-reactive protein. Only men with the highest C-reactive protein levels seemed to gain a statistically significant benefit from taking aspirin -- a 55.7% reduction in risk of heart attack.
In light of that finding, the researchers hypothesize that aspirin may be effective in reducing heart attack risk partly due to its anti-inflammatory properties, as well as its anticlotting properties.
Senior study author and Harvard professor of medicine, Dr. Charles H. Hennekens, notes that future studies need to look at the source of inflammation, including possible infectious agents. "We also need to directly evaluate the effect of C-reactive protein in women, where no data currently exist," he says.
"The long-term prognostic value of C-reactive protein levels, even when they are within the normal range... may open new avenues for research on the stimuli leading to irreversible ischemic events," writes Dr. Attilo Maseri of the Catholic University of the Sacred Heart in Rome in an editorial also published in The New England Journal of Medicine. "The intriguing findings of Ridker et al. suggest that the time has come to reexamine the pathogenetic components of myocardial infarction and ischemic stroke in the hope of identifying the patients who would benefit most from particular therapies."
SOURCE: The New England Journal of Medicine (1997;336:973-979,1014-1015)
