TUESDAY, Dec. 9, 2003 (HealthDayNews) -- Elevated blood levels of an inflammation-related molecule, C-reactive protein, warn of future high blood pressure, a study finds, but researchers say more work is needed before that finding can be put to use.
"C-reactive protein may have a role in identifying those at high risk of developing high blood pressure," says study leader Howard D. Sesso, an epidemiologist at Brigham and Women's Hospital in Boston. "But we need other studies to verify our results so that we can make recommendations for screening."
A basic unanswered question is whether C-reactive protein is a cause or an effect of the process that leads to high blood pressure, Sesso says.
"It may be an important marker for damage that occurs in the arteries," he says. "It is not perfectly clear whether it is the cause of high blood pressure or just reflects the damage being done to the arteries. Is it a direct link to the inflammatory process that is causing damage? Perhaps other processes are taking place."
Still, Sesso says, the study results "have the potential to have some very useful clinical utility."
The findings, appearing in the Dec. 10 issue of the Journal of the American Medical Association, are the latest in a series that have linked inflammation to heart attack, stroke and other cardiovascular problems. The inflammatory process that creates C-reactive protein is believed to attack blood vessels, causing damage that eventually interrupts the flow of blood, causing a heart attack or stroke.
The newly reported results come from the Women's Health Study, which has been following more than 20,000 female health professionals for years.
"This is the first observational study in which we have been able to demonstrate that high levels of C-reactive protein are associated with an increased risk of developing high blood pressure," Sesso says.
The women were 45 or older when the study began, and all had normal blood pressure of no more than 140/90. C-reactive protein levels were measured at the start. In an average follow-up period of almost eight years, those with the highest levels of C-reactive protein were twice as likely to develop high blood pressure as those with the lowest levels.
The association between inflammatory markers such as C-reactive protein and the arterial damage leading to heart attack and stroke "is now well-established," says an accompanying editorial by Dr. Scott C. Grundy, director of the Center for Human Nutrition at the University of Texas Southwestern Medical Center in Dallas.
"What is lacking is an adequate causal explanation for these associations," Grundy writes. "Undoubtedly, the causal connections are complex and, in many cases, undiscovered."
Dr. Robert A. Phillips, chairman of the department of medicine at Lenox Hill Hospital in New York City and an officer of the American Society on Hypertension, was skeptical of the marker's importance before this study.
"I have not been a proponent of testing for C-reactive protein," Phillips says. "I didn't think the evidence was strong enough. But here is evidence that there might be something to it. We have data showing it can identify a group of people who are more likely to develop hypertension, something we did not have before."
A blood test for C-reactive protein is easily available, and Phillips has ideas for its use.
"You may want to use it as a screen for people at risk because of family history," he says. "If blood levels are high, you might be more aggressive with those people, getting them to lose weight and perhaps starting drug therapy earlier."