Hypertension may be an inflammatory disease
In an eight-year study of more than 20,000 women, researchers at Brigham and Women’s Hospital (BWH) in Boston have found for the first time that high levels of C-reactive protein (CRP), a marker of inflammation proven to predict risk of heart attack and stroke, also may predict the future development of hypertension. BWH is a 725-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare System, an integrated health care delivery network.
These findings provide key evidence that hypertension may be, in part, an inflammatory disease. The study appears in the Dec. 10, 2003, issue of Journal of the American Medical Association.
In the study, researchers monitored 20,525 women, ages 45 or older, for the development of high blood pressure over approximately an eight-year period, during which those with elevated levels of CRP when they entered the study had a 52% increase in the risk of developing hypertension.
"We were surprised by the vigorousness of our findings that associated [CRP] with the ultimate development of hypertension; even in women with low blood pressure, it remained significant," notes the study’s lead author, Howard D. Sesso, ScD, MPH, an associate epidemiologist at BWH. "This significant increase in risk also was seen among healthier women without many traditional coronary risk factors."
The study’s senior author, Paul M. Ridker, MD, MPH, BWH’s director of the Center of Cardiovascular Disease Prevention and Harvard Medical School professor, adds, "Beyond the immediate significance in terms of risk prediction, the new data raise the intriguing possibility that lowering blood pressure might also lower CRP, an issue we now need to investigate directly."
If, in fact, elevated CRP levels do predict the risk of developing high blood pressure, these findings can help improve primary prevention efforts, Sesso says. How might that change the health care provider’s approach to patients with high levels of CRP?
"That’s really the central question we authors went back and forth on," he concedes. "It’s hard to make sweeping generalizations at this point. As we begin other studies to support our findings, the real question is not just whether elevated CRP is associated with hypertension, or if it adds clinical utility above and beyond what we know. If you look at the existing risk factors, they include smoking, obesity, physical inactivity, and dietary factors. In our study, CRP seemed to be independent [of those factors]."
A potential response to the findings can be found in the current protocols for patients with certain cardiovascular risks. Many clinicians now routinely order CRP levels whenever they measure cholesterol, a policy endorsed for millions of patients by both the Centers for Disease Control and Prevention and the American Heart Association.
"There are not that many biochemical risk factors for high blood pressure; other types of studies need to be done over time," Sesso adds. "Do we need a whole panel, or just one or two biomarkers?"
The authors are clear on just how much remains to be learned. For example, Ridker postulates that lowering blood pressure could lower CRP, which seems a bit confusing if high blood pressure is the effect and CRP the cause. "There are two differing views on CRP with hypertension," Sesso remarks. "There is much stronger literature on lab studies that basically postulate that it seems plausible CRP may have a causal link, yet it may go in hand that by lowering blood pressure you get the converse."
For example, he points out, if you put an overweight patient on a strict weight management program, not only will his or her cholesterol go down, but his or her CRP will go down. "But we don’t know which is really coming before and which is coming after. I would argue, [however], that while this is a useful exercise, our prime goal should be to identify those who haven’t developed hypertension yet and keep them in primary prevention," Sesso continues.
"[Hypertension] is arguably the most common preventive chronic disease in the U.S.; perhaps 50 million people have been diagnosed," he adds. "Any new risk fact we can find to identify [at-risk individuals] long before they develop high blood pressure has the potential to make a very strong public health impact."
Need More Information?
For more information, contact:
• Howard D. Sesso, ScD, MPH, Associate Epidemiologist, Brigham and Women’s Hospital, Boston. Phone: (617) 732-8837.