High Blood Pressure Linked to Inflammation
by Elizabeth Smoots, MD
Data from the Women’s Health Study, published in 1998, indicated that women with the most inflammation in their blood had a seven-fold increased risk of heart attack or stroke. Since then, research has continued in this area. For example, Harvard Medical School researchers have shown that inflammation may trigger high blood pressure.
About the Study
Researchers from Brigham and Women’s Hospital and Harvard Medical School published their results in the Journal of the American Medical Association. Lead researcher Dr. Howard Sesso and his colleagues studied 21,000 women health professionals aged 45 years or older for an average period of eight years. All the women were participants in the larger Women’s Health Study who were initially free of high blood pressure and other cardiovascular disease.
For each woman, Dr. Sesso and his colleagues recorded a baseline blood level of C-reactive protein, a marker of inflammation in the body. During the study period, about ¼ of the women went on to develop hypertension. Researchers then correlated each woman’s initial blood level of C-reactive protein with her risk of later developing high blood pressure. In the analysis, they corrected for other cardiovascular risk factors such as older age, obesity, inactivity, smoking, heavy alcohol intake, family history of premature heart disease, high cholesterol, diabetes, and use of hormone replacement therapy.
The researchers found that C-reactive protein levels are significantly and independently associated with the future development of hypertension. After correcting for other coronary risk factors, women in the study with the highest levels at baseline were about 50% more likely to develop high blood pressure than those with the lowest levels. This result held true, Dr. Sesso says, even for women with no coronary risk factors and those with very low levels of baseline blood pressure. “These data provide evidence that inflammation may be an important mechanism through which hypertension develops,” the researchers conclude.
Explaining the Connection
“Although the data provides evidence for a critical role of inflammation in the development of hypertension,” Dr. Sesso notes, “the mechanisms of this effect are uncertain and require further evaluation.”
In an accompanying editorial, Scott Grundy, MD, professor at the Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, says that metabolic factors may explain the connection. For example, excess body fat—a known risk factor for high blood pressure—stimulates the release of inflammatory substances from fat cells. Other factors such as high LDL ("bad" cholesterol), low HDL ("good" cholesterol), insulin resistance, and diabetes can further injur arterial walls and elicit an inflammatory response, he says. These factors, clustered together, are referred to as metabolic syndrome, which is associated with increased inflammation in the body, as well as heart disease and hypertension.
Other explanations for the connection also exist. Dr. Grundy says smoking can trigger both inflammatory changes and high blood pressure. Dr. Sesso’s research suggests that having an elevated blood level of C-reactive protein, in itself, may contribute to complex processes (such as arterial narrowing, plaque formation, and blood clotting) that can lead to high blood pressure and heart disease.
Applying the Results
Other researchers have continued to explore the intriguing connection between inflammation and hypertension. In the meantime, says Dr. Sesso, “Identification of people at risk for hypertension remains a high priority.” Blood tests for C-reactive protein are available and used to look for evidence of increased cardiovascular risk. The vast majority of people may eventually develop high blood pressure needing some kind of treatment. C-reactive protein measurements may help predict people with the highest risk of developing a variety of heart and circulatory disorders. If you are at risk for high blood pressure, consult your doctor about the best ways to monitor your risk and reduce your chance of getting this condition.
American Heart Association
National Heart, Lung, and Blood Institute
Heart and Stroke Foundation of Canada
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