High levels of C-reactive protein are associated with an increased risk of hypertension, according to an article in the December 10th issue of The Journal of the American Medical Association.

According to information in the article, increased levels of C-reactive protein are associated with a chronic inflammatory response. Elevated C-reactive protein levels have already been linked to an increased risk for myocardial infarction and stroke. Because of this association, some researchers believe that hypertension may be in part an inflammatory disorder.

Howard D. Sesso, ScD, MPH, and his American colleagues examined whether C-reactive protein levels were associated with hypertension by studying 20,525 women who participated in the Women's Health Study, which began in 1992. Participants had a baseline age of 45 years or older and had normal blood pressures (systolic blood pressure less than 140 mm Hg; diastolic blood pressure less than 90 mm Hg). Baseline blood samples were used to obtain C-reactive protein levels. Women were followed for a median of 7.8 years for development of hypertension.

Over the follow-up period, 5,365 women developed hypertension. The researchers wrote that "Overall, there was a positive association between increasing levels of C-reactive protein and risk of developing hypertension." Participants with the highest levels of C-reactive protein at the beginning of the study were about twice as likely to develop hypertension during the follow-up period.

The authors concluded, "This study provides evidence that baseline levels of C-reactive protein are modestly but independently associated with an increased risk of incident hypertension, even among those with very low initial [blood pressures]. This finding for C-reactive protein was independent of baseline levels of [blood pressure]. Similar effects were observed among those participants without baseline coronary risk factors and in analyses where C-reactive protein was considered a continuous variable. These data suggest that inflammation may have a potentially important role in the development of hypertension.

In an accompanying editorial, Scott M. Grundy, MD., PhD, discussed the link found by Sesso et al between inflammation and hypertension, noting a similar association between low-grade inflammation and metabolic syndrome. "[Metabolic syndrome] consists of a clustering of several metabolic components in one individual," wrote Grundy, including obesity and dyslipidemia.

He added that "Sesso et al did not specifically address the question of what proportion of individuals with high-normal levels of C-reactive protein actually met criteria for the metabolic syndrome," but "nonetheless, the present demonstration of an apparent connection between low-grade inflammation and hypertension supports the concept that elevated blood pressure should be listed as one of the components of the metabolic syndrome."

Dr. Grundy also noted that more research is needed to explain the relationship between inflammatory markers like C-reactive protein, the metabolic syndrome, and cardiovascular and arterial disease.