Winston-Salem, NC - Among the middle-aged men and women of the Atherosclerosis Risk in Communities (ARIC) study, being African American and having above-median serum uric acid values strongly portended developing hypertension, according to a recent study [1].

The group's lead author, Dr Phillip B Mellen (Wake Forest University Health Sciences, Winston-Salem, NC) said: "The unique thing about our study is that we were able to evaluate a large number of African Americans who did not have hypertension at baseline, and we actually found a much stronger association between uric acid and subsequent development of hypertension in African Americans."

The article is published online October 23, 2006 in Hypertension.

Mellen explained that several factors influence blood uric acid levels. The kidney clears uric acid from the diet and from cell breakdown, so derangements in any of those mechanisms can lead to increased serum uric acid. The group writes that the positive relationship between serum uric acid and hypertension was observed more than 100 years ago. They add that the Coronary Artery Risk Development in (Young) Adults (CARDIA) study suggested that the relationship between serum uric acid and incident hypertension was stronger in young African Americans. But African Americans, who have a high prevalence of hypertension, have been underrepresented in most studies. The goal of the current study was to evaluate the longitudinal relationship between serum uric acid and incident hypertension in a large, biethnic cohort of middle-aged adults.

ARIC is a prospective, epidemiologic cohort study in four US communities. Participants were evaluated at baseline from 1987 to 1989 and at three follow-up exams at three-year intervals. The current analysis, which excluded participants who at baseline were hypertensive or had renal insufficiency, comprised 9104 participants: 677 black men, 1010 black women, 3465 white men, and 3952 white women. At enrollment, they had a mean age of 53 years (range 44 to 65 years), a mean blood pressure of 113.8/70.2 mm Hg, and a mean serum uric acid of 5.7 mg/dL. Blood pressure was assessed at each follow-up exam, and hypertension was defined as >140/90 mm Hg or use of antihypertensive medication.

After adjustment for multiple covariates, each incremental standard deviation (SD) increase in serum uric acid in the total group was independently linked with a 7% increased risk of developing hypertension in the 9-year follow-up. The positive association was stronger in blacks. In a subset analysis of 7603 participants, these findings did not change when the model was also adjusted for alcohol intake, sodium intake, and physical activity.

In a similar pattern, each incremental SD increase in serum uric acid was linked with a significantly increased risk for blood pressure progression of >1 JNC7 category.

The group writes that their determinations add to previous knowledge, because ARIC had nearly twice as many cases of incident hypertension among blacks (n = 626) as any previous prospective study. They conclude: "More research is warranted concerning the physiological and clinical consequences of hyperuricemia, especially in blacks."

Mellen added: "There are studies under way evaluating whether or not lowering uric acid can actually prevent hypertension. If that proves to be the case, this could provide a novel tool for alleviating the burden of hypertension and its consequences."