BP, Uric Acid Linked in Adolescents
- Each 0.1 mg/dL increment in uric acid is associated with a 38% increased odds of having elevated BP
- The association between uric acid and BP persisted after adjusting for body mass index.
- It remains unclear if uric acid is merely a marker or is involved in the causal pathway leading to hypertension
Increasing levels of uric acid are associated with elevated blood pressure among adolescents in the United States, according to researchers.
In a study of 6,036 individuals aged 12-17 years examined in 1999-2006 as part of the National Health and Nutrition Examination Survey (NHANES), researchers at Johns Hopkins University in Baltimore found that each 0.1 mg/dL increment in uric acid level was associated with a 38% increased odds of having elevated BP, after adjusting for age, gender, race/ethnicity, and body mass index. The researchers, led by Lauren F. Loeffler, MD, defined elevated BP as a systolic or diastolic pressure in the 95th or higher percentile for age, gender, and height.
In addition, compared with a uric acid level below 5.5 mg/dL, levels of 5.5 mg/dL or higher were associated with a twofold increased risk of elevated BP, Dr. Loeffler's team reported online ahead of print in Hypertension.
The investigators noted that their study expands the evidence provided by a previous study showing a positive association between blood pressure and serum uric acid, after adjusting for age, gender, race, weight, height, and sexual maturity rating.
They observed that their study cohort had normal kidney function, “making it a desirable population in which to independently assess the association of uric acid and blood pressure.”
Their sample of U.S. adolescents had a high prevalence of overweight and obesity, but the association of uric acid and BP persisted after adjusting for BMI, they noted.
Seventeen percent study subjects were obese; the proportion was 16% among those with normal BP and 41% among those with elevated BP.
“Given the burden of chronic hypertension, cardiovascular disease, and chronic kidney disease in adulthood, identifying novel ways to intervene in the prevention and early treatment of hypertension is a priority,” the researchers concluded.
Hypertension is growing in prevalence among children and adolescents in the United States, the authors observed. Hypertension in children frequently is attributable to secondary causes, but in adolescents, primary or “essential” hypertension is the most common etiology, they explained.
Prior studies have shown that uric-acid lowering therapy improves BP targets, suggesting that uric acid may be in the causal pathway in hypertension development, the authors pointed out. For example, in a randomized, placebo-controlled study of 30 adolescents (aged 11-17 years) with high serum uric acid levels and essential hypertension, researchers showed that allopurinol treatment resulted in a significant reduction in BP, according to findings published in the Journal of the American Medical Association (2008;300:924-932).
Determining the role of uric acid in hypertension development is complicated by the fact that serum uric acid level and BP are associated with kidney function and other common metabolic disorders, the authors noted.