The association of obesity and hyperuricemia with ambulatory blood pressure in children.

Background: Primary hypertension (HTN) in children is on the rise and linked to the childhood obesity epidemic. Recent studies support the role of hyperuricemia in the pathogenesis of HTN. With this study we intend to evaluate the effect of body mass index (BMI) and uric acid levels on daily blood pressure (BP) parameters/phenotypes and target organ damage (TOD).

Methods: A mean ambulatory systolic and/or diastolic BP ≥ 95th percentile or above the adolescent cut points was defined as 'HTN'. Patients were grouped as group 1 normal weight, and group 2 overweight/obese.

Results: Of the 140 children (89 male/51 female) with a mean age of 13.9 ± 2.6 years, 21 were overweight and 86 were obese. Mean 24-h systolic BP (SBP) and daytime SBP were higher in group 2 (p = 0.015, p = 0.011). BMI was positively correlated with 24-h SBP (r = 0.272, p = 0.001) and daytime SBP (r = 0.280, p = 0.001). Uric acid level showed a moderate correlation with daytime SBP (r = 0.311, p < 0.01). Logistical regression analysis showed that daytime SBP is independently associated with obesity (OR 7.44, 95%CI 2.7-20.6, p < 0.001) and male sex (OR 4.60, 95%CI 2.0-10.2, p < 0.001), but not uric acid. Left ventricular hypertrophy was more common in non-dippers (p = 0.044).

Conclusions: Male sex and BMI are independently associated risk factors for systolic BP. The association between non-dipping pattern and TOD suggests the widespread use of ambulatory blood pressure monitoring (ABPM) in childhood HT. In this paper, we could not demonstrate an independent association between uric acid and SBP. The effect of uric acid on SBP seems to be regulated by other metabolic factors in addition to uric acid.