Correlation of Urinary Excretion of Sodium With Severity of Sleep-Disordered Breathing in Children: A Preliminary Study

Abstract

Background: Nocturnal urinary sodium excretion is related to blood pressure (BP) levels. Elevated BP and increased nocturnal natriuresis have been demonstrated in adults with sleep apnea. Although evidence indicates increased BP in children with obstructive sleep-disordered breathing (SDB), it is unknown whether these children have also enhanced urinary sodium excretion. Objective: To evaluate the effects of SDB and morning BP on urinary sodium excretion. Methods: Consecutive children with snoring (n = 95) underwent polysomnography and morning BP measurement. Fractional excretion of sodium (FE(Na)) was the primary outcome measure and was calculated using sodium and creatinine concentrations in early morning serum and urine specimens. Results: Subjects with moderate-to-severe SDB had similar log-transformed FE(Na) to that of children with mild SDB and higher than children with primary snoring: -0.13 +/- 0.53 versus -0.28 +/- 0.41 versus -0.61 +/- 0.65 (P = 0.657 and P = 0.003). Obstructive apnea-hypopnea index was significantly related to FE(Na) after adjustment for age, gender and body mass index z-score (P = 0.002). Children with moderate-to-severe SDB had similar systolic BP z-scores to those of subjects with mild SDB and higher than participants with primary snoring: 0.7 +/- 1.2 versus 0.1 +/- 1.0 versus -0.02 +/- 1.0 (P = 0.074 and P = 0.046). In addition, participants with diastolic BP z-scores in the upper quartile of measured values had higher FE(Na) than subjects with z-scores in the lower quartiles: -0.08 +/- 0.39 versus -0.41 +/- 0.57 (P = 0.007). Conclusions: Morning natriuresis is related to severity of SDB in children and this association maybe mediated in part by elevated BP. Pediatr Pulmonol. 2010; 45:999-1004. (C) 2010 Wiley-Liss, Inc.