Correlation of urinary excretion of sodium with severity of sleep-disordered breathing in children: a preliminary study.
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 may be mediated in part by elevated BP.
Kaditis
Athanasios G
AG
Sleep Disorders Laboratory, University of Thessaly School of Medicine, Larissa, Greece. kaditia@hotmail.com
Alexopoulos
Emmanouel I
EI
Evangelopoulos
Konstantinos
K
Kostadima
Eleni
E
Varlami
Vasiliki
V
Boultadakis
Evangelos
E
Liakos
Nikolaos
N
Zakynthinos
Epameinondas
E
Zintzaras
Elias
E
Gourgoulianis
Konstantinos
K
D001794:Blood Pressure; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D009318:Natriuresis; D017286:Polysomnography; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000652:urine*; D012964:Sodium / Q000652:urine*
D012964:Sodium