Elsevier

Sleep Medicine

Volume 12, Issue 5, May 2011, Pages 483-488
Sleep Medicine

Original Article
Increased sympathetic activity in children with obstructive sleep apnea: Cardiovascular implications

https://doi.org/10.1016/j.sleep.2010.09.015Get rights and content

Abstract

Background

Obstructive sleep apnea (OSA) is associated with increased sympathetic activity and hypertension in adults. We tested the hypothesis that children with OSA also have increased sympathetic activity as measured by overnight urinary catecholamines, and that this increase is related to the severity of OSA and to blood pressure (BP).

Methods

Seventy snoring children referred for assessment of sleep disordered breathing and 26 healthy non-snoring control children (age range: 3–12 years, 59M/37F) were studied. Overnight polysomnography was performed coincident with a 12 h overnight urine collection. Urinary catecholamine levels were determined using high performance liquid chromatography (noradrenaline, adrenaline and dopamine, with levels adjusted for creatinine excretion). Simple linear and stepwise multiple linear regressions were used to determine the independent associations between catecholamine levels and age, gender, BMI z-score, systolic BP z-score, diastolic BP z-score, and apnea hypopnea index (AHI).

Results

Simple linear regressions revealed significant associations between noradrenaline and AHI (r = 0.32) and age (r = −0.20, p < 0.05 for both). Significant associations were also found between adrenaline and AHI (r = 0.27) and age (r = −0.25, p < 0.05 for both). Systolic BP z-score and diastolic z-score were both significantly associated with adrenaline (r = 0.22 and r = 0.20 respectively, p < 0.05 for both). Multivariate analysis revealed that only AHI was a significant independent predictor of noradrenaline (model R2 = 0.10, p = 0.001). Similarly, only AHI and age were significant independent predictors of adrenaline (model R2 = 0.12, p < 0.05).

Conclusions

This study demonstrates that levels of overnight urinary noradrenaline and adrenaline are related to the severity of OSA in children. These data indicate that children with OSA have increased sympathetic tone that may contribute to the cardiovascular consequences of the condition.

Introduction

Obstructive sleep apnea (OSA) in adults is associated with increased sympathetic activity and cardiovascular morbidities such as hypertension, ischemic heart disease and stroke [1]. The mechanisms responsible for these cardiovascular complications in OSA include frequent arousal from sleep and intermittent hypoxia and hypercapnia, which can each elicit sustained activation of the sympathetic nervous system [2], [3]. There are now increasing reports that pediatric OSA is also associated with cardiovascular changes that could lead to cardiovascular disease over time, including acute increases in heart rate (HR) and blood pressure (BP) during sleep [4], [5], as well as increased diurnal and nocturnal BP [6], [7], [8], [9]. Furthermore, there are reports of left ventricular hypertrophy [10] and decreased diastolic [11] and systolic function [12] associated with pediatric OSA.

Isolated reports on children with OSA have indicated abnormal autonomic control in this group. Children with OSA have been shown to have increased HR variability during sleep [13], [14], which reduces after treatment with adenotonsillectomy [15]. Furthermore, sympathetic vascular reactivity, measured using pulse arterial tonometry, has been shown to be increased during wakefulness in children with OSA [16]. These modifications in autonomic function may alter BP via persistent increases in systemic vascular resistance.

Recently there have also been reports of increased morning urinary [17], [18] and serum [19] catecholamines in children with OSA. However, these reports have not included a healthy non-snoring control group confirmed by polysomnography (PSG). In this study we hypothesized that, similar to adults, children with OSA have increased sympathetic activity as measured by overnight urinary catecholamines, and that this increase is related to the severity of OSA and elevated BP.

Section snippets

Methods

The Monash University and Southern Health Human Research Ethics Committees granted ethical approval for this project. Written informed consent was obtained from parents and verbal assent from the children prior to commencement of the study.

Results

Demographic and polysomnographic data of the 96 children studied are presented according to severity of SDB in Table 1. Of the 70 children referred for investigation of SDB, 33 were diagnosed with primary snoring, 20 with mild OSA and 17 with moderate/severe OSA. There were no significant differences between groups for age, BMI or office BP. As expected, subjects with OSA had a significantly increased OAHI compared to controls and subjects with PS (p < 0.001). Furthermore, the OSA groups (both

Discussion

This study has demonstrated that levels of overnight urinary noradrenaline and adrenaline are independently related to the AHI in children. Furthermore, overnight urinary adrenaline is related to both systolic and diastolic BP z-scores in children.

As urine collection in our study was performed on one night, our data indicate that the catecholamine levels are related to AHI measured on the study night. In an assessment of night-to-night variability of PSG measures in children, Katz et al. [32]

Conflict of Interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: doi:10.1016/j.sleep.2010.09.015.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgments

The authors would like to thank all the children and their parents who participated in this study and all the staff of the Melbourne Children’s Sleep Unit for invaluable technical assistance.

Dr. O’Driscoll is the recipient of a Thoracic Society of Australia and New Zealand/Allen and Hanburys Respiratory Research Fellowship. This project was supported by a Windermere Foundation Special Grant (SG130-08) and NHMRC Project Grants (384142 and 491001).

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