Elsevier

Sleep Medicine

Volume 13, Issue 2, February 2012, Pages 178-184
Sleep Medicine

Original Article
REM and NREM sleep-state distribution of respiratory events in habitually snoring school-aged community children

https://doi.org/10.1016/j.sleep.2011.10.025Get rights and content

Abstract

Background

Studies ascribe different functions to rapid eye movement (REM) and non-rapid eye movement (NREM) sleep, such that their disruption could result in discrepant clinical outcomes. Although sleep architecture is globally preserved in children with obstructive sleep apnoea (OSA), it is considered to be an REM sleep REMS disorder. Furthermore, body position during sleep affects the occurrence of respiratory events, while the presence of obesity has been claimed to affect sleep-state distribution of respiratory disturbance.

Methods

To explore the distribution of respiratory events during REMS and NREM sleep NREMS and its potential predictors, a cross-sectional analysis of 335 overnight sleep studies in snoring children from the community was conducted. The ratio of REMS to NREMS respiratory events was compared, and potential associations were assessed using general linear modelling (GLM).

Results

Children were 7.3 ± 1.2 years old and had a body mass index (BMI) z-score of 1.0 ± 1.3. The obstructive apnoea–hypopnea index (OAHI) was 1.7 ± 3 and 45.8% of children had an apnoea–hypopnea index (AHI) >1 h−1 total sleep time (TST). Obstructive respiratory events were 3.8 times more likely in REMS (2.0 h−1) than NREMS (0.5 h−1), and the GLM revealed distinctive predictive associations for the apnoeic and hypopneic indices separately, and for body position, the latter indicating that the REMS/NREMS distribution of respiratory events depends on body position.

Conclusion

Obstructive respiratory events are predominantly, albeit not exclusively, present in REMS in school-aged children. NREMS respiratory events are more likely in the presence of lower oxyhaemoglobin saturations during event, side body position and in African–American children. However, REMS dominance is not affected by either BMI z-score or obesity. Our findings suggest that incorporating comprehensive respiratory event profiles of children may enhance our understanding of the pathophysiology and adverse outcomes in the context of paediatric OSA.

Introduction

Substantial discrepancies have emerged among studies examining the clinical characteristics of paediatric sleep-disordered breathing (SDB). Considering the high prevalence of this disorder, as evidenced by a mean in the 10–12% range [1], [2], [3], it is generally believed that the occurrence of respiratory disturbance will be predominantly manifest during rapid eye movement sleep (REMS) when compared to non-rapid eye movement sleep (NREMS) [4], [5]. Moreover, it has been suggested that, in children, sleep architecture is preserved [4] and that body position does not influence frequency nor severity of respiratory events [6], [7], even if such findings have been challenged in the context of concurrent presence of obesity [8], [9].

Hitherto, the most common overnight polysomnographic metric applied to the assessment of the severity of SDB is the apnoea–hypopnea index (AHI). This index reflects a composite score essentially composed by the summation of the number of obstructive and central apnoeic events, and the number of hypopneas per hour of sleep. Tang et al. [10] studied the home-based plethysmography, pulse oximetry, body position, and heart rate parameters of 433 children, ages 8–11 years, who were not referred for clinical assessment of SDB, and concluded that different approaches for quantifying respiratory disturbance indices would contribute to substantial variability in the identification and classification of SDB. Furthermore, their findings were suggestive that central apnoeas in children should be computed and reported separately from obstructive events. In addition, arousals have been recently proposed as an important protective mechanism for termination of an obstructive apnoea event; however, the definition of a respiratory arousal being based on its proximity to a respiratory event should not be mistaken to imply a causal relationship between these two. Independently, the number as well as the duration of arousals may cause sleep fragmentation and disruption of sleep architecture. As a consequence, respiratory events may exert a distinctive impact on sleep integrity, and therefore on daytime well-being.

In adults with obstructive sleep apnoea (OSA) respiratory events occur predominantly during NREMS, and, more recently, this pattern was also reported in up to a third of children with moderate to severe OSA [11]. In other words, the ratio of REMS to NREMS obstructive apnoea–hypopnea index (OAHI) showed an NREMS predominance in older children with higher arousal indices and less severe desaturations with events. Based on the impression that such a pattern was only seldom encountered in our clinical practice, we sought to explore the distribution of REMS and NREMS respiratory events, and analysed potential predictors towards such distribution.

Section snippets

Subjects

The study was approved by the University of Louisville Human Research Committee (Protocol #474.99) and the Boards of the participating schools. Parents were invited to complete the Gozal questionnaire [12], [13], which, in addition to demographic information and information on the significant medical history of the child, included sleep questions concerns difficulty initiating sleep, restless sleep, enuresis, and apnoea, and other questions such as appetite and overall activity. From the

Results

Children were 7.3 ± 1.2 years old (38.6% girls, 57.5% white non-Hispanic [WNH], 29.9% African-American [AA], 12.6% mixed ethnicity [M]) and had a BMI z-score of 1.0 ± 1.3 (2.1% underweight, 5.1% at risk underweight, 42.5% normal weight, 13% overweight and 37.3% obese). OAHI was 1.7 ± 3 h−1 TST (minimum: 0 to maximum: 30.91) and 45.8% of children had AHI >1 h−1 TST. Descriptives of the NPSG can be found in Table 1. In addition, among the covariates the DI ⩾2% was higher in REMS than NREMS (2.6 ± 8.3 h−1 vs.

Discussion

This study shows that respiratory events are 3.8 times more likely to occur in REMS in school-aged children. However, predominance of NREMS respiratory events is not uncommon and occurs in about 1/6 of children. Current findings also suggest that, depending on sleep position, the respiratory event profiles of children are modified and therefore need to be considered as potential confounders in our exploration and understanding of pathophysiological mechanisms and outcomes.

Some methodological

Conflicts 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.2011.04.006.

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

Acknowledgements

This study was supported by National Institutes of Health Grant HL65270.

We thank Ahmad Shata for his assistance in data management.

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