Elsevier

Sleep Medicine

Volume 14, Issue 10, October 2013, Pages 1005-1012
Sleep Medicine

Original Article
Subjective and objective daytime sleepiness in schoolchildren and adolescents: results of a community-based study

https://doi.org/10.1016/j.sleep.2013.05.014Get rights and content

Abstract

Objectives

We aimed to assess subjective and objective sleepiness in schoolchildren and adolescents by using questionnaires and the Pupillographic Sleepiness Test (PST).

Methods

An observational, cross-sectional, community-based study was performed. Participants were recruited and balanced by age and gender from schools using stratified random sampling. Sleep problems and subjective sleepiness were assessed using parent- and self-reported questionnaires. Objective sleepiness was assessed in schools under standardized conditions by using the PST and by calculating the natural logarithm of the pupillary unrest index (lnPUI).

Results

In total 163 children (82 boys; age range, 6.6–17.8 years) were enrolled. Age and sleep problems were predictors of subjective sleepiness. Nine PST recordings (5.5%) were excluded due to artifacts (feasibility, 94%). Gender, sleep problems, and sleep duration were predictors of objective sleepiness. Compared to adults (age range, 20–60 years), the lnPUI was higher in children (mean ± standard deviation [SD], 1.5 ± 0.4 vs 2.0 ± 0.4; P < .001) and showed significant gender differences. There was no agreement between measures of subjective sleepiness and the lnPUI (r < 0.3). After excluding children with sleep problems, preliminary reference values (mean ± SD) for the lnPUI were 2.01 ± 0.43 for boys and 1.93 ± 0.43 for girls, respectively.

Conclusions

The PST is a feasible method in schoolchildren and adolescents. Sleep problems are predictors of both subjective and objective sleepiness; there is no agreement between the latter. Results of the PST are influenced by sleep duration and specific pediatric gender-stratified reference values are definitively needed.

Introduction

There are a variety of subjective and objective instruments to assess daytime sleepiness in children and young adults [1]. Evaluations usually include some kind of structured sleep history, sleep logs, and sleep questionnaires, as well as objective tests like the multiple sleep latency test (MSLT) [1], [2], [3]. The MSLT is a diagnostic test to measure sleep propensity in the diagnostic workup of narcolepsy and other hypersomnias of central origin [4]. Its use to assess sleepiness is questionable, given the large overlap between normal subjects, with reduced mean sleep latency found in subjects with sleep disorders [4]. Therefore, some authors have questioned its status as a gold standard for the evaluation of daytime sleepiness [5]. Furthermore, it is costly and time consuming, lacks sufficient normative data in pediatric patients, and suffers from motivational influences and the last nap effect [3]. Consequently, a feasible, convenient, and time-saving method that also is less dependent on motivation would be a major improvement.

A possible alternative could be pupillography. More than 40 years ago, Lowenstein et al. [6] first observed characteristic fluctuations in pupil size in sleepy individuals. Meanwhile, the Pupillographic Sleepiness Test (PST) is a standardized, valid, and reliable physiologic test to assess the level of sleepiness in otherwise healthy adults and in those with sleep apnea and narcolepsy [7], [8], [9], [10], [11], [12], [13], [14]. Moreover, it also has been discussed for the laboratory assessment of daytime sleepiness in children [2]. However, the need for cooperation and sitting still as well as keeping fixation stable for several minutes was considered problematic for use in children [2]. In addition, sensitivity was questioned and the lack of validation data in children was emphasized [2]. These factors may be the reasons why there is not yet widespread use of the PST in children.

As part of an interdisciplinary project on daytime sleepiness in schoolchildren and adolescents (i.e. TUPEDS: Tuebingen project on excessive daytime sleepiness in childhood), we aimed to assess the distribution of sleepiness and its main determinants by using parent- and self-reported questionnaires and the PST. Concerning the latter, additional goals were aimed to investigate the feasibility of PST performed in the field, detect its main determining factors, compare PST results to subjective measures of sleepiness, and detect differences to adult reference values.

Section snippets

Study design and subjects

Our study was performed in two regular public schools in Tuebingen, Germany (108 square kilometers; 85,300 inhabitants). One primary school (first–fourth grade) and one high school (fifth–12th grade) were selected to cover the total age span of schoolchildren. Schools were approached following approval by the institutional review board and the regional directorate of education. Detailed study information including a parental and child consent form was distributed by teachers. Using a stratified

Sample and questionnaires

Of all children whose parents provided consent (N = 251), 168 were randomly selected and 163 fulfilled the inclusion criteria for age (ages, 6–17 years). Demographic characteristics for this sample are given in Table 1; descriptive statistics for questionnaire scales are provided in Table 2. The proportion of nonwhites was <5%. Stratification by ethnic group therefore was not appropriate.

Linear regression analysis revealed that all questionnaire scales depended on age (all P < .05) and two scales

Discussion

In our study, we confirmed earlier observations that sleep problems in schoolchildren may be linked to subjective and objective measures of sleepiness [28], [29], [30], [31]. In addition, age and gender were significant predictors for some instruments assessing subjective sleepiness. Initially, we also aimed at proposing reference values for these instruments. However, due to the age dependency of all sleepiness scales and gender dependency of some, our sample size was not large enough to

Limitations

Although the participants in our study were schoolchildren from the community between the ages of 6 and 17 years, we cannot prove the representativeness of our sample. The uncertain representativeness, the small sample size, and the lack of a generally accepted definition prevented us from reporting estimates for the prevalence of daytime sleepiness. If the PUI depends on socioeconomic status, the type of secondary school may be a confounding factor. In Germany, children are streamed to

Conclusions

The PST is feasible in children and adolescents from ages 6 to 17 years and may be a simple screening tool for daytime sleepiness in children. The lnPUI as main parameter of the PST is higher in children compared to adults and depends on gender, which makes specific pediatric gender-stratified reference values necessary. The lnPUI is related to sleep duration in the night before testing and sleep problems, which supports the assumption that pupillary instability does reflect the level of

Funding sources

This project was partly supported by a research grant of the University Hospital Tuebingen (AKF program, grant application number 226-0-0).

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: http://dx.doi.org/10.1016/j.sleep.2013.05.014.

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

Acknowledgments

We thank all the pupils, parents, teachers, and headmasters of the 2 participating schools (primary school “Hechinger Eck”, high school “Carlo-Schmid-Gymnasium”) for their motivating interests, support, and participation in our study. We thank Jutta Diem and Katharina Weible for obtaining questionnaires and pupillographic recordings in schools and Anne Kurtenbach for her native speaker criticism and thorough review of the manuscript.

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