Original articleHigh incidence of sleep problems in children with developmental disorders: Results of a questionnaire survey in a Japanese elementary school
Introduction
The way in which sleep disturbances may detrimentally affect children’s cognitive function, developmental behavior, and academic performance is a growing field of research [1], [2], [3], [4]. In addition, there is interest in the association between poor sleep in children and poor parental mental health [5], [6]. Previous studies have estimated that the prevalence of sleep disturbances in typically developing children is in the range 20–40% [7], [8], [9], [10]; conversely, the prevalence of sleep disturbances in children with developmental disorders, such as pervasive developmental disorder (PDD) and attention deficit hyperactivity disorder (ADHD), has been reported to be two- to threefold higher [11], [12], [13], [14]. Furthermore, because of poorer prosocial skills and peer relationships, children with PDD and ADHD could experience considerably more psychological stress than healthy children [13], [15], resulting in secondary sleep disturbance. Studies using parental subjective questionnaires have consistently reported that children with developmental disorders exhibit difficulties in initiating and/or maintaining sleep. For example, parents have reported sleep onset delays, decreased sleep duration, and parasomnias in children with developmental disorders, in addition to sleep disordered breathing and daytime sleepiness [16], [17], [18].
The biological mechanisms underlying sleep disturbances in children with ADHD or PDD are not completely understood. For example, decreased melatonin concentrations in the pineal gland have been proposed to account for sleep disturbances in children with PDD [19]. Another study in autistic children has reported a significant association between sleep disturbances and abnormalities in the expression of acetyl serotonin methyl transferase (ASMT) genes, which are involved in melatonin production, as well as polymorphisms of the clock genes per1 and Npas2, which control the biological clock [20]. Dopaminergic disruption is likely to be the mechanism underlying the association between ADHD and restless leg syndrome (RLS), which is considered to be a sleep disorder and has been reported to occur in 10–40% of patients with ADHD [21], [22]. Other studies also suggest an association between sleep disordered breathing, such as snoring, hypopnea, and apnea, and inattention or hyperactivity, with evidence indicating impaired central nervous system function in the regulation of sleep and attention/arousal [13], [15], [23], [24], [25]. However, the precise mechanisms underlying sleep disturbances in ADHD remain unknown. Objective sleep assessment using polysomnography (PSG) and actigraphy has revealed consistent evidence of differences between healthy children and children with developmental disorders, such as night hyperkinesis, changes in sleep onset latency, increased night waking, decreased total sleep time, and decreased rapid eye movement (REM) latency [13], [14], [15], [26], [27], [28]. However, the results are inconsistent between studies because of methodological limitations, such as investigations in children from different age groups, the inclusion of subjects with comorbid psychiatric problems, small sample size, and the confounding effects of stimulant medication.
Previous sleep studies in children with PDD or ADHD have been performed primarily in clinical samples in university hospitals or sleep clinics. Sampling from such institutions could result in a bias towards a higher prevalence of sleep disturbance: many of the families of PDD and ADHD children who participate in such studies of sleep disturbance are likely to have some concerns about their child’s sleep compared with control families. Furthermore, these institutions tend to provide medical care to children with more severe and complicated PDD or ADHD, and these children are more likely to exhibit poor sleeping patterns. Thus, the selection biases involved with the use of clinical samples may have a critical effect on the results of the study. To minimize the effects of any such bias, we planned a school-based sleep survey for PDD or ADHD children in which all the study participants (i.e. PDD and ADHD children, as well as healthy controls) were recruited from a single elementary school.
The Children’s Sleep Habits Questionnaire (CSHQ) has been used in several countries to assess children’s sleep patterns and sleep problems as reported by parents [29], [30], [31]. The Japanese version of the CSHQ was created in 2007 [32]; however, as yet there has been no study that has used this questionnaire to evaluate sleep patterns and/or problems in children with developmental disorders. The present study is the first in Japan that has used the CSHQ in this group of children. The aim of the present questionnaire survey was to compare the sleep patterns and sleep problems of children with PDD and ADHD with those of healthy children from the same elementary school, focusing on age-related changes, any association between sleep patterns and/or problems and academic performance, and the impact of sleep patterns and/or problems on the parents’ sleep.
Section snippets
Methods
The design of the study and the procedures for obtaining informed consent were approved by the Medical Ethics Committee of Kurume University School of Medicine. Informed consent was obtained from each child and his/her parents prior to their participation in the study.
Study participants
As indicated in Fig. 1, 415 of 436 students (age range 6–12 years; 221 boys, 194 girls) participated in the present study, yielding a response rate of 95.2%. Students were divided into a control group (n = 372; 182 boys, 190 girls) and children with developmental disorders (n = 43; 39 boys, four girls). Children with developmental disorders were further divided into three subgroups: 31 children in the PDD group (29 boys, two girls), nine children in the ADHD group (seven boys, two girls), and three
Discussion
The present school-based questionnaire survey was conducted with the aim of comparing sleep problems in children with developmental disorders, such as PDD and ADHD, with those of a control group. By performing the study at one school, we tried to eliminate the bias towards a higher prevalence of sleep disturbances associated with many hospital-based surveys. In the present study, the total CSHQ score and the parasomnia and sleep disordered breathing subscale scores were significantly higher in
Conclusion
The aim of the present school-based questionnaire was to analyze the sleep problems of children with developmental disorders, such as PDD and ADHD, without the potential bias of a high prevalence of sleep disturbance in studies that use hospital-based surveys. The results of the present study indicate that there are no significant differences in sleep/wake patterns between the control group and children with developmental disorders, but that children in the latter group have significantly
Acknowledgments
This work was supported by a Grant from the Ministry of Education, Culture, Sports, Science, and Technology (No. 22591143) and, in part, by an Intramural Research Grant (22-6; Clinical Research for Diagnostic and Therapeutic Innovations in Developmental Disorders) for Neurological and Psychiatric Disorders of NCNP.
References (45)
- et al.
Cognitive and academic functions are impaired in children with all severities of sleep-disordered breathing
Sleep Med
(2011) - et al.
Short sleep duration is associated with poor performance on IQ measures in healthy school-age children
Sleep Med
(2010) - et al.
Parental functioning and pediatric sleep disturbance: an examination of factors associated with parenting stress in children clinically referred for evaluation of insomnia
Sleep Med
(2011) - et al.
Sleep in attention-deficit/hyperactivity disorder in children and adults: past, present, and future
Sleep Med Rev
(2012) - et al.
Sleep study abnormalities in children with attention deficit hyperactivity disorder
Pediatr Neurol
(2009) - et al.
Sleep problems as possible predictors of intensified symptoms of autism
Res Dev Disabil
(2004) - et al.
Sleep disorders in children with attention-deficit/hyperactivity disorder (ADHD) recorded overnight by video-polysomnography
Sleep Med
(2009) - et al.
The prefrontal cortex in sleep
Trends Cogn Sci
(2002) - et al.
Sleep in children with autistic spectrum disorder: a questionnaire and polysomnographic study
Sleep Med
(2007) - et al.
The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research
Psychiatry Res
(1989)