Connecting attention-deficit/hyperactivity disorder and disturbed sleep in children.

Most of us are familiar with what a night of poor or absent sleep feels like. Sleepless nights can leave us feeling nauseous, disoriented, and irritable. Technologists performing sleep studies are all too familiar with these feelings and the additional consequences of sleep deprivation that can include cognitive problems such as poor attention and loss of productivity associated with sleepiness. However, the exact nature of the consequences of poor sleep in children has been harder to document with accuracy.

Evidence on the manifestations of poor sleep in children illustrates the point that sleep variables in this population should be viewed differently from those variables associated with disturbed sleep in adult populations. Sleepiness in children is only one possible variable and can take different forms. Subsequently, a sleep history and evaluation designed for an adult could be inappropriate for a child with a suspected sleep disorder.

There is still much research to be done to answer the fundamental questions regarding the basic physiologic processes affecting sleepiness and alertness in the developing brain. The following is a summary and review of recent studies that perhaps suggest a link between sleep disturbances in children and deficits in cognition, mood, behavior, and performance that can adversely affect academic success and daytime functioning.

One persistent theme in the recent research on the consequences of pediatric sleep disorders is the potential relationship with attention-deficit/hyperactivity disorder (ADHD or ADD). According to the National Institutes of Health, the incidence rate of ADHD is estimated to be between approximately 3% and 5% of school-aged children, though these rates can vary widely depending on the geographical location and populations sampled. ADHD is characterized by at least two of the following behaviors:

• poor attention
• impulsivity
• hyperactivity

ADD is sometimes used as a generic term for these impairments, but ADHD more accurately communicates that the attention deficit disorder may take different forms: either inattentive or hyperactive/impulsive. Although children are more often the ones diagnosed with ADHD and treated, we now know that these behaviors can persist into adulthood. While everyone may exhibit some of these signs and symptoms from time to time, a person with ADHD is likely to have more of these symptoms consistently since early childhood. Symptoms generally are present in at least two settings, such as school and home, and can cause significant impairment in daily functioning.

While the cause of ADHD remains unknown, multiple influences likely are involved in addition to dopaminergic, adrenergic, and glutamatergic alterations in brain regions.1 As an ADD child matures into a teenager and then an adult, they often gain self-control over hyperactivity symptoms. The lack of hyperactivity in an adult with ADD may be the reason that more adults do not recognize that they still have ADD. While the hyperactivity may diminish over time, inattentiveness usually remains consistent.

Some of the symptoms of childhood ADHD are commonly seen in sleepy adults. These include ignoring details, being unable to sustain attention or listen, being easily distractible, and having memory problems and forgetfulness. However, the manifestation of excessive daytime sleepiness (EDS), often seen in the adult with sleep disruption, is commonly absent in children except in the more severe cases of obstructive sleep apnea (OSA).2

Differences in the fragmented nature of sleep in children as compared to adults may have several causes that underline the importance of accurately evaluating this population. Adopting a clear consensus for scoring apneic events, periodic limb movements in sleep (PLMS), and a clear definition of cortical arousal in children could have major implications for correlational analyses and enable sleep clinicians and researchers to provide a more thorough understanding of the effects of sleep disorders in the pediatric population. For example, the severity of the hypoxemia and the density of apneic events in children are diminished overall when compared to adults with apnea.3 Further, it appears that the fragmenting effects of sleep disordered breathing (SDB) on sleep architecture commonly seen in adults are not as disruptive to sleep in pediatric populations, and their sleep architecture is more preserved.4,5

While EDS cannot reliably predict the severity of pediatric SDB or the presence of other sleep disorders that may influence daytime functioning, there is increasing evidence that disturbed sleep may be associated with more intrinsic deficits in daytime alertness. Behavioral problems, including ADHD6,7 and related cognitive executive dysfunction8 and, perhaps more extrinsically, poor school performance,9 have now been documented in children with suspected poor sleep.

One of the more obvious examples of the adverse impact on cognitive function, development, and behavior following hypoxia are the devastating consequences of serious hypoxic ischemic events. Less drastic effects of chronic or intermittent hypoxia on childhood cognitive outcomes and attention problems have been studied recently as well with some interesting results. In a recent comprehensive literature review,6 the effects of five clinical categories that included SDB were analyzed. ADHD was frequently listed as one of the major effects documented for SDB in this review in addition to impaired attention, hyperactivity, and behavioral disturbances.

The evidence-based conclusions are made more compelling in those studies documenting improvement in school performance and attention following treatment by either adenotonsillectomy or CPAP administration, suggesting a causal relationship. Other studies have supported these findings for primary or habitual snoring in children.9,10 It was found that even primary snoring (PS)—snoring that does not meet the criteria for OSA—in children was associated with significant alterations in respiratory arousal and REM percentage compared to nonsnoring control subjects.

Additionally, children with PS performed worse on measures related to attention, social problems, and anxious/depressive symptoms. If a child presents with a history of nightly snoring, a more extensive history regarding labored breathing during sleep should be obtained. This history should include observed apnea, restless sleep, diaphoresis (copious sweating), enuresis (bed wetting), cyanosis (bluish skin tone from too little oxygen), signs of EDS, and behavioral or learning problems, including ADHD.11

Further support for the potential relationship between ADHD symptoms and SDB was found when polysomnographic evaluations were conducted on children whose parents reported ADHD symptoms.12 In these children, REM sleep was disturbed and may have contributed to the severity of their daytime behavioral manifestations. Those children whose parents reported significant ADHD symptoms were not more likely to have SDB, but SDB was found to be highly prevalent in children whose parents reported mild ADHD symptoms. Perhaps this finding is additional support for the notion that ADHD-like symptoms are simply a daytime manifestation of sleep alteration for a subset of children. All three of these studies seem to suggest that a sleep evaluation to rule out SDB be performed as close as possible to the onset of symptoms, since early detection can at least partially ameliorate one or more aspects of impaired neurocognitive function with appropriate treatment.

The early documentation and treatment of SDB in those children who snore are supported by another study documenting poor school performance in 13- to 14-year-old children ranked as habitual snorers in early childhood—a period believed to be a critical phase for brain growth and substantial acquisition of cognitive and intellectual capabilities.13 The authors compared these children to children performing well in school matched for age, gender, race, school, and area of residence. These findings led to speculation that even after the resolution of snoring, adverse academic outcomes can still be present several years later, and that academic compromise from SDB during this critical phase may be partially irreversible.

The frank cortical arousals and fragmented sleep architecture usually associated with sleep-related problems in adults with EDS are less obvious or frequent in pediatric populations. It seems apparent, though, that an instability in the sleep-wake system of children does have some predictive value for children with ADHD.14 An increase in the instability of sleep onset, sleep duration, and true sleep was found in boys with ADHD as compared to a control group when measured by movement sensors and sleep diaries. This alteration in sleep variables seems to support the notion that movement disorders as well as SDB may yield ADHD symptoms in children. Out of 129 children and adolescents with specific sleep-related movement disorders such as PLMS and restless leg syndrome (RLS), 117 had ADHD.15

Other studies also seem to support a connection between ADHD and movement disorders,16,17 although there also have been studies where the connection between PLMS or RLS with ADHD has not been supported.12 Perhaps the discrepancy in results may be due to the lack of consistency in the definition of what constitutes PLMS/RLS in children or perhaps laboratory-to-laboratory variability in standards associated with evaluating these types of movements.

Parents and their children with ADHD also reported more sleep disturbances as compared to controls18 in a study that excluded those children with ADHD symptoms and sleep-related respiratory impairments. These children were reported to have a higher incidence of bedtime resistance, sleep-onset delay, abnormal sleep duration, sleep-related anxiety, parasomnias, night wakings, total sleep disturbance, and even reported daytime sleepiness. It seems that at least some children with ADHD-like symptoms are simply not getting enough sleep, and that this lack of sleep may not always be attributed to obvious physiological causes, such as apnea or movement disorders.

It is important for sleep professionals and the community as a whole to have an increased awareness of the effect of pediatric sleep disturbances on the daytime functioning of children, including the apparent link with ADHD symptoms and other potential effects on daytime cognitive function. Disturbed sleep in children and adults can affect cognition, mood, behavior, and performance; but in children, these effects can also adversely influence academic achievement and social interactions that can have potential long-term consequences. The clear vulnerability in the pediatric population illustrates the urgent need for sleep professionals to establish standards in monitoring and evaluating children. When consistent laboratory standards are adopted, it will be possible to more accurately diagnose and treat sleep disorders in this age group. Promoting awareness of the consequences of pediatric sleep disorders, as well as the link to ADHD symptoms, will hopefully lead to early evaluation, treatment, and, ultimately, the subsequent enhancement of the quality of children’s lives and those of their families.

References
1. National Institutes of Health. Diagnosis and Treatment of Attention-Deficit Hyperactivity Disorder. Washington, DC: US Government Printing Office; 1998. NIH Consensus Statement.

2. Gozal D, Wang W, Pope DW. Objective sleepiness measures in pediatric obstructive sleep apnea. Pediatrics. 2001;108:693-697.

3. Marcus CL, Omlin KJ, Basinki DJ, et al. Normal polysomnographic values for children and adolescents. Am Rev Respir Dis. 1992;146: 1235-1239.

4. Bonnet M, Carley D, Carskadon M, et al. EEG arousals: scoring rules and examples: a preliminary report from the Sleep Disorders Atlas Task Force of the American Sleep Disorders Association. Sleep. 1992;15:173-184.

5. Guilleminault C, Billiard M, Montplaisir J, Dement WC. Altered states of consciousness in disorders of daytime sleepiness. J Neurol Sci.1975;26:377-393.

6. Bass JL, Corwin M, Gozal D, et al. The effect of chronic or intermittent hypoxia on cognition in childhood: a review of the evidence. Pediatrics. 2004;114: 805-816.

7. Picchietti DL, Walters AS. Moderate to severe periodic limb movement disorder in childhood and adolescence. Sleep. 1999;22:297-300.

8. Archbold KH, Giordani B, Ruzicka DL, Chervin RD. Cognitive executive dysfunction in children with mild sleep-disordered breathing. Biol Res Nurs. 2004;5(3):168-176.

9. Gozal D. Sleep-disordered breathing and school performance in children. Pediatrics. 1998;102:616-620.

10. O’Brien LM, Mervis CB, Holbrook CR, et al. Neurobehavioral implications of habitual snoring in children. Pediatrics. 2004;114:44-49.

11. American Academy of Pediatrics Policy Statement. Clinical practice guideline: diagnosis and management of childhood obstructive sleep apnea syndrome. Pediatrics. 2002;109:704-712.

12. O’Brien LM, Holbrook CR, Mervis CB, et al. Sleep and neurobehavioral characteristics of 5- to 7-year-old children with parentally reported symptoms of attention-deficit/hyperactivity disorder. Pediatrics. 2003;111:554-563.

13. Gozal D, Pope DW. Snoring during early childhood and academic performance at ages 13 to 14 years. Pediatrics. 2001;107:1394-1399.

14. Gruber R, Sadeh A, Raviv A. Instability of sleep patterns in children with attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc Psychiatry. 2000;39:495-501.

15. Picchietti DL, Walters AS. Moderate to severe periodic limb movement disorder in childhood and adolescence. Sleep. 1999;22:297-300.

16. Picchietti DL, England DL, Walters AS, et al. Periodic limb movement disorder and restless legs syndrome in children with attention-deficit hyperactivity disorder. J Child Neurology. 1998;13:588-594.

17. Picchietti DL, Underwood DJ, Farris WA, et al. Further studies on periodic limb movement disorder and restless legs syndrome in children with attention-deficit hyperactivity disorder. Movement Disord. 1999;14: 1000-1007.

18. Owens JA, Maxim R, Nobile C, McGuinn M, Msall M. Parental and self-report of sleep in children with attention-deficit/hyperactivity disorder. Arch Pediatr Adolesc Med. 2000;154:549-55.

Patrick Sorenson, MA, RPSGT, worked at the Boston Children’s Hospital Center for Pediatric Sleep Disorders-Hunnewell in Massachusetts prior to taking a teaching position with Syntech Solutions, LLC, in Rockford, Ill, in May. He can be reached at [email protected]