The largest research base that links sleep in children to daytime functioning comes from correlational studies in epidemiological samples. As summarized in recent major reviews 13-16
, children's quantity and/or quality of sleep repeatedly has been shown to correlate with their levels of daytime sleepiness and performance in school. The strength of that association may vary by student age and sex; one recent meta-analysis of sleep and school functioning reported that studies of younger children, particularly those that enrolled more boys, tended to show the largest effects.16
To some degree, research in this area could be criticized for an overreliance on parent- or self-report of sleep and academic performance. However, such reports correlate well with objective measures 15, 17
and, importantly, the association between sleep and academic functioning has been reported even when both constructs were measured objectively 18
Even so, findings have not been universal. At least one large study has suggested that sleep is minimally associated with academic knowledge 19
. Of note, that study relied heavily on office-based tests of academic knowledge
, which are only partial predictors of classroom performance.
Classroom performance is also dependent upon skills that are difficult to test in the office, including sustained attention, behavior regulation, planning, and organization 20
. Indeed, school-identified learning problems did
significantly correlate with poor parent-reported sleep quality in that study. However, this effect disappeared after statistically covarying for symptoms of attention-deficit/hyperactivity disorder (ADHD), which led the authors to speculate that any apparent link between sleep and learning problems could be due to the confounding effects of ADHD. Alternatively, however, symptoms of ADHD may not represent confounding factors, but rather the mechanism
by which poor sleep quality was linked to learning problems.
Indeed, inadequate sleep has been linked to difficulties with attention, impulse control, and behavior regulation 21-24
, with potential consequences that extend beyond the classroom. Poor sleep quality is associated with crash risk in teen drivers 25
, and short sleep has been linked to accidental injuries in young children 26-28
and adolescents 27
, as well as risk-taking behaviors in adolescents 29
. Because poor regulation of attention and behavior are key features of ADHD, some have concluded that a subgroup of children with primary sleep problems may be misdiagnosed with ADHD. The relationship between ADHD and sleep is complex, however, and the reader is referred to the relevant chapter in this volume and several other recent reviews for detailed coverage 30-32
The links between sleep and other psychiatric diagnoses, including depression and anxiety disorders, are similarly complex and extend beyond the current discussion. Briefly, sleep problems are disproportionately present in many psychiatric conditions, and the direction of causation appears to be reciprocal, rather than unidirectional (see ref 33
for reviews). There is also evidence that the presence or severity of sleep disturbance predicts psychiatric symptom severity and functional impairment e.g. 34-35
. However, it is difficult to know how to apply this information to the general population; whereas sleep disruption appears to be linked to mood, studies have yielded mixed associations between sleep duration and emotional functioning 36-38
. Indeed, within one study, parent-reported mood problems and behavior problems had variable associations with sleep duration depending on the source of information on behavior/ mood (parent vs self-report) and sleep duration (parent versus actigraphy)39
Of perhaps greater interest are studies of the daytime functioning of children and adolescents with obstructive sleep apnea (OSA), a largely treatable disorder in which the upper airway is chronically and/or repeatedly obstructed during sleep. As reviewed by Beebe 40
, OSA has been linked to poor classroom grades, sleepiness, inattention, hyperactivity, oppositional behaviors, and mood dysregulation (but not ongoing mood disturbance) in the vast majority of relevant studies, most of which have targeted children aged 5-12 years of age. We recently extended those findings through the adolescent years 20
. Office-based tests of intelligence have yielded inconsistent results in children with OSA, with the most consistent evidence of IQ deficits during the preschool and early grade-school years 40
. Other tests of cognition have yielded mixed results, but there is some evidence of poor scores on tests of attention, executive functioning, and learning/memory in children with OSA 40-42
. OSA is of particular interest here not only because a large number of studies have examined behavioral outcomes of children with this condition, but also because treatments focus on the airway and would not be expected to impact behavior in a manner independent of sleep. Non-randomized studies have shown improved daytime functioning following surgical intervention for uncomplicated OSA 40, 43
, bolstering the suggestion that OSA is causally related to daytime dysfunction. However, the field awaits the results of the CH
onsillectomy (CHAT) study, an ongoing large randomized adenotonsillectomy trial for OSA with blinded outcome measures.
There have been studies that have linked other treatable sleep conditions, most notably Restless Legs Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD), to daytime dysfunction, particularly to hyperactivity/impulsivity and inattention 44-45
. However, compared to OSA, studies have been few, causal implications are unclear, and intervention data are difficult to interpret because the relevant sleep treatments can also directly impact daytime functioning. For more information on RLS, see Durmer and colleagues’ paper in this volume.
Outside of OSA, only a handful of correlational and case-controlled studies of pediatric sleep have employed objective measures of cognitive functioning. In two, poor quality sleep was significantly associated with poor attention, working memory, and/or impulse control 22-23
. A recent study linked objectively-defined short sleep with lower IQ test scores 46
. However, others have reported either no relationship between sleep duration and IQ 47
or an association only for males and on selected aspects of intelligence 48
. Two large-sample studies on young children have arrived at conflicting results with respect to overall cognitive functioning and sleep 49-50
In summary, correlational and case-control studies have yielded good evidence of associations between inadequate sleep and disturbances in children's behavior and attention regulation, daytime sleepiness, academic performance and, to the extent that it has been explored, executive functioning. However, the possibility of uncontrolled confounding factors limits the degree to which causal inferences can be drawn these studies.