The role of NREM sleep instability in child cognitive performance

Sleep-dependent memory consolidation in young and aged brains

Young children and aged individuals are more prone to memory loss than young adults. One probable reason is insufficient sleep-dependent memory consolidation. Sleep timing and sleep-stage duration differ between children and aged individuals compared to adults. Frequent daytime napping and fragmented sleep architecture are common in children and older individuals. Moreover, sleep-dependent oscillations that play crucial roles in long-term memory storage differ among age groups. Notably, the frontal cortex, which is important for long-term memory storage undergoes major structural changes in children and aged subjects. The similarities in sleep dynamics between children and aged subjects suggest that a deficit in sleep-dependent consolidation contributes to memory loss in both age groups.

Does the brain sleep differently depending on intellectual abilities?

AIMS

To compare the children's sleep electroencephalogram according to their intellectual profile.

METHODS

Children were grouped according to their Wechsler Intelligence Scale for Children (WISC) scores (17 with normal intelligence quotient [IQ, NIQ] and 24 with high IQ [HIQ]). Comparisons of spectral power between groups and its relationship with WISC scores were assessed using analyses of variance and linear regression models, adjusted for age and sex.

RESULTS

Children with HIQ had more rapid eye movement (REM) sleep, especially late at night, and more power in slow-frequency bands during REM sleep than those with NIQ. There were also positive associations between the processing speed index and the spectral power in β bands in NREM sleep, and with the spectral power in α, σ, β, and γ bands in REM sleep, with different associations between groups.

CONCLUSION

The enhanced power in slow bands during REM sleep in children with HIQ overlaps with that of typical REM sleep oscillations thought to be involved in emotional memory consolidation. The dissimilar relationships between spectral power and WISC scores in NIQ and HIQ groups may underlie functional differences in brain activity related to cognitive efficiency, questioning the direction of the relationship between sleep and cognitive functioning.

Association of early bedtime at 3 years of age with higher academic performance and better non-cognitive skills in elementary school

This study investigated the relationship between sleep habits in early childhood and academic performance and non-cognitive skills in the first grade. We retrospectively analyzed a longitudinal population-based cohort from birth through early childhood, up to elementary school, in Amagasaki City, Japan. The primary outcome was academic performance in the first grade. Other outcomes were self-reported non-cognitive skills. Overall, 4395 children were enrolled. Mean national language scores for children with bedtimes at 18:00-20:00, 21:00, 22:00, and ≥ 23:00 were 71.2 ± 19.7, 69.3 ± 19.4, 68.3 ± 20.1, and 62.5 ± 21.3, respectively. Multiple regression analysis identified bedtime at 3 years as a significant factor associated with academic performance. However, sleep duration was not significantly associated with academic performance. Bedtime at 3 years also affected non-cognitive skills in the first grade. Diligence decreased with a later bedtime (21:00 vs. 18:00-20:00; odds ratio [OR]: 1.98, 95% confidence interval [CI] 1.27-3.09; 22:00 vs. 18:00-20:00; OR: 2.15, 95% CI 1.37-3.38; ≥ 23:00 vs. 18:00-20:00; OR: 2.33, 95% CI 1.29-4.20). Thus, early bedtime at 3 years may be associated with a higher academic performance and better non-cognitive skills in the first grade. Optimum early-childhood sleep habits may positively impact academic future.

Neuropsychological Profile in Pediatric Migraine without Aura: A Pilot Study

Despite the high prevalence of headache in developmental age, current reports about its neuropsychological effects are still lacking. The aim of the present pilot study is to assess the neuropsychological skills among children affected by migraine without aura (MwoA). Fifteen children (7M/8F) (mean age 10.73 ± 2.13) with MwoA, consecutively referred to the Center for Childhood Headache at Università degli Studi della Campania “Luigi Vanvitelli”, underwent the Italian version of the NEPSY-2 after cognitive evaluation. Moreover, to assess the pain level and disability grade during daily activity, the VAS and PedMIDAS scales were used. MwoA children were comparable with the control group of 38 children with respect to age, gender, language, and education level. Written informed consent was obtained from all parents and from children directly, when appropriate. MwoA children differed from controls significantly among the NEPSY-2 subscales, with a relevant relationship between the frequency and intensity of the attacks. In conclusion, the results of the present pilot study may suggest that MwoA could impact significantly neuropsychological functioning in children.

Cyclic alternating pattern in children with obstructive sleep apnea and its relationship with adenotonsillectomy, behavior, cognition, and quality of life

STUDY OBJECTIVES

To determine in children with obstructive sleep apnea (OSA) the effect of adenotonsillectomy (AT) on the cyclic alternating pattern (CAP) and the relationship between CAP and behavioral, cognitive, and quality-of-life measures.

METHODS

CAP parameters were analyzed in 365 overnight polysomnographic recordings of children with mild-to-moderate OSA enrolled in the Childhood Adenotonsillectomy Trial (CHAT), randomized to either early AT (eAT) or watchful waiting with supportive care (WWSC). We also analyzed CAP in a subgroup of 72 children with moderate OSA (apnea-hypopnea index > 10) that were part of the CHAT sample. Causal mediation analysis was performed to determine the independent effect of changes in CAP on selected outcome measures.

RESULTS

At baseline, a higher number of A1 phases per hour of sleep was significantly associated with worse behavioral functioning (caregiver Behavior Rating Inventory of Executive Function (BRIEF) Global Executive Composite (GEC): ρ = 0.24, p = 0.042; caregiver Conners' Rating Scale Global Index: ρ = 0.25, p = 0.036) and lower quality of life (OSA-18: ρ = 0.27, p = 0.022; PedsQL: ρ = -0.29, p = 0.015) in the subgroup of children with moderate OSA, but not across the entire sample. At 7-months follow-up, changes in CAP parameters were comparable between the eAT and WWSC arms. CAP changes did not account for significant proportions of variations in behavioral, cognitive, and quality-of-life performance measures at follow-up.

CONCLUSIONS

We show a significant association between the frequency of slow, high-amplitude waves with behavioral functioning, as well as the quality of life in children with moderate OSA. Early AT in children with mild-to-moderate OSA does not alter the microstructure of nonrapid eye movement sleep compared with watchful waiting after an approximately 7-month period of follow-up.

CLINICAL TRIAL

The study "A Randomized Controlled Study of Adenotonsillectomy for Children With Obstructive Sleep Apnea Syndrome" was registered at Clinicaltrials.gov (#NCT00560859).

Effects of insomnia symptoms and objective short sleep duration on memory performance in youths

Sleep quantity and quality are both important for optimal development and functioning during youth. Yet few studies have examined the effects of insomnia symptoms and objective short sleep duration on memory performance among adolescents and young adults. One-hundred and ninety participants (female: 61.6%) aged from 12 to 24 years completed this study. All participants underwent a clinical interview, a 7-day actigraphic assessment, a battery of self-report questionnaires and cognitive tests to assess working memory and episodic memory. Insomnia symptoms were defined as a score ≥ 9 on the Insomnia Severity Index, and objective short sleep duration was defined as average total sleep time less than 7 hr for those aged 12-17 years, and 6 hr for those aged 18 years and above as assessed by actigraphy. Insomnia symptoms were significantly associated with worse self-perceived memory (p < .05) and poorer performance on the digit span task (p < .01), but not the dual N-back task and verbal learning task. There was no significant difference in any of the memory measures between participants with objective short sleep duration and their counterparts. No interaction effect was found between insomnia and short sleep duration on any of the objective memory outcomes. Insomnia symptoms, but not objective short sleep duration, were associated with poorer subjective memory and objective working memory performance in youths. Further studies are needed to investigate the underlying mechanisms linking insomnia and memory impairments, and to delineate the long-term impacts of insomnia on other aspects of neurocognitive functioning in youth.

Association of sleep spindle activity and sleepiness in children with sleep-disordered breathing

STUDY OBJECTIVES

The association of snoring and sleep-disordered breathing (SDB) with daytime sleepiness is well documented; however, the exact mechanisms, and especially the role of sleep microstructure that may account for this association remain incompletely understood. In a cohort of children with SDB, we aimed to compare sleep spindle activity between children with daytime sleepiness versus those without daytime sleepiness.

METHODS

Children with SDB who reported daytime sleepiness were recruited and compared with age- and sex-matched SDB controls. Polysomnographic recordings were analyzed evaluating sleep spindle activity. A statistical comparison was carried out in both groups to assess the association between sleepiness and sleep spindle activity.

RESULTS

Thirty-three children with SDB (mean age: 7.5 ± 1.7 years) were included, 10 with and 23 without daytime sleepiness. Spindle activity was lower in children with daytime sleepiness compared with those without; in stage N2, median (interquartile range) sleep spindle indexes were 77.5 (37.3) and 116.9 (71.2) (P = .015), respectively.

CONCLUSIONS

Spindles were significantly reduced in children with SDB and daytime sleepiness. The exact mechanisms of this association remain unknown and future research is needed in order to establish the exact role of sleep spindle activity on daytime symptoms in children with SDB.

Correlation of sleep microstructure with daytime sleepiness and cognitive function in young and middle-aged adults with obstructive sleep apnea syndrome

PURPOSE

To compare microstructural features of sleep in young and middle-aged adults with differing severities of obstructive sleep apnea syndrome (OSAS), and to investigate the relationship between sleep microstructural fragmentation and cognitive impairment, as well as daytime sleepiness, in these patients.

METHODS

A total of 134 adults with snoring (mean age, 37.54 ± 7.66 years) were classified into four groups based on apnea-hypopnea index: primary snoring, mild OSAS, moderate OSAS, and severe OSAS. Overnight polysomnography was performed to assess respiratory, sleep macrostructure (N1, N2, N3, and R), and sleep microstructure (arousal, cyclic alternating pattern [CAP]) parameters. Cognitive function and daytime sleepiness were assessed using Montreal Cognitive Assessment (MoCA) and Epworth Sleepiness Scale (ESS).

RESULTS

As OSAS severity increased, MoCA gradually decreased and ESS gradually increased. N1%, N2%, and N3% sleep were significantly different between the severe OSAS group and the primary snoring, mild OSAS, and moderate OSAS groups (all P < 0.05). Overall arousal index, respiratory-related arousal index, CAP time, CAP rate, phase A index, number of CAP cycles, and phase A average time differed significantly in the moderate and severe OSAS groups compared with the mild OSAS and primary snoring groups (all P < 0.05). The strongest correlations identified by stepwise multiple regression analysis were between phase A3 index and the MoCA and ESS scores.

CONCLUSIONS

Sleep microstructure exhibited significant fragmentation in patients with moderate and severe OSAS, which was associated with decreased MoCA and increased ESS scores. This suggests that phase A3 index is a sensitive indicator of sleep fragmentation in OSAS.

Reasoning Abilities and Potential Correlates Among Jordanian School Children

Objectives To investigate factors related to reasoning skills in 434 school children aged 5-9 years. Methods The Leiter International Performance Scale-Revised was used to assess reasoning skills. Demographic, work and family income data, information on child's daily behavior and school academic achievement were provided by the participating children's parents. Results Reasoning scores increased by 4.56 points with increasing subject's age, 1.71 points with increasing level of father's occupation, 1.86 points with each increase in the subject's GPA, 1.13 points with consumption of breakfast at home and 1.81 points when child slept more hours. Having a father who smoked and living in a rural area decreased scores in reasoning. Conclusions for Practice Screening of reasoning and associated factors is essential for a comprehensive and accurate understanding of the child's abilities and limitations. Understanding the child's reasoning abilities is critical for establishing intervention goals and planning therapeutic activities.

Sleep Instabilities Assessed by Cardiopulmonary Coupling Analysis Increase During Childhood and Adolescence

The electrocardiogram-based cardiopulmonary coupling (CPC) technique may be used to track sleep instabilities. With progressing age, maturational changes during childhood and adolescence affect sleep. The objective was to assess developmental changes in sleep instabilities in a natural setting. ECGs during nighttime sleep on regular school days were recorded from 363 subjects aged 4 to 22 years (204 females). The estimated total sleep time (ETST) decreased from 598 to 445 min during childhood and adolescence. Stable sleep linearly decreased with progressing age (high frequency coupling (HFC): 70–48% ETST). Unstable sleep [low frequency coupling (LFC): 9–19% ETST], sleep fragmentation or disordered breathing (elevated LFC: 4–12% ETST), and wake/REM states [very low frequency coupling (VLFC): 20–32% ETST] linearly increased with age. Hence, with progressing age the sleep of children and adolescents shortens, becomes more unstable and is more often affected by fragmentation or sleep disordered breathing, especially in the age group >13 years. It remains to be clarified whether some of the changes are caused by a social jetlag, i.e., the misalignment of body clock and social time especially in adolescents.

Orexin System: The Key for a Healthy Life

The orexin-A/hypocretin-1 and orexin-B/hypocretin-2 are neuropeptides synthesized by a cluster of neurons in the lateral hypothalamus and perifornical area. Orexin neurons receive a variety of signals related to environmental, physiological and emotional stimuli, and project broadly to the entire CNS. Orexin neurons are “multi-tasking” neurons regulating a set of vital body functions, including sleep/wake states, feeding behavior, energy homeostasis, reward systems, cognition and mood. Furthermore, a dysfunction of orexinergic system may underlie different pathological conditions. A selective loss orexin neurons was found in narcolepsia, supporting the crucial role of orexins in maintaining wakefulness. In animal models, orexin deficiency lead to obesity even if the consume of calories is lower than wildtype counterpart. Reduced physical activity appears the main cause of weight gain in these models resulting in energy imbalance. Orexin signaling promotes obesity resistance via enhanced spontaneous physical activity and energy expenditure regulation and the deficiency/dysfunction in orexins system lead to obesity in animal models despite of lower calories intake than wildtype associated with reduced physical activity. Interestingly, orexinergic neurons show connections to regions involved in cognition and mood regulation, including hippocampus. Orexins enhance hippocampal neurogenesis and improve spatial learning and memory abilities, and mood. Conversely, orexin deficiency results in learning and memory deficits, and depression.

The relationship between sleep-wake cycle and cognitive functioning in young people with affective disorders

Although early-stage affective disorders are associated with both cognitive dysfunction and sleep-wake disruptions, relationships between these factors have not been specifically examined in young adults. Sleep and circadian rhythm disturbances in those with affective disorders are considerably heterogeneous, and may not relate to cognitive dysfunction in a simple linear fashion. This study aimed to characterise profiles of sleep and circadian disturbance in young people with affective disorders and examine associations between these profiles and cognitive performance. Actigraphy monitoring was completed in 152 young people (16–30 years; 66% female) with primary diagnoses of affective disorders, and 69 healthy controls (18–30 years; 57% female). Patients also underwent detailed neuropsychological assessment. Actigraphy data were processed to estimate both sleep and circadian parameters. Overall neuropsychological performance in patients was poor on tasks relating to mental flexibility and visual memory. Two hierarchical cluster analyses identified three distinct patient groups based on sleep variables and three based on circadian variables. Sleep clusters included a ‘long sleep’ cluster, a ‘disrupted sleep’ cluster, and a ‘delayed and disrupted sleep’ cluster. Circadian clusters included a ‘strong circadian’ cluster, a ‘weak circadian’ cluster, and a ‘delayed circadian’ cluster. Medication use differed between clusters. The ‘long sleep’ cluster displayed significantly worse visual memory performance compared to the ‘disrupted sleep’ cluster. No other cognitive functions differed between clusters. These results highlight the heterogeneity of sleep and circadian profiles in young people with affective disorders, and provide preliminary evidence in support of a relationship between sleep and visual memory, which may be mediated by use of antipsychotic medication. These findings have implications for the personalisation of treatments and improvement of functioning in young adults early in the course of affective illness.

Do respiratory cycle-related EEG changes or arousals from sleep predict neurobehavioral deficits and response to adenotonsillectomy in children?

STUDY OBJECTIVES

Pediatric obstructive sleep apnea (OSA) is associated with hyperactive behavior, cognitive deficits, psychiatric morbidity, and sleepiness, but objective polysomnographic measures of OSA presence or severity among children scheduled for adenotonsillectomy have not explained why. To assess whether sleep fragmentation might explain neurobehavioral outcomes, we prospectively assessed the predictive value of standard arousals and also respiratory cycle-related EEG changes (RCREC), thought to reflect inspiratory microarousals.

METHODS

Washtenaw County Adenotonsillectomy Cohort II participants included children (ages 3-12 years) scheduled for adenotonsillectomy, for any clinical indication. At enrollment and again 7.2 ± 0.9 (SD) months later, children had polysomnography, a multiple sleep latency test, parent-completed behavioral rating scales, cognitive testing, and psychiatric evaluation. The RCREC were computed as previously described for delta, theta, alpha, sigma, and beta EEG frequency bands.

RESULTS

Participants included 133 children, 109 with OSA (apnea-hypopnea index [AHI] ≥ 1.5, mean 8.3 ± 10.6) and 24 without OSA (AHI 0.9 ± 0.3). At baseline, the arousal index and RCREC showed no consistent, significant associations with neurobehavioral morbidities, among all subjects or the 109 with OSA. At follow-up, the arousal index, RCREC, and neurobehavioral measures all tended to improve, but neither baseline measure of sleep fragmentation effectively predicted outcomes (all p > 0.05, with only scattered exceptions, among all subjects or those with OSA).

CONCLUSION

Sleep fragmentation, as reflected by standard arousals or by RCREC, appears unlikely to explain neurobehavioral morbidity among children who undergo adenotonsillectomy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT00233194.

Long-term changes in neurocognition and behavior following treatment of sleep disordered breathing in school-aged children

STUDY OBJECTIVES

Sleep disordered breathing (SDB) in children is associated with detrimental neurocognitive and behavioral consequences. The long term impact of treatment on these outcomes is unknown. This study examined the long-term effect of treatment of SDB on neurocognition, academic ability, and behavior in a cohort of school-aged children.

DESIGN

Four-year longitudinal study. Children originally diagnosed with SDB and healthy non-snoring controls underwent repeat polysomnography and age-standardized neurocognitive and behavioral assessment 4y following initial testing.

SETTING

Melbourne Children's Sleep Centre, Melbourne, Australia.

PARTICIPANTS

Children 12-16 years of age, originally assessed at 7-12 years, were categorized into Treated (N = 12), Untreated (N = 26), and Control (N = 18) groups.

INTERVENTIONS

Adenotonsillectomy, Tonsillectomy, Nasal Steroids. Decision to treat was independent of this study.

MEASUREMENTS AND RESULTS

Changes in sleep and respiratory parameters over time were assessed. A decrease in obstructive apnea hypopnea index (OAHI) from Time 1 to Time 2 was seen in 63% and 100% of the Untreated and Treated groups, respectively. The predictive relationship between change in OAHI and standardized neurocognitive, academic, and behavioral scores over time was examined. Improvements in OAHI were predictive of improvements in Performance IQ, but not Verbal IQ or academic measures. Initial group differences in behavioral assessment on the Child Behavior Checklist did not change over time. Children with SDB at baseline continued to exhibit significantly poorer behavior than Controls at follow-up, irrespective of treatment.

CONCLUSIONS

After four years, improvements in SDB are concomitant with improvements in some areas of neurocognition, but not academic ability or behavior in school-aged children.