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 ß bands in NREM sleep, and with the spectral power in α, σ, ß, 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.

Sleep Stage Transitions and Sleep-Dependent Memory Consolidation in Children with Narcolepsy-Cataplexy.

Electroencephalographic sleep stage transitions and altered first REM sleep period transitions have been identified as biomarkers of type 1 narcolepsy in adults, but not in children. Studies on memory complaints in narcolepsy have not yet investigated sleep-dependent memory consolidation. We aimed to explore stage transitions; more specifically altered REM sleep transition and its relationship with sleep-dependent memory consolidation in children with narcolepsy. Twenty-one children with narcolepsy-cataplexy and twenty-three healthy control children completed overnight polysomnography and sleep-dependent memory consolidation tests. Overnight transition rates (number of transitions per hour), global relative transition frequencies (number of transitions between a stage and all other stages/total number of transitions × 100), overnight transitions to REM sleep (transition from a given stage to REM/total REM transitions × 100), and altered first REM sleep period transitions (transitions from wake or N1 to the first REM period) were computed. Narcoleptic children had a significantly higher overnight transition rate with a higher global relative transition frequencies to wake. A lower sleep-dependent memory consolidation score found in children with narcolepsy was associated with a higher overnight transition frequency. As observed in narcoleptic adults, 90.48% of narcoleptic children exhibited an altered first REM sleep transition. As in adults, the altered sleep stage transition is also present in children with narcolepsy-cataplexy, and a higher transition rate could have an impact on sleep-dependent memory consolidation. These potential biomarkers could help diagnose type 1 narcolepsy in children more quickly; however, further studies with larger cohorts, including of those with type 2 narcolepsy and hypersomnia, are needed.

Sleep and Psychosocial Characteristics of Children with Narcolepsy According to Their Intellectual Profile: A Case-Control Study.

Adequate intellectual abilities are a protective factor for psychosocial adjustments in chronic disorders. The main objective of this study was to assess the cognitive abilities, sleep, and psychosocial characteristics of children with narcolepsy compared to controls, according to their intellectual profile. Children underwent a polysomnography, completed an intellectual ability assessment, and filled out standardized questionnaires. The group with an intelligence quotient (IQ) in the area of high intellectual potential (high IQ, HIQ) consisted of 25 children with narcolepsy (HIQ-N, 40% boys, median age 11.5 years, 48% with obesity, 60% under treatment) and 25 controls (HIQ-C, 68% boys, median age 11.7 years). Compared to HIQ-C, HIQ-N had a lower perceptual reasoning index and fewer conduct disorders. The group with an IQ in the normal range (NIQ) consisted of 22 children with narcolepsy (NIQ-N, 55% boys, median age 12.1 years, 59% with obesity, 64% under treatment) and 21 controls (NIQ-C, 68% boys, median age 10 years). NIQ-N presented the same intellectual profile as NIQ-C but reported more school difficulties. In children with HIQ, those with narcolepsy appear to have a different cognitive profile than controls. NIQ seems to predict a greater impact of narcolepsy on daily-life functioning.

Intellectual Abilities of Children with Narcolepsy.

High cognitive functioning could be a protective factor for school difficulties, behavioral and mood impairments in children with narcolepsy. To investigate this factor, we studied the intellectual abilities of 74 children with narcolepsy (43 boys, 11.7 years old at diagnosis, 91% of cataplexies, 64% obese, 100% HLA positive for DR-DQB1*06:02). All children underwent a one-night polysomnography followed by Multiple Sleep Latency Tests, an evaluation of intelligence quotient (IQ), and filled standardized questionnaires. Thirty-eight percent had high potentialities (HP defined by IQ > 130) and 48% had school difficulties. Using non-parametric tests, we found that HP children reported less difficulties at school and tended to have less impulsivity, conduct, and learning disorders than those without HP. They also tended to be less obese and had less desaturation. Using a multivariate regression analysis, we found an association between the REM sleep percentage and the IQ. REM sleep could be involved in the dynamic changes contributing to the equilibrium of intellectual functioning. This study highlights that despite their frequent school difficulties, narcolepsy per se is unlikely to be a cause of intellectual disability in children. Prompt diagnosis and management of comorbidities such as obesity and obstructive sleep apnea (OSA) could improve cognitive and school performances in these children.

Sleep of Children with High Potentialities: A Polysomnographic Study.

The involvement of sleep in cognitive functioning is well known, but only a few studies have examined objective sleep parameters in children with high intellectual potential (HP). The main objective of this study was to compare sleep characteristics of 33 children with high intellectual potentialities (HP) (median 10 years old, 64% of boys) compared to 25 controls (median 11 years old, 64% of boys) and assess the difference between children with a homogeneous vs. a heterogeneous intelligence quotient (IQ) (i.e., a difference ≥15 points between verbal and non-verbal IQ). All children underwent a one-night polysomnography, an evaluation of intellectual quotient (IQ) and filled standardized questionnaires. Using non-parametric tests to compare groups' characteristics, we found that children with HP had more heterogeneous IQ, more rapid eyes movement (REM) sleep and tended to have less stage 1 sleep than controls. They also had more insomnia and sleep complaints. The high amount of REM sleep in children with HP could be advantageous for learning and could partially explain their gift. This study highlights the necessity of investigating sleep disorders in children with HP during clinical routine and reinforces the hypothesis of the involvement of nocturnal sleep, and especially REM sleep, in daytime cognition and behavior.

Sleep during development: Sex and gender differences.

Sleep occupies a substantial proportion of life. Sleep modifications parallel brain development during childhood. Sex and gender differences have been reported in brain development and many clinical and psychosocial conditions. This narrative review provides insight into the differences between girls and boys in terms of brain maturation and plasticity related to sleep and sleep characteristics (physiology, sleep duration) during development.

The French Sleep Disturbance Scale for Children.

OBJECTIVE: The psychometric properties of the Sleep Disturbance Scale for Children (SDSC) have been shown to be accurate, even when translated into several languages. The aim of the present study was to translate, adapt, and validate the SDSC for a French-speaking population. METHODS: After forward- and back-translation, the tool was further translated and adapted into the French language. It was then pretested in terms of clarity on 33 French-speaking parents. Pretesting demonstrated that the questionnaire was well understood, indicating good clarity. During the validation phase, a total of 447 French-speaking parents of children aged between 4 and 16  years completed the SDSC. Among these, 66 children were diagnosed with sleep disorders by a pediatric specialist after a sleep consultation and polysomnographic recordings. RESULTS: The factor analysis revealed five factors: difficulty in initiating and maintaining sleep (DIMS), sleep breathing disorders (SBD), disorders of excessive somnolence (DOES), parasomnias (PARA) and non-restorative sleep (NRS). This psychometric structure is reliable and logical in comparison with the experts' diagnoses. Convergent validity, divergent and internal reliability are very good. Inter-parental concordance in scoring the child's sleep problem does show differences in the ways in which parents report their children's sleep patterns. Cut-off was calculated for the total score (45). CONCLUSION: This study validated a 25-item French version of the questionnaire. The French SDSC could therefore be used to aid screening of sleep disorders in the general population.

High bicarbonate levels in narcoleptic children.

The objective of this study was to evaluate the levels of plasma bicarbonate levels in narcoleptic children. Clinical, electrophysiological data and bicarbonate levels were evaluated retrospectively in children seen in our paediatric national reference centre for hypersomnia. The cohort included 23 control subjects (11.5 ± 4 years, 43% boys) and 51 patients presenting de-novo narcolepsy (N) (12.7 ± 3.7 years, 47% boys). In narcoleptic children, cataplexy was present in 78% and DQB1*0602 was positive in 96%. The control children were less obese (2 versus 47%, P = 0.001). Compared with control subjects, narcoleptic children had higher bicarbonate levels (P = 0.02) as well as higher PCO2 (P < 0.01) and lower venous pH gas (P < 0.01). Bicarbonate levels higher than 27 mmol L(-1) were found in 41.2% of the narcoleptic children and 4.2% of the controls (P = 0.001). Bicarbonate levels were correlated with the Adapted Epworth Sleepiness Scale (P = 0.01). Narcoleptic patients without obesity often had bicarbonate levels higher than 27 mmol L (-1) (55 versus 25%, P = 0.025). No differences were found between children with and without cataplexy. In conclusion, narcoleptic patients had higher bicarbonate plasma levels compared to control children. This result could be a marker of hypoventilation in this pathology, provoking an increase in PCO2 and therefore a respiratory acidosis, compensated by an increase in plasma bicarbonates. This simple screening tool could be useful for prioritizing children for sleep laboratory evaluation in practice.

Quality of life in children with narcolepsy.

AIMS: To evaluate the health-related quality of life (HRQL) and its correlates in children and adolescents with narcolepsy. METHODS: We compared the clinical characteristics of control subjects and patients with primary narcolepsy from data collected at the National Reference Centers for Narcolepsy. RESULTS: The cohort included 69 control subjects (29 boys) and 117 patients (65 boys; 59 de novo patients). Cataplexy was present in 81% and DQB1*0602 was positive in 91%. The control children were older (13.5±3.2 vs. 11.6±3.1 years, P<0.001) and less obese (1.4% vs. 60%, P<0.001). Twenty-five percent of the patients and 15.6% of the control subjects had clinically significant depressive feelings on Children's Depression Inventory (CDI≥16) (NS). Fifty-three narcoleptic and 43 control adolescents, 31 narcoleptic children and 23 control children filled out the HRQL questionnaires as well as 83 parents of patients and 60 parents of control subjects. Narcolepsy seriously impacts HRQL in terms of vitality, physical well-being, relations with friends and leisure activities, especially in adolescents. Depression was the factor that most affected HRQL in both narcoleptic and control subjects. For the control subjects and the narcoleptic patients, when the CDI score was entered into the multivariable regression model adjusted for gender and age, no other continuous independent variable could significantly increase the likelihood of the model. When the CDI score increased by 1, the mean HRQL score decreased by 1.7 for narcoleptic patients and 1.5 for control subjects. Apnea-hypopnoea index, diagnosis delay, disease duration, obesity, the presence of cataplexy or treatment had no effects on HRQL. CONCLUSIONS: Narcoleptic children and adolescents were at high risk for poor HRQL. Depressive symptoms had a major impact on HRQL. We recommend a more thorough assessment and management of psychological health in this population.

Depressive feelings in children with narcolepsy.

OBJECTIVES: We aimed to evaluate depressive feelings and their correlations in children and adolescents with narcolepsy collected in national reference centers for narcolepsy. METHODS: We compared clinical and sleep characteristics of patients with and without depressive symptoms evaluated on the Children's Depression Inventory (CDI). RESULTS: Our study sample included 88 children (44 boys; 44 de novo patients) with a mean age of 11.9 ± 3.1 years at diagnosis (37.5% were aged ⩽ 10 years). Obesity was found in 59% of the sample and cataplexy was present in 80.7%. The DQB1*0602 allele was positive in 93.5% of our sample. There were 25% of children who had clinically depressive feelings (CDI>16), especially girls older than the age of 10 years. Bivariate associations indicated that depressive feelings were associated with fatigue (48%), hyperactivity (31%), insomnia (16%), and excessive daytime sleepiness (EDS) (14-24%). In the multivariate model adjusted for gender and age, only fatigue explained the variability of the depression score. CONCLUSION: In our large cohort, high levels of depressive symptoms essentially expressed by fatigue affected 25% of children with narcolepsy. The girls older than 10 years of age were especially vulnerable. The similar prevalence of depressive feelings in treated vs never-treated patients suggests a specific need for diagnosing and managing this symptom in young patients with narcolepsy.