Dagmara Dimitriou

Cross syndrome comparison of sleep problems in children with Down syndrome and Williams syndrome

Based on previous findings of frequent sleep problems in children with Down syndrome (DS) and Williams syndrome (WS), the present study aimed to expand our knowledge by using parent report and actigraphy to define sleep problems more precisely in these groups. Twenty-two school-aged children with DS, 24 with WS and 52 typically developing (TD) children took part in the study. Each child wore an actiwatch for a minimum of four nights and parents completed the Childrens Sleep Habits Questionnaire (CSHQ). Sleep problems were common in both developmental disorders. Children with DS had the greatest sleep disruption, with frequent and longer night wakings as well as restlessness. Parents reported symptoms of sleep-disordered breathing and a range of other problems including grinding teeth, bedtime resistance and sleep anxiety. Children with WS had problems initiating sleep and parents also reported bed-wetting and body pain. Despite these problems, the mean actual sleep time, as measured by actigraphy, did not differ between the three groups. CSHQ reports were in agreement with actigraphy for childrens sleep duration, but this was not the case for sleep latency, restlessness and the night wakings variables. Sleep problems in DS and WS are common and appear to be syndrome-specific. Due to the inaccuracy of parent report, it is recommended that children at risk undergo objective measures of sleep assessment.

Sleep enhances memory consolidation in children

Sleep is an active state that plays an important role in the consolidation of memory. It has been found to enhance explicit memories in both adults and children. However, in contrast to adults, children do not always show a sleep‐related improvement in implicit learning. The majority of research on sleep‐dependent memory consolidation focuses on adults; hence, the current study examined sleep‐related effects on two tasks in children. Thirty‐three typically developing children aged 6–12 years took part in the study. Actigraphy was used to monitor sleep. Sleep‐dependent memory consolidation was assessed using a novel non‐word learning task and the Tower of Hanoi cognitive puzzle, which involves discovering an underlying rule to aid completion. Children were trained on the two tasks and retested following approximately equal retention intervals of both wake and sleep. After sleep, children showed significant improvements in performance of 14% on the non‐word learning task and 25% on the Tower of Hanoi task, but no significant change in score following the wake retention interval. Improved performance on the Tower of Hanoi may have been due to children consolidating explicit aspects of the task, for example rule‐learning or memory of previous sequences; thus, we propose that sleep is necessary for consolidation of explicit memory in children. Sleep quality and duration were not related to childrens task performance. If such experimental sleep‐related learning enhancement is generalizable to everyday life, then it is clear that sleep plays a vital role in childrens educational attainment.

Development of novel metaphor and metonymy comprehension in typically developing children and Williams syndrome

This study investigated the development of novel metaphor and metonymy comprehension in both typically developing (TD) children and individuals with Williams syndrome (WS). Thirty-one TD children between the ages of 3;09 and 17;01 and thirty-four individuals with WS between the ages of 7;01 and 44 years old were administered a newly developed task examining novel metaphor and metonymy comprehension, as well as a range of standardised tests that assess semantic knowledge. This age range and the background measures allowed construction of developmental trajectories to investigate whether chronological age or mental age, represented by word knowledge, relate to novel metaphor and metonymy comprehension. The results showed that comprehension of figurative language did not increase with chronological age in WS, in contrast to TD. Although there was no difference for the different types of metaphors, certain metonymy expressions were found to be easier than others in the TD group. In addition, semantic knowledge was a reliable predictor for novel metaphor and metonymy comprehension in the TD but only for metonymy in the WS group. In sum, development of novel metonymy in the WS group is only delayed while comprehension of novel metaphor is both delayed and atypical. However, future research should further investigate differences between sub-types, as well as what cognitive factors relate to novel metaphor comprehension in individuals with Williams syndrome.

Sleep problems and language development in toddlers with Williams syndrome

Sleep and related maternal beliefs were assessed in a narrow age range of 18 children with Williams syndrome (WS) and 18 typically developing (TD) children. WS is a rare genetic disorder characterised by a complex physical, cognitive and behavioural phenotype. High prevalence of sleep difficulties in older children and adults with WS have been reported. Parents completed 6 questionnaires: the Brief Infant Sleep Questionnaire, Infant Sleep Vignettes Interpretation Scale, Pittsburgh Sleep Quality Index of Parents, Child Behaviour Checklist, MacArthur Communicative Development Inventory for Infants - Words and Gestures, and the Major (ICD-10) Depression Inventory. Compared to TD children, those with WS had shorter night sleep, more night wakings and wakefulness according to parental report. Regression analyses revealed that a proportion of the variance in language development scores in WS children could be explained by night sleep duration. Compared to control parents, the mothers of the WS group were more likely to describe their childs sleep as problematic and had higher rates of involvement with child sleep, yet they had a lesser tendency to interpret sleep problems as signs of distress and a greater tendency to emphasise limit setting. Approximately half of both groups of mothers experienced poor sleep quality. This was also related to maternal mood, and night wakefulness in the children with WS. This is the first study to quantify sleep difficulties in young children with WS in a narrow age range using maternal report. The possible negative effects on maternal sleep and mood, and the link between night sleep and language development in young children with WS, requires further detailed investigation.

Abnormal secretion of melatonin and cortisol in relation to sleep disturbances in children with Williams syndrome

OBJECTIVE A high rate of sleep disturbances has been reported in individuals with Williams syndrome (WS) but the underlying aetiology has yet to be identified. Melatonin and cortisol levels display circadian rhythmicity and are known to affect and regulate sleep/wake patterns. The current study examined the levels of these two endocrine markers and explored a possible relationship with sleep patterns in children with WS. METHODS Twenty-five children with WS and 27 typically developing age- and gender-matched comparison children were recruited. Saliva was collected from each child at three time points: 4-6 pm, before natural bedtime, and after awakening. The levels of salivary melatonin and cortisol were analysed by specific enzyme-linked immunoassays. Sleep patterns were examined using actigraphy and the Childrens Sleep Habit Questionnaire. RESULTS The WS group had shallower drops in cortisol and less pronounced increase in melatonin at bedtime compared to the controls. Furthermore, they also had significantly higher levels of cortisol before bedtime. CONCLUSIONS Increased bedtime cortisol and less pronounced rise in melatonin levels before sleep may play a role in the occurrence of sleep disturbances, such as delayed sleep onset, observed in children with WS. As both markers play a significant role in our circadian rhythm and sleep/wake cycle, it is necessary to examine sleep using multi-system analysis.

Performance on verbal and low-verbal false belief tasks : Evidence from children with Williams syndrome

UNLABELLED Previous studies that have investigated the relationship between performance on theory of mind (ToM) tasks and verbal abilities in individuals with Williams syndrome (WS) have reported contradictory findings with some showing that language abilities aid performance on ToM tasks while others have found that participants with WS fail these tasks because of their verbal demands. The current study investigated this relationship again comparing performance on a classical change-location task to two newly developed low-verbal tasks, one change-location task and one unexpected content task. Thirty children with WS (aged 5-17;01 years) and 30 typically developing (TD) children (aged between 2;10 years and 9;09 years), who were matched for vocabulary comprehension scores were included in the study. Although performance in the WS group was significantly poorer compared to the TD group on all three tasks, performance was not predicted by their receptive vocabulary or grammatical ability scores. In addition, ToM abilities in both groups depended on the cognitive demands of the task at hand. This finding shows that performance on ToM tasks in WS is not necessarily hindered by their delayed language abilities but rather by the task administered. This could potentially affect the diagnosis of developmental disorders, such as Autism Spectrum Disorders, and comparison of ToM abilities across developmental disorders. LEARNING OUTCOMES Readers of this article should be able to (1) describe the current state of theory of mind research in Williams syndrome, (2) identify which cognitive abilities might explain performance on theory of mind tasks in both typically developing children and in children with Williams syndrome, and (3) interpret the importance of task demands when assessing childrens theory of mind abilities.

The Role of Environmental Factors on Sleep Patterns and School Performance in Adolescents

Background: Modern life, with its many distractions, is seeing sleep quantity and quality decline during adolescence. This is a concern as research persuasively demonstrates the negative impact of reduced sleep on academic achievement, both in terms of learning and behavior. Aims: This study examined the relationship between sleep and school functioning in adolescence, with a focus on environmental factors that might mediate this relationship. Sample and Method: Forty-seven adolescents took part. Sleep was measured using the School Sleep Habits Survey (SSHS) and a sleep diary. School records of year grade point averages provided a measure of academic achievement. Ravens Standard Progressive Matrices gave a measure of general cognitive processing. Environmental sleep factors falling into three groups, namely, stimulant consumption, media use and exercise, were measured using a self-report questionnaire. Results: An average of 7.08 h of sleep was reported. Correlations revealed that Total sleep time (TST) and bedtimes on weekdays were strongly associated with academic achievement. Morning/eveningness and sleep/wake behavior problems had a strong relationship with performance on the Ravens. Stimulant consumption and media use before bed revealed strong relationships with TST and bedtimes on weekdays. Crucially, mediation analyses confirmed that both caffeine consumption and electronic media use before bedtime were negatively associated with academic performance, via the mediating pathway by affecting sleep. Exercise was not associated with any of the sleep variables, but was associated with better academic performance. Conclusion: The current findings highlight that, now more than ever, parents, schools and policy makers must be aware of the negative effects of caffeinated substances marketed to students, and electronic media use on their sleep habits. Our findings suggest that targeting caffeine consumption and electronic media use before bed may represent effective routes in alleviating modern teenage sleep debt, and in turn enhancing academic performance.

Impaired Sleep-Related Learning in Children with Williams Syndrome

Recent research has established that sleep is essential for memory consolidation in learning and academic performance of children and adults. Similar evidence in childhood is emerging. Conversely, sleep deprivation and/or sleep problems usually weaken these functions. The present study investigates the association between sleep related learning in school-aged children with Williams syndrome (N=14) compared to the typically developing children (N=14). Sleep was measured using actigraphy and parents completed the Child Sleep Health Questionnaire. Accuracy performance on a well-characterised procedural learning task- the finger tapping motor sequence task (FTT) was assessed on three sessions. Children in the typically developing group showed increased accuracy scores following a period of sleep (14% improvement) compared with wake (drop of 2%). In contrast children with Williams syndrome showed an initial improvement in accuracy on the training session, albeit slow, but their accuracy deteriorated following a period of sleep. The sleep-related decrement in performance on the procedural task may reflect sleep problems that are now well characterised in the WS group. This study demonstrated the contribution of sleep to procedural learning in typically developing children. Further studies may elucidate the reasons why similar sleep related benefits are not seen in children with Williams syndrome. Meanwhile practitioners and families should ensure that children obtain adequate sleep in order to maximise their attention readiness to learn and achieve optimum cognitive performance.

Determination of urinary cortisol, cortisone and 6-sulfatoxymelatonin using dilute and shoot ultra-high pressure liquid chromatography–tandem mass spectrometry

Human sleep is a natural part of every individuals life. Clear relationship between sleep and endocrine system has been already established. In particular, melatonin and cortisol are known to affect and regulate sleep/wake patterns. Here we report the development of an ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous measurement of 6-sulfatoxymelatonin (MT6s), cortisol and cortisone in urine. A separate method was developed for measurement of creatinine in urine. These levels were used to normalise the levels of analytes. First void morning urine samples were collected from 24 healthy volunteers. Samples were diluted 1:1 in water prior to injection onto reversed-phase C18 column and analysed using UHPLC-MS/MS method. Linear calibrations were obtained for all analytes with correlation coefficient in the range 0.998-0.999. The observed concentration was found to be in the range 92-105% for cortisol, 92-107% for cortisone and between 93 and 120% for MT6s of the reference levels. The total run time of 6 min with all peaks of interest eluting within 3 min was obtained. This demonstrates the feasibility of utilising the method for large multi-scale studies, where high throughput is required for studying the circadian rhythm of melatonin and cortisol secretion. These hormones play significant role in circadian rhythm and sleep/wake cycle; therefore it is important to monitor the levels of these endocrine markers in individuals suffering from sleep disorders. It is also beneficial with clinical applications to analyse melatonin and cortisol simultaneously in order to assess their interrelationships of these substances, such as their effect on diurnal rhythm and sleep.

The Importance of Sleep: Attentional Problems in School-Aged Children With Down Syndrome and Williams Syndrome

In typically developing (TD) children, sleep problems have been associated with day-time attentional difficulties. Children with developmental disabilities often suffer with sleep and attention problems, yet their relationship is poorly understood. The present study investigated this association in school-aged children with Down syndrome (DS) and Williams syndrome (WS). Actigraphy and pulse oximetry assessed sleep and sleep-disordered breathing respectively, and attention was tested using a novel visual Continuous Performance Task (CPT).Attentional deficits were evident in both disorder groups. In the TD group, higher scores on the CPT were related to better sleep quality, higher oxyhemoglobin saturation (SpO2), and fewer desaturation events. Sleep quality, duration, and SpO2 variables were not related to CPT performance for children with DS and WS.