Sleep quality and cognitive performance in 8-year-old children

Post-adoption experiences of discrimination moderated by sleep quality are associated with depressive symptoms in previously institutionalized youth over and above deprivation-induced depression risk

The association of post-adoption experiences of discrimination with depressive symptoms was examined in 93 previously institutionalized (PI) youth (84% transracially adopted). Additionally, we explored whether sleep quality statistically moderated this association. Notably, we examined these associations after covarying a measure of autonomic balance (high/low frequency ratio in heart rate variability) affected by early institutional deprivation and a known risk factor for depression. PI youth exhibited more depressive symptoms and experiences of discrimination than 95 comparison youth (non-adopted, NA) raised in their biological families in the United States. In the final regression model, there was a significant interaction between sleep quality and discrimination, such that at higher levels of sleep quality, the association between discrimination and depression symptoms was non-significant. Despite being cross-sectional, the results suggest that the risk of depression in PI youth involves post-adoption experiences that appear unrelated to the impacts of early deprivation on neurobiological processes associated with depression risk. It may be crucial to examine methods of improving sleep quality and socializing PI youth to cope with discrimination as protection against discrimination and microaggressions.

Childhood sleep: physical, cognitive, and behavioral consequences and implications

BACKGROUND

Sleep problems in children have been increasingly recognized as a major public health issue. Previous research has extensively studied and presented many risk factors and potential mechanisms for children's sleep problems. In this paper, we aimed to identify and summarize the consequences and implications of child sleep problems.

DATA SOURCES

A comprehensive search for relevant English language full-text, peer-reviewed publications was performed focusing on pediatric sleep studies from prenatal to childhood and adolescence in a variety of indexes in PubMed, SCOPUS, and Psych Info published in the past two decades. Both relevant data-based articles and systematic reviews are included.

RESULTS

Many adverse consequences are associated with child sleep deficiency and other sleep problems, including physical outcomes (e.g., obesity), neurocognitive outcomes (e.g., memory and attention, intelligence, academic performance), and emotional and behavioral outcomes (e.g., internalizing/externalizing behaviors, behavioral disorders). Current prevention and intervention approaches to address childhood sleep problems include nutrition, exercise, cognitive-behavioral therapy for insomnia, aromatherapy, acupressure, and mindfulness. These interventions may be particularly important in the context of coronavirus disease 2019. Specific research and policy strategies can target the risk factors of child sleep as well as the efficacy and accessibility of treatments.

CONCLUSIONS

Given the increasing prevalence of child sleep problems, which have been shown to affect children's physical and neurobehavioral wellbeing, understanding the multi-aspect consequences and intervention programs for childhood sleep is important to inform future research direction as well as a public health practice for sleep screening and intervention, thus improving sleep-related child development and health.

Association between sleep hours and changes in cognitive function according to the morningness-eveningness type: A population-based study

OBJECTIVE

The aim of this study was to investigate proper sleep hours to reduce the risk of cognitive decrease considering morningness-eveningness type.

METHODS

The Korean Community Health Survey was used, which includes adults aged over 19 years old. These data were obtained from a cross-sectional study and assessed sleep hours using questionnaire of Pittsburgh Sleep Quality Index. Based on the wake-up time of each participant, they were classified into the morningness, intermediate, eveningness, and none groups. The change in cognitive function was determined by a single question about memory loss experience.

RESULTS

A total of 224,714 participants were included in the analysis. Of the participants, 55.6 % and 5.0 % of whom had morningness and eveningness, respectively. The risk of cognitive decline was significantly different by sleep hours and morningness-eveningness type. Without considering sleep quality, the intermediate and eveningness groups showed a higher risk of cognitive decline than the morningness group, and the risk was lowest in those with 7-9 sleep hours. However, when sleep quality showing significant effect was included in the analysis, sleep hours showing the lowest risk were different among morningness, intermediate, eveningness groups, and it was the shortest in the morningness type at 5-6 h and the longest in the eveningness type at 7-8 h.

CONCLUSION

Proper sleep hours to decrease the risk of cognitive decline may be different by morningness-eveningness types. However, when considering sleep quality, sleep duration had little influence on cognitive decline. Future studies investigating healthy sleep hours need to consider sleep quality as well as the habitual sleep schedules.

LIMITATIONS

The morningness-eveningness types were classified based on wake-up time not morningness-eveningness types. The morningness-eveningness types in this study would be interpreted as habitual sleep schedule rather than chronotype.

Emotion regulation difficulties and sleep quality in adolescence during the early stages of the COVID-19 lockdown

INTRODUCTION

Adolescence is a period of vulnerability for emotion regulation and sleep difficulties, risks that might be compounded by intense COVID-19 lockdowns and challenges. The aim of this study was to investigate how sleep quality related to emotion regulation difficulties in adolescents during lockdown in Perú.

METHODS

Participants were 2563 adolescents enrolled in Innova school in Perú (11 - -17 years) in May 2020. Hypotheses were derived from exploring one half of the sample, preregistered at https://osf.io/fuetz/, and then confirmed in the second half of the sample. Participants completed subjective surveys of sleep quality (short PSQI) and the Difficulties in Emotion Regulation Scale Short Form (DERS-SF).

RESULTS

Worse sleep quality was robustly associated with more difficulties in emotion regulation across both samples. The association was found particularly for emotion regulation subscales related to the ability to engage in goal directed behavior in the face of distress, emotional clarity and strategies to deal with feeling distressed. In contrast, there was no robust association between sleep and the ability to regulate impulses in the context of negative emotions, and no association with the ability to accept emotions. Girls and older adolescents robustly endorsed worse sleep quality and more difficulties in emotion regulation.

LIMITATIONS

The cross-sectional nature of this study prevents us from determining the direction of the association. Data were collected using adolescent self-report which, while informative of adolescent perceptions, might diverge from objective measures of sleep or emotion regulation difficulties.

CONCLUSIONS

Our findings with adolescents in Perú contribute to our understanding of the association between sleep and emotion regulation at a broader global scale.

Introduction to Pediatric Sleep Medicine

Sleep is a key component of life to maintain our health, performance, safety and quality of life. In fact, sleep has been implicated in the optimal functioning of all organ systems - brain, heart, lung, metabolism, immune function, and hormonal balance too. One of the most common reasons for poor-quality sleep in children is a group of conditions termed sleep disordered breathing (SDB). Obstructive sleep apnea (OSA) is the most severe form of SDB. A good history and clinical examination is likely to reveal features of SDB including snoring, restless sleep, morning sleepiness, irritability or exhibit signs of hyperactivity. Examination may also reveal evidence of underlying pathology e.g., Craniofacial abnormalities, obesity and neuromuscular disorders that creates higher risk of developing SDB. Further investigation using polysomnography (PSG) is considered a gold-standard assessment of SDB and allows for scoring using Obstructive Apnoea-Hypopnea scale. Adenotonsillectomy is used as the first-line management in patients who otherwise have normal anatomy. Parents often approach their pediatricians with concerns regarding their child's sleeping habits and given the significant role sleep has on child development, it is essential that doctors are equipped to provide good care and advice for this population. This article aims to summarise presentation of SDB and common risk factors, investigations and management options to aid clinicians in managing SDB.

Effects of smartphone addiction on cognitive function and physical activity in middle-school children: a cross-sectional study

Introduction

This study aimed to investigate the effects of smartphone addiction on cognitive function and physical activity in middle-school children.

Methods

A population of 196 children (boys and girls) from middle schools were recruited for this study with an average age of 12.99 ± 0.81 years, a height of 153.86 ± 6.50 meters, a weight of 48.07 ± 7.31 kilograms, and a body mass index of 20.22 ± 2.08 kg/m2. Smartphone addiction was determined using Arabic versions of the Smartphone Addiction Scale-Short Version, and physical activity levels were assessed by a physical activity questionnaire for older children. The working memory and selective attention domains of cognitive function were evaluated using a laptop screen's digital version of the memory automaticity and Flanker tasks, respectively. A one-way MANOVA was conducted to determine the differences in working memory between the smartphone-addicted and non-addicted groups. The relationship between smartphone addiction and physical activity was analyzed using Pearson's chi-squared test.

Results

The cognitive function-attention domain accuracy component showed a statistically significant difference between the groups, with a p-value of 0.05). The reaction time between smartphone-addicted and non-addicted children showed no statistically significant difference (p = 0.817). The relationship between smartphone addiction and physical activity was statistically significant (p < 0.001).

Discussion

The interaction effects between physical activity and smartphone addiction on reaction times showed statistically insignificant (p = 0.25) differences, showing that physical activity's effect on reaction times did not depend on smartphone addiction levels. The non-addicted children had significantly higher physical activity levels than the addicted children, indicating that smartphone addiction reduced physical activity.

Associations between parental relationship dissolution and child sleep: A systematic review

Parental relationship dissolution is considered one of the most common adverse childhood experiences. Although sleep is crucial for healthy development of children and very sensitive to environmental changes, it is poorly studied in the context of parental relationship dissolution. The aim of the current study was to systematically review and critically assess the existing literature on the associations between parental relationship dissolution and child sleep (0-18 years old; registered on PROSPERO (CRD42021272720)). PsycInfo, MEDLINE, Scopus, ProQuest Dissertations and Theses Global, Social Work abstracts, and Web of Science Core Collection were searched. Published empirical quantitative studies were included if they reported statistics regarding the association between parental relationship dissolution and any child sleep variable. Out of the 358 articles screened, 14 articles met inclusion criteria and reported on several sleep dimensions: sleep quality, dreams and nightmares, and sleep disorders (enuresis, night terrors, and bruxism). Out of the 14 articles, six were longitudinal studies and eight were cross-sectional studies. While most studies found that parental relationship dissolution was associated with some indices of poorer child sleep, studies were generally of low to moderate quality. Health professionals should assess child sleep in the context of a parental relationship dissolution.

Associations between Sleep, Depression, and Cognitive Performance in Adolescence

The relevance of cognitive performance during adolescence requires further studies that analyze potential associated factors. This study aimed to analyze inductive reasoning, reading comprehension, and mathematical thinking (problem-solving and number and calculation) in relation to sleep and depression in 244 students aged 12-17 years (47.6% boys and 52.4% girls). Daytime sleepiness, sleep quality, dysthymia, and euthymia (state and trait) were assessed by self-reported questionnaires. Moreover, correlations between these variables and cognitive performance, and differences depending on sociodemographic variables (sex, age, or academic year) were analyzed using non-parametric tests. Robust regression models were also conducted to evaluate the predictive role of significant variables on cognitive performance. The results showed significant bidirectional relationships between sleep- and depression-related variables, and between the latter ones and cognitive performance. Depression-trait was more related to cognitive performance than depression-state, and euthymia more than dysthymia, but neither daytime sleepiness nor sleep quality significantly correlated with it. As for sociodemographic variables, girls reported worse sleep and more depressive symptoms than boys did, and younger students reported better sleep but performed worse than the older ones. Although these findings should be further explored in forthcoming studies adding other promising variables, they highlight the importance of promoting euthymia to improve cognitive performance in adolescents.

Trajectories of reported sleep duration associate with early childhood cognitive development

STUDY OBJECTIVES

Examine how different trajectories of reported sleep duration associate with early childhood cognition.

METHODS

Caregiver-reported sleep duration data (n = 330) were collected using the Brief Infant Sleep Questionnaire at 3, 6, 9, 12, 18, and 24 months and Children's Sleep Habits Questionnaire at 54 months. Multiple group-based day-, night-, and/or total sleep trajectories were derived-each differing in duration and variability. Bayley Scales of Infant and Toddler Development-III (Bayley-III) and the Kaufman Brief Intelligence Test- 2 (KBIT-2) were used to assess cognition at 24 and 54 months, respectively.

RESULTS

Compared to short variable night sleep trajectory, long consistent night sleep trajectory was associated with higher scores on Bayley-III (cognition and language), while moderate/long consistent night sleep trajectories were associated with higher KBIT-2 (verbal and composite) scores. Children with a long consistent total sleep trajectory had higher Bayley-III (cognition and expressive language) and KBIT-2 (verbal and composite) scores compared to children with a short variable total sleep trajectory. Moderate consistent total sleep trajectory was associated with higher Bayley-III language and KBIT-2 verbal scores relative to the short variable total trajectory. Children with a long variable day sleep had lower Bayley-III (cognition and fine motor) and KBIT-2 (verbal and composite) scores compared to children with a short consistent day sleep trajectory.

CONCLUSIONS

Longer and more consistent night- and total sleep trajectories, and a short day sleep trajectory in early childhood were associated with better cognition at 2 and 4.5 years.

Sleep disorder as a clinical risk factor of major depression: associated with cognitive impairment

BACKGROUND

This research aims explored the sleep disorder (SD) role in major depressive disorder (MDD), and the SD influencing their cognition.

METHODS

372 MDD patients and 457 healthy controls (HCs) were enrolled.

RESULTS

Patients increased a 38.88 times SD risk compared with HCs. In patients, visuospatial/constructional score was lower in SD than non-SD, and PSQI score was negatively associated with visuospatial/constructional score of SD. In SD and non-SD, RBANS scores were lower in MDD than HCs, excepted for visuospatial/constructional in non-SD.

CONCLUSION

The SD as a MDD risk factor, has more serious visuospatial/constructional impairment alleviated via improving sleep/depression in patients.

The associations of insomnia symptoms with daytime behavior and cognitive functioning in children with attention deficit hyperactivity disorder

STUDY OBJECTIVES

The current study aimed to examine the association of insomnia symptoms with daytime behavior and cognitive functioning in children with attention deficit hyperactivity disorder (ADHD).

METHODS

Thirty-six children with ADHD and insomnia symptoms, 27 children with ADHD without insomnia symptoms and 21 age-matched healthy controls were recruited in this study (age range: 6-12 years, 70% male). They were assessed by parent-report questionnaires on insomnia symptoms (Children's Sleep Habit Questionnaire) and ADHD symptoms (Strengths and Weaknesses of ADHD Symptoms and Normal Behavior Scale, SWAN), and completed a battery of cognitive tests including Continuous Performance Test (CPT) for sustained attention, Letter-digit test for processing speed, Digit Span forward test and N-back task for working memory, Tower of London (TOL) test for planning skills and Bergs Card Sorting Test (BCST) for set-shifting ability.

RESULTS

Children with ADHD and insomnia symptoms had the highest scores on SWAN total, and inattention and hyperactivity subscales, followed by children with ADHD without insomnia and healthy controls (all ps < 0.05). After controlling for potential confounders, children with ADHD and insomnia symptoms showed poorer performance on CPT and Letter-digit test as compared to children with ADHD without insomnia and healthy controls (all ps < 0.05).

CONCLUSIONS

Insomnia symptoms are associated with more severe ADHD symptoms and cognitive impairments in children with ADHD, especially deficits on sustained attention and processing speed. Future longitudinal studies are needed to explore the long-term impacts of insomnia symptoms and the effects of sleep-focused intervention on cognitive functioning in children with ADHD.

Effects of Sensory Garments on Sleep of Children with Autism Spectrum Disorder

Objective

The purpose of this study is to assess the effectiveness of the use of sensory garments for improving sleep in children with autism spectrum disorder.

Method

Using a single-subject ABAB reversal design, the researchers evaluated the effectiveness of a sensory garment on sleep duration, sleep latency, and parental stress related to a child's sleep. Four children aged 4–10 participated. We measured sleep duration and sleep latency using the Garmin watches and parent-report sleep logs, parent stress using the Parenting Stress Index Short Form, and sleep behaviors using the Children's Sleep Habits Questionnaire. Results/Discussion. Data showed variable effects on sleep duration and latency across children. The oldest child with the hyposensitive sensory patterns experienced the greatest sleep improvements. All parents experienced stress from daily life, and some reported increased stress due to study participation. Future research is recommended to further investigate the effectiveness of sensory garments on sleep for children with ASD. Therapists are encouraged to evaluate children's development and sensory preferences prior to recommending sensory garments for sleep.

Relationship between sleep disorders and attention-deficit-hyperactivity disorder in children

OBJECTIVE

To explore the correlation between sleep disorders and attention-deficit-hyperactivity disorder (ADHD) in children.

METHODS

We studied 100 Chinese children (70 boys and 30 girls; mean age, 8.77 ± 2.39 years). Parents completed the Children's Sleep Disturbance Scale (SDSC) and the Swanson Nolan and Pelham Version IV Scale (SNAP-IV) questionnaires. SNAP-IV and SDSC scores were compared in children with and without sleep disorders and ADHD.

RESULTS

There were significant differences in SDSC scores, Arousal Disorder (AD) scores, and Sleep Breathing Disorder (SBD) scores between children with and without ADHD (P < 0.05). The sleep disorder group had higher SNAP-IV scores than the non-sleep disorder group (P < 0.05). Children with sleep disorders showed higher ADHD symptom values (inattention, hyperactivity/impulsivity, and oppositional defiance) than children without sleep disorders (P < 0.01). There was a moderate correlation between SDSC scores and SNAP-IV scores (r = 0.486, P < 0.05). Using SNAP-IV scores as the dependent variable, multiple linear regression analysis was applied, and a statistically significant effect of AD and Sleep-Wake Transition Disorder (SWTD) scores on SNAP-IV scores was found (P < 0.05). The area under the curve (95% CI) of the SDSC score for predicting sleep disorders with ADHD was 0.714 (0.606, 0.821; P = 0.0005).

CONCLUSION

Children with ADHD are prone to sleep disorders. The higher the ADHD symptom score, the more sleeping problems. Sleep disorders can also cause or exacerbate ADHD symptoms, and the ADHD symptom score correlates with sleep disorder severity. We can reduce the severity of attention-deficit-hyperactivity in children with ADHD by improving their sleep with behavioral sleep interventions.

Sleep Measure Validation in a Pediatric Neurocritical Care Acquired Brain Injury Population

BACKGROUND/OBJECTIVE

Lingering morbidities including physical, cognitive, emotional, and psychosocial sequelae, termed the Post-Intensive Care Syndrome, persist years after pediatric neurocritical care (PNCC) hospitalization. Sleep disturbances impact other Post-Intensive Care Syndrome domains and are under-evaluated to date due to a lack of appropriate measurement tools. The present study evaluated the validity of the Sleep Disturbance Scale for Children (SDSC) to address the growing need for assessing sleep problems after PNCC.

METHODS

We conducted a prospective observational study of youth aged 3-17 years with acquired brain injury (N = 69) receiving care through longitudinal PNCC programs at two tertiary academic medical centers. Parents completed the SDSC and provided proxy reports of internalizing symptoms, health-related quality of life (HRQOL), fatigue, pain behavior, and cognitive function within 3 months of hospital discharge. Evidence for the validity of the SDSC was established by utilizing the full sample for psychosocial measure comparisons and by comparing SDSC outcomes by severity (Low Risk, Mild-Moderate Risk, and High Risk defined by reported standardized T-scores).

RESULTS

Internal consistency of the SDSC was good (α = .81). Within the full sample, increased sleep disturbances on the SDSC were significantly correlated with Post-Intensive Care Syndrome measures, including worse physical (r = .65), psychological (r = .62), and cognitive (r = - .74) sequelae. Youth in the High Risk group evidenced greater dysfunction in mental acuity, pain behavior, internalizing symptoms, and social engagement. Findings revealed both statistically and clinically significant impacts of sleep disturbances as measured by the SDSC on HRQOL.

CONCLUSIONS

The SDSC is a valid and reliable measure for assessing sleep disturbances in children after PNCC. Results support the use of the SDSC to measure sleep disturbances after PNCC. Targeted interventions for sleep disturbances may be key to overall patient recovery.

Newly walking infants' night sleep impacts next day learning and problem solving

Sleep is part of the process that prepares children and adults for next day cognitive activity. Insufficient or fragmented sleep has a detrimental impact on subsequent encoding (Rouleau et al., 2002) and cognitive functioning (Joo et al., 2012). However, fragmented sleep early in life is a developmental norm, limiting the extent to which conclusions derived from older populations can be generalized. To directly test the continuity of this relationship, newly-walking infants' (N=58) sleep was monitored overnight using actigraphy. The next morning they were taught a motor problem-solving task. The task required infants to navigate through a tunnel to reach a goal at the other end. We coded infants' exploratory behaviors and the extent of training required to solve the task. Using a cluster analysis that accounted for exploratory behaviors and number of training prompts, infants were sorted into three profiles: those who found the task Easy to solve, those who found it Difficult, and those who Never solved it. Wake episodes and sleep efficiency were entered as predictors of cluster membership in a multinomial logistic regression. Of the infants who ultimately solved the task, those with more wake episodes and lower sleep efficiency had more difficulty. Specifically, fragmentation appeared to negatively impact preparedness to learn. Contrary to our expectations, infants who Never solved the task had the least fragmented sleep, indicating that an optimal level of fragmentation is needed for efficient problem-solving. For infants, some level of sleep fragmentation is needed the night before learning in order to solve a task efficiently. These findings highlight the interaction between developmental domains, from sleep quality to motor experience, and their impact on infant learning in real time.

An investigation of the link between prenatal alcohol exposure and sleep problems across childhood

OBJECTIVE

To investigate the association between dose and frequency of prenatal alcohol exposure (PAE) and sleep problems in children, after controlling for established risk factors for sleep problems.

METHODS

Data from the birth cohort of the Longitudinal Study of Australian Children (LSAC) was used. Mothers of 3447 children provided information on alcohol consumption during pregnancy, children's sleep problems from 2- to 9-years, and potential confounders associated with sleep problems. Children were classified into PAE groups based on distinct patterns of maternal drinking during pregnancy: abstinent, occasional, low, moderate, and heavy. The effect of PAE on the number and persistence of sleep problems across childhood (2-9 years) was examined.

RESULTS

After controlling for multiple covariates that impact sleep, children with heavy PAE had 1.13 more sleep problems across childhood (2-9 years) relative to children whose mothers were abstainers, in particular 0.37 more at 2- to 3-years (0.504, 95 % CI 0.053, 0.956), and 0.34 more at 6- to 7-years (0.847, 95 % CI 0.299, 1.396). Compared to children of abstainers, heavy PAE increases the probability of having persistent sleep problems from 2- to 9-years by 22.57 %. No negative associations between moderate or low PAE and sleep were observed. Parenting, family, economic, and child health factors also significantly affected child sleep.

CONCLUSION

Heavy PAE was associated with significantly more sleep problems across childhood and a higher probability of reporting persistent sleep problems, relative to children with no PAE. Implications for the understanding and management of sleep in young children with PAE and FASD are discussed.

Evaluation of symptoms of preopoperative and postoperative psychosomatic screening in children with adenoidectomy and adenotonsillectomy

INTRODUCTION

Adenoidectomy and adenotonsillectomy are very common operations in childhood. It is important to clarify their effects on this age group; in this study, we aimed to investigate the effects of the causative agent on children's mental health by using scales that help to screen for indications of mental disorders in children, who have had adenoidectomy or adenotonsillectomy, both before and after surgery. In this way, we aimed to investigate the effects of this factor on children's mental health.

MATERIALS AND METHODS

The study included 82 children aged 6-12 years with signs of upper respiratory tract obstruction or recurrent adenotonsilitis. Adenotonsillectomy was performed in 41 patients included in the study and adenoidectomy was performed in 41 patients included in the study. 40 healthy children matched with the patient groups in terms of age and gender were included in the control group. Patients, were divided into three groups, those who underwent adenoidectomy, patients undergoing adenotonsillectomy and those in the control group Preoperative and postoperative questionnaires were used to investigate the effect of tonsillectomy or adenoidectomy on the mental health of children. The Parents' Form for the Strengths and Difficulties Questionnaire, the Parental Form for the Children's Anxiety Screening Scale, the Sleeping Scale for Children and the Quality of Life Scale for Children were used in the screening.

RESULTS

In children, who underwent adenoidectomy/adenotonsillectomy due to recurrent infection and adeno/adenotonsillar hypertrophy; it was seen that there was a significant decrease in the scores for the Strengths and Difficulties Questionnaire, the Anxiety Screening Scale in Children, and the Sleep Scale in Children, and a significant increase in Quality of Life Scale for Children scores.

OUTCOME

In conclusion, adenoidectomy/adenotonsillectomy in children with sleep apnea due to recurrent episodes of infection and adeno/adenotonsillar hypertrophy was thought to prevent further neurobehavioral problems, likely to become more complex in the future, and to improve quality of life.

Do motor coordination and sleep difficulties predict peer functioning in children and adolescents with attention-deficit and hyperactivity disorder after accounting for existing ADHD symptomology?

Children with attention-deficit and hyperactivity disorder (ADHD) are more likely to experience peer problems compared to their non-ADHD peers, though ADHD-specific symptoms only partially explain this association. This study examined whether sleep difficulties and motor coordination problems are additional predictors of peer problems in an ADHD population. An ADHD sample of 72 participants aged 6-14 years (M = 9.86 years, SD = 1.79 years) was evaluated for an association of peer problems with measures of motor coordination, sleep difficulties as well as ADHD and comorbidity symptoms. Hierarchical multiple regression analysis (HMRA) was used to test the current study aims. Motor coordination, but not sleep difficulties, predicted additional variance in peer problems after controlling for inattention, hyperactivity/impulsivity, internalizing problems, oppositionality, and conduct problems. Poor motor coordination predicts peer problems beyond ADHD symptoms. Clinicians seeking to improve peer functioning in children with ADHD should also consider motor coordination difficulties in addition to existing treatment strategies. Statement of contribution What is already known Children with attention-deficit and hyperactivity disorder (ADHD) experience greater peer problems (i.e., making friends, being victimized, participating in play) than their typically developing peers. Previous studies have attributed this association between ADHD and peer problems to the symptoms of ADHD (i.e., inattention and/or hyperactivity) disrupting the typical trajectory of social development. However, quantitative studies have identified that symptoms of ADHD predict only portion of the variance in a child's peer problems - highlighting that there may be other unique factors that contribute to the higher incidence of peer problems typically observed in this population. What this study adds This study tested whether additional theoretically relevant factors could predict levels of peer problems in children with ADHD beyond the primary symptoms of the disorder. Internalizing symptomatology, conduct problems, oppositionality, motor coordination, and sleep difficulties were added to a regression model already including inattention and hyperactivity symptoms. These factors explained 51% of the variability in peer problems. In this sample of 72 ADHD children, the results of the final model highlighted that only motor coordination and conduct problems remained significant predictors of peer problems - highlighting two potentially important target areas for screening and intervention.

Effects of Sleep Extension on Inhibitory Control in Children With ADHD: A Pilot Study

Objective: Children with ADHD often have sleep complaints and cognitive deficits. The aim of this pilot study was to determine whether sleep extension improves inhibitory control, a primary cognitive deficit in ADHD. Method: Children with (n = 11) and without (n = 15) ADHD participated in a within-subject sleep extension intervention that targeted nocturnal sleep duration. Sleep was assessed with actigraphy and polysomnography. Inhibitory control was assessed with a Go/No-Go task. Results: For children without ADHD, there was a significant main effect of time, such that morning inhibitory control was 10% greater than evening inhibitory control. However, inhibitory control did not differ between the baseline and extension conditions in this group. For children with ADHD, although morning inhibitory control did not differ from evening inhibitory control, sleep extension improved inhibitory control by 13% overall. Conclusion: These results suggest that a sleep extension intervention improves inhibitory control in children with ADHD.

Hormonal Contraception and the Brain: Examining Cognition and Psychiatric Disorders

Background:

The combined oral contraceptive pill (OC), containing synthetic estrogens and progestins, is used by millions of women worldwide, yet little is known about its effects on cognition or on psychiatric disorders. The progestin component of OCs determines their androgenicity, i.e. whether the OC has androgen binding components with masculinising effects or antiandrogenic components with feminising effects.

Objective:

The present review discusses the literature surrounding OC use and cognition in healthy women. Given the important role that sex hormones play in psychiatric disorders, we also consider the influence of OCs on symptoms of schizophrenia, post-traumatic stress disorder, depression, bipolar disorder, anxiety disorders and indirectly, sleep quality.

Results:

Research has shown that while there are no differences between OC users and non-users, androgenic OCs enhance visuospatial ability and anti-androgenic OCs enhance verbal fluency. Little is known about OCs effects on other cognitive domains, such as memory and executive function. There is little research examining OC use in schizophrenia, post-traumatic stress disorder, bipolar disorder and anxiety disorders. There is some evidence that OC use is associated with depression, however the exact causality of this association remains to be verified.

Conclusion:

We maintain that future studies need to address several methodological limitations, such as separating OCs based on androgenicity to avoid the masking effects that occur when various OCs are considered as one group. As this review highlights several significant effects of OC use on the brain, the implications of OC use needs to be considered in future research.

Circadian ontogeny through the lens of nonparametric variables of actigraphy

Studies focusing on human rhythmicity show that human circadian rhythm suffers constant changes across lifespan. Changes in rest-activity patterns can be studied through nonparametric variables of actigraphy: L5 (an individual's least active 5 h), M10 (an individual's most active 10 h) and RA (relative amplitude of the rest-activity rhythm). The variable RA is the normalized difference between L5 and M10 - the higher the RA, the greater the difference between these two variables. This study used the data bank of the Human Chronobiology Laboratory of Federal University of Paraná (Brazil). It analyzed actimetric data of 93 children between 4 and 11 years of age in their naturalistic context in order to describe the development of nonparametric variables. Correlation between age and L5 was significantly negative (rho = - 0.29, p = 0.004), while correlation between age and RA was significantly positive (rho = 0.31, p = 0.003). The variables M10, sL5 (start of L5) and sM10 (start of M10) did not show significant correlation to age. Furthermore, there were no statistical differences between genders. The population of this study, healthy children, has been poorly assessed by similar literature. Through our results, we have demonstrated that, as children age, L5 significantly decreases, which reflects a smaller fragmentation of circadian rhythm. As an expected consequence, RA significantly increases. In other words, these nonparametric variables of actimetry successfully demonstrate that children tend to reduce nocturnal activity as they age, a phenomenon that reflects the ongoing consolidation of circadian rhythm.

The association between sleep and dual-task performance in preterm and full-term children: an exploratory study

OBJECTIVES

The present study explored associations between sleep and children's dual-task performance using cognitive-motor dual tasks (eg, walking and talking). Previous research with older adults indicated correlations between higher gait variability and unfavorable sleep continuity variables. Based on this research, as a first objective, we investigated similar correlations in a sample of children. Second, we explored correlations between dual-task performance and dimensions of sleep architecture. Third, we tested moderating effects of prematurity on these associations.

METHODS

In this study, 7-to 12-year-old children were tested in dual-task situations; of those, 39 were formerly preterm, and 59 were full-term born children. They were asked to walk and simultaneously perform different cognitive tasks. Gait was measured using an electronic walkway system. Sleep was measured using in-home sleep-electroencephalography.

RESULTS

After accounting for age and cognition, regression analyses revealed correlations between a higher number of awakenings after sleep onset and lower dual-task performance; concerning sleep architecture, analyses revealed correlations between a higher amount of rapid-eye-movement (REM) sleep and lower gait variability. Furthermore, associations between a higher amount of slow wave sleep (SWS) and children's higher cognitive performance were found. Moderation analyses indicated no effects of prematurity.

CONCLUSIONS

Our exploratory study suggests that a more disrupted sleep was related to children's poorer dual-task performance. Our findings support claims that REM sleep seems more related to performance in procedural tasks whereas SWS seems more related to performance in declarative tasks, suggesting that different sleep stages may support the processing of different performance types.

Early polysomnographic characteristics associated with neurocognitive development at 36 months of age

BACKGROUND

Few studies on the relationship between sleep quantity and/or quality and cognition have been conducted among preschoolers from the healthy general population. We aimed to identify, among 3-year-old children, early polysomnography (PSG) sleep factors associated with estimated intelligence quotient (IQ) using the Weschler Preschool and Primary Scale Intelligence-III test (WPPSI-III) and its indicators: full-scale (FISQ), verbal (VIQ), and performance (PIQ) intelligence quotients.

METHODS

We included full-term children from the French birth-cohort AuBE with PSG recording at term (M0) and/or six months (M6), and available WPPSI-III scores at three years. Sleep and arousal characteristics of these infants were evaluated during day and night sleep periods. Relationships between IQ scores and sleep parameters were estimated using models with the child as a repeated effect adjusted for time (night/day), maturation (M0/M6), tobacco exposure (yes/no), anxiety-depressive scores during pregnancy, maternal age, duration of breastfeeding and child's gender.

RESULTS

A total of 118 PSG recordings were obtained, representing a total of 78 unique children (38 with one PSG and 40 with two PSG). No correlations were found between night and day sleep durations at M0 or M6. Mean VIQ, PIQ, and FSIQ scores were within normal ranges. In multivariate models, longer sleep duration and higher sleep efficiency during the day were negatively associated with all IQ scores. More frequent arousals during the night were associated with lower VIQ scores.

CONCLUSION

Early sleep characteristics such as night sleep fragmentation or longer naps could be associated with impaired cognitive function at three years of age.

The Relationship Between Sleep and Cognition in Children Referred for Neuropsychological Evaluation: A Latent Modeling Approach

Children with conditions affecting cognitive processes experience high levels of sleep disturbance, which may further compound the cognitive ramifications of their disorders. Despite this, existing studies in this area have been primarily confined to only particular diagnostic groups and/or a limited scope of sleep and cognitive parameters. The current study characterized the nature of sleep problems and examined the relationship between a wide range of sleep-related problems and cognitive functioning in a large (N = 103) diagnostically heterogeneous sample of youth (aged 6–16) referred for neuropsychological assessment. Structural equation modeling was used to examine the relationship between sleep-related problems (i.e., daytime sleepiness, sleep onset latency, sleep fragmentation, sleep time variability, sleep debt) and cognitive performance (i.e., executive functioning, sustained attention, memory, processing speed). Sleep fragmentation emerged as the most prominent sleep-related problem in the present sample. Structural equation modeling demonstrated a negative association between sleep-related problems and cognition that did not reach statistical significance (β = −0.084, p = 0.629). The current statistical approach may be used as a conceptual framework for future work examining these multi-dimensional constructs in a parsimonious fashion.

Child Sleep and Socioeconomic Context in the Development of Cognitive Abilities in Early Childhood

Despite a robust literature examining the association between sleep problems and cognitive abilities in childhood, little is known about this association in toddlerhood, a period of rapid cognitive development. The present study examined the association between various sleep problems, using actigraphy, and performance on a standardized test of cognitive abilities, longitudinally across three ages (30, 36, and 42 months) in a large sample of toddlers (N = 493). Results revealed a between-subject effect in which the children who had more delayed sleep schedules on average also showed poorer cognitive abilities on average but did not support a within-subjects effect. Results also showed that delayed sleep explains part of the association between family socioeconomic context and child cognitive abilities.

Relationship Between Sensory Processing and Sleep in Typically Developing Children

OBJECTIVE. The relationship between sensory processing factors and the sleep habits and patterns of typically developing children ages 8–12 yr was investigated.

METHOD. Forty-five typically developing children and their parents or caregivers took part. Parents completed the Sensory Processing Measure–Home Form, Children’s Sleep Hygiene Scale, and Children’s Sleep Habits Questionnaire, and the children completed the Children’s Report of Sleep Patterns. Spearman ρ correlation and linear regression analyses were completed with the children’s sleep habits and patterns as the dependent variables and the sensory processing factors as the independent variables.

RESULTS. Sensory processing factors were significantly associated with the children’s sleep habits and patterns, as reported by parents and children. Predictive relationships were established between the children’s sensory processing factors and sleep habits and patterns.

CONCLUSION. Occupational therapy practitioners should consider sensory processing factors when working with children who present with suspected sleep problems.

Infant sleep and its relation with cognition and growth: a narrative review

OBJECTIVE

Infant sleep development is a highly dynamic process occurring in parallel to and in interaction with cognitive and physical growth. This narrative review aims to summarize and discuss recent literature and provide an overview of the relation between infant sleep and cognitive development as well as physical growth.

METHODS

We conducted online literature search using MEDLINE, Embase, and Cochrane Library databases. We considered original research on humans published in the English language from January 2005 to December 2015. Search terms included "sleep" AND "infant" AND "cognition" OR "memory" OR "executive functioning", OR "growth" OR "obesity" OR "growth hormone" OR "stunting", and combinations thereof.

RESULTS

Ten studies on infant sleep and cognition were included in this review. Overall, findings indicated a positive association between sleep, memory, language, executive function, and overall cognitive development in typically developing infants and young children. An additional 20 studies support the positive role of infant sleep in physical growth, with the current literature focusing largely on weight gain and obesity rather than healthy growth. Existing evidence in both the domains is mainly based on cross-sectional designs, on association studies, and on parental reports. In contrast, there were limited studies on longitudinal sleep trajectories and intervention effects, or studies have not used more objective sleep measures such as actigraphy and polysomnography.

CONCLUSION

The reviewed studies support a critical and positive role of infant sleep in cognition and physical growth. Future studies should consider key environmental and parental confounders, include a combination of more objective (actigraphy) and subjective measures (sleep diaries and questionnaires), and move towards longitudinal trajectory designs of infant sleep and development.

Shorter sleep duration is associated with social impairment and comorbidities in ASD

Sleep disturbance, particularly insomnia, is common in children with autism spectrum disorders (ASD). Furthermore, disturbed sleep affects core symptoms and other related comorbidities. Understanding the causes and consequences of sleep disturbances in children with ASD is an important step toward mitigating these symptoms. To better understand the connection between sleep duration and ASD severity, we analyzed ASD-related symptoms using the Autism Diagnostic Interview-Revised (ADI-R), Autism Diagnostic Observation Schedule (ADOS), IQ scores, and parent reports of the average amount of time slept per night that were available in the medical histories of 2,714 children with ASD in the Simons Simplex Collection (SSC). The mean (SD) sleep duration was 555 minutes. Sleep duration and severity of core ASD symptoms were negatively correlated, and sleep duration and IQ scores were positively correlated. Regression results indicated that more severe social impairment, primarily a failure to develop peer relationships, is the core symptom most strongly associated with short sleep duration. Furthermore, increased severity for numerous maladaptive behaviors assessed on the Child Behavior Checklist, as well as reports of attention deficit disorder, depressive disorder, and obsessive compulsive disorder were associated with short sleep duration. Severity scores for social/communication impairment and restricted and repetitive behaviors (RRB) were increased, and IQ scores were decreased, for children reported to sleep ≤420 minutes per night (lower 5th percentile) compared to children sleeping ≥660 minutes (upper 95th percentile). Our results indicate that reduced amounts of sleep are related to more severe symptoms in children with ASD. Autism Res 2017. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 1221-1238. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Sleep habits and pattern in 1-14 years old children and relationship with video devices use and evening and night child activities

BACKGROUND

Sleep in childhood and adolescence is crucial for mental and physical health; however several researches reported an increasing trend towards a sleep deprivation in this age. Due to the lack of recent epidemiological studies in Italy, the aim of our study was to depict sleep habits and patterns in Italian children aged 1-14 years and to evaluate their relationships with video devices use (TV, tablet, smartphone, PC) and evening/night child activities.

METHODS

A structured interview was conducted during 2015 by 72 Family Pediatricians in 2030 healthy children aged 1-14 years by a cross-sectional survey named "Ci piace sognare". Total sleep duration was calculated, 2015 National Sleep Foundation Recommendations were used as reference. Optimal sleepers were defined children sleeping in own bed all night without awakenings. Multivariable median regression was performed to identify predictors of sleep duration and multivariable logistic regression for predictors of optimal sleep.

RESULTS

Total sleep duration and numbers of awakenings decreased with age. Only 66.9% of children had sleep duration in agreement with Recommendations (50% in 10-14 years group). Before sleeping 63.5% of children used video devices (39.6% at 1-3 years), 39.1% read, 27.5% drank and 19.5% ate. Bottle users at bedtime were 30.8% at 1-3 years, 16.6% at 3-5 years and 4.9% at 5-7 years. Overall, 23.4% of children changed sleeping place during the night, 22.4% referred sleeping problems in the first year of life. Video devices use was negative predictor of sleep duration (-0.25 h [95%CI:-0.35,-0.14], p < 0.001). Optimal sleep was inversely related with bedroom TV (OR 0.63 [0.50,0.79], p < 0.001), with sleeping disorders in the first year (OR 0.62 [0.48,0.80], p < 0.001)), with bottle use (OR 0.64 [0.44,0.94], p < 0.05) and posivively related with high mother's education level (OR 1.44 [1.11,1.88], p < 0.01).

CONCLUSIONS

About one third of 1 to 14 year Italian children sleep less than recommended, one half in teenage. Modifiable risk factors for sleep abnormalities such as video devices use, bedroom TV and bottle use should be target of preventive strategies for a correct sleep. Pediatricians should give priority to the identification of sleep disorders early in life.

Neurocognitive Game between Risk Factors, Sleep and Suicidal Behaviour

INTRODUCTION

Sleep and lifestyles interact to allow the appropriate development of cerebral structures, and prevention of mood disorders. But just a hand of articles identified a precise relationship between these two above, and the probability to develop a suicidal behaviour.

OBJECTIVE

The aim of this study is to explore how the suicidal behaviour is associated in simultaneous with sleep components, psychological stress, depression, anxiety, well-being, addiction, and global health of participants; and if it is also influenced by the sociodemographic profile of each subject.

METHODS

The present study was led by a questionnaire incorporating McNair test, and an incorporated score to evaluate suicide tendencies. The questionnaire also included socio-demographic items and other questions to exhibit a profile of suicide tendency for each individual.

RESULTS

Our results showed that the stress levels and well-being are comparable according to gender. Specifically the results showed that lack of sleep combined with a low score to McNair test strongly affects the suicidal tendency, while score of memory and attention decreased.

CONCLUSIONS

The suicidal behaviour is closely linked with sleep parameters which decreased accordingly, and the family's history of medication and suicidal behaviour.

Brief Behavioral Sleep Intervention for Adolescents: An Effectiveness Study

Sleep disturbances are common among adolescents, but there are no brief interventions to treat them. The objective of this study was to evaluate the effectiveness of a brief semistructured, individually delivered sleep intervention to ameliorate adolescents' sleeping difficulties and lengthen sleep duration. All students aged 16-18 years in a high school were screened for sleeping difficulties and 36 students with the highest sleep problem scores were invited to the intervention. Postintervention improvements were observed on self-reported and actiwatch-registered sleep duration, self-reported sleep quality and sleep latency, perceived stress and anxiety (all p values < 0.001). However, objectively measured sleep efficiency and sleep latency did not change (p > 0.05). A brief individual sleep intervention can be effective in lengthening sleep duration and improving subjective sleep quality and well-being among adolescents.

In school-age children who were born very preterm sleep efficiency is associated with cognitive function

AIMS

This study examined whether the association between sleep duration, as well as sleep continuity, and cognitive function differs between normally developing preterm children compared to full-term children during middle childhood.

METHODS

A total of 58 early preterm (<32 weeks' gestation) and 55 full-term children, aged 6-10 years and enrolled in elementary school, were assessed on sleep duration, sleep continuity and cognitive function. We used in-home polysomnographic recordings of total sleep time, sleep efficiency and nocturnal awakenings. Cognitive tests included intelligence, arithmetic, selective attention, verbal memory, and visuospatial memory.

RESULTS

Preterm children showed poorer performance in intelligence, arithmetic, selective attention, and visuospatial memory (d = 0.38-0.79, p < 0.05) and more objectively assessed nocturnal awakenings (d = 0.40, p = 0.03) than full-term children. Associations of sleep efficiency and cognitive functions (intelligence, arithmetic, selective attention, visuospatial memory) were positive and stronger for preterm children (β = 0.17-0.31, p < 0.05), while they were nonsignificant for full-term children.

CONCLUSION

Results confirm lower cognitive test scores and more nocturnal awakenings in normally developing early preterm children compared to full-term children. Furthermore, poor sleep efficiency may aggravate cognitive deficits, particularly in children who are more vulnerable due to premature birth.

Poor sleep and neurocognitive function in early adolescence

BACKGROUND

Evidence regarding the associations between sleep duration and quality, and neurocognitive function in adolescents remains scanty. This study examined the associations in early adolescence between: sleep duration; efficiency; fragmentation; wake-after-sleep-onset (WASO); catch-up sleep; intelligence; memory; and executive function, including attention.

METHODS

This study included 354 girls and boys with a mean age 12.3 years (SD = 0.5) from a birth cohort born in 1998. Sleep was measured with accelerometers for an average of eight nights. Cognitive function was evaluated with subtests from the Wechsler Intelligence Scale for Children-III (WISC-III), the Developmental Neuropsychological Assessment 2 (NEPSY-2), the Wisconsin Card Sorting Task (WCST), Conners' Continuous Performance Task (CPT), and the Trail Making Test (TMT).

RESULTS

In girls, a higher WASO and fragmentation index were associated with poorer executive functioning (higher number of perseverative errors in the WCST), and longer catch-up sleep was associated with longer reaction times and better performance in one verbal intelligence test (Similarities subtest of the WISC-III). In boys, shorter sleep duration, lower efficiency, higher WASO, higher sleep fragmentation and shorter catch-up sleep were associated with lower executive functioning (more commission errors, shorter reaction times, and had lower D Prime scores in CPT).

CONCLUSIONS

In adolescent girls, poorer sleep quality was only weakly associated with poorer executive functioning, while in boys, poorer sleep quantity and quality were associated with an inattentive pattern of executive functioning. The amount of catch-up sleep during weekends showed mixed patterns in relation to neurocognitive function.

Sleep complaints in survivors of pediatric brain tumors

PURPOSE

Pediatric brain tumor survivors have increased risk of sleep problems, particularly excessive daytime sleepiness (EDS). Few studies have examined sleep disturbances in this population.

METHODS

153 children and adolescents ages 8-18 and their parents completed questionnaires (Modified Epworth Sleepiness Scale, Kosair Children's Hospital Sleep Questionnaire, Children's Report of Sleep Patterns, Children's Sleep Hygiene Scale) during clinic visits. Participants were at least 5 years from diagnosis and 2 years post-treatment. Group differences in age at diagnosis, body mass index, type of treatment received, and tumor location were examined.

RESULTS

One-third of adolescents and one-fifth of children reported EDS. Children and parents had fair concordance (kappa coefficient = .64) in their report of EDS, while adolescents and parents had poor concordance (kappa coefficient = .37). Per parents, most children slept 8 to 9 h per night. Poor bedtime routines were reported for children, while adolescents endorsed poor sleep stability. Extended weekend sleep was reported across age groups. A BMI in the obese range was related to higher parent-reported EDS in children. Sleep-disordered breathing was associated with elevated BMI in adolescents.

CONCLUSIONS

While survivors reported achieving recommended amounts of sleep each night, 20 to 30% reported EDS. Poor concordance among parent and adolescent report highlights the importance of obtaining self-report when assessing sleep concerns. Obesity is a modifiable factor in reducing symptoms of EDS in this population. Finally, the lack of association between EDS and brain tumor location, BMI, or treatment received was unexpected and warrants further investigation.

Psychosocial and somatic outcomes of sleep problems in children: a 4-year follow-up study

BACKGROUND

Inadequate sleep in children relates to medical and psychosocial problems. However, not much is known about the effects of sleep problems persisting from pre-school to school age on somatic and psychosocial symptoms.

OBJECTIVES

To examine the associations between sleep disturbances and psychosocial symptoms, somatic complaints, medical problems at school age.

METHODS

This was a population-based 4-year follow-up study of sleep problems in Finnish children (n = 470). Parents filled in Sleep Disturbance Scale for Children during pre-school and school years. Children were categorized into four groups: no sleep problems, sleep problems only at pre-school or only at school age, and persistent sleep problems. At follow-up the parents filled in Child Behavior Checklist and a background questionnaire.

RESULTS

The children with persistent sleep problems (9%) had a 16-fold risk of having psychosocial symptoms on subclinical/clinical range compared with the children without sleep problems. The psychosocial symptoms that were related strongest to prolonged sleep problems were aggression, social and attention problems, and anxious/depressed mood. Also, somatic complaints (ninefold risk) and medical problems (P < 0.001) were typical for children with persistent sleep problems.

CONCLUSIONS

Persistent sleep problems in children associate with high levels of psychosocial, somatic and medical problems. In paediatric health care more attention should be paid to recognizing, monitoring of the persistence and treatment of sleep problems before school transition period.

Environmental factors, sleep duration, and sleep bruxism in Brazilian schoolchildren: a case-control study

OBJECTIVE

The purpose of our study was to evaluate the association between environmental factors, sleep duration, and sleep bruxism (SB) in schoolchildren.

METHODS

A case-control study was performed. Individuals participating in the study were randomly chosen from public and private schools in Belo Horizonte, Brazil. A total of 120 children with bruxism and 240 without bruxism (mean age, 8 years) participated in our study. A questionnaire for parents was used to collect data based on criteria taken from the American Academy of Sleep Medicine. Conditional binary logistic regression statistical tests and χ2 tests were used for analysis.

RESULTS

The final logistical model found that children with a median sleep time < or = 8 h per night (odds ratio [OR], 2.561 [95% confidence interval {CI}, 1.480-4.433]), who did not enjoy a good night's sleep (OR, 3.253 [95% CI, 1.600-6.615]), who slept with noise in the room (OR, 2.699 [95% CI, 1.645-4.429]), and who had the light on (OR, 2.370 [95% CI, 1.446-3.884]), were more likely to have SB.

CONCLUSION

Children who sleep for less than 8h a night are more likely to have SB. Light and noise in the room were two predisposing factors for the occurrence of SB.