Factors Affecting the Quality of Sleep in Children

Children's nocturnal awakenings and sleep duration during the first two years of life in the NASCITA cohort study

PURPOSE

Previous studies have analyzed the characteristics and prevalence of sleep disturbances among Italian children. Less attention has been paid, however, to the factors involved in sleep disturbances in the first two years of life. The goals of the present study were, therefore: 1) to provide a developmental trajectory of Italian infants' night awakenings and duration during the first two years of life and 2) to analyze which factors affect night awakenings the most over time.

METHODS

Data for this study were collected in the NASCITA cohort. During the well-child visits conducted at 6, 12, and 24 months, pediatricians asked parents to report if the child had any sleep disturbances, especially frequent night awakenings. Univariate and multivariable analyses were performed to test the association between child and family variables and the likelihood of frequent awakenings.

RESULTS

2973 toddlers, out of 5054 initially enrolled newborns, were included in this study; 875 (29.4 %) of whom presented frequent awakenings in at least one visit (peak of prevalence of 19.8 % at 12 months). Bed-sharing (adjusted OR 2.53; 95%CI:2.05-3.12) and living in the northern Italy (aOR 2.25; 95%CI:1.80-2.81) were the variables more strongly associated with an increased likelihood of frequent awakenings in the binomial logistic regression, while sleeping alone was associated with a decreased chance (aOR 0.62; 95%CI 0.45-0.89). A short sleep duration (<11 h/day) was reported for 801 (26.9 %) at 12 months, for 743 (25.0 %) at 24 months of age; in 383 cases, the short sleep duration was reported at both time points. An association was observed between frequent awakenings at 12 or 24 months and short sleep duration (OR 1.23; 95%CI 1.05-1.44 -ꭓ2 6.25, p = 0.012).

CONCLUSIONS

The current study identified some early predictors of frequent awakenings during the first two years of life. Since optimal sleep practices in children are essential for their development, effective, early interventions must be defined and integrated into pediatric care practices.

Comparison of sleep quality between outpatient and hospitalized children with respiratory tract dysfunction

OBJECTIVES

The main objective of the study to compare the effect of hospitalized and outpatient settings on quality of sleep in children with respiratory tract dysfunction.

METHODOLOGY

A descriptive correlational study was carried out at Dhi-Qar Health Directorate pediatric hospitals. The period of the study was from the November 19, 2023 to March 10, 2024. Purposive sample (non-probability) of 250 children (male and female). A total of (125) children were chosen from the children whose admitted to the hospitals, and a total of (125) children were chosen from the outpatient settings. The study instrument consisted of three parts: the sociodemographic sheet, clinical diagnosis sheet, and sleep quality scale. The questionnaire was modified according to experts' recommendation to use it for children with respiratory tract dysfunction. The questionnaire was evaluated by a panel of 15 experts from diverse medical and nursing professions. Both descriptive and inferential statistics were used to analyze the data.

RESULTS

The study findings that effect outpatient settings have more effect from hospitalized settings on quality of sleep in children with respiratory tract dysfunction (M ± SD = 1.322 ± 0.1522).

CONCLUSION

A study showed that the quality of sleep in children with respiratory tract dysfunction was generally average, whether in hospitalized or outpatient settings, outpatient settings had greater difficulties falling asleep and waking than children in hospitalized.

NAPping PAnts (NAPPA): An open wearable solution for monitoring Infant's sleeping rhythms, respiration and posture

Study objectives

To develop a non-invasive and practical wearable method for long-term tracking of infants' sleep.

Methods

An infant wearable, NAPping PAnts (NAPPA), was constructed by combining a diaper cover and a movement sensor (triaxial accelerometer and gyroscope), allowing either real-time data streaming to mobile devices or offline feature computation stored in the sensor memory. A sleep state classifier (wake, N1/REM, N2/N3) was trained and tested for NAPPA recordings (N = 16649 epochs of 30 s), using hypnograms from co-registered polysomnography (PSG) as a training target in 33 infants (age 2 weeks to 18 months; Mean = 4). User experience was assessed from an additional group of 16 parents.

Results

Overnight NAPPA recordings were successfully performed in all infants. The sleep state classifier showed good overall accuracy (78 %; Range 74-83 %) when using a combination of five features related to movement and respiration. Sleep depth trends were generated from the classifier outputs to visualise sleep state fluctuations, which closely aligned with PSG-derived hypnograms in all infants. Consistently positive parental feedback affirmed the effectiveness of the NAPPA-design.

Conclusions

NAPPA offers a practical and feasible method for out-of-hospital assessment of infants' sleep behaviour. It can directly support large-scale quantitative studies and development of new paradigms in scientific research and infant healthcare. Moreover, NAPPA provides accurate and informative computational measures for body positions, respiration rates, and activity levels, each with their respective clinical and behavioural value.

European expert guidance on management of sleep onset insomnia and melatonin use in typically developing children

Sleeping problems are prevalent among children and adolescents, often leading to frequent consultations with pediatricians. While cognitive-behavioral therapy has shown effectiveness, especially in the short term, there is a lack of globally endorsed guidelines for the use of pharmaceuticals or over-the-counter remedies in managing sleep onset insomnia. An expert panel of pediatric sleep specialists and chronobiologists met in October 2023 to develop practical recommendations for pediatricians on the management of sleep onset insomnia in typically developing children. When sleep onset insomnia is present in otherwise healthy children, the management should follow a stepwise approach. Practical sleep hygiene indications and adaptive bedtime routine, followed by behavioral therapies, must be the first step. When these measures are not effective, low-dose melatonin, administered 30-60 min before bedtime, might be helpful in children over 2 years old. Melatonin use should be monitored by pediatricians to evaluate the efficacy as well as the presence of adverse effects.    Conclusion: Low-dose melatonin is a useful strategy for managing sleep onset insomnia in healthy children who have not improved or have responded insufficiently to sleep hygiene and behavioral interventions.

The role of perceived social support from family, friends and significant others in the association between childhood maltreatment on sleep quality in adolescents: Evidence from a weekly diary study

BACKGROUND

Childhood maltreatment is a common problem that can have lasting effects on the physical and mental health of adolescents who have experienced it, including sleep quality.

OBJECTIVE

This study will investigate the relationship between childhood maltreatment and sleep quality in adolescents using a weekly diary method.

PARTICIPANTS AND SETTING

In this study, students from a middle school in central China were recruited as research subjects, and a total of 11 classes with 470 students were investigated.

METHODS

In order to fill in the gaps of previous studies, a weekly diary method was used to collect data. Subjects were required to complete three scales once a week for seven consecutive weeks, including the Childhood Trauma Questionnaire (CTQ), the Multidimensional Scale of Perceived Social Support (MSPSS), and the Pittsburgh Sleep Quality Index scale (PSQI).

RESULTS

Findings suggest that childhood maltreatment has a negative impact on adolescent's sleep quality at the weekly level (γ01c = -0.07, t = -5.71, p < .001) . The negative effect of childhood maltreatment on sleep quality was significantly reduced with the addition of perceived social support (γ01c' = -0.03, t = -2.83, p < .01). Notably, support from friends (γ01a*γ02b = -0.01) and significant others (γ01a*γ02b = -0.02) also played an important mediating role in child maltreatment and adolescent sleep quality, but family support remained the most important support in adolescents (γ01a*γ02b = -0.04).

CONCLUSIONS

The present study has confirmed the negative correlation between childhood maltreatment and sleep quality in adolescents. Furthermore, it has clarified the mechanism of perceived social support and the separate mediating roles of perceived family support, perceived friend support, and perceived significant other support.

Sleep Duration Is Associated with Household Food Insecurity and Sugar-Sweetened Beverage Intake Among Women, Infants and Children Participating Children Ages 0-5

PURPOSE

To determine associations between child and household characteristics and sleep duration among low-income children in Los Angeles County.

DESIGN

Cross-sectional study.

SETTING

Survey data collected in 2017 and 2020 in Los Angeles County, California.

SAMPLE

Special Supplemental Nutrition Program for Women, Infants and Children (WIC) households with children ages 4-60 months.

MEASURES

Sleep duration for children 4-60 months old (less than recommended (LTR), recommended range, more than recommended (MTR)), household food insecurity (HFI), sociodemographics, and daily servings of sugar-sweetened beverages (SSB).

ANALYSIS

Multinomial logistic regression, stratified by child age, was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for associations between household/child characteristics and LTR or MTR sleep compared to recommended duration among WIC participating children 4-60 months old.

RESULTS

The final sample included 3512 children ages 4-23 months and 6035 children ages 24-60 months. In the study population, 32% (3-5 years old) to 44% (4-11months) of children under 5 did not meet the recommended hours of sleep per night. HFI was associated with higher odds of LTR (OR 1.27, CI 1.12-1.45) and MTR (OR 1.46, CI 1.15-1.87) sleep among 24-60 month-old children. Each additional daily SSB serving was associated with higher odds of LTR sleep (4-23 months: OR 1.10, CI 1.02-1.19; 24-59 months: OR 1.12, CI 1.08-1.17).

CONCLUSIONS

HFI and SSB intake are associated with not getting the recommended amount of sleep among low-income WIC participating children. Nutrition assistance program participants may benefit from receiving information about recommended sleep duration for young children and how to establish sleep routines to optimize sleep duration.

A Good Night's Sleep in Malta in 2023: A Cross-sectional Study Exploring Sleep Quality and its Determinants via Social Media

BACKGROUND

Sleep quality is affected by a plethora of different factors, although its relationship with chronic diseases is still unclear. This study explored perceived sleep quality and its associated determinants among the adult population of Malta. Study Design: A cross-sectional study.

METHODS

An anonymous online survey was distributed through social media targeting adults residing in Malta. Data pertaining to socio-demographic, medical history, lifestyle, well-being, sleep, and daytime sleepiness were gathered, and descriptive, univariant, and multiple binary logistic regression modelling analyses were performed.

RESULTS

A total of 855 adults responded, out of whom 35.09% (95% confidence interval [CI]: 31.90, 38.41) reported sleep difficulties, especially females (81.33%; 95% CI: 76.36, 85.49), while 65.33% (95% CI: 59.61, 70.65) reported suffering from chronic disease(s). Sleep problems were positively associated with multimorbidity (odds ratio [OR]: 2.17; 95% CI: 1.38, 3.40; P=0.001), sleeping<6 hours (OR: 3.79; 95% CI: 1.54, 9.30; P=0.040), and the presence of moderate anxiety symptoms (OR: 1.99; 95% CI: 1.10, 3.59; P=0.020). They were also related to the presence of mild (OR: 2.25; 95% CI: 1.46, 3.45; P=0.001), moderate (OR: 2.40; 95% CI: 1.24, 4.64; P=0.010), and moderately severe (OR: 15.35; 95% CI: 4.54, 31.86; P=0.001) depressive symptoms after adjusting for confounders.

CONCLUSION

Chronic conditions, including anxiety and depression, along with short sleep duration, appear to contribute to poor sleep quality in Malta. A multifaceted approach is required to deal with the issue holistically and safeguard the health of current and future generations.

Associations between Parental Educational Attainment, Children's 24-h Behaviors and Children's Hyperactivity Behavior in the COVID-19 Pandemic

BACKGROUND

Parental Educational Attainment and children's 24-h behaviors significantly influenced children's hyperactivity symptoms. This study aimed to examine the mediating role of children's 24-h behavior changes due to the COVID-19 pandemic between Parental Educational Attainment and children's hyperactivity index. It also aimed to investigate the associations between Children's Physical Activity, digital media use, sleep, and hyperactivity index between two clusters of Parental Educational Attainments. The goal was to provide targeted behavioral optimization recommendations for caregivers to reduce the risk of children's hyperactivity.

METHODS

The study was a collaborative extension of the International iPreschooler Surveillance Study Among Asians and otheRs project and the Chinese Children and Adolescent Sports Health Promotion Action Project. The Parent-Surveillance of Digital Media in Childhood Questionnaire® and the Abbreviated Rating Scales from the Conners Parent Symptom Questionnaire were used to measure Parental Educational Attainment, children's behavior changes during the COVID-19 pandemic, and hyperactivity indexes. A total of 11,190 parents of 6-to-12-year-old children completed the online surveys in mainland China. A structural equation model was established by using Smart-PLS, and the linear regression model, and isotemporal substitution models were established by using a Compositional Data Analysis package with R program to achieve the research objectives.

RESULTS

Changes in children's 24-h behaviors due to the COVID-19 pandemic had a significant mediation effect on the negative associations between Parental Educational Attainment and children's hyperactivity index (β = 0.018, T = 4.521, p < 0.001) with a total effect (β = -0.046, T = 4.521, p < 0.001) and a direct effect (β = -0.064, T = 6.330, p < 0.001). Children's Digital Media use was significantly and negatively associated with hyperactivity index among all children. Reallocated time from digital media use to both sleep and physical activity decreased the hyperactivity index, and vice-versa. For parents without tertiary education (R2 = 0.09, p < 0.001), sleep was significantly and negatively associated with the hyperactivity index (βilr-CSL = -0.06, p < 0.001); for parents with tertiary education (R2 = 0.07, p < 0.001), physical activity was significantly and negatively associated with the hyperactivity index (βilr-CPA = -0.05, p < 0.001), and sleep was significantly and positively associated with the hyperactivity index (βilr-CSL = 0.03, p < 0.001). A significant increase in the hyperactivity index was detected when physical activity time was reallocated to sleep, with a significant decrease in the opposite direction.

CONCLUSIONS

Parental Educational Attainment and children's 24-h behaviors directly influenced children's hyperactivity index. However, a purposeful and targeted optimization of children's 24-h behaviors-namely, physical activity, digital media use, and sleep-could assist parents with different educational attainments to reduce their children's hyperactivity index and mitigate the risk of hyperactivity.

A Semi-Supervised Multi-Scale Arbitrary Dilated Convolution Neural Network for Pediatric Sleep Staging

Sleep staging is essential for assessing sleep quality and diagnosing sleep disorders. However, sleep staging is a labor-intensive process, making it arduous to obtain large quantities of high-quality labeled data for automatic sleep staging. Meanwhile, most of the research on automatic sleep staging pays little attention to pediatric sleep staging. To address these challenges, we propose a semi-supervised multi-scale arbitrary dilated convolution neural network (SMADNet) for pediatric sleep staging using the scalogram with a high height-to-width ratio generated by the continuous wavelet transform (CWT) as input. To extract more extended time dimensional feature representations and adapt to scalograms with a high height-to-width ratio in SMADNet, we introduce a multi-scale arbitrary dilation convolution block (MADBlock) based on our proposed arbitrary dilated convolution (ADConv). Finally, we also utilize semi-supervised learning as the training scheme for our network in order to alleviate the reliance on labeled data. Our proposed model has achieved performance comparable to state-of-the-art supervised learning methods with 30% labels. Our model is tested on a private pediatric dataset and achieved 79% accuracy, 72% kappa, and 75% MF1. Therefore, our model demonstrates a powerful feature extraction capability and has achieved performance comparable to state-of-the-art supervised learning methods with a small number of labels.

Are 24-hour movement recommendations associated with obesity-related indicators in the young population? A meta-analysis

OBJECTIVE

This study aimed to determine the relationship between meeting all three 24-hour movement recommendations (i.e., physical activity, sleep duration, and screen time) and obesity-related indicators among young people.

METHODS

Four databases were systematically searched (PubMed, Scopus, Web of Science, and Cochrane Library).

RESULTS

Meeting the 24-hour movement recommendations was cross-sectionally associated with lower overall obesity-related indicators (r = -0.09, 95% CI: -0.11 to -0.06), but no longitudinal association was found. Regarding each obesity-related indicator separately, meeting all three recommendations was related to lower odds of overweight/obesity (odds ratio = 0.65, 95% CI: 0.56 to 0.76) and obesity alone (odds ratio = 0.28, 95% CI: 0.16 to 0.50). An inverse relationship between meeting 24-hour movement recommendations and BMI, BMI z score, waist circumference, and body fat was also found. Regarding subgroup analysis, the association between 24-hour movement recommendations and overall obesity-related indicators was similar regardless of sex, comparison used (meeting all three vs. not meeting [i.e., those who met zero to two of the movement behaviors] or meeting all three vs. none), and type of measure to assess 24-hour movement recommendations (i.e., self-reported or accelerometer-based measures).

CONCLUSIONS

Meeting all 24-hour movement recommendations may be a crucial factor in maintaining a healthy weight status in the young population.

Dietary and Sleep Quality Association in Hemodialysis Patients

Background

Poor sleep quality is a common issue among patients with end-stage renal disease (ESRD) who undergo dialysis. Nutritional habits are associated with sleep hygiene in patients undergoing dialysis. The objective of this study was to examine the potential correlation between nutritional status and sleep quality in individuals receiving hemodialysis treatment.

Materials and Methods

This cross-sectional study included 160 hemodialysis patients. A food frequency questionnaire (FFQ) was used to measure food intake in participants. The Persian-validated version of the Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality. Patients were classified as poor or good sleepers with a PSQI score of <5 and >5, respectively.

Results

Eighty-four percent of hemodialysis patients had bad sleep hygiene. There was a significant association between sleep quality and educational status and age (P < 0.001). Poor sleepers were older (61.65 years versus 51.12) and less educated (31.1% versus 4%). However, there was no significant difference in the intake of micro- and macronutrients between poor and good sleepers (P > 0.05).

Conclusion

The results of this study suggest that sleep quality has no significant relationship with nutrient intake in hemodialysis patients. Demographic factors, such as age and educational status, have played a more effective role than nutritional factors in patients' sleep quality.

Translation and adaptation into Brazilian Portuguese and investigation of the psychometric properties of the Children's Sleep Habits Questionnaire (CSHQ-BR)

OBJECTIVES

To translate to Brazilian Portuguese, culturally adapt and confirm the psychometric parameters of validity and reliability of the Children's Sleep Habits Questionnaire (CSHQ-BR) in children.

METHODS

A sample of 314 typically developing children, 51% girls, mean age 7.12 years (SD = 2.04 years) were assessed, comprising 227 from São Paulo and 87 from the Amazon region. Translation, back translation, cultural adaptation, a pilot study and item review were carried out, yielding the final version of the CSHQ. Psychometric parameters were determined based on content validity coefficient (CVC), test-retest, internal consistency, evidence of convergent validity and internal structure.

RESULTS

The final CVC for the scale was 0.88. Intraclass correlation was 0.98 for the overall questionnaire and ranged from 0.88 to 0.98 for subscales. CSHQ-BR internal consistency was α = 0.81 for the CSHQ-BR total score (95% CI) and from 0.51 to 0.75 for subscales. Exploratory factor analysis suggested a novel 4-factor structure. A positive correlation was found between the CSHQ and the Questionnaire on Sleep Behavior. Mean total CSHQ score in Brazilian children was 46.85 (SD = 9.43), and boys had a higher mean total score than girls, although not statistically significant.

CONCLUSION

The CSHQ-BR exhibited satisfactory equivalence for the original English abbreviated form and the Brazilian Portuguese version, proving a useful sleep screening instrument for identifying sleep problems in Brazilian children aged 4-10 years.

Sleep dimensions are associated with obesity, poor diet quality and eating behaviors in school-aged children

Objectives

The aim of this cross-sectional study was to investigate the association between sleep dimensions (duration, patterns, and disturbances) with body mass index (BMI), diet quality, and eating behaviors in school-aged children. Additionally, we aimed to investigate whether obesogenic eating behaviors (higher food responsiveness, lower satiety responsiveness, and less slowness in eating) and poor diet quality could mediate the potential association between sleep and obesity in school-aged children.

Materials and methods

For all participants (n = 588 children, age 5–12 years; 51% girls) we evaluated: sleep dimensions, BMI, diet quality, eating behaviors (food responsiveness, satiety responsiveness and slowness in eating). Linear regression models were used to test associations between exposure and outcome variables. Additionally, path analysis was conducted to test whether eating behaviors mediated the relationship between sleep and obesity.

Results

Shorter sleep duration (β = −0.722, p = 0.009) and greater sleep disturbances (β = 0.031, p = 0.012) were significantly associated with BMI. Additionally, we observed that diet quality was significantly associated with sleep duration (β = 0.430, p = 0.004), the midpoint of sleep (β = −0.927, p < 0.001), and sleep disturbances (β = −0.029, p < 0.001). Among other findings, greater sleep disturbances were associated with food responsiveness (β = 0.017, p < 0.001), satiety responsiveness (β = 0.015, p < 0.001), and slowness in eating (β = 0.012, p < 0.001). Importantly, food responsiveness was found as significant mediator of the relationship between sleep and BMI (R = 0.427, R² = 0.182, p < 0.001).

Conclusions

Late sleep patterns, short sleep duration, and greater sleep disturbances are significantly related with what and how school-aged children eat. Importantly, poor diet quality was significantly related to all three sleep dimensions, while eating behaviors had a significant relationship with greater sleep disturbances. These findings may be relevant to the development of behavioral targets to prevent childhood obesity, including sleep hygiene guidelines as a strategy to improve children's eating habits, as well as their BMI.

Horticulture therapy affected the mental status, sleep quality, and salivary markers of mucosal immunity in an elderly population

Horticultural therapy (HT) has been reported to be beneficial to mental and physical health. This study investigated the effects of HT on the psychological status and mucosal immunity of elderly individuals. Twenty-four participants aged 70-93 were recruited from residential facilities and adult day-care services. Six different HT activities were designed and guided by licensed instructors who performed saliva collection and helped the participants complete the questionnaires before and after each activity. The sleep quality scores were collected during the 6 weeks of HT activities. Saliva was collected and analyzed to determine the concentrations of immunoglobulin A (IgA), lactoferrin, chromogranin A (CgA), α-amylase (AA) and total protein (TP). Comparisons of the questionnaire scores between preactivity and postactivity showed that feelings of satisfaction and happiness were significantly enhanced after each activity. In addition, sleep quality was significantly improved after the 6-week course of HT activities. Regarding mucosal immunity, the preactivity IgA and IgA/TP were significantly increased at week 3 and week 6; in addition, the ratio of lactoferrin/TP was significantly decreased at week 6 compared to week 1. The postactivity AA and CgA levels were significantly enhanced at weeks 2, 3 and 5 compared to the corresponding preactivity levels. In conclusions, HT activities significantly improved the happiness, satisfaction, well-being and sleep quality of the elderly. Moreover, mucosal immunity proteins, including IgA, lactoferrin, CgA and AA, were significantly increased.

Impact of the COVID-19 virus outbreak on 24-h movement behaviours among children in Saudi Arabia: A cross-sectional survey

BACKGROUND

In March 2020, the World Health Organization (WHO) declared the coronavirus (COVID-19) outbreak as a pandemic. This led many governments to place restrictions on population movement to aid in pandemic control. These restrictions were expected to produce some type of impact on the daily lives of children and their families. The purpose of this study was to investigate the impact of COVID-19 on 24-h movement behaviours among Saudi children aged 6-12 years, during the pandemic.

METHODS

An online survey of Saudi parents (n = 1021) was conducted between 1 October to 11 November 2020 to gather information about the impact of the COVID-19 outbreak on children's 24-h movement behaviours, parent and child factors that may be associated with movement behaviours, and perceived changes in children's movement behaviours.

RESULTS

Only 3.4% of Saudi children met all components of 24-h movement guidelines. Compared with before COVID-19, children's PA levels declined, they slept more, and their use of electronic screen devices significantly increased. The perceived changes in PA and SB were more unfavourable among girls than boys. Children of older parents, mothers, and those with lower education levels and lower monthly incomes were more likely to meet 24-h movement guidelines.

CONCLUSION

The COVID-19 virus outbreak unfavourably affected Saudi children's movement behaviours, more specifically, girls, which should be taken into account in future research. The results provide an insight into what has changed because of the COVID-19 restrictions and could be considered as part of the response strategies in Saudi Arabia.

Which Is More Important for Health: Sleep Quantity or Sleep Quality?

Sleep is one of the basic physiological processes for human survival. Both sleep quantity and sleep quality are fundamental components of sleep. This review looks at both sleep quantity and sleep quality, considering how to manage the complex but probably unavoidable physiological phenomenon of sleep. The need for sleep has marked variations between individuals, in addition to the effects of variable conditions. Studies on sleep quality started later than those on sleep quantity, beginning in 1989 when Ford and Kamerow revealed that insomnia increases the risk of psychiatric disorders. According to the nationwide research team on the quality of sleep (19FA0901), sleep quality is superior to sleep quantity as an index for assessing sleep, and that restfulness obtained through sleep is a useful index for assessing sleep quality. We should pay more attention to obtaining sleep of good quality (restfulness, no sleepiness, no need for more sleep, sufficient objective sleep depth, etc.), although there have not been enough studies on the associations between sleep quality and health or disorders in children and adolescents. Further studies using the deviation from an individual’s optimal sleep quantity may show us another aspect of the effects of sleep quantity on various life issues.

Bullying Victimization and Friendship as Influences on Sleep Difficulty among Brazilian Adolescents

Bullying victimization is associated with poor health-related outcomes, including sleeping problems. The present study aimed to investigate the impact of bullying victimization on sleep difficulty, and the moderating effect of the number of close friends on this association, also exploring differences across genders. The study was based on a nationally-representative survey on adolescent health conducted in Brazilian schools, involving a total of 109,104 participants, enrolled at the 9th year in 2012. The measures used in the analysis included socio-demographic characteristics, bullying victimization, sleep difficulty, and number of close friends. In the multilevel models, reporting more peer victimization was associated with more sleep difficulties (b = .18, t = 50.17, p < .05), with girls reporting more sleep difficulties in association with peer victimization than boys. Reporting having more friends was inversely linked to sleep difficulties (b = -.08, t = -15.26, p < .05), and the association between peer victimization and sleep difficulties was significantly buffered by the number of friends. Moreover, in a three way interaction, there was a marginally significant difference in the effect of friends on the link between victimization and sleep difficulties between boys and girls (b = .02, t = 1.86, p = .06), with the buffering effect of friendships being negligible among girls as opposed to boys. The results indicate a significant association between bullying victimization and sleep difficulties, which seems to be more pronounced among girls, also suggesting that the number of close friends may buffer this association, mainly for boys.