Secular trends in physical growth, biological maturation, and intelligence in children and adolescents born between 1978 and 1993

Introduction

Human physical growth, biological maturation, and intelligence have been documented as increasing for over 100 years. Comparing the timing of secular trends in these characteristics could provide insight into what underlies them. However, they have not been examined in parallel in the same cohort during different developmental phases. Thus, the aim of this study was to examine secular trends in body height, weight, and head circumference, biological maturation, and intelligence by assessing these traits concurrently at four points during development: the ages of 4, 9, 14, and 18 years.

Methods

Data derived from growth measures, bone age as an indicator of biological maturation, and full-scale intelligence tests were drawn from 236 participants of the Zurich Longitudinal Studies born between 1978 and 1993. In addition, birth weight was analyzed as an indicator of prenatal conditions.

Results

Secular trends for height and weight at 4 years were positive (0.35 SD increase per decade for height and an insignificant 0.27 SD increase per decade for weight) and remained similar at 9 and 14 years (height: 0.46 SD and 0.38 SD increase per decade; weight: 0.51 SD and 0.51 SD increase per decade, respectively) as well as for weight at age 18 years (0.36 SD increase per decade). In contrast, the secular trend in height was no longer evident at age 18 years (0.09 SD increase per decade). Secular trends for biological maturation at 14 years were similar to those of height and weight (0.54 SD increase per decade). At 18 years, the trend was non-significant (0.38 SD increase per decade). For intelligence, a positive secular trend was found at 4 years (0.54 SD increase per decade). In contrast, negative secular trends were observed at 9 years (0.54 SD decrease per decade) and 14 years (0.60 SD decrease per decade). No secular trend was observed at any of the four ages for head circumference (0.01, 0.24, 0.17, and - 0.04 SD increase per decade, respectively) and birth weight (0.01 SD decrease per decade).

Discussion

The different patterns of changes in physical growth, biological maturation, and intelligence between 1978 and 1993 indicate that distinct mechanisms underlie these secular trends.

Child eating behavior predicts body mass index after 1 year: results from the Swiss Preschooler's Health Study (SPLASHY)

Child obesity is a growing global issue. Preventing early development of overweight and obesity requires identifying reliable risk factors for high body mass index (BMI) in children. Child eating behavior might be an important and malleable risk factor that can be reliably assessed with the parent-report Child Eating Behavior Questionnaire (CEBQ). Using a hierarchical dataset (children nested within child care centers) from a representative cohort of Swiss preschool children, we tested whether eating behavior, assessed with a 7-factor solution of the CEBQ, and BMI at baseline predicted the outcome BMI after 1 year, controlling for socioeconomic status (n = 555; 47% female; mean age = 3.9 years, range: 2.2-6.6; mean BMI = 16 kg/m2, range: 11.2-23; mean age- and sex-corrected z-transformed BMI, zBMI = 0.4, range -4 to +4.7). The statistical model explained 65.2% of zBMI at follow-up. Baseline zBMI was a strong positive predictor, uniquely explaining 48.8% of outcome variance. A linear combination of all CEBQ scales, taken together, explained 10.7% of outcome variance. Due to their intercorrelations, uniquely explained variance by any individual scale was of negligible clinical relevance. Only food responsiveness was a significant predictor, when accounting for all other predictors and covariates in the model, and uniquely explained only 0.4% of outcome variance. Altogether, our results confirm, extend, and refine previous research on eating behavior and zBMI in preschool children, by adjusting for covariates, accounting for intercorrelations between predictors, partitioning explained outcome variance, and providing standardized beta estimates. Our findings show the importance of carefully examining the contribution of predictors in multiple regression models for clinically relevant outcomes.

Bedtime to the brain: how infants' sleep behaviours intertwine with non-rapid eye movement sleep electroencephalography features

Adequate sleep is critical for development and facilitates the maturation of the neurophysiological circuitries at the basis of cognitive and behavioural function. Observational research has associated early life sleep problems with worse later cognitive, psychosocial, and somatic health outcomes. Yet, the extent to which day-to-day sleep behaviours (e.g., duration, regularity) in early life relate to non-rapid eye movement (NREM) neurophysiology-acutely and the long-term-remains to be studied. We measured sleep behaviours in 32 healthy 6-month-olds assessed with actimetry and neurophysiology with high-density electroencephalography (EEG) to investigate the association between NREM sleep and habitual sleep behaviours. Our study revealed four findings: first, daytime sleep behaviours are related to EEG slow-wave activity (SWA). Second, night-time movement and awakenings from sleep are connected with spindle density. Third, habitual sleep timing is linked to neurophysiological connectivity quantified as delta coherence. And lastly, delta coherence at 6 months predicts night-time sleep duration at 12 months. These novel findings widen our understanding that infants' sleep behaviours are closely intertwined with three particular levels of neurophysiology: sleep pressure (determined by SWA), the maturation of the thalamocortical system (spindles), and the maturation of cortical connectivity (coherence). The crucial next step is to extend this concept to clinical groups to objectively characterise infants' sleep behaviours 'at risk' that foster later neurodevelopmental problems.

Wake EEG oscillation dynamics reflect both sleep need and brain maturation across childhood and adolescence

An objective measure of brain maturation is highly insightful for monitoring both typical and atypical development. Slow wave activity, recorded in the sleep electroencephalogram (EEG), reliably indexes changes in brain plasticity with age, as well as deficits related to developmental disorders such as attention-deficit hyperactivity disorder (ADHD). Unfortunately, measuring sleep EEG is resource-intensive and burdensome for participants. We therefore aimed to determine whether wake EEG could likewise index developmental changes in brain plasticity. We analyzed high-density wake EEG collected from 163 participants 3-25 years old, before and after a night of sleep. We compared two measures of oscillatory EEG activity, amplitudes and density, as well as two measures of aperiodic activity, intercepts and slopes. Furthermore, we compared these measures in patients with ADHD (8-17 y.o., N=58) to neurotypical controls. We found that wake oscillation amplitudes behaved the same as sleep slow wave activity: amplitudes decreased with age, decreased after sleep, and this overnight decrease decreased with age. Oscillation densities were also substantially age-dependent, decreasing overnight in children and increasing overnight in adolescents and adults. While both aperiodic intercepts and slopes decreased linearly with age, intercepts decreased overnight, and slopes increased overnight. Overall, our results indicate that wake oscillation amplitudes track both development and sleep need, and overnight changes in oscillation density reflect some yet-unknown shift in neural activity around puberty. No wake measure showed significant effects of ADHD, thus indicating that wake EEG measures, while easier to record, are not as sensitive as those during sleep.

Eating behaviour in Swiss preschool children-Validation of a German and a French version of the Children's Eating Behaviour Questionnaire (CEBQ)

Young children's eating behavior is crucial for any further development of healthy eating. Early eating behavior are often assessed through parental report. The Children's Eating Behaviour Questionnaire (CEBQ) is a widely used parental questionnaire that has been validated in families of different gender, age and cultural background. Research has shown that the 8-factor structure has some inconsistencies and sample characteristics such as age, gender, and culture can influence the results. To which extent such sample characteristics might influence results within a multi-lingual culture has not been investigated so far. Therefore, the aim of the study was to evaluate the factor structure of the CEBQ among 511 preschool children of the French and German parts of Switzerland, aged 2 to 6 years (Mean 3.85 years; SD 0.69). Confirmatory Factor Analysis showed a modified structure of the original questionnaire, with a 7-factor structure providing a reasonable fit to the data (TLI = 0.954, CFI = 0.952, RMSEA = 0.063 and SRMR = 0.067). The subscale 'Desire to drink' was removed, and a few items moved to other subscales as they loaded higher on a different subscale compared to the original model. Reliabilities based on the coefficient omega were acceptable to satisfying across the seven factors, ranging from 0.66 to 0.90. There were no significant gender or age differences, but French speaking children showed higher levels of 'Satiety responsiveness' and lower 'Enjoyment of food' than German speaking children. Yet, these effects were small. The German and French CEBQ are valid and reliable versions of the original CEBQ and can be used in a multicultural context.

Visuomotor adaptation, internal modelling, and compensatory movements in children with developmental coordination disorder

BACKGROUND

Developmental coordination disorder (DCD) is one of the most prevalent developmental disorders in school-aged children. The mechanisms and etiology underlying DCD remain somewhat unclear. Altered visuomotor adaptation and internal model deficits are discussed in the literature.

AIMS

The study aimed to investigate visuomotor adaptation and internal modelling to determine whether and to what extent visuomotor learning might be impaired in children with DCD compared to typically developing children (TD). Further, possible compensatory movements during visuomotor learning were explored.

METHODS AND PROCEDURES

Participants were 12 children with DCD (age 12.4 ± 1.8, four female) and 18 age-matched TD (12.3 ± 1.8, five female). Visuomotor learning was measured with the Motor task manager. Compensatory movements were parameterized by spatial and temporal variables.

OUTCOMES AND RESULTS

Despite no differences in visuomotor adaptation or internal modelling, significant main effects for group were found in parameters representing movement accuracy, motor speed, and movement variability between DCD and TD.

CONCLUSIONS AND IMPLICATIONS

Children with DCD showed comparable performances in visuomotor adaptation and internal modelling to TD. However, movement variability was increased, whereas movement accuracy and motor speed were reduced, suggesting decreased motor acuity in children with DCD.

Comparing neuromotor functions in 45- and 65-year-old adults with 18-year-old adolescents

Aim

This cross-sectional analysis investigates how neuromotor functions of two independent cohorts of approximately 45- and 65-year-old individuals are different from 18-year-old adolescents using the Zurich Neuromotor Assessment-2 (ZNA-2).

Methods

A total of 186 individuals of the Zurich Longitudinal Studies (ZLS) born in the 1950s (mean age 65.1 years, SD = 1.2 year, range of ages 59.0-67.5 years, n = 151, 82 males) and 1970s (mean age 43.6 years, SD = 1.3 year, range of ages 40.8-46.6 years, n = 35, 16 males) were tested with the ZNA-2 on 14 motor tasks combined in 5 motor components: fine motor, pure motor, balance, gross motor, and associated movements. Motor performance measures were converted into standard deviation scores (SDSs) using the normative data for 18-year-old individuals as reference.

Results

The motor performance of the 45-year-old individuals was remarkably similar to that of the 18-year-olds (SDS from -0.22 to 0.25) apart from associated movements (-0.49 SDS). The 65-year-olds showed lower performance than the 18-year-olds in all components of the ZNA-2, with the smallest difference observed for associated movements (-0.67 SDS) and the largest for gross motor skills (-2.29 SDS). Higher body mass index (BMI) was associated with better performance on gross motor skills for 45-year-olds but with worse performance for 65-year-olds. More educational years had positive effects on gross motor skills for both ages.

Interpretation

With the exception of associated movements, neuromotor functions as measured with the ZNA-2 are very similar in 45- and 18-year-olds. In contrast, at age 65 years, all neuromotor components show significantly lower function than the norm population at 18 years. Some evidence was found for the last-in-first-out hypothesis: the functions that developed later during adolescence, associated movements and gross motor skills, were the most vulnerable to age-related decline.

The role of well-child visits in detecting developmental delay in preschool children

BACKGROUND

Early detection of developmental delay (DD) in preschool children is crucial for counselling parents, initiating diagnostic work-up, and starting early intervention (EI).

METHODS

We conducted a register study of all preschool children referred for EI in the Canton of Zurich, Switzerland, in 2017 (N = 1,785) and used an online survey among primary care physicians (PCPs, N = 271) to evaluate the care service of DD children.

RESULTS

PCPs accounted for 79.5% of all referrals by physicians and had correctly referred over 90% of the children in need of EI at an average age of 39.3 months (SD 8.9). In the survey, which represents 59.2% of all pediatricians and 11.3% of all general practitioners in the Canton, PCPs reported performing a mean of 13.5 (range 0-50, SD 10.7) well-child visits per week to preschool children and estimated well-child visits to be the most frequent type of consultation (66.7%) for the identification of DD. Parents' hesitancy in accepting further evaluation or support were reported by 88.7%.

CONCLUSIONS

Most preschool children with DD are identified in well-child visits. These visits represent an ideal opportunity for early detection of developmental impairment and initiation of EI. Carefully addressing parents' reservations could reduce the rate of refusal, thus improving early support for children with DD.

Secular trends in motor performance in Swiss children and adolescents from 1983 to 2018

Introduction

Environmental changes, including globalization, urbanization, social and cultural changes in society, and exposure to modern digital technology undoubtedly have an impact on children’s activity and lifestyle behavior. In fact, marked reductions in children’s physical activity levels have been reported over the years and sedentary behavior has increased around the world. The question arises whether these environmental changes had an impact on general motor performance in children and adolescents. The study aimed to investigate secular trends of motor performance in Swiss children and adolescents, aged between 7 and 18 years, over a period of 35 years from 1983 to 2018.

Methods

Longitudinal data on the five motor components of the Zurich Neuromotor Assessment (ZNA) – pure motor (PM), fine motor (FM), dynamic balance (DB), static balance (SB), and contralateral associated movements (CAM) – were pooled with cross-sectional data on PM and FM from eight ZNA studies between 1983 and 2018. Regression models were used to estimate the effect of the year of birth on motor performance and body mass index (BMI) measurements. Models were adjusted for age, sex, and socioeconomic status.

Results

The secular trend estimates in standard deviation scores (SDS) per 10 years were − 0.06 [−0.33; 0.22, 95% Confidence Interval] for PM, −0.11 [−0.41; 0.20] for FM, −0.38 [−0.66; −0.09] for DB (−0.42 when controlled for BMI), −0.21 [−0.47; 0.06] for SB, and − 0.01 [−0.32; 0.31] for CAM. The mean change in BMI data was positive with 0.30 SDS [0.07; 0.53] over 10 years.

Discussion

Despite substantial societal changes since the 1980s, motor performance has remained relatively stable across generations. No secular trend was found in FM, PM, SB, and CAM over a period of 35 years. A secular trend in DB was present independent of the secular trend in body mass index.

Development of the circadian system in early life: maternal and environmental factors

In humans, an adaptable internal biological system generates circadian rhythms that maintain synchronicity of behavior and physiology with the changing demands of the 24-h environment. Development of the circadian system begins in utero and continues throughout the first few years of life. Maturation of the clock can be measured through sleep/wake patterns and hormone secretion. Circadian rhythms, by definition, can persist in the absence of environmental input; however, their ability to adjust to external time cues is vital for adaptation and entrainment to the environment. The significance of these external factors that influence the emergence of a stable circadian clock in the first years of life remain poorly understood. Infants raised in our post-modern world face adverse external circadian signals, such as artificial light and mistimed hormonal cues via breast milk, which may increase interference with the physiological mechanisms that promote circadian synchronization. This review describes the very early developmental stages of the clock and common circadian misalignment scenarios that make the developing circadian system more susceptible to conflicting time cues and temporal disorder between the maternal, fetal, infant, and peripheral clocks.

The relationship of parenting style and eating behavior in preschool children

BACKGROUND

Eating behavior represents individual appetitive traits which are related to the individual's regulation of food intake. Eating behavior develops at an early age. There is some evidence that parenting styles might impact on the child's eating behavior. The aim of this study was to investigate the relationship of different dimensions of positive and negative parenting styles with the child's eating behavior at a critical age period of the child's early development.

METHODS

Parents of 511 preschool children (aged 2-6 years) completed the Children Eating Behavior Questionnaire and the Alabama Parenting Questionnaire.

RESULTS

Analyses revealed that different dimensions of negative parenting styles were associated with eating behavior of the child. In details, inconsistent parenting showed a consistent association with eating behavior of a child (i.e. higher emotional eating, higher food responsiveness, higher food fussiness, higher satiety responsiveness and more enjoyment of food), whereas corporal punishment was associated with more emotional overeating and more food responsiveness but less satiety responsiveness. Further, powerful implementation was related to higher food responsiveness and less enjoyment of food and low monitoring was associated with higher emotional overeating and more slowness in eating. There was no such consistent association of positive parenting and eating behavior.

CONCLUSIONS

More negative parenting styles were associated with eating behavior which is more often related to potential weight problems in a long term, whereas positive parenting did not show such a consistent relationship with eating behavior. Negative parenting should be in the focus of prevention and treatment of eating behavior problems in young children.

TRIAL REGISTRATION

ISRCTN41045021 (06/05/2014).

The LifeStories project: Empowering voices and avoiding harm—Ethics protocol of a long-term follow-up study of individuals placed in infant care institutions in Switzerland

Little empirical data exist to guide ethical decisions when conducting research with vulnerable populations. The current study assesses a protocol designed to mitigate risks in a population-based cohort of 246 individuals placed in care institutions as infants in a non-selective 60-year follow-up. In total, 116 (47%) individuals chose to participate, of whom 53 (55%) reported positive effects of participation such as the opportunity to fill some gaps in their life stories, to better deal with their past, and to understand previous family dynamics. Only three individuals (2.5%) explicitly reported negative short-term consequences such as feeling upset as a result of thinking about stressful times, but they nonetheless rated the usefulness of the study as high. For six participants (5%), psychological counseling sessions were initiated as a support measure. Our findings suggest that risk of harm can be managed with a rigorous ethics protocol when conducting research with a vulnerable cohort and therefore enable the voices of survivors to be heard. A step wise approach in which increasing amounts of information were presented at each step, clearly operationalized passive decline, and direct and consistent contact with highly trained staff were considered key to mitigating distress.

Integration of Speed and Quality in Measuring Graphomotor Skills: The Zurich Graphomotor Test

IMPORTANCE

In educational settings, children are under pressure to finish their work successfully within required time frames. Existing tools for assessing graphomotor skills measure either quality or speed of performance, and the speed-accuracy trade-off (SAT) in such tools has never been investigated.

OBJECTIVE

We aimed to evaluate a newly developed tool for measuring graphomotor skills, the Zurich Graphomotor Test (ZGT), that assesses both speed and quality of performance. We also explored whether graphomotor tests are affected by the SAT and, if so, the effects it has on graphomotor test results.

DESIGN

Cross-sectional study.

SETTING

Educational institutions in Switzerland.

PARTICIPANTS

Children, adolescents, and young adults (N = 547) ages 4-22 yr (50.3% female).

OUTCOMES AND MEASURES

Graphomotor performance was measured with the ZGT and the Developmental Test of Visual Perception, Second Edition (DVTP-2). Standard deviation scores were used to quantify performance. We combined ZGT speed and quality measurements into a performance score adjusted for age and sex.

RESULTS

ZGT results indicated a marked developmental trend in graphomotor performance; older children were faster than younger children. Girls showed higher overall performance than boys. The pattern of making more mistakes when being faster and making fewer mistakes when being slower was observed for both graphomotor tests, regardless of time pressure, indicating that the SAT affected the children's scores on both tests.

CONCLUSIONS AND RELEVANCE

SAT is influential in graphomotor assessment. The ZGT captures this trade-off by combining accuracy and speed measurements into one score that provides a realistic assessment of graphomotor skills. What This Article Adds: The newly developed ZGT provides occupational therapy practitioners with more precise information on graphomotor skills in children, adolescents, and young adults than currently available tools.

Association Between Homeschooling and Adolescent Sleep Duration and Health During COVID-19 Pandemic High School Closures

IMPORTANCE

Although negative associations of COVID-19 pandemic high school closures with adolescents' health have been demonstrated repeatedly, some research has reported a beneficial association of these closures with adolescents' sleep. The present study was, to our knowledge, the first to combine both perspectives.

OBJECTIVE

To investigate associations between adolescents' sleep and health-related characteristics during COVID-19 pandemic school closures in Switzerland.

DESIGN, SETTING, AND PARTICIPANTS

This survey study used cross-sectional online surveys circulated among the students of 21 public high schools in Zurich, Switzerland. The control sample completed the survey under regular, prepandemic conditions (May to July 2017) and the lockdown sample during school closures (May to June 2020). Survey respondents were included in the study if they provided their sex, age, and school.

EXPOSURES

High school closures during the first COVID-19 pandemic wave in Switzerland (March 13 to June 6, 2020).

MAIN OUTCOMES AND MEASURES

Sleep-wake patterns, health-related quality of life (HRQoL, assessed by the KIDSCREEN-10 questionnaire), substance use (caffeine, alcohol, and nicotine), and depressive symptoms (lockdown sample only; assessed using the withdrawn/depressed scale from the Youth Self Report). Multilevel regression models were used to assess sample differences and associations of health-related characteristics with sleep duration and depressive symptoms.

RESULTS

The total sample consisted of 8972 students, including 5308 (59.2%) in the control sample (3454 [65.1%] female) and 3664 (40.8%) in the lockdown sample (2429 [66.3%] female); the median age in both samples was 16 years (IQR, 15-17 years). During school closures, the sleep period on scheduled days was 75 minutes longer (semipartial R2 statistic [R2β*], 0.238; 95% CI, 0.222-0.254; P < .001) and the students had better HRQoL (R2β*, 0.007; 95% CI, 0.004-0.012; P < .001) and less consumption of caffeine (R2β*, 0.010; 95% CI, 0.006-0.015; P < .001) and alcohol (R2β*, 0.014; 95% CI, 0.008-0.022; P < .001). Longer sleep duration was associated with better HRQoL (R2β*, 0.027; 95% CI, 0.020-0.034; P < .001) and less caffeine consumption (R2β*, 0.013; 95% CI, 0.009-0.019; P < .001). In the lockdown sample, an inverse association was found between depressive symptoms and HRQoL (R2β*, 0.285; 95% CI, 0.260-.0311; P < .001) and a positive association was found with caffeine consumption (R2β*, 0.003; 95% CI, 0.000-0.008; P = .01).

CONCLUSIONS AND RELEVANCE

In this survey study, 2 opposing associations between school closures and adolescents' health were identified: a negative association with psychological distress and a beneficial association with increased sleep duration. These findings should be considered when evaluating and implementing school closures. Furthermore, the findings provide support for delaying school start times for adolescents.

Teachers' preference for later school start times

Early morning school start times conflict with biologically determined sleep phase preference and thus contribute to common sleep deficits. This conflict is most pronounced in adolescents, and numerous studies have confirmed that later school start times are beneficial for their sleep and health. However, the conflict continues to exist beyond adolescence and, accordingly, also teachers might benefit from later school start times, but this has gained little attention so far. Importantly, teachers’ resistance to delay school start time is one of the key barriers for a successful implementation and, therefore, teachers’ school start time preferences and influencing factors are important to consider. To this end, we conducted an online survey. Teachers (n = 694, 56.1% female) from 17 high schools in Zurich, Switzerland, participated in the study. They indicated their school start time preference. In addition, four predictor blocks were assessed: sociodemographic, school‐/work‐related, and sleep characteristics, as well as teachers’ perception of students in the first morning lesson. Mixed models were applied to predict the preference. The majority (51%) endorsed later school start times (median preferred delay 25.2 min). School start time, sleep characteristics and perception of students in the first morning lesson were significant predictors for the preference. Thus, teachers with more misaligned sleep and higher awareness for students’ issues in the early morning were more likely to report a preference. This suggests psychoeducation about sleep biology throughout life span to be an effective measure to increase teachers’ support to delay school start time, especially because also they themselves are likely to benefit from later school start times.

Walking onset: a poor predictor for motor and cognitive skills in healthy preschool children

Background

The onset of walking is thought to be an indicator of early development. However, evidence is mixed and clear data on this relationship at preschool age is missing. The study aimed at investigating if walking onset and motor and cognitive development in preschool children are related.

Methods

A total of 555 children (mean age 3.86 years) of the Swiss Preschoolers’ Health Study SPLASHY were tested twice at their childcare center (at baseline and one year later). Motor skills and cognitive skills were assessed by standardized testing procedures and parents were asked to provide information on walking onset of their child.

Results

Late onset of walking was related to poorer motor skills (fine motor skills, static and dynamic balance (all p < 0.003)) and poorer cognitive skills (selective attention and visual perception (p = 0.02; p = 0.001) in late preschool age.

Conclusions

For children with late walking onset a close monitoring of their development in the regular pediatric child health visits may be reasonable.

Trial registration: ISRCTN41045021.

Adolescents' preference for later school start times

As the chronotype delays progressively throughout puberty, early morning school start times (SSTs) contradict the sleep biology of adolescents. Various studies have demonstrated beneficial effects of later SSTs on sleep and health; however, adolescents’ preferences for SSTs have to date never been investigated in detail. The present online survey study aimed to fill this gap and explored influencing factors. A total of 17 high schools in the Canton of Zurich, Switzerland, circulated the survey among their students. Participants were included if they reported their sex, age, and school (n = 5,308). Students indicated whether they preferred later SSTs. Additionally, five predictor blocks were assessed: sociodemographic, school‐related, sleep, leisure‐time, and health‐related characteristics. We applied multivariate logistic regression models with fixed and random effects to predict the preference. The mean (SD) age of the students was 16.09 (1.76) years (65.1% female). The majority (63.2%) endorsed later SSTs with a preferred delay of 55 min (interquartile range 25–75 min). In the multilevel analysis (n = 2,627), sex, mother tongue, sleep characteristics, mobile device use at bedtime, caffeine consumption, and health‐related quality of life were significant predictors for the preference. Hence, the majority of adolescents preferred later SSTs, and especially those with sleep or health‐related problems. These characteristics have been consistently shown to improve after delaying SSTs. Thus, also from adolescents’ view, later SSTs should be considered to improve the adolescents’ health.

The Importance of Childhood for Adult Health and Development-Study Protocol of the Zurich Longitudinal Studies

Evidence is accumulating that individual and environmental factors in childhood and adolescence should be considered when investigating adult health and aging-related processes. The data required for this is gathered by comprehensive long-term longitudinal studies. This article describes the protocol of the Zurich Longitudinal Studies (ZLS), a set of three comprehensive cohort studies on child growth, health, and development that are currently expanding into adulthood. Between 1954 and 1961, 445 healthy infants were enrolled in the first ZLS cohort. Their physical, motor, cognitive, and social development and their environment were assessed comprehensively across childhood, adolescence, and into young adulthood. In the 1970s, two further cohorts were added to the ZLS and assessed with largely matched study protocols: Between 1974 and 1979, the second ZLS cohort included 265 infants (103 term-born and 162 preterm infants), and between 1970 and 2002, the third ZLS cohort included 327 children of participants of the first ZLS cohort. Since 2019, the participants of the three ZLS cohorts have been traced and invited to participate in a first wave of assessments in adulthood to investigate their current health and development. This article describes the ZLS study protocol and discusses opportunities, methodological and conceptual challenges, and limitations arising from a long-term longitudinal cohort recruited from a study about development in early life. In the future, the ZLS will provide data to investigate childhood antecedents of adult health outcomes and, ultimately, will help respond to the frequent call of scientists to shift the focus of aging research into the first decades of life and, thus, to take a lifespan perspective on aging.

Development and Health of Adults Formerly Placed in Infant Care Institutions - Study Protocol of the LifeStories Project

A growing volume of research from global data demonstrates that institutional care under conditions of deprivation is profoundly damaging to children, particularly during the critical early years of development. However, how these individuals develop over a life course remains unclear. This study uses data from a survey on the health and development of 420 children mostly under the age of three, placed in 12 infant care institutions between 1958 and 1961 in Zurich, Switzerland. The children exhibited significant delays in cognitive, social, and motor development in the first years of life. Moreover, a follow-up of a subsample of 143 children about 10 years later revealed persistent difficulties, including depression, school related-problems, and stereotypies. Between 2019 and 2021, these formerly institutionalized study participants were located through the Swiss population registry and invited to participate once again in the research project. Now in their early sixties, they are studied for their health, further development, and life-course trajectories. A mixed-methods approach using questionnaires, neuropsychological assessments, and narrative biographical interviews was implemented by a multidisciplinary team. Combining prospective and retrospective data with standardized quantitative and biographical qualitative data allows a rich reconstruction of life histories. The availability of a community sample from the same geographic location, the 1954-1961 cohort of the Zurich Longitudinal Studies, described in detail in a paper in this issue (Wehrle et al., 2020), enables comparison with an unaffected cohort. This article describes the study design and study participants in detail and discusses the potential and limitations of a comparison with a community sample. It outlines a set of challenges and solutions encountered in the process of a lifespan longitudinal study from early childhood into the cusp of old age with a potentially vulnerable sample and summarizes the lessons learned along the way.

Impact of body mass index and socio-economic status on motor development in children and adolescents

This study assessed the impact of body mass index (BMI) and socioeconomic status (SES) on the Zurich Neuromotor Assessment, second version (ZNA-2), a battery of tests of motor development in typically developing children between 3 and 18 years of age. BMI measurements and international socio-economic index data were taken from the normative sample of the ZNA-2 for 321 children (158 boys, 163 girls) with a median age of 9.3 years. The age- and gender-adjusted motor performance of these children was quantified and grouped into five components: fine, pure, and gross motor tasks, static balance, and contralateral associated movements. A total score was also calculated. The associations of BMI and SES with the motor scores contribute to less than 5.1% of the total variance.Conclusion: The ZNA-2 for motor development is suitable for measuring motor abilities' development as it is largely independent of the BMI of the child and the SES of the family. What is Known: • Typical motor development, as measured with the Zurich Neuromotor Assessment, second edition (ZNA-2), is strongly dependent on age and gender. • The ZNA-2 focusses on motor performance, motor quality and simple motor skills. What is New: • Higher socio-economic status (SES) is associated with slightly better motor performance as measured by the ZNA-2 total score. • In the ZNA-2 less than 5.1% of the variability in motor performance is attributable to the combined effect of body mass index and SES.

The experience-dependent increase in deep sleep activity is reduced in children with attention-deficit/hyperactivity disorder

OBJECTIVE/BACKGROUND

Learning of a visuomotor adaptation task during wakefulness leads to a local increase in slow-wave activity (SWA, EEG power between 1 and 4.5 Hz) during subsequent deep sleep. Here, we examined this relationship between learning and SWA in children with attention-deficit/hyperactivity disorder (ADHD).

PATIENTS/METHODS

Participants were 15 children with ADHD (9.7-14.8 y, one female) and 15 age-matched healthy controls (9.6-15.7 y, three female). After the completion of a visuomotor adaptation task in the evening, participants underwent an all-night high-density (HD, 128 electrodes) sleep-EEG measurement.

RESULTS

Healthy control children showed the expected right-parietal increase in sleep SWA after visuomotor learning. Despite no difference in visuomotor learning, the local up-regulation during sleep was significantly reduced in ADHD patients compared to healthy controls.

CONCLUSIONS

Our results indicate that the local, experience-dependent regulation of SWA is different in ADHD patients. Because the customarily observed heightened regulation in children was related to sensitive period maturation, ADHD patients may lack certain sensitive periods or show a developmental delay.

Sensory stimulation in the treatment of children with sleep-related rhythmic movement disorder: a feasibility and acceptability study

Background

Sleep-related rhythmic movement disorder is characterized by repetitive gross-motor movements at sleep onset or during sleep, which result in clinical consequences such as impact on daytime functioning and injury. No well-established therapies exist today. Substituting the patient’s movements with external sensory stimulation may offer a treatment modality. The aim of the current study was to test the feasibility and acceptability of vestibular stimulation using a rocking bed (Somnomat) in children with rhythmic movement disorder and to assess children’s movement preference.

Methods

Children with rhythmic movement disorder (n = 6, Age: 5–14 years) were studied over three nights in a sleep laboratory: adaptation night (normal bed) and randomised-order baseline (Somnomat) and intervention nights (Somnomat). Child’s preferred movement direction (head-to-toe or side-to-side) and frequency (between 0.25 and 2 Hz), determined during an afternoon protocol, were applied using the Somnomat for 1 h after lights out, and in response to subsequent episodes of rhythmic movement during intervention nights. Comfort assessed using a questionnaire, and objective sleep parameters assessed using videosomnography, were compared.

Results

The participants’ sometimes violent rhythmic movements did not disturb device performance. All children rated intervention nights equally or more comfortable than baseline nights. Self-reported sleep quality, as well as the number and duration of movement episodes did not significantly differ between baseline and intervention nights.

Conclusions

Providing rocking movements using the Somnomat is both technically feasible and acceptable to the target population. The therapeutic value of this novel stimulus substitution for rhythmic movement disorder should now be evaluated in a larger sample over a longer period in the home setting.

Trial registration

The trial was retrospectively registered at clinicaltrials.gov (NCT03528096) on May 17th 2018.

Association of sleep characteristics with adiposity markers in children

Background Accumulating evidence suggests a relationship between sleep alterations and overweight/obesity in children. Our aim was to investigate the association of sleep measures other than obstructive sleep apnea or sleep duration with overweight/obesity and metabolic function in children. Methods We conducted a prospective cohort study in school- aged children (aged 5 to 8 years, prepubertal, and 12 to 15 years, pubertal) with overweight/obesity and normal-weight children. All children underwent a standardized in-laboratory polysomnography followed by a fasting blood assessment for glucose and metabolic testing. Subjective sleep measures were investigated by a 7-day sleep diary and questionnaire. We analyzed prepubertal and pubertal groups separately using logistic regression and partial correlation analyses. Results A total of 151 participants were analyzed. Overweight/obese children had significantly higher odds for arousal index (prepubertal children: 1.28, Confidence interval (CI): 1.06, 1.67; pubertal children: 1.65, CI: 1.19, 2.29) than normal-weight children, independent of age and gender. In prepubertal children, arousal-index was positively associated with C-peptide (r=0.30, p=0.01), whereas Minimum O2 saturation was negatively associated with triglycerides (r=-0.34, p=0.005), adjusting for age and sex. However, associations were attenuated by further adjustment for body mass index standard deviation scores (BMI-SDS). In pubertal children, higher level of apnea-hypopnea-index and pCO2 predicted increased lipoprotein (a) levels (r=0.35, p=0.03 and r=0.40, p=0.01, respectively), independent of age, sex, and BMI-SDS. A negative association was found between pCO2 and high-density lipoprotein (HDL)-cholesterol (r=-0.40, p=0.01). Conclusions Overall, we report that sleep quality as measured by arousal index may be compromised by overweight and obesity in children and warrants attention in future intervention programs.

Cardiac vagal tone in preschool children: Interrelations and the role of stress exposure

INTRODUCTION

Cardiac vagal tone has been understood as the biological correlate of emotion regulation and can be divided into emotion regulation (tonic cardiac vagal tone (TCVT)) and the flexibility to adapt to changing conditions (phasic cardiac vagal tone (PCVT)). There is evidence that TCVT influences PCVT dynamics in adults and that stress exposure impacts on cardiac vagal tone in adults and older children. The aim of the study was to investigate the impact of TCVT on PCVT dynamics in preschoolers and to identify the influence of stress exposures on cardiac vagal tone.

METHOD

Measures of heart rate variability including baseline (TCVT), during an age-adapted stress task (PCVT stress reactivity) and during recovery (PCVT recovery) were assessed in 222 children aged 2-6 years of the SPLASHY study. Further, parents were asked to complete questionnaires on early stress exposure (including pregnancy, birth and early life) and current stress exposure (including family stress and parenting).

RESULTS

Preschool children with high TCVT showed less PCVT reactivity (p < 0.001) and more increase of vagal tone (PCVT) during early recovery (p = 0.016). Further only child's low birth weight was a relevant stress exposure impacting on early and late PCVT recovery (p = 0.03/p = 0.005). None of the other early or late stress exposure conditions, nor the accumulation of stress exposures influenced TCVT or PCVT dynamics in these healthy preschoolers.

DISCUSSION

TCVT impacts on PCVT dynamics in a lab-based stress task in healthy preschool children and only low birth weight is related to more change during early and to less late PCVT recovery.

Motor Competence and Physical Activity in Early Childhood: Stability and Relationship

Background: Normal motor development and adequate levels of physical activity engagement during the early years of life form the foundation of long-term psychological and physiological health. This is one of the very few studies that investigate the stability and relationships of motor competence and physical activity in preschool children.

Methods: Baseline and 12 month follow-up data of physical activity and motor competence of 550 preschool children aged 2–6 years from the Swiss Preschoolers' Health Study were used for this work. Physical activity data, expressed in counts per minute for total physical activity and minutes per day for time spent moderately-to-vigorously physically active, were collected over 1 week using accelerometers. Motor competence was assessed with the Zurich Neuromotor Assessment. Both motor competence and physical activity were age- and sex-adjusted. To examine the individual stability of physical activity and motor competence and reciprocal cross-sectional and longitudinal effects between these two domains, a latent variable cross-lagged panel model where motor competence was represented through a latent construct was examined using structural equation modeling.

Results: A weak cross-sectional correlation of motor competence with total physical activity (r = 0.24) and moderate-to-vigorous physical activity (r = 0.23) was found. Motor competence exhibited high stability (β = 0.82) in the preschool years and physical activity was moderately stable with estimates ranging from β = 0.37 for total physical activity to β = 0.48 for moderate-to-vigorous physical activity. In contrast to the autoregressive coefficients denoting individual stability, both cross-lagged effects were negligible indicating that physical activity was not a determinant of motor competence or vice versa.

Conclusions: Motor competence and physical activity developed independently of each other in early childhood. Although measures of quantity and intensity of physical activity were not related to motor development, specific movement experiences and practice—which are not reflected by accelerometry—may be needed for skill development. Future research should focus on examining what type of physical activity is important for motor development and how to assess it, and also whether the relationship between physical activity and motor competence evolves over time.

Clinical Trial Registration: Current Controlled Trials ISRCTN41045021 (date of registration: 21.03.14)

Association of physical activity with adiposity in preschoolers using different clinical adiposity measures: a cross-sectional study

Background

More research is needed about the association between physical activity (PA), sedentary behaviour (SB), and adiposity in preschoolers, particularly using more direct clinical measures of adiposity. Therefore, the main objective of this study was to investigate the association between objectively measured PA and different clinical adiposity measures in a large sample of preschoolers.

Methods

Four hundred sixty-three predominantly normal-weight (77%) 2–6-year-old preschool children participated in the Swiss Preschoolers’ Health Study (SPLASHY). Physical activity was measured using accelerometers and was analyzed using 15-s (uni-axial) epoch length using validated cut-offs. Adiposity measures included body mass index (BMI), the sum of four skinfolds, and waist circumference (WC). Multilevel linear regression modeling, adjusted for age, sex and wear time, was used to assess the association between PA and SB with BMI, WC, and skinfold thickness.

Results

Total PA and different PA intensities were positively and SB was inversely associated with BMI in the total sample and in the normal-weight children (p < 0.05). Total PA was inversely associated with skinfold thickness in overweight and obese children (p < 0.05), while there was only a weak association for vigorous PA (p > 0.05). Moderate and moderate-to-vigorous PA were positively, and SB was negatively associated with WC in the total sample and in the normal-weight children (p < 0.05). Additional adjustment for potential sociocultural and biological confounding variables attenuated some of the results.

Conclusions

In this very young and predominantly normal-weight population, PA is positively related to BMI and WC, but this relationship is not observed in overweight and obese children. In this latter population, PA is inversely, and SB is positively related to skinfold thickness. Skinfold thickness could represent a useful and simple clinical measure of body fat in preschoolers. The role of vigorous PA in the prevention of early childhood obesity should be further investigated in future studies.

Trial registration

ISRCTN ISRCTN41045021. Retrospectively registered 06 May 2014.

Actimetry in infant sleep research: an approach to facilitate comparability

STUDY OBJECTIVES

Only standardized objective assessments reliably capture the large variability of sleep behavior in infancy, which is the most pronounced throughout the human lifespan. This is important for clinical practice as well as basic research. Actimetry is a cost-efficient method to objectively estimate infant sleep/wake behavior from limb movements. Nevertheless, the standardization of actimetry-based sleep/wake measures is limited by two factors: the use of different computational approaches and the bias towards measuring only nighttime sleep-neglecting ~20 % of sleep infants obtain during daytime. Thus, we evaluate the comparability of two commonly used actimetry algorithms in infants and propose adjustments to increase comparability.

METHODS

We used actimetry in 50 infants for 10 continuous days at ages 3, 6, and 12 months in a longitudinal approach. We analyzed the infants' sleep/wake behaviors by applying two algorithms: Sadeh and Oakley/Respironics. We compared minute-by-minute agreement and Kappa between the two algorithms, as well as the algorithms with sleep/wake measures from a comprehensive 24-hour parent-reported diary.

RESULTS

Agreement between uncorrected algorithms was moderate (77%-84%). By introducing a six-step adjustment, we increased agreement between algorithms (96%-97%) and with the diary. This decreased the difference in estimated sleep behaviors, e.g. Total Sleep Duration from 4.5 to 0.2 hours.

CONCLUSIONS

These adjustments enhance comparability between infant actimetry studies and the inclusion of parent-reported diaries allows the integration of daytime sleep. Objectively assessed infant sleep that is comparable across different studies supports the establishment of normative developmental trajectories and clinical cutoffs.

Prevalence and Predictors of Behavioral Problems in Healthy Swiss Preschool Children Over a One Year Period

Behavioral problems impair children's health but prevalence rates are scarce and persistence rates vary due to divergence in age ranges, assessment methods and varying environmental factors. The aim of this study was to assess prevalence rates of behavioral problems, their persistence over a 1-year period, and the impact of child- and parent-related factors on behavioral problems. 555 2-6-year-old healthy preschool children were assessed at baseline and 382 of the initial sample at 1-year follow-up. Assessment included questionnaires concerning behavioral problems and their potential predictors (e.g. socio-economic status or parenting style). Altogether, nearly 7% of these children showed clinically relevant behavioral problems, and 3% showed persistent symptoms. Low SES, inconsistent parenting and corporal punishment were positively associated with behavioral problems. The prevalence rates of behavioral problems in Swiss preschoolers are similar to other European countries, but persistence is still rather low within preschool age. These findings need further confirmation in longitudinal studies.

Accelerometer-derived physical activity estimation in preschoolers - comparison of cut-point sets incorporating the vector magnitude vs the vertical axis

Background

ActiGraph accelerometers are a widely used tool to objectively measure physical activity (PA) behavior in young children and several validated cut-point sets exist to estimate time spent in different PA intensities (sedentary time, light PA, moderate-to-vigorous PA). Applying different cut-point sets leads to large and meaningful differences in results. So far, only cut-point sets validated for the vertical axis have been compared and only the influence on time spent in moderate-to-vigorous PA has been analyzed.

Methods

A range of validated cut-point sets with their respective epoch length was applied to analyze cross-sectional data of the Swiss Preschoolers’ Health Study (SPLASHY): 1) Vertical axis in combination with an epoch length of 15 s (VA-15), 2) Vertical axis in combination with an epoch length of 60 s (VA-60) and 3) Vector magnitude in combination with an epoch length of 60 s (VM-60). PA was measured for eight consecutive days using ActiGraph accelerometers (wGT3X-BT). Three days were required to be included in the analysis (minimum two weekdays and one weekend-day with at least ten hours recording per day).

Results

Four hundred forty-five preschoolers (mean age 3.9 ± 0.5 years; 46% girls) had valid accelerometer measurements. A longer epoch (VA-60 vs VA-15) resulted in 2% less sedentary time (ST), 18% more light PA (LPA) and 51% less moderate-to-vigorous PA (MVPA); using the vector magnitude compared to the vertical axis (VM-60 vs VA-60) resulted in 34% less ST, 27% more LPA and 63% more MVPA (all p ≤ 0.001). Comparing all three sets of cut-points, ST ranged from 4.0 to 6.2 h, LPA from 5.1 to 7.6 h and MVPA from 0.8 to 1.6 h.

Conclusions

Estimated time spent in different PA intensities was strongly influenced by the choice of cut-point sets. Both, axis selection and epoch length need to be considered when comparing different studies especially when they relate PA behavior to health. The differences in the prevalence of children fulfilling PA guidelines highlight the relevance of these findings.

Trial registration

Current Controlled Trials ISRCTN41045021 (date of registration: 21.03.2014).

Electronic supplementary material

The online version of this article (10.1186/s12889-019-6837-7) contains supplementary material, which is available to authorized users.

A quick and qualitative assessment of gross motor development in preschool children

There is a need for a quick, qualitative, reliable, and easy tool to assess gross motor development for practitioners. The aim of this cross-sectional study is to present the Zurich Neuromotor Assessment-Q (ZNA-Q), which assesses static and dynamic balance in children between 3 and 6 years of age in less than 5 min. A total of 216 children (103 boys; 113 girls; median age 4 years, 4 months; interquartile range 1 year, 3 months) were enrolled from day-care centers, kindergartens, and schools, and were tested with 5 different gross motor tasks: standing on one leg, tandem stance, hopping on one leg, walking on a straight line, and jumping sideways. All ordinal measures (consisting of qualitative measures and scales) featured a marked developmental trend and substantial inter-individual variability. Test-retest reliability was assessed on 37 children. It varied from .17 for tandem stance to .43 for jumping sideways for the individual tasks, and it was .41 and .67 for the static and dynamic balance components, respectively. For the whole ZNA-Q, test-retest reliability was .7.Conclusion: Ordinal scales enable practitioners to gather data on children's gross motor development in a fast and uncomplicated way. It offers the practitioner with an instrument for the exploration of the current developmental motor status of the child. What is Known: • Measurement of gross motor skills in the transitional period between motor mile stones and quantitative assessments is difficult. • Assessment of gross motor skills is relatively easy. What is New: • Supplementary and quick gross motor test battery for children for practitioners. • Normative values of five gross motor skills measured with ordinal scales.

A Novel Approach to Assess Sleep-Related Rhythmic Movement Disorder in Children Using Automatic 3D Analysis

Background: Unlike other episodic sleep disorders in childhood, there are no agreed severity indices for rhythmic movement disorder. While movements can be characterized in detail by polysomnography, in our experience most children inhibit rhythmic movement during polysomnography. Actigraphy and home video allow assessment in the child's own environment, but both have limitations. Standard actigraphy analysis algorithms fail to differentiate rhythmic movements from other movements. Manual annotation of 2D video is time consuming. We aimed to develop a sensitive, reliable method to detect and quantify rhythmic movements using marker free and automatic 3D video analysis. Method: Patients with rhythmic movement disorder (n = 6, 4 male) between age 5 and 14 years (M: 9.0 years, SD: 4.2 years) spent three nights in the sleep laboratory as part of a feasibility study (https://clinicaltrials.gov/ct2/show/NCT03528096). 2D and 3D video data recorded during the adaptation and baseline nights were analyzed. One ceiling-mounted camera captured 3D depth images, while another recorded 2D video. We developed algorithms to analyze the characteristics of rhythmic movements and built a classifier to distinguish between rhythmic and non-rhythmic movements based on 3D video data alone. Data from 3D automated analysis were compared to manual 2D video annotations to assess algorithm performance. Novel indices were developed, specifically the rhythmic movement index, frequency index, and duration index, to better characterize severity of rhythmic movement disorder in children. Result: Automatic 3D video analysis demonstrated high levels of agreement with the manual approach indicated by a Cohen's kappa >0.9 and F1-score >0.9. We also demonstrated how rhythmic movement assessment can be improved using newly introduced indices illustrated with plots for ease of visualization. Conclusion: 3D video technology is widely available and can be readily integrated into sleep laboratory settings. Our automatic 3D video analysis algorithm yields reliable quantitative information about rhythmic movements, reducing the burden of manual scoring. Furthermore, we propose novel rhythmic movement disorder severity indices that offer a means to standardize measurement of this disorder in both clinical and research practice. The significance of the results is limited due to the nature of a feasibility study and its small number of samples. A larger follow up study is needed to confirm presented results.

Childcare Correlates of Physical Activity, Sedentary Behavior, and Adiposity in Preschool Children: A Cross-Sectional Analysis of the SPLASHY Study

Background

The childcare (CC) environment can influence young children's physical activity (PA), sedentary behavior (SB), and adiposity. The aim of the study was to identify a broad range of CC correlates of PA, SB, and adiposity in a large sample of preschoolers.

Methods

476 preschool children (mean age 3.9 yrs; 47% girls) participated in the Swiss Preschoolers' Health Study (SPLASHY). PA and SB were measured by accelerometry. Outcome measures included total PA (TPA), moderate-to-vigorous PA (MVPA), SB, body mass index (BMI), and skinfold thickness (SF). PA measures consisted of both daily PA during CC attendance days and overall daily PA (CC and non-CC days).

Results

We identified the following CC correlates for higher TPA and/or higher MVPA or lower SB during CC attendance days: older age, sex (boys), more frequent child-initiated interactions during CC, mixing different ages within a group, and the presence of a written PA policy in the CC (all p ≤ 0.02). The CC correlates for overall TPA and/or MVPA or lower overall SB including both CC and non-CC days were the following: older age, sex (boys), more frequent child-initiated interactions during CC, mixing different ages within a group, less parental PA involvement in the CC, and having a larger surface area in CC (all p ≤ 0.046). Correlates for lower SF were sex (boys) and parental PA involvement in the CC (all p ≤ 0.02), and, for lower BMI, only increased age (p=0.001) was a correlate.

Conclusions

More frequent child-initiated interactions and mixing different ages in CC, the presence of a written PA policy, and a larger CC surface are correlates of PA and SB during CC attendance days and/or of overall PA. Parental involvement in CC PA projects was a correlate for reduced body fat. These novel factors are mostly modifiable and can be tackled/addressed in future interventions.

Predictors of Executive Functions in Preschoolers: Findings From the SPLASHY Study

Executive functions (EFs) have been reported to play a crucial role in children's development, affecting their academic achievement, health, and quality of life. This study examined individual and interpersonal predictors for EFs in 555 typically developing preschool children aged 2-6 years. Children were recruited from 84 child care centers in the German- and French-speaking parts of Switzerland within the Swiss Preschoolers' Health Study (SPLASHY). A total of 20 potential predictors were assessed at the first measurement (T1). These included eight demographic/biological predictors, such as socioeconomic status, preterm birth, physical activity, and motor skills; six psychological predictors, such as hyperactivity, visual perception, and emotionality; and six interpersonal predictors, such as parenting style and stress, presence of siblings, and days spent in the child care center. The predictive value of these variables on EFs 1 year later (T2) was assessed using both standard multiple regression analysis and penalized regression to avoid overfitting due to the number of potential predictors. Female sex (β = 0.14), socio-economic status (β = 0.15), fine motor skills (β = 0.17), visual perception at T1 (β = 0.16), and EFs at T1 (β = 0.30) were all associated with EFs at T2, exhibiting small to medium effect sizes. All predictors together accounted for 31% of the variability in EFs. However, none of the interpersonal predictors were significant. Thus, we conclude that most of the factors that can predict EFs in preschool age are individual variables, and these tend to be more difficult to influence than interpersonal factors. In fact, children from families with low socio-economic status may be particularly vulnerable to poor EFs. Furthermore, encouraging fine motor skills early in life may support the development of EFs.

Age-Adapted Stress Task in Preschoolers Does not Lead to Uniform Stress Responses

Acute stress response measures serve as an indicator of physiological functioning, but have previously led to contradictory results in young children due to age-related cortisol hypo-responsivity and methodological inconsistencies in assessment. The aim of this study was to investigate stress responses during a validated age-adapted socio-evaluative stress task in children aged 2-6 years in a child care environment and to detect socio-demographic, task- and child-related characteristics of stress responses. Stress responses were assessed in 323 children for salivary cortisol and salivary alpha amylase (sAA), and in 328 children for changes in heart rate variability (HRV). These data were then associated with socio-demographic (e.g. SES), task-related (e.g. task length) and child-related characteristics (e.g. self-regulation) of stress responses using multilevel models. Analyses revealed elevated sympathetic reactivity (sAA: Coeff=0.053, p=0.004) and reduced HRV (Coeff=-0.465, p<0.001), but no hypothalamic-pituitary-adrenal (HPA) response (Coeff=0.017, p=0.08) during the stress task. Child's age (Coeff=-5.82, p<0.001) and movement during the task (Coeff=-0.17, p=0.015) were associated with acute cortisol release, while diurnal sAA was associated with acute sAA release (Coeff=0.24, p<0.001). Age (Coeff=-0.15, p=0.006) and duration of the task (Coeff=0.13, p=0.015) were further associated with change of HRV under acute stress condition. Children showed inconsistent stress responses which contradicts the assumption of a parallel activation of both stress systems in a valid stress task for young children and might be explained by a pre-arousal to the task of young children in a child care setting. Further results confirm that child- and task-related conditions need to be considered when assessing stress responses in these young children.

Neuromotor development in children. Part 4: new norms from 3 to 18 years

AIM

The aim of this cross-sectional study was to provide normative data for motor proficiency (motor performance and contralateral associated movements [CAMs]) in typically developing children between 3 years and 18 years of age using an updated version of the Zurich Neuromotor Assessment (ZNA-2).

METHOD

Six-hundred and sixteen typically developing children between 3 years and 18 years of age were enrolled from day-care centres, kindergartens, and schools, and were tested using the ZNA-2 with improved items of the original battery. Motor proficiency was assessed on five components (fine motor tasks, pure motor tasks, static balance, dynamic balance, and CAMs) as a function of age and sex to determine centile curves for each task. Intraobserver, interobserver, and test-retest reliabilities were evaluated.

RESULTS

Most ZNA-2 tasks featured a marked developmental trend and substantial interindividual variability. Test-retest reliability was generally high (e.g. static balance 0.67; CAMs 0.81; and total scores 0.84).

INTERPRETATION

The ZNA-2 is a reliable and updated test instrument to measure motor proficiency in children from 3 to 18 years with improved properties for assessing motor performance. It allows continuous measurement without changing items for the entire age range; this feature of the ZNA-2 is unique and makes the instrument suitable for clinical purposes. The reduction of CAMs scoring simplifies the clinical procedure and increases its reliability.

WHAT THIS PAPER ADDS

The Zurich Neuromotor Assessment, Second Edition (ZNA-2) provides new norms for motor proficiency in children between 3 years and 18 years. High reliabilities suggest that the revised test battery is a useful tool for assessing neuromotor development. Integration of a 'not able to perform' category makes the ZNA-2 suitable for clinical purposes.

Traveling Slow Oscillations During Sleep: A Marker of Brain Connectivity in Childhood

Slow oscillations, a defining characteristic of the nonrapid eye movement sleep electroencephalogram (EEG), proliferate across the scalp in highly reproducible patterns. In adults, the propagation of slow oscillations is a recognized fingerprint of brain connectivity and excitability. In this study, we (1) describe for the first time maturational features of sleep slow oscillation propagation in children (n = 23; 2-13 years) using high-density (hd) EEG and (2) examine associations between sleep slow oscillatory propagation characteristics (ie, distance, traveling speed, cortical involvement) and white matter myelin microstructure as measured with multicomponent Driven Equilibrium Single Pulse Observation of T1 and T2-magnetic resonance imaging (mcDESPOT-MRI). Results showed that with increasing age, slow oscillations propagated across longer distances (average growth of 0.2 cm per year; R(21) = 0.50, p < .05), while traveling speed and cortical involvement (ie, slow oscillation expanse) remained unchanged across childhood. Cortical involvement (R(20) = 0.44) and slow oscillation speed (R(20) = -0.47; both p < .05, corrected for age) were associated with myelin content in the superior longitudinal fascicle, the largest anterior-posterior, intrahemispheric white matter connectivity tract. Furthermore, slow oscillation distance was moderately associated with whole-brain (R(21) = 0.46, p < .05) and interhemispheric myelin content, the latter represented by callosal myelin water fraction (R(21) = 0.54, p < .01, uncorrected). Thus, we demonstrate age-related changes in slow oscillation propagation distance, as well as regional associations between brain activity during sleep and the anatomical connectivity of white matter microstructure. Our findings make an important contribution to knowledge of the brain connectome using a noninvasive and novel analytic approach. These data also have implications for understanding the emergence of neurodevelopmental disorders and the role of sleep in brain maturation trajectories.

Physical activity and sedentary behavior in preschoolers: a longitudinal assessment of trajectories and determinants

BACKGROUND

Despite physical activity (PA) being recognized as a critically important factor for good physical and mental health already early in life and throughout the life course, prospective data on activity behavior during the preschool years remains scarce. This study examined trajectories and determinants of levels and change in total PA (TPA), moderate-to-vigorous PA (MVPA) and sedentary behavior (SB) in a representative sample of Swiss preschoolers.

METHODS

Data were drawn from the Swiss Preschoolers' Health Study (SPLASHY), a multi-site prospective cohort study including 555 children (53% boys) aged 2-to-6 years at baseline. A follow-up was conducted after 12 months. Activity behavior was measured using accelerometers. Information on 35 potential determinants from different socio-ecological domains was either directly measured or parent-reported. Trajectories of TPA, MVPA and SB over time were described for boys and girls. Linear mixed models were used to investigate factors that predicted levels and change in TPA, MVPA and SB.

RESULTS

All children were sufficiently physically active according to published recommendations for preschoolers. Trajectory profiles revealed a marked increase in TPA and MVPA in boys and girls whereas SB remained fairly stable over time. Mixed modeling demonstrated that variables most relevant to determining PA levels were sex, age and activity temperament (all positively associated). Together with gross motor skills, birth weight, family structure (only for TPA) and season (only for MVPA), these factors accounted for 26 and 32% of total variance explained in TPA and MVPA, respectively. Activity temperament emerged as the strongest determinant of SB (negative association) and explained with sex, season and family structure 20% of total variance in SB. The presence of older siblings was the only factor that predicted change in PA over time.

CONCLUSIONS

In this healthy physically active cohort of preschoolers, non-modifiable individual-level factors had the greatest influence on PA. The limited success of this and previous studies to identify modifiable determinants and the finding that most preschoolers were sufficiently active suggest that future attempts should provide insights into how preschoolers' activity levels can be maintained and fostered to prevent subsequent harmful declines attributable, amongst others, to educational transitions. Thus, good-quality longitudinal studies are needed.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN41045021 (date of registration: 21.03.14).

Interventions to Promote Fundamental Movement Skills in Childcare and Kindergarten: A Systematic Review and Meta-Analysis

BACKGROUND

Proficiency in fundamental movement skills (FMS) lays the foundation for being physically active and developing more complex motor skills. Improving these motor skills may provide enhanced opportunities for the development of a variety of perceptual, social, and cognitive skills.

OBJECTIVE

The objective of this systematic review and meta-analysis was to assess the effects of FMS interventions on actual FMS, targeting typically developing young children.

METHOD

Searches in seven databases (CINAHL, Embase, MEDLINE, PsycINFO, PubMed, Scopus, Web of Science) up to August 2015 were completed. Trials with children (aged 2-6 years) in childcare or kindergarten settings that applied FMS-enhancing intervention programs of at least 4 weeks and meeting the inclusion criteria were included. Standardized data extraction forms were used. Risk of bias was assessed using a standard scoring scheme (Effective Public Health Practice Project-Quality Assessment Tool for Quantitative Studies [EPHPP]). We calculated effects on overall FMS, object control and locomotor subscales (OCS and LMS) by weighted standardized mean differences (SMDbetween) using random-effects models. Certainty in training effects was evaluated using GRADE (Grading of Recommendations Assessment, Development, and Evaluation System).

RESULTS

Thirty trials (15 randomized controlled trials and 15 controlled trials) involving 6126 preschoolers (aged 3.3-5.5 years) revealed significant differences among groups in favor of the intervention group (INT) with small-to-large effects on overall FMS (SMDbetween 0.46), OCS (SMDbetween 1.36), and LMS (SMDbetween 0.94). Our certainty in the treatment estimates based on GRADE is very low.

CONCLUSIONS

Although there is relevant effectiveness of programs to improve FMS proficiency in healthy young children, they need to be interpreted with care as they are based on low-quality evidence and immediate post-intervention effects without long-term follow-up.

Theta waves in children's waking electroencephalogram resemble local aspects of sleep during wakefulness

Vyazovskiy and colleagues found in rats’ multi-unit recordings brief periods of silence (off-states) in local populations of cortical neurons during wakefulness which closely resembled the characteristic off-states during sleep. These off-states became more global and frequent with increasing sleep pressure and were associated with the well-known increase of theta activity under sleep deprivation in the surface EEG. Moreover, the occurrence of such off-states was related to impaired performance. While these animal experiments were based on intracranial recordings, we aimed to explore whether the human surface EEG may also provide evidence for such a local sleep-like intrusion during wakefulness. Thus, we analysed high-density wake EEG recordings during an auditory attention task in the morning and evening in 12 children. We found that, theta waves became more widespread in the evening and the occurrence of widespread theta waves was associated with slower reaction times in the attention task. These results indicate that widespread theta events measured on the scalp might be markers of local sleep in humans. Moreover, such markers of local sleep, seem to be related to the well described performance decline under high sleep pressure.

Contralateral Associated Movements Correlate with Poorer Inhibitory Control, Attention and Visual Perception in Preschool Children

Contralateral associated movements (CAMs) frequently occur in complex motor tasks. We investigated whether and to what extent CAMs are associated with inhibitory control among preschool children in the Swiss Preschoolers' Health Study. Participants were 476 healthy, typically developing children (mean age = 3.88 years; 251 boys) evaluated on two consecutive afternoons. The children performed the Zurich Neuromotor Assessment, the statue subtest of the Neuropsychological Assessment for Children (NEPSY), and cognitive tests of the Intelligence and Development Scales-Preschool (IDS-P). CAMs were associated with poor inhibitory control on the statue test and poor selective attention and visual perception on the IDS-P. We attributed these findings to preschoolers' general immaturity of the central nervous system.

Low-Level Chromosomal Mosaicism in Neurodevelopmental Disorders

Chromosomal mosaicism, which represents a diagnostic challenge for detection and interpretation, has been described in several genetic conditions. It can contribute to a large phenotypic variation in diseases. At analysis of a well-characterized cohort of 714 patients with neurodevelopmental disorders (NDDs) of unknown etiology using a high-resolution chromosomal microarray platform, we found 2 cases (0.28%) of low-level mosaicism and defined a previously detected extra chromosome in a third patient. Two of the cases were mosaics for segmental imbalances (a partial trisomy 3q26.1q27.3 and a partial monosomy 18q21.2qter with 14.6 and 20% mosaic ratios in lymphocytes, respectively), and 1 was a mosaic for an entire chromosome (trisomy 14, mosaic ratio 20%). Our diagnostic yield is in line with the ratios previously published in patients with intellectual disability. Notably, the partial trisomy 3q26.1q27.3 case is an example of a rare and unusual class of a rearranged neocentric ring chromosome, which can neither be categorized in class I, nor in class II of such rearrangements. Our cases further elucidate the phenotypes related to the aberrations of the specific chromosome segments observed and underline the important role of low-level mosaics in the pathogenesis of NDDs of unknown etiology even in the absence of clinical signs of mosaicism.

Relation of Heart Rate and its Variability during Sleep with Age, Physical Activity, and Body Composition in Young Children

Background: Recent studies have claimed a positive effect of physical activity and body composition on vagal tone. In pediatric populations, there is a pronounced decrease in heart rate with age. While this decrease is often interpreted as an age-related increase in vagal tone, there is some evidence that it may be related to a decrease in intrinsic heart rate. This factor has not been taken into account in most previous studies. The aim of the present study was to assess the association between physical activity and/or body composition and heart rate variability (HRV) independently of the decline in heart rate in young children.

Methods: Anthropometric measurements were taken in 309 children aged 2–6 years. Ambulatory electrocardiograms were collected over 14–18 h comprising a full night and accelerometry over 7 days. HRV was determined of three different night segments: (1) over 5 min during deep sleep identified automatically based on HRV characteristics; (2) during a 20 min segment starting 15 min after sleep onset; (3) over a 4-h segment between midnight and 4 a.m. Linear models were computed for HRV parameters with anthropometric and physical activity variables adjusted for heart rate and other confounding variables (e.g., age for physical activity models).

Results: We found a decline in heart rate with increasing physical activity and decreasing skinfold thickness. HRV parameters decreased with increasing age, height, and weight in HR-adjusted regression models. These relationships were only found in segments of deep sleep detected automatically based on HRV or manually 15 min after sleep onset, but not in the 4-h segment with random sleep phases.

Conclusions: Contrary to most previous studies, we found no increase of standard HRV parameters with age, however, when adjusted for heart rate, there was a significant decrease of HRV parameters with increasing age. Without knowing intrinsic heart rate correct interpretation of HRV in growing children is impossible.

Correlates of preschool children's objectively measured physical activity and sedentary behavior: a cross-sectional analysis of the SPLASHY study

BACKGROUND

Identifying ways to promote physical activity and decrease sedentary time during childhood is a key public health issue. Research on the putative influences on preschool children's physical activity (PA) and sedentary behavior (SB) is limited and has yielded inconsistent results. Our aim was to identify correlates of PA and SB in preschool children.

METHODS

Cross-sectional data were drawn from the Swiss Preschoolers' Health Study (SPLASHY), a Swiss population-based cohort study. Of 476 two to six year old children, 394 (54% boys) had valid PA data assessed by accelerometry. Information on exposure data was directly measured or extracted from parental questionnaires. Multilevel linear regression modeling was used to separately assess associations between 35 potential correlates and total PA (TPA), moderate-to-vigorous PA (MVPA) and SB.

RESULTS

In total, 12 correlates from different domains were identified. TPA and MVPA were greater in boys than girls, increased with age and were positively associated with gross motor skills. Children from single parent families had a higher level of TPA and spent less time sedentary than those living with two parents. Time spent outdoors was positively associated with TPA and negatively with SB. The child's activity temperament was related all three outcomes, whereas parental sports club membership, living area per person and neighborhood safety were associated with SB only. Fixed and random factors in the final models accounted for 28%, 32% and 22% of the total variance in TPA, MVPA and SB, respectively. Variance decomposition revealed that age, sex and activity temperament were the most influential correlates of both, TPA and MVPA, whereas the child's activity temperament, time outdoors and neighborhood safety were identified as the most important correlates of SB.

CONCLUSIONS

A multidimensional set of correlates of young children's activity behavior has been identified. Personal factors had the greatest influence on PA, whereas environmental-level factors had the greatest influence on SB. Moreover, we identified a number of previously unreported, potentially modifiable correlates of young children's PA and SB. These factors could serve to define target groups or become valuable targets for change in future interventions.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN41045021 (date of registration: 21.03.14).

Association between Body Composition and Motor Performance in Preschool Children

OBJECTIVE

Being overweight makes physical movement more difficult. Our aim was to investigate the association between body composition and motor performance in preschool children.

METHODS

A total of 476 predominantly normal-weight preschool children (age 3.9 ± 0.7 years; m/f: 251/225; BMI 16.0 ± 1.4 kg/m2) participated in the Swiss Preschoolers' Health Study (SPLASHY). Body composition assessments included skinfold thickness, waist circumference (WC), and BMI. The Zurich Neuromotor Assessment (ZNA) was used to assess gross and fine motor tasks.

RESULTS

After adjustment for age, sex, socioeconomic status, sociocultural characteristics, and physical activity (assessed with accelerometers), skinfold thickness and WC were both inversely correlated with jumping sideward (gross motor task β-coefficient -1.92, p = 0.027; and -3.34, p = 0.014, respectively), while BMI was positively correlated with running performance (gross motor task β-coefficient 9.12, p = 0.001). No significant associations were found between body composition measures and fine motor tasks.

CONCLUSION

The inverse associations between skinfold thickness or WC and jumping sideward indicates that children with high fat mass may be less proficient in certain gross motor tasks. The positive association between BMI and running suggests that BMI might be an indicator of fat-free (i.e., muscle) mass in predominately normal-weight preschool children.