Der Mittagsschlaf im Kindergartenalter

Due to changes in legal regulation, the number of daycare facilities for children in Germany has increased in recent. There is uncertainty of dealing with regards to the benefit of napping in these facilities from the side of the caregivers and the parents. The prevalence of napping in children aged between three and six years depends mostly on environmental factors, such as the attitude of the caregivers and the parents. That’s why there are big differences in the prevalence of napping between countries. Some children of this age seem still to profit from extra sleep for their emotional and cognitive development. Just 45 min seem to be sufficient. Children who skip their nap seem not to need it anymore, because they don’t profit from it. To force these children to take a nap, a very long nap or a very late nap could result in sleep disturbances the following night. A sustained nighttime sleep is probably more important than a long nap.     

An ultra short episode of sleep is sufficient to promote declarative memory performance

Various studies have demonstrated that a night of sleep has a beneficial effect on the retention of previously acquired declarative material. In two experiments, we addressed the question of whether this effect extends to daytime naps. In the first experiment we assessed free recall of a list of 30 words after a 60 min retention interval that was either filled with daytime napping or waking activity. Memory performance was significantly enhanced after napping as opposed to waking but was not correlated with time spent in slow wave sleep or total sleep time within the napping condition. The second experiment was designed to clarify the role of total sleep time and therefore included an additional third group, which was allowed to nap for no longer than 6 min on average. In comparing word recall after conditions of no napping (waking), short napping, and long napping, we found superior recall for both nap conditions in contrast to waking as well as for long naps in contrast to short naps. These results demonstrate that even an ultra short period of sleep is sufficient to enhance memory processing. We suggest that the mere onset of sleep may initiate active processes of consolidation which - once triggered - remain effective even if sleep is terminated shortly thereafter.     

Impact of total sleep duration on blood pressure in preschool children

The onset of some adult diseases, e.g., cardiovascular disease, is known to be associated with lifestyles in childhood. The objective of this study was to clarify the relationship between total sleep duration (TSD) and systolic and diastolic blood pressure (SBP and DBP) among 117 children at ages 5-6 years. Parents reported their children's typical bedtimes and wake times for weekdays, and questions about mandatory nap times were answered by the preschool teachers. In the children, the mean TSD, SBP, and DBP were 624 +/- 57 (standard deviation) min, 99 +/- 10 mmHg, and 62 +/- 9 mmHg, respectively. When the children were divided into quartile groups based on TSD, the SBP was significantly higher in the highest group (TSD > 660 min) than in the lowest group (TSD < or = 585 min). The TSD was significantly correlated with SBP (r = 0.265) but not with DBP (r = 0.105), these relationships were similar when TSD and possible confounders such as age and body mass index were set as independent variables of multiple regression analysis. These findings suggest that sleep duration in preschool children is associated with SBP, and extremely short or long sleep may invite subclinical health problems.     

The Alerting Effects of Naps in Sleep-Deprived Subjects

The effect of napping for varying durations after one night of sleep deprivation was examined. Sleep latency tests were used to determine levels of sleepiness/alertness at 2, 4, 6, and 8 hrs following a morning nap of 0, 15, 30, 60, or 120 min duration. Ten normal-sleeping, young adult volunteers spent two consecutive days and the intervening night in the sleep laboratory on each of five weeks. Baseline sleep latencies were recorded the first day, sleep was deprived that night, a nap was taken at 0900 hrs, and sleep latencies were again recorded on the second day. The naps had differential alerting effects related to their duration, but none of the naps returned mean sleep latency for the 8 hrs to its basal levels. Alertness increased with nap duration, reaching its highest level with a 60-min nap; the 120-min nap was no more alerting than the 60-min nap. During the second hour of the 120-min nap, sleep became more fragmented with more shifts to stage 1 sleep or wake. Increased alertness was not strongly related to the sleep stage composition of the naps, the best predictor being minutes of slow wave sleep. Increased alertness was not detected until the second latency test 4 hrs after napping.     

The cortisol awakening response (CAR) in 2- to 4-year-old children: effects of acute nighttime sleep restriction, wake time, and daytime napping

The cortisol awakening response (CAR) is presumed critically important for healthy adaptation. The current literature, however, is hampered by systematic measurement difficulties relative to awakening, especially with young children. While reports suggest the CAR is smaller in children than adults, well‐controlled research in early childhood is scarce. We examined whether robust CARs exist in 2‐ to 4‐year‐old children and if sleep restriction, wake timing, and napping influence the CAR (n = 7). During a 25‐day in‐home protocol, researchers collected four salivary cortisol samples (0, 15, 30, 45 min post‐wake) following five polysomnographic sleep recordings on nonconsecutive days after 4 hr (morning nap), 7 hr (afternoon nap), 10 hr (evening nap), 13 hr (baseline night), and 16 hr (sleep restriction night) of wakefulness (20 samples/child). The CAR was robust after nighttime sleep, diminished after sleep restriction, and smaller but distinct after morning and afternoon (not evening) naps. Cortisol remained elevated 45 min after morning and afternoon naps. © 2011 Wiley Periodicals, Inc. Dev Psychobiol 54:412–422, 2012.     

A cross-sectional study of children and their families in different child care environments: Some data and conclusions

This study compared children and families involved in four child care environments—all day center care (n = 35), all day sitter (family) care (n = 15), partial center/sitter-home (mixed) care (n = 31), and exclusive at home care (n = 43). These 124 two-parent families were predominately white and middle class. Measures included the Peabody Picture Vocabulary Test, the Illinois Test of Psycholinguistic Abilities, a preschool test, a social developmental scale, indices of parent-child interactions, parental engagement in child care tasks and household chores, leisure time activity, behavior management style, quality of center care, and length of time in care outside the home. Demographic differences (SES, race, age of child, birth order, number of children in the family, wife's age, and wife working) that existed between the groups were seen as representing particularly important, naturally occurring social patterns, and therefore were separately analyzed and presented. The results indicated that the mixed group tended to score higher than the other groups on measures of intellectual ability, but it was nuclear whether these differences reflected the higher SES of this group or the partial child care situation. The day care and at-home groups were well matched and did not differ significantly on child measures. Greater paternal involvement in child and home care was associated with the use of child care outside the home and maternal employment. Lower SES was significantly related to lower Peabody scores, a more punitive discipline style, and more time spent in child care outside the home. Number of children in the family showed a curvilinear relationship (high scores = two children) with some ITPA scales; and a pattern of low ITPA scores for only children emerged. The results were discussed in terms of developing methodologies to examine the interrelationships of family patterns and child care modalities, the design and evaluation of day care centers, and some social policy implications of the effects of SES on child development.     

Development of nap neurophysiology: preliminary insights into sleep regulation in early childhood

Although all young children nap, the neurophysiological features and associated developmental trajectories of daytime sleep remain largely unknown. Longitudinal studies of napping physiology are fundamental to understanding sleep regulation during early childhood, a sensitive period in brain and behaviour development and a time when children transition from a biphasic to a monophasic sleep–wakefulness pattern. We investigated daytime sleep in eight healthy children with sleep electroencephalography (EEG) assessments at three longitudinal points: 2 years (2.5–3.0 years), 3 years (3.5–4.0 years) and 5 years (5.5–6.0 years). At each age, we measured nap EEG during three randomized conditions: after 4 h (morning nap), 7 h (afternoon nap) and 10 h (evening nap) duration of prior wakefulness. Developmental changes in sleep were most prevalent in the afternoon nap (e.g. decrease in sleep duration by 30 min from 2 to 3 years and by 20 min from 3 to 5 years). In contrast, nap sleep architecture (% of sleep stages) remained unchanged across age. Maturational changes in non‐rapid eye movement sleep EEG power were pronounced in the slow wave activity (SWA, 0.75–4.5 Hz), theta (4.75–7.75 Hz) and sigma (10–15 Hz) frequency ranges. These findings indicate that the primary marker of sleep depth, SWA, is less apparent in daytime naps as children mature. Moreover, our fundamental data provide insight into associations between sleep regulation and functional modifications in the central nervous system during early childhood.     

Integrating nap and night‐time sleep into sleep patterns reveals differential links to health‐relevant outcomes

Both night‐time sleep and nap behaviour have been linked consistently to health outcomes. Although reasons for napping are usually tied to night‐time sleep, the majority of studies assess their effects independently. The current study thus aimed to examine the health relevance of patterns of sleep behaviour that take into account both night‐time and daytime sleep habits. Night‐time sleep, recorded during 7 days via actigraphy from 313 participants (aged 34–82 years) of the Midlife in the United States II Biomarker study, was assessed. Blood and urine specimens were assayed for noradrenaline, interleukin‐6 and C‐reactive protein. Participants self‐reported nap behaviour, depressive symptoms, perceived chronic stress and the presence of medical symptoms and conditions. Overall, nappers (n = 208) showed elevated waist–hip ratios, C‐reactive protein and interleukin‐6 levels compared to non‐nappers and reported more physiological symptoms and conditions (all P ≤ 0.019). Within nappers, cluster analysis revealed three patterns of sleep behaviour—infrequent nappers with good night‐time sleep, frequent nappers with good night‐time sleep and nappers with poor night‐time sleep. Nappers with poor night‐time sleep thereby exhibited elevated noradrenaline levels, depressive symptoms and perceived stress scores compared to other groups (all P ≤ 0.041). These findings support the idea that nap–health relationships are complex, in that frequency of napping and accumulation of nap sleep is not related linearly to health consequences. Assessing nap behaviour in conjunction with night‐time sleep behaviour appeared crucial to elucidate further the health relevance of napping, particularly in terms of psychological health outcomes, including chronic stress and depressive symptoms.     

Napping versus Resting: Effects on Performance and Mood

In order to determine the effects of napping and resting on mood and performance for nappers and nonnappers, 48 habitual nappers and 46 habitual nonnappers were randomly assigned to take a nap, to rest in bed without falling asleep, or to watch a neutral videotape (control group). Measurements were obtained from a 10-min auditory reaction time task, a 10-min addition task, and three self-report mood measures 15 min before and after each condition. Subjects in the nap and rest conditions had electrodes attached for recording EEG, EOG, and EMG during the hour-long treatments. Results showed that napping and resting served to improve mood regardless of whether a person habitually naps or not. Sleep itself may not be crucial in improving mood; what may be more important is the period of relaxation common to napping and resting in bed. Overall, performance measures were not affected by either napping or resting.     

Rising cortisol at childcare: relations with nap, rest, and temperament

An unexpected rise in cortisol across the day in full-day, center-based childcare has been recently observed. Most of the children in these studies exhibited the rise across the day at childcare, but the expected drop at home. Possible explanations include more or less napping at childcare than at home. This study measured cortisol during childcare at 10:30 a.m., pre-rest, post-rest, and 3:30 p.m. for 35 children, and at 10:30 a.m. and 3:30 p.m. at home for 8 children. Duration and quality of rest were coded during nap periods. For 91% of children, cortisol rose at childcare and for 75% dropped at home. None of the napping variables were related to the rise at childcare nor were differences found between home and childcare rest. Factors other than daytime rest periods seem likely to account for the rise in cortisol across the childcare day, possibly factors involving the interactional demands of group settings during this developmental period.     

Effects of napping on cognitive function modulation in elderly adults with a morning chronotype: A nationwide survey

Circadian rhythms and napping habits have been associated with cognitive function; however, little is known about the interaction effects on cognitive function. The present study examined the moderating effects of napping habits on the relationship between chronotypes and cognitive function decline in elderly adults. This cross‐sectional study analysed data from the 2009 Taiwan National Health Interview Survey. A total of 1,724 elderly adults (aged ≥65 years) were included. Cognitive function was determined by the Mini‐Mental State Examination. Participants’ chronotypes were assessed using the midpoint of sleep. Napping habits were assessed by self‐report questions. Demographic data, health‐related factors and sleep characteristics of the participants were also assessed as potential confounding factors. A hierarchical regression will be used to test the moderating role of napping habits in the relationship between chronotype and cognitive function level after adjustment for potential confounders. A significant interaction effect between chronotype and napping habits was observed with the MMSE score (b = ?0.29, SE = 0.14, p = 0.03). Morning‐type elderly patients with nap durations >60 min exhibited significantly higher MMSE scores than non‐nappers (F = 7.48; p = 0.00). This nationwide survey confirms that in morning‐type elderly adults, nap durations >60 min are associated with less cognitive decline; however, napping habits are not associated with cognitive function level in evening‐type and intermediate‐type elderly adults.     

The effect of nap frequency on daytime sleep architecture

It is well documented that the quality and quantity of prior sleep influence future sleep. For instance, nocturnal sleep restriction leads to an increase in slow wave sleep (SWS) (i.e. SWS rebound) during a subsequent sleep period. However, few studies have examined how prior napping affects daytime sleep architecture. Because daytime naps are recommended for management of disrupted sleep, understanding the impact of napping on subsequent sleep may be important. We monitored sleep-wake patterns for one week with actigraphy followed by a 75-minute polysomnographically-recorded nap. We found that greater nap frequency was correlated with increased Stage 1 and decreased SWS. We categorized subjects based on nap frequency during the prior week (0 nap, 1 to 2 naps, and 3 to 4 naps) and found differences in Stage 1, Stage 2, and SWS between groups. Subjects who took no naps had the greatest amount of SWS, those who took 1 to 2 naps had the most Stage 2 sleep, and those who took 3 to 4 naps had the most Stage 1. While correlations were not found between nap frequency and nocturnal sleep measures, frequent napping was associated with increased subjective sleepiness. Therefore, frequent napping appears to be associated with lighter daytime sleep and increased sleepiness during the day. Speculatively, low levels of daytime sleepiness and increased SWS in non-nappers may help explain why these individuals choose not to nap.     

Laboratory and field studies of naps and caffeine as practical countermeasures for sleep-wake problems associated with night work

STUDY OBJECTIVES: To evaluate the effects of napping, caffeine, and napping plus caffeine on performance and alertness in both laboratory and field settings. DESIGN: (1) Laboratory Study: parallel-groups design with random assignment to 1 of 4 experimental conditions. (2) Field Study: crossover design. SETTING: Sleep laboratory and field settings. PARTICIPANTS: (1) Laboratory Study: 68 healthy individuals; (2) Field Study: 53 shiftworkers who worked nights or rotating shifts. INTERVENTIONS: (1) Laboratory Study: an evening nap opportunity before the first 2 of 4 consecutive simulated night shifts plus placebo taken all 4 nights, caffeine taken nightly, the combination of the nap and caffeine conditions, or placebo. (2) Field Study: an evening nap on the first 2 of 4 consecutive night shifts plus caffeine taken nightly versus placebo taken nightly without naps. MEASUREMENTS AND RESULTS: (1) Laboratory Study: Napping, caffeine, and their combination all improved alertness and performance as measured by Maintenance of Wakefulness Test and Psychomotor Vigilance Task, but the combination of napping and caffeine was best in improving alertness. (2) Field Study: Napping plus caffeine improved performance as measured by Psychomotor Vigilance Test and decreased subjective sleepiness in individuals working the night shift. CONCLUSIONS: Napping plus caffeine helps improve performance and alertness of night-shift workers.     

Sleep hygiene practices in two community dwelling samples of older adults

STUDY OBJECTIVES: Common sleep hygiene practices were examined in 2 community-based samples of older adults to determine which practices differentiated 4 sleep subgroups: noncomplainers without insomnia symptoms, complainers without insomnia symptoms, noncomplainers with insomnia symptoms, and complainers with insomnia symptoms. DESIGN: Two weeks of sleep diaries provided napping and bed/out-of-bed time variability data. A retrospective questionnaire provided data on caffeine, cigarette, and alcohol usage. Recruitment involved random digit dialing (Sample 1) and advertisements (Sample 2). SETTING: Memphis, TN area (Sample 1); Gainesville, FL area (Sample 2). PARTICIPANTS: 310 individuals 60-96 years (Sample 1); 103 individuals 60-89 years (Sample 2). INVENTIONS: N/A. MEASUREMENTS AND RESULTS: Older individuals with sleep complaints did not report engaging in poorer sleep hygiene practices than those without complaints with the exception of frequency of napping. For Sample 1 only, complainers reported napping on 1.5-2.0 more days per week than noncomplainers. Sleep subgroups in both samples did not differ for the other sleep hygiene practices studied. CONCLUSIONS: Overall, sleep hygiene behaviors did not differentiate the 4 sleep subgroups. The efficacy of sleep hygiene as a therapy for late life insomnia appears questionable in this context. Both complaining sleep subgroups napped more frequently than both noncomplaining subgroups in Sample 1. Additional research is needed to clarify the clinical implications of nap frequency as these results did not replicate in Sample 2, and the impact of napping on nighttime sleep remains unclear. Inconsistencies with previous research in younger samples support the need for more research specifically targeting older individuals' sleep patterns and behaviors.     

Defining the roles of actigraphy and parent logs for assessing sleep variables in preschool children

Actigraphy provides a non-invasive objective means to assess sleep-wake cycles. In young children, parent logs can also be useful for obtaining sleep-wake information. The authors hypothesized that actigraphy and parent logs were both equally valid instruments in healthy preschool-aged children. The authors studied 59 children aged 3 to 5 years in full-time day care. Each child was screened for medical problems and developmental delays before being fitted with an actigraphy watch, which was worn for 1 week. Parents maintained logs of sleep and wakefulness during the same period, with input from day care workers. In general, parents overestimated the amount of nighttime sleep measured by actigraphy by 13% to 22% (all significant). Although there was no difference in sleep onset times, parents reported later rise times on the weekend and fewer nighttime awakenings. There was no significant difference between parent logs and actigraphy with regard to daytime napping. The authors conclude that parent logs are best utilized in assessing daytime sleep and sleep onset, whereas actigraphy should be used to assess nighttime sleep and sleep offset time.     

The prevalence of daytime napping and its relationship to nighttime sleep.

Many healthy adults report daytime napping. Surprisingly few studies, however, have examined spontaneous napping behavior, especially very short naps, in healthy adults. The authors examined the prevalence of power naps (lasting less than 20 minutes) and longer naps (20 minutes or more) and their effects on nighttime sleep in a group of healthy young and middle-aged adults. The young and middle-aged adults reported very similar sleep and napping patterns, with approximately 74% of the participants in both groups reporting they had napped during a 7-day sleep-log period. Almost half of the participants reported that the average nap lasted less than 20 minutes. A multivariant analysis of variance (MANOVA) found no significant differences between the no-nap and the power-nap or long-nap groups in sleep quantity or quality for either age group. The current data suggested that power napping occurs frequently in healthy adults and that spontaneous napping does not negatively affect nighttime sleep.     

Birth order effects and their implications for child care research and programs

Using previously collected data on the effects of different child care environments on children 4 to 5 1/2 years old, results supporting Zajonc and Markus's confluence model of the interactive effects of family size, birth order, and age between siblings as predictors of intelligence were found for only children. Consistent with an ecological perspective, family patterns were seen as important in evaluating the impact of different child care modalities and in finding optimal child care settings for children from different family structures.     

Agreement in Regard to Total Sleep Time During a Nap Obtained Via a Sleep Polygraph and Accelerometer: A Comparison of Different Sensitivity Thresholds of the Accelerometer

Background

Appropriate sensitivity threshold of accelerometer to measure total sleep time during nap is not established.

Purpose

Actigraphy-derived total sleep times during naps were calculated using three different sensitivity threshold values and compared with polysomnography.

Method

The mean age of the 60 subjects (53 men and 7 women) was 22.8, ranging from 22 to 27?years. Determination of the sleep stage by the polygraph and the sleep/wake judgment by the accelerometer obeyed the sleep/wake judgment, and the accelerometer was monitored under different sensitivity threshold settings. The study was carried out during one afternoon with a 3-h nap opportunity. Kappa statistics, correlations, and several indices of accuracy were compared using statistical methods.

Results

The mean total sleep times during a nap set for 180?min were 160.4, 151.8, and 140.5?min, respectively, as judged under the low-sensitive, middle-sensitive, high-sensitive settings of an accelerometer worn on the non-dominant wrist. The corresponding mean total sleep time as calculated using a sleep polygraph was 133.0?min. Sleep/wake judgment by three levels of threshold values for the accelerometer showed that high-sensitive threshold showed relatively high specificity (0.452) compared with specificities by the low-sensitive threshold (0.249) or by the middle-sensitive threshold (0.358). The concordance correlation coefficients and 95% confidence intervals (in parenthesis) between the total sleep time judged by polygraph and low-sensitive, middle-sensitive, or high-sensitive accelerometer were 0.40 (0.26?C0.51), 0.53 (0.38?C0.65), and 0.64 (0.49?C0.75), respectively. The Bland?CAltman plot of the measurements showed higher agreement between the total sleep time by polygraph and by the accelerometer using the high-sensitive threshold.

Conclusions

From the result obtained in this study, the high-sensitive accelerometer showed the strongest agreement of total sleep time and sleep/wake judgment with the calculated value using the sleep polygraph.