Midday Nap Research Articles

080 Is Napping Only Beneficial to Evening Chronotypes? A Pilot Study

Abstract Introduction Research shows associations between chronotype and behavior. While eveningness is associated with lower levels of self-control, morningness is associated with increased conscientiousness. Additionally, throughout the day, the increase in homeostatic sleep pressure due to wakefulness can affect executive functioning, including emotional regulation. Napping is an effective countermeasure to sleepiness and associated emotional dysregulation, but the impact of chronotype on this benefit is unknown. Therefore, this study aimed to examine the impact of chronotype and a midday nap on an aspect of emotional regulation: frustration tolerance. Methods 40 participants between the ages of 18–50 were randomized into a 60-minute, midday nap or no-nap condition. Chronotype was measured using the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ). Frustration tolerance (FT) was measured pre and post nap using an adaption of Feather’s frustration tolerance task where FT was measured as the time spent on an impossible task. To examine the association of chronotype and FT, correlational analysis was used. Chronotype was also determined using a median split of the MEQ due to few true morning and evening types in the sample. This data was then subjected to a repeated measures ANOVA with condition (pre or post-nap) as a within-subjects factor and group (nap or no-nap; high or low MEQ score) as between-subject factors. Results Results revealed a significant correlation between MEQ score and change in time spent on the impossible task, with those with lower MEQ scores (more evening) showing an increase in time spent on the impossible task, r(20) = -.51, p = .016. Similarly, results of the ANOVA revealed a significant condition (pre or post-nap) by group (nap, no nap; high, low MEQ) interaction, F(1,1) = 4.694, p = .039, such that, those in the nap group with lower MEQ (more evening) spent more time on the impossible task following the nap. Conclusion Our results indicate that chronotype may impact a nap’s positive effect on emotional regulation, with greater benefit for those with the eveningness chronotype. Because napping is currently practiced by 1/3 of American adults, from a personalized medicine perspective, it’s imperative that its chronotype-dependent benefits be investigated further to effectively guide evidence-based recommendations. Support (if any):

585 The Relationship between Napping and Behavioral Problems among Vocational High School Students in China

Abstract Introduction Although napping is very common and related to the outcome of individual development, the relationship between napping and health is not the same in different social and cultural contexts. In China, napping is considered as a healthy lifestyle and is often associated with better adolescent development outcomes. As a special group of teenagers (the academic level does not meet the requirements of ordinary high school), vocational high school students have a higher incidence of behavioral problems than ordinary high school students. Therefore, the purpose of this study is to explore the characteristics of napping and its relationship with behavioral problems in vocational high school students. Methods The napping questionnaire, Youth Self Report (YSR), general information questionnaire and other tools for covariates were used to measure 2505 high school students (62.04% boys, 37.96% girls, 16.71±0.02 years), recruited by convenient sampling. The relationship between nappingand behavioral problems was analyzed by multiple linear regression. Results 72.58% of the participants reported taking a midday nap at least three days per week during the past month, and 55.79% of our sample reported naps more than 30 minutes. Multiple regression analysis showed that nap frequency was negatively associated with high school students’ behavior problems after controlling for general characteristics and other important covariates. Compared with high school students who did not nap or napped less than 1 time/week, high school students who napped 1–2 times/week or 3–4 times/week had lower level of both internalizing behavior problems and externalizing behavior problems. There was no statistically significant association between nap duration and behavior problems. Conclusion This study finds that when napping is allowed, moderate frequency of napping is associated with lower level of internalizing and externalizing behavioral problems in vocational high school students, while nap duration is not significantly associated with behavioral problems. Further research is needed to explore the mechanism of the relationship between napping and behavior problems. Support (if any):

THE EFFECTS OF MIDDAY NAP DURATION ON THE RISK OF HYPERTENSION IN CHINESE RURAL POPULATION

Abstract Objective: Most previous epidemiological studies regarding sleep and risk of hypertension focused on the association between night sleep duration and hypertension. However, data on the effect of midday nap duration on hypertension are scarce, especially among rural population. The study was conducted to evaluate the associations of the midday nap duration with blood pressure and hypertension in Chinese rural population. Design and method: From August 2016 to July 2017, a total of 1755 eligible participants were consecutively enrolled in our study in Hunan province, China. Hypertension was defined as systolic blood pressure/diastolic blood pressure > = 140/90mmHg or self-reported hypertension and current use of anti-hypertensive medicines. Participants were categorized into three groups according to midday nap duration, such as no napping (reference), short (<1 h), and long (> = 1 h). Multivariable regression models were applied to assess the potential association. Results: Of the 1755 included participants, 908 suffered from hypertension. Participants’ mean age was 55.86 years. 638 (36.35%) were men and 1117 (63.65%) were women. Compared to reference (no napping), fully adjusted odd ratios (ORs) and 95% confidence interval (CI) of hypertension were 0.72 (0.57–0.92) in participants with long midday napping duration (> = 1 h). Linear regression analyses showed that long midday nap duration (b = -2.78, 95% CI: -4.89, -0.67, P = 0.010) were significantly negative association with systolic blood pressure. Conclusions: Our findings suggest that long midday nap duration might decrease the risk of hypertension and reduce the levels of systolic blood pressure among rural population. These findings warrant further prospective studies in a larger population.

Midday Nap Duration and Hypertension among Middle-Aged and Older Chinese Adults: A Nationwide Retrospective Cohort Study.

The goal of this study was to investigate the associations of midday nap duration and change in midday nap duration with hypertension in a retrospective cohort using a nationwide representative sample of middle-aged and older Chinese adults. Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS) database during 2011–2015. Information on midday nap duration was collected via a self-reported questionnaire and blood pressure was objectively measured. Hazard ratios (HR) with 95% confidence interval (CI) were estimated using Cox proportional hazards regression models to quantify the associations. A sample of 5729 Chinese adults (≥45 years old) were included in the longitudinal analysis. Relative to non-nappers, participants who napping for ≥90 min/day was associated with significantly larger HR for hypertension at four-year follow-up (HR = 1.18, 95% CI = 1.01–1.40, p = 0.048). Compared with people who napped ≥90 min/day both at baseline (2011) and follow-up (2013), hypertension risk at four-year follow-up declined in individuals whose midday nap durations decreased in the 2-year study period from ≥ 90 min/day to 1–59 min/day (HR = 0.59, 95% CI = 0.36–0.97, p = 0.037) and 60–89 min/day (HR = 0.68, 95% CI = 0.47–0.99, p = 0.044). Among middle-aged and older Chinese adults, relative to non-nappers, people who had longer midday nap duration (≥90 min/day) were associated with significantly larger HR for hypertension and decreased napping duration may confer benefit for hypertension prevention.

Factors associated with insomnia among Chinese front-line nurses fighting against COVID-19 in Wuhan: A cross-sectional survey.

AimTo investigate the prevalence of insomnia among front‐line nurses fighting against COVID‐19 in Wuhan, China, and analyse its influencing factors.BackgroundInsomnia is an important factor that can affect the health and work quality of nurses. However, there is a lack of big‐sample studies exploring factors that affect the insomnia of nurses fighting against COVID‐19.MethodThis cross‐sectional study using the Ascension Insomnia Scale, Fatigue Scale‐14 and Perceived Stress Scale took place in March 2020. Participants were 1,794 front‐line nurses from four tertiary‐level general hospitals.ResultsThe prevalence of insomnia among participants was 52.8%. Insomnia was predicted by gender, working experience, chronic diseases, midday nap duration, direct participation in the rescue of patients with COVID‐19, frequency of night shifts, professional psychological assistance during the pandemic, negative experiences (such as family, friends or colleagues being seriously ill or dying due to COVID‐19), the degree of fear of COVID‐19, fatigue and perceived stress.ConclusionThe level of insomnia among participants was higher than the normal level. Interventions based on influencing factors should be implemented to ensure nurses’ sleep quality.Implications for Nursing ManagementAn in‐depth understanding of the influencing factors of insomnia among front‐line nurses can help nurse managers develop solutions to improve front‐line nurses’ sleep quality, which will enhance the physical and mental conditions of nurses and promote the quality of care.

Gender and age differences in the association between sleep characteristics and fasting glucose levels in Chinese adults

AimThe present study examined the associations between night-time sleep duration, midday napping duration and bedtime, and fasting glucose levels, and whether or not such associations are dependent on gender and age. MethodsThis study was a cross-sectional analysis of 172,901 adults aged≥40 years living in mainland China. Sleep duration was obtained by self-reports of bedtime at night, waking-up time the next morning and average napping duration at midday. Fasting plasma glucose (FPG)≥7.0mmol/L was defined as hyperglycaemia. Independent associations between night-time sleep duration, midday naptime duration and bedtime with hyperglycaemia were evaluated using regression models. ResultsCompared with night-time sleep durations of 6–7.9h, both short (<6h) and long (≥8h) night-time sleep durations were significantly associated with an increased risk of hyperglycaemia in women [odds ratio (OR): 1.12, 95% confidence interval (CI): 1.01–1.29 and OR: 1.14, 95% CI: 1.08–1.21, respectively], and revealed a U-shaped distribution of risk in women and no significant association in men. Long midday nap durations (≥1h) were significantly but weakly associated with hyperglycaemia (OR: 1.04, 95% CI: 1.01–1.09) compared with no napping without interactions from gender or age, whereas the association between bedtime and fasting glucose levels did vary according to gender and age. ConclusionNight-time sleep duration, midday napping duration and bedtime were all independently associated with the risk of hyperglycaemia, and some of the associations between these sleep characteristics and hyperglycaemia were gender- and age-dependent.

0321 Increased Slow-Wave Activity Predicts Slower Processing Speed in Toddlers

Abstract Introduction Slow-wave activity (SWA) shows an inverted U-shaped time course during development. Specifically, maximal SWA undergoes a posteroanterior shift from 2 to 20 years of age, which may reflect cortical maturation. Previously, we showed that greater slow sigma power during sleep predicted faster reaction time in preschool-aged children. To date, little is known about the relationship between SWA and processing speed (PS), a basic fundament underlying complex cognitive skills in early development. Methods This project examined the relationship between SWA and PS in 2.5-3.0-year-old children (n=26, 50% males) via home-based assessments. After a 5-day stabilization sleep schedule, a baseline sleep EEG recording was performed on participants at 4 electrode placements: Fz, Oz, C3, and C4. SWA EEG spectral power was quantified in the 0.75-4.5 Hz rangeduring the first 60 minutes of NREM sleep. PS was obtained as part of a standard cognitive assessment via a computer-based task one hour after waking from a midday nap. Results On average, reaction time (PS) was 2111 ± 08 ms and SWA was 856.4 ± 300.7 µV2/Hz. Increased SWA in the occipital region was predictive of a longer reaction time and therefore slower PS (r = 0.44, p = 0.03). This relationship showed differences between sexes, suggesting that females (r = 0.26, p = 0.07) may show a stronger association between SWA in the occipital brain region and PS than males (r = 0.09, p = 0.33). Conclusion Interestingly, these findings contradict our hypothesis based on previous data with older children indicating that greater SWA was associated with more advanced behavioral and cognitive skills. This discrepancy may reflect the stark individual differences present within this rapidly maturing age group. Support Research support from NIH R01-MH086566 to MKL.

0207 The Effect of Naps on Inhibitory Control and Sustained Attention in Early Childhood

Abstract Introduction Sleep in adults and school-age children has been shown to improve regulatory behaviors. Specifically, slow wave sleep (SWS) disruptions have been positively associated with decreased levels of sustained attention and inhibitory control in adults, while REM sleep has been associated with inhibitory control in typically developing children. However, it is unknown whether midday naps confer a similar benefit in preschool-aged children, particularly since REM sleep is often lacking in their naps. In this study, we used a Go/No-Go task to determine whether SWS during early childhood naps benefits sustained attention and inhibitory control. We also explored nap habituality as a factor given that habitual and non-habitual nappers have different sleep architecture in adults and children. Methods Preschool children (N=22, 38–69 months) completed a Go/No-Go task, after which they either napped with polysomnography (nap condition) or stayed awake (wake condition) for an equivalent amount of time (within subject; order counterbalanced; ~1 week apart). After their nap and wake sessions, they completed the Go/No-Go task again. Results When controlling for nap frequency, participant performance (accuracy) post-session did not differ across conditions. However, by examining only the habitual nappers (5–7 days/week, N=9), we found a moderate positive correlation between percent of sleep spent in SWS and post-nap accuracy (r=0.335, p=0.037). Interestingly, we did not see the same relationship with non-habitual nappers (0–4 days/week, N=13) and found a weak negative correlation with SWS (r=0.007, p=0.031). Conclusion The findings suggest that habitually napping children show a benefit of nap SWS on regulatory behaviors while non-habitual nappers do not. Such results have important translational significance for early education settings. Support NIH R01 HL111695.

Effect of nighttime sleep duration and midday napping in early pregnancy on gestational diabetes mellitus.

To explore the effect of nighttime sleep duration and midday napping in early pregnancy on gestational diabetes mellitus (GDM) among Chinese women. Information on midday napping and nighttime sleep duration was assessed by a questionnaire. Diagnostic information of GDM was derived from the routine oral glucose tolerance test (OGTT) during the second trimester of pregnancy. A total of 500 pregnant women, including 196 patients with GDM and 304 controls, were included in the present study. In the case group, 47% of women took a midday nap > 1h/day, and the proportion was 22% in the control group. Compared with women who had a midday nap ≤ 1h/day, women who had a nap > 1h/day had a significantly increased risk of GDM (OR 3.00, 95% CI 1.87, 4.82, p < 0.001). Compared with women who had a nighttime sleep of 7 to 8.9h/night, women who slept < 7 or ≥ 9h/night all had a significantly increased risk of GDM. Stratified analyses showed that compared with the nighttime sleep duration of 7 to 8.9h/day, the GDM risk of the < 7h/night group increased among mothers who had a midday nap ≤ 1h/day. The impact was stronger than among women who had a nap > 1h/day (p = 0.006). Shorter or longer nighttime sleep duration and longer midday napping duration in early pregnancy were all related to GDM. Midday napping would reduce the risk of GDM among mothers with shorter nighttime sleep duration.

Sleep Time in the European Starling Is Strongly Affected by Night Length and Moon Phase.

Sleep is considered to be of crucial importance for performance and health, yet much of what we know about sleep is based on studies in a few mammalian model species under strictly controlled laboratory conditions. Data on sleep in different species under more natural conditions may yield new insights in the regulation and functions of sleep. We therefore performed a study with miniature electroencephalogram (EEG) data loggers in starlings under semi-natural conditions, group housed in a large outdoor enclosure with natural temperature and light. The birds showed a striking 5-h difference in the daily amount of non-rapid-eye-movement (NREM) sleep between winter and summer. This variation in the amount of NREM sleep was best explained by night length. Most sleep occurred during the night, but when summer nights became short, the animals displayed mid-day naps. The decay of NREM sleep spectral power in the slow-wave range (1.1-4.3Hz) was steeper in the short nights than in the longer nights, which suggests that birds in summer have higher sleep pressure. Additionally, sleep was affected by moon phase, with 2h of NREM sleep less during full moon. The starlings displayed very little rapid-eye-movement (REM) sleep, adding up to 1.3% of total sleep time. In conclusion, this study demonstrates a pronounced phenotypical flexibility in sleep in starlings under semi-natural conditions and shows that environmental factors have a major impact on the organization of sleep and wakefulness.

Gender Differences in the Relationship Between Sleep Problems and Suicide Attempt in Adolescents.

There are few studies examining which types of sleep problems are independently associated with suicide attempt (SA) and gender difference in adolescents. The aim of the present study was to examine whether specific sleep problems were uniquely associated with suicide attempt in adolescents and explore gender differences in the association. A school-based health survey was conducted in four provinces within China from November 2014 to January 2015. A total of 15,132 students aged 10–21 years completed standard questionnaires assessing past 12 month suicide attempt in addition to measures of sleep quality, quantity and sleep beliefs. 5.4% of participants reported a suicide attempt within the last 12 months. After adjustment for sociodemographic variables and psychological symptoms, almost all sleep problems remained significantly associated with a greater endorsement of suicide attempt. Further adjustment for co-occurring sleep problems revealed that weekday sleep duration (<6, 8–10, and ≥10 h), insomnia (often), and nightmares (sometimes and often) remained independently associated with suicide attempt in boys (p < 0.05). However in girls, weekday sleep duration (<6 and ≥10 h), weekend sleep duration (<6 h), midday nap (0 or 1–2 d/week), insomnia (sometimes and often), nightmare (often) and sleep beliefs (high) were independently associated with suicide attempt (p < 0.05). Multiple sleep problems are associated with suicide attempt in adolescents, however the relationship varies by gender.

HYPNOTIC SUGGESTIONS GIVEN BEFORE NIGHTTIME SLEEP EXTEND SLOW-WAVE SLEEP AS COMPARED TO A CONTROL TEXT IN HIGHLY HYPNOTIZABLE SUBJECTS

ABSTRACT While slow-wave sleep (SWS) is fundamental for maintaining health and well-being, it is typically reduced with stress or age. The authors have previously reported that hypnotic suggestions before sleep increased SWS duration and slow-wave activity (SWA) during a midday nap in hypnotizable younger and older women. To test generalizability, they investigated this effect across 8 hours nighttime sleep in 43 healthy young French-speaking subjects (19 males) of high and low hypnotizability. In accordance with their previous results, listening to hypnotic suggestions before sleep was followed by higher amounts of SWS in highly hypnotizable subjects and higher SWA power compared to a control condition. The effects were most pronounced at the beginning of the night. Further studies are needed to examine whether hypnotic suggestions can deepen sleep also above non-intervention nights. The findings provide a basis for the examination and potential application of hypnosis to improve sleep in clinical populations.

Development Signs in Healthy Toddlers in Different Stages of Toilet Training: Can They Help Define Readiness and Probability of Success?

There is much uncertainty about when to start toilet training. Age cannot be a strict stand-alone criterion, as every child has its own pace of development. We observed toilet training (TT) related development signs (DS) in healthy toddlers and determined which can help to define the proper time to start TT and to predict success. The study group consisted of 269 healthy children, in different stages of TT: not started, during, and after completion. Sitting stable, picking up small objects, and spontaneously putting objects in containers were present in all children and had no predictive value. All other DS were significantly more present in those who had started and became more prevalent during completion of TT. Age had a significant association with 13/15 DS. Understanding and following instructions, and having a broader vocabulary were significantly more present when TT had been started. Dry during midday nap reached no significance.

Associations between nocturnal sleep duration, midday nap duration and body composition among adults in Southwest China.

ObjectiveWe aim to explore the relationship between nocturnal sleep duration (NSD) and midday nap duration (MND) with body composition among Southwest Chinese adults.MethodsData on sleep duration of 3145 adults in Southwest China (59.4% women) were obtained between 2014 and 2015 through questionnaires. Height, weight, and waist circumference (WC) were measured to calculate body composition (body mass index (BMI), percentage of body fat (%BF), and fat mass index (FMI)). Linear regression models were used to assess gender-specific associations between NSD and body composition. The relationship between MND with the odds of overweight and central obesity has been evaluated by logistic regression models.ResultsNSD has the inverse relation with males’ BMI, WC, %BF and FMI after adjusting for all covariates (all P <0.0007), exclusive of females’ (all P >0.4). After adjustment for potential confounders, compared to the subjects in the no midday nap group, the subjects who napped 0.1–1 hour were independently associated with a less prevalence of overweight in both women (OR: 0.72, 95%CI: 0.55–0.95) and men (OR: 0.71, 95%CI: 0.52–0.98). MND was not associated with central obesity.ConclusionsAmong Southwest Chinese adults, lower NSD might be related to higher BMI, WC, %BF and FMI among men. Additionally, MND is associated with overweight in adults.

The effect of Ramadan related activities (Mid_day nap), early night prayers, and late night prayers on seizure frequency during Ramadan among fasting epileptic patients

Epilepsy is one of the common neurological disorders; many factors can precipitate on attack of convulsion like sleep deprivation, infection, dehydration, sudden cessation of treatment. To study the effect of Ramadan related activities (Midday nap “qaylola”, Early night prayers “Tarawih”, and late night prayers “tahajud”)and seizure frequency during Ramadan among fasting epileptic patients. This non interventional descriptive study. It was conducted in daoud charity clinic during the period from May to July 2018.Almost 75Sudanese epileptic patients who were fasting Ramadan were included in this study. 53% of them male and 46% female.75% of our patients have generalized tonic clonic, 13% have focal with impairment, 8% have focal to bilateral 2.7% have myclonus, 1.3% have more than one type.The study show the number of attack decrease with the midday nap and early night prayers. Late night prayers don't affect the frequency of attack. There was no relationship between type of epilepsy and developing convulsion during Ramadan. Sleep deprivation in Eltahajud doesn't affect developing convulsion while midday nap and early night prayers decrease the chance of developing the attack.

Association of long-term sleep habits and hypertension: a cross-sectional study in Chinese adults.

Poor sleep has been associated with risk of hypertension, but previous studies were limited by treating one or two sleep factors as predictor. Our previous study has developed a sleep factor questionnaire (SFQ) to comprehensively assess wide range of sleep characteristics including sleep duration, sleep quality, light at night (LAN) exposure, night/shift work, daytime napping, and frequency of nighttime waking, insomnia, and snoring. In this cross-sectional study we used the SFQ to evaluated the associations between these sleep domains and hypertension. Comparing with the subjects who slept 7-8 h, subjects with sleep duration 6-7 h (OR = 1.42, 95% CI: 1.01, 2.00), 8-9 h (OR = 1.60, 95% CI: 1.07, 2.40), and over 9 h (OR = 2.39, 95% CI: 1.60, 3.58) had an increased prevalence of hypertension. The associations were significant among individuals under 45 years sleeping 6-7 h and those over 45 years sleeping over 8 h. The OR of prevalent hypertension was 0.80 (95% CI: 0.62, 0.97) for habitual daytime napping compared with never napping, and the association was also significant among individuals over 45 years old. Moreover, among subjects with sleep duration 7-8 h, habitual daytime napping may decrease prevalent hypertension (OR = 0.635, 95% CI: 0.437, 0.924). In conclusion, our data suggested a positive association between both short (6-7 h) and long sleep duration and hypertension, and a preventive pattern for habitual daytime napping among over 45 years old and hypertension. Moreover, interaction analysis indicated that habitual midday nap may decrease prevalent hypertension among subjects with sleep duration 7-8 h.

The interactive effect of habitual midday napping and nighttime sleep duration on impaired fasting glucose risk in healthy adolescents

ObjectivesTo investigate the association between habitual midday napping and impaired fasting glucose (IFG), and the interactive effect of napping and time in bed (TIB) at night on IFG among healthy adolescents. MethodsThe sample comprised 625 early adolescents (12.26 ± 0.63 years old) who self-reported good health status from Jintan, China. Midday napping and nighttime sleep were measured using the Youth Self-report Sleep Questionnaire. Fasting plasma glucose was dichotomized into normal (<5.6 mmol/L) and impaired (≥5.6 mmol/L) levels. The multivariate random-effect logistic regression examined the nap-glucose relationship and the interaction between nap and TIB. Marginal effects of napping were calculated when TIB was held constant at different values. ResultsOf the participants, 83.20% (n = 520) took naps and 62.28% reported average nap durations ≥31 min in the past month. Moreover, 16% (n = 101) of participants had IFG. After adjusting for covariates, early adolescents who napped 3–4 days/week (OR = 1.72, p < 0.001), 5–7 days/week (OR = 1.34, p = 0.02) or ≥31 min/nap (OR = 1.52, 1.56, p's < 0.05) were associated with increased likelihoods of IFG compared to non-nappers. There was an inverse relationship between TIB and IFG among non-nappers (OR = 0.45, p = 0.03). Interaction analyses also showed significantly increased likelihoods of IFG only among nappers with TIB ≥9 hours. ConclusionThe relationship between midday napping and IFG is dependent on TIB. Midday naps may increase the risk for IFG among early adolescents who have sufficient nighttime sleep. However, further research is needed to confirm our preliminary findings.

Daywake, an Anti-siesta Gene Linked to a Splicing-Based Thermostat from an Adjoining Clock Gene

Sleep is fundamental to animal survival but is a vulnerable state that also limits how much time can be devoted to critical wake-dependent activities [1]. Although many animals are day-active and sleep at night, they exhibit a midday nap, or "siesta," that can vary in intensity and is usually more prominent on warm days. In humans, the balance between maintaining the wake state or sleeping during the day has important health implications [2], but the mechanisms underlying this dynamic regulation are poorly understood. Using the well-established Drosophila melanogaster animal model to study sleep [3], we identify a new wake-sleep regulator that we term daywake (dyw). dyw encodes a juvenile hormone-binding protein [4] that functions in neurons as a day-specific anti-siesta gene, with little effect on sleep levels during the nighttime or in the absence of light. Remarkably, dyw expression is stimulated in trans via cold-enhanced splicing of the dmpi8 intron [5] from the reverse-oriented but slightly overlapping period (per) clock gene [6]. Thefunctionally integrated dmpi8-dyw genetic unitoperates as a "behavioral temperate acclimator" by increasingly counterbalancing siesta-promoting pathways as daily temperatures become cooler and carry reduced risks from daytime heat exposure. While daily patterns of when animals are awake and when they sleep are largely scheduled by the circadian timing system, dyw implicates a less recognized class of modulatory wake-sleep regulators that primarily function to enhance flexibility in wake-sleep preference, a behavioral plasticity that is commonly observed in animals during the midday, raising the possibility of shared mechanisms.

0234 Role of Midday Naps on Episodic Memory Consolidation in Preschool Children

0234 Role of Midday Naps on Episodic Memory Consolidation in Preschool Children

Psychosocial Stress Before a Nap Increases Sleep Latency and Decreases Early Slow-Wave Activity.

Sleep disturbances are an important risk factor for stress-related diseases such as burnout or depression. In particular, slow-wave activity (SWA) during sleep might be eminently relevant for optimal maintenance of mental health and cognitive functioning. In spite of the clinical importance and the pertinence of stress-related processes in everyday life, the physiological mechanisms of the association between stress, sleep, and cognition are not well-understood. In the present study, we carefully mapped the time course of the influence of a psychosocial stressor on sleep architecture and sleep-related oscillations during a midday nap. We induced stress using a psychosocial laboratory stressor, the Montreal Imaging Stress Task, vs. a neutral control task. Afterward, participants were allowed to take a 90-min nap (n = 20) or stayed awake (n = 19) and cortisol was measured via saliva samples. We hypothesized that stress would decrease sleep efficiency and SWA in a time-dependent manner, with impairing effects on cognitive functioning. Psychosocial stress resulted in increased cortisol levels, which were elevated throughout the study interval. In the nap group, psychosocial stress increased sleep latency, but had only minor effects on sleep architecture. Still, SWA in the first 30 min of sleep was significantly reduced, whereas alpha activity was enhanced. These effects vanished after approximately 30 min. No impairing effect on cognitive functioning occurred. Our results show that psychosocial stress before sleep has an impact on sleep latency and early SWA during sleep. In contrast to our hypothesis, the effects were rather small and short-lasting. Importantly, cognitive functioning was maintained. We conclude that the effects of psychosocial stress before a nap are possibly better compensated than previously believed.