Neurobehavioral functions during recurrent periods of sleep restriction: effects of intra-individual variability in sleep duration.

STUDY OBJECTIVES: To investigate whether neurobehavioral impairments are exacerbated during successive cycles of sleep restriction and recovery in young adults, and whether a variable short sleep schedule can mitigate these impairments relative to a stable one. METHODS: Fifty-two healthy young adults (25 males, aged: 21-28) were randomly assigned to the stable short sleep group, the variable short sleep group, or the control group in this laboratory-based study. They underwent two baseline nights of 8-hour time-in-bed (TIB), followed by two cycles of "weekday" sleep opportunity manipulation and "weekend" recovery (8-hour TIB). During each manipulation period, the stable short sleep and the control groups received 6- and 8-hour TIBs each night respectively, while the variable short sleep group received 8-hour, 4-hour, 8-hour, 4-hour, and 6-hour TIBs from the first to the fifth night. Neurobehavioral functions were assessed five times each day. RESULTS: The stable short sleep group showed faster vigilance deterioration in the second week of sleep restriction as compared to the first. This effect was not observed in the variable short sleep group. Subjective alertness and practice-based improvement in processing speed were attenuated in both short sleep groups. CONCLUSIONS: In young adults, more variable short sleep schedules incorporating days of prophylactic or recovery sleep might mitigate compounding vigilance deficits resulting from recurrent cycles of sleep restriction. However, processing speed and subjective sleepiness were still impaired in both short sleep schedules. Getting sufficient sleep consistently is the only way to ensure optimal neurobehavioral functioning. CLINICAL TRIAL: Performance, Mood, and Brain and Metabolic Functions During Different Sleep Schedules (STAVAR), https://www.clinicaltrials.gov/study/NCT04731662, NCT04731662.

A pilot study of light exposure as a countermeasure for menstrual phase-dependent neurobehavioral performance impairment in women.

OBJECTIVE: To examine effects of menstrual phase and nighttime light exposure on subjective sleepiness and auditory Psychomotor Vigilance Task performance. METHODS: Twenty-nine premenopausal women (12 =Follicular; 17 =Luteal) completed a 6.5-hour nighttime monochromatic light exposure with varying wavelengths (420-620 nm) and irradiances (1.03-14.12 µW/cm2). Subjective sleepiness, reaction time, and attentional lapses were compared between menstrual phases in women with minimal (<33%) or substantial (≥33%) light-induced melatonin suppression. RESULTS: When melatonin was not suppressed, women in the follicular phase had significantly worse reaction time (mean difference=145.1 ms, 95% CI 51.8-238.3, p < .001, Cohen's D=1.9) and lapses (mean difference=12.9 lapses, 95% CI 4.37-21.41, p < .001, Cohen's D=1.7) compared to women in the luteal phase. When melatonin was suppressed, women in the follicular phase had significantly better reaction time (mean difference=152.1 ms, 95% CI 43.88-260.3, p < .001, Cohen's D=1.7) and lapses (mean difference=12.3 lapses, 95% CI 1.14-25.6, p < .01, Cohen's D=1.6) compared to when melatonin was not suppressed, such that their performance was not different (p > .9) from women in the luteal phase. Subjective sleepiness did not differ by menstrual phase (mean difference=0.6, p > .08) or melatonin suppression (mean difference=0.2, p > .4). CONCLUSIONS: Nighttime light exposure sufficient to suppress melatonin can also mitigate neurobehavioral performance deficits associated with the follicular phase. Despite the relatively small sample size, these data suggest that nighttime light may be a valuable strategy to help reduce errors and accidents in female shift workers.

Preconception sleep quality moderates the association between preconception hair cortisol levels and mental health in pregnant women.

BACKGROUND: Poor sleep quality may elevate cortisol levels and affect prenatal mental health through altered HPA axis functioning. This study aims to examine whether subjective sleep quality during preconception moderates the association between preconception hair cortisol levels and mental health from preconception to pregnancy trimesters. METHODS: Women from a prospective cohort study completed the Pittsburgh Sleep Quality Index (PSQI), the Edinburgh Postnatal Depression Scale (EPDS), and the State-Trait Anxiety Inventory (STAI) questionnaires during preconception (T0) and at each pregnancy trimesters (T1, T2, and T3). We analyzed 266 of these women who conceived and had fully completed measures at preconception for hair cortisol, sleep quality and either EPDS or STAI-state. Changes in EPDS and STAI-state scores were derived (i.e., T1-T0, T2-T0, T3-T0). Johnson-Neyman technique identified PSQI scores with significant moderation of cortisol on mental health. RESULTS: After adjusting for potential covariates, there was a significant positive correlation between preconception hair cortisol levels and depressive symptom at the second trimester (rs (144) = 0.22, p = 0.008), but not the first and third trimesters (all ps > 0.05). The positive association between preconception hair cortisol and change in depressive symptoms between third trimester and preconception was significant only among women with poor preconception sleep quality (PSQI ≥ 7). LIMITATIONS: Sleep quality and prenatal mood were derived from self-reported questionnaires, which may be more susceptible to bias. CONCLUSIONS: The positive association between preconception hair cortisol and change in prenatal depressive symptoms is significant among women who reported poor sleep quality during preconception. Improving preconception sleep quality can potentially mitigate the association between preconception hair cortisol and depressive symptoms during pregnancy.

University students' diurnal learning-directed behavior is strongly influenced by school start times with implications for grades.

STUDY OBJECTIVES: School start times impose constraints on sleep-wake timing that may influence academic achievement. We used large university archived datasets to test the hypothesis that larger differences in timing of students' diurnal learning behavior on school days relative to non-school days would be associated with lower grades. METHODS: Diurnal learning-directed behavior was examined in 33 645 university students by analyzing their learning management system (LMS) login rhythm. We tested the associations between the phase-difference in students' behavioral rhythm on school days versus non-school days with grade point average, LMS-login phase on non-school days (LMS-login chronotype), and school start time. We also tested the chronotype-dependent effects of school start times on diurnal behavior to determine whether students obtained better course grades when their first class of the day was in synch with their LMS-login chronotype. RESULTS: Students whose LMS-login rhythm was more than 2 hours earlier on school days had significantly lower grades than their peers. The change in LMS-login phase was larger in students with a later LMS-login chronotype and for earlier school start times. Minimal changes in LMS-login phase and higher course grades were observed when students' first class of the day was aligned with their LMS-login chronotype. CONCLUSIONS: Our findings demonstrate that school start times have a profound impact on students' diurnal learning behavior with implications for grades. Universities can potentially improve learning by starting school later to minimize differences in diurnal learning behavior between school days and non-school days.

Chronotype and time-of-day effects on spatial working memory in preschool children.

STUDY OBJECTIVES: Spatial working memory (SWM) capacity subserves complex cognitive functions, yet it is unclear whether individual diurnal preferences and time-of-day influence SWM in preschool children. The main and interaction effects of chronotype and time-of-day on SWM and SWM differences in preschoolers with different chronotypes within each time-of-day group will be examined. METHODS: We studied a subset of typically developing 4.5-year-olds taking part in a birth cohort study (n = 359). The Children's Chronotype Questionnaire categorized children into morning-, intermediate-, and evening-types. Using a computerized neuropsychological test (Cambridge Neuropsychological Test Automated Battery), SWM was determined from the total number of between-search errors (ie, between search-total errors) and Strategy scores. Higher between search-total errors or lower Strategy scores indicated worse SWM. Time-of-day was categorized into late morning (10:00 am to 11:59 am), afternoon (12:00 pm to 3:59 pm), and late afternoon (4:00 pm to 6:30 pm). In a subsample (n = 199), caregiver-reported chronotype was validated using actigraphy-measured sleep midpoint. RESULTS: After controlling for ethnicity, no significant main and interaction effects of chronotype and time-of-day on between search-total errors and Strategy scores were seen (all P > .05). However, evening-types outperformed morning-types (ie, lower mean between search-total errors) in the late afternoon (P = .013) but not in the late morning and afternoon (all P > .05). Actigraphy data in the subsample confirmed that evening-types had later sleep midpoints during weekdays and weekends (P < .001). CONCLUSIONS: Since evening-type preschoolers had better SWM in the late afternoon compared to morning-type preschoolers, this gives insights into optimal learning opportunities in early childhood education. CITATION: Abdul Jafar NK, Tham EKH, Eng DZH, et al. Chronotype and time-of-day effects on spatial working memory in preschool children. J Clin Sleep Med. 2023;19(10):1717-1726.

Associations between sleep trajectories up to 54 months and cognitive school readiness in 4 year old preschool children.

Purpose: This study explores the association between the duration and variation of infant sleep trajectories and subsequent cognitive school readiness at 48-50 months. Methods: Participants were 288 multi-ethnic children, within the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. Caregiver-reported total, night and day sleep durations were obtained at 3, 6, 9, 12, 18, 24 using the Brief Infant Sleep Questionnaire and 54 months using the Child Sleep Habits Questionnaire. Total, night and day sleep trajectories with varying durations (short, moderate, or long) and variability (consistent or variable; defined by standard errors) were identified. The cognitive school readiness test battery was administered when the children were between 48 and 50 months old. Both unadjusted adjusted analysis of variance models and adjusted analysis of covariance models (for confounders) were performed to assess associations between sleep trajectories and individual school readiness tests in the domains of language, numeracy, general cognition and memory. Results: In the unadjusted models, children with short variable total sleep trajectories had poorer performance on language tests compared to those with longer and more consistent trajectories. In both unadjusted and adjusted models, children with short variable night sleep trajectories had poorer numeracy knowledge compared to their counterparts with long consistent night sleep trajectories. There were no equivalent associations between sleep trajectories and school readiness performance for tests in the general cognition or memory domains. There were no significant findings for day sleep trajectories. Conclusion: Findings suggest that individual differences in longitudinal sleep duration patterns from as early as 3 months of age may be associated with language and numeracy aspects of school readiness at 48-50 months of age. This is important, as early school readiness, particularly the domains of language and mathematics, is a key predictor of subsequent academic achievement.

Early morning university classes are associated with impaired sleep and academic performance.

Attending classes and sleeping well are important for students' academic success. Here, we tested whether early morning classes are associated with lower attendance, shorter sleep and poorer academic achievement by analysing university students' digital traces. Wi-Fi connection logs in 23,391 students revealed that lecture attendance was about ten percentage points lower for classes at 08:00 compared with later start times. Diurnal patterns of Learning Management System logins in 39,458 students and actigraphy data in 181 students demonstrated that nocturnal sleep was an hour shorter for early classes because students woke up earlier than usual. Analyses of grades in 33,818 students showed that the number of days per week they had morning classes was negatively correlated with grade point average. These findings suggest concerning associations between early morning classes and learning outcomes.

Trajectories of reported sleep duration associate with early childhood cognitive development.

STUDY OBJECTIVES: Examine how different trajectories of reported sleep duration associate with early childhood cognition. METHODS: Caregiver-reported sleep duration data (n = 330) were collected using the Brief Infant Sleep Questionnaire at 3, 6, 9, 12, 18, and 24 months and Children's Sleep Habits Questionnaire at 54 months. Multiple group-based day-, night-, and/or total sleep trajectories were derived-each differing in duration and variability. Bayley Scales of Infant and Toddler Development-III (Bayley-III) and the Kaufman Brief Intelligence Test- 2 (KBIT-2) were used to assess cognition at 24 and 54 months, respectively. RESULTS: Compared to short variable night sleep trajectory, long consistent night sleep trajectory was associated with higher scores on Bayley-III (cognition and language), while moderate/long consistent night sleep trajectories were associated with higher KBIT-2 (verbal and composite) scores. Children with a long consistent total sleep trajectory had higher Bayley-III (cognition and expressive language) and KBIT-2 (verbal and composite) scores compared to children with a short variable total sleep trajectory. Moderate consistent total sleep trajectory was associated with higher Bayley-III language and KBIT-2 verbal scores relative to the short variable total trajectory. Children with a long variable day sleep had lower Bayley-III (cognition and fine motor) and KBIT-2 (verbal and composite) scores compared to children with a short consistent day sleep trajectory. CONCLUSIONS: Longer and more consistent night- and total sleep trajectories, and a short day sleep trajectory in early childhood were associated with better cognition at 2 and 4.5 years.

The spectral sensitivity of human circadian phase resetting and melatonin suppression to light changes dynamically with light duration.

Human circadian, neuroendocrine, and neurobehavioral responses to light are mediated primarily by melanopsin-containing intrinsically-photosensitive retinal ganglion cells (ipRGCs) but they also receive input from visual photoreceptors. Relative photoreceptor contributions are irradiance- and duration-dependent but results for long-duration light exposures are limited. We constructed irradiance-response curves and action spectra for melatonin suppression and circadian resetting responses in participants exposed to 6.5-h monochromatic 420, 460, 480, 507, 555, or 620 nm light exposures initiated near the onset of nocturnal melatonin secretion. Melatonin suppression and phase resetting action spectra were best fit by a single-opsin template with lambdamax at 481 and 483 nm, respectively. Linear combinations of melanopsin (ipRGC), short-wavelength (S) cone, and combined long- and medium-wavelength (L+M) cone functions were also fit and compared. For melatonin suppression, lambdamax was 441 nm in the first quarter of the 6.5-h exposure with a second peak at 550 nm, suggesting strong initial S and L+M cone contribution. This contribution decayed over time; lambdamax was 485 nm in the final quarter of light exposure, consistent with a predominant melanopsin contribution. Similarly, for circadian resetting, lambdamax ranged from 445 nm (all three functions) to 487 nm (L+M-cone and melanopsin functions only), suggesting significant S-cone contribution, consistent with recent model findings that the first few minutes of a light exposure drive the majority of the phase resetting response. These findings suggest a possible initial strong cone contribution in driving melatonin suppression and phase resetting, followed by a dominant melanopsin contribution over longer duration light exposures.

Staying vigilant during recurrent sleep restriction: dose-response effects of time-in-bed and benefits of daytime napping.

STUDY OBJECTIVES: We characterized vigilance deterioration with increasing time-on-task (ToT) during recurrent sleep restriction of different extents on simulated weekdays and recovery sleep on weekends, and tested the effectiveness of afternoon napping in ameliorating ToT-related deficits. METHODS: In the Need for Sleep studies, 194 adolescents (age = 15-19 years) underwent two baseline nights of 9-h time-in-bed (TIB), followed by two cycles of weekday manipulation nights and weekend recovery nights (9-h TIB). They were allocated 9 h, 8 h, 6.5 h, or 5 h of TIB for nocturnal sleep on weekdays. Three additional groups with 5 h or 6.5 h TIB were given an afternoon nap opportunity (5 h + 1 h, 5 h + 1.5 h, and 6.5 h + 1.5 h). ToT effects were quantified by performance change from the first 2 min to the last 2 min in a 10-min Psychomotor Vigilance Task administered daily. RESULTS: The 9 h and the 8 h groups showed comparable ToT effects that remained at baseline levels throughout the protocol. ToT-related deficits were greater among the 5 h and the 6.5 h groups, increased prominently in the second week of sleep restriction despite partial recuperation during the intervening recovery period and diverged between these two groups from the fifth sleep-restricted night. Daytime napping attenuated ToT effects when nocturnal sleep restriction was severe (i.e. 5-h TIB/night), and held steady at baseline levels for a milder dose of nocturnal sleep restriction when total TIB across 24 h was within the age-specific recommended sleep duration (i.e. 6.5 h + 1.5 h). CONCLUSIONS: Reducing TIB beyond the recommended duration significantly increases ToT-associated vigilance impairment, particularly during recurrent periods of sleep restriction. Daytime napping is effective in ameliorating such decrement. CLINICAL TRIAL REGISTRATION: NCT02838095, NCT03333512, and NCT04044885.

A targeted e-learning approach for keeping universities open during the COVID-19 pandemic while reducing student physical interactions.

The COVID-19 pandemic led to widespread closure of universities. Many universities turned to e-learning to provide educational continuity, but they now face the challenge of how to reopen safely and resume in-class learning. This is difficult to achieve without methods for measuring the impact of school policies on student physical interactions. Here, we show that selectively deploying e-learning for larger classes is highly effective at decreasing campus-wide opportunities for student-to-student contact, while allowing most in-class learning to continue uninterrupted. We conducted a natural experiment at a large university that implemented a series of e-learning interventions during the COVID-19 outbreak. The numbers and locations of 24,000 students on campus were measured over a 17-week period by analysing >24 million student connections to the university Wi-Fi network. We show that daily population size can be manipulated by e-learning in a targeted manner according to class size characteristics. Student mixing showed accelerated growth with population size according to a power law distribution. Therefore, a small e-learning dependent decrease in population size resulted in a large reduction in student clustering behaviour. Our results suggest that converting a small number of classes to e-learning can decrease potential for disease transmission while minimising disruption to university operations. Universities should consider targeted e-learning a viable strategy for providing educational continuity during periods of low community disease transmission.

Variability of Lipids in Human Milk.

Lipids in breastmilk play a critical role in infant growth and development. However, few studies have investigated sources of variability of both high- and low-abundant milk lipids. The objective of our study was to investigate individual and morning-evening differences in the human milk lipidome. In this study, a modified two-phase method (MTBE: Methanol 7:2) was validated for the extraction of lipids from human breastmilk. This method was then applied to samples from a group of 20 healthy women to measure inter- and intra-individual (morning versus evening) variability of the breastmilk lipidome. We report here the levels of 237 lipid species from 13 sub-classes using reversed-phase liquid chromatography mass spectrometry (RP-LCMS) and direct-infusion mass spectrometry (DI-MS). About 85% of lipid species showed stable inter-individual differences across time points. Half of lipid species showed higher concentrations in the evening compared with the morning, with phosphatidylethanolamines (PEs) and triacylglycerols (TAGs) exhibiting the largest changes. In morning and evening samples, the biological variation was greater for diacylglycerols (DAGs) and TAGs compared with phospholipids and sphingolipids, and the variation in DAGs and TAGs was greater in evening samples compared with morning samples. These results demonstrate that variation in the milk lipidome is strongly influenced by individual differences and time of day.

Circadian regulation of breath alcohol concentration.

STUDY OBJECTIVES: The role of the circadian clock in regulating blood/breath alcohol levels after consuming alcohol is uncertain. Our goal was to evaluate the degree to which the circadian system regulates breath alcohol concentration (BrAC) pharmacokinetic parameters. METHODS: Twenty healthy adults aged 21-30 years took part in a 4-day laboratory study. A 40-h constant routine procedure was used to assess circadian rhythms. Every 4 h, participants were given a fixed oral dose of alcohol with breathalyzer measurements taken every 5 min to construct BrAC curves. Sinusoidal models were used to test for circadian variation of the peak BrAC, the time to reach peak BrAC, the absorption rate, the elimination rate, and the time for BrAC to return to zero after alcohol was ingested. RESULTS: A significant circadian rhythm was detected for group-averaged peak BrAC values and the time for BrAC to return to zero, but not other BrAC variables. Peak BrAC values were lowest in the evening near the peak of the core body temperature rhythm and nadir of the salivary cortisol rhythm. Peak BrAC values increased during the night and reached their highest levels in the morning and afternoon. The time needed for BrAC to return to zero was also longest in the late morning and afternoon. CONCLUSION: The circadian system modulates some BrAC pharmacokinetic parameters. In normally entrained individuals, taking the same oral dose of alcohol at different times of day can result in different BrAC responses. These findings have potential implications for alcohol-related accidents and alcohol toxicity.

Multiple modifiable lifestyle factors and the risk of perinatal depression during pregnancy: Findings from the GUSTO cohort.

BACKGROUND: Studies have identified lifestyle risk factors for perinatal depression, but none have examined the cumulative effect of these risk factors in pregnant women. METHODS: We considered the following six factors during pregnancy: poor diet quality (Healthy eating index for Singapore pregnant women 5), physical inactivity (<600 MET-minutes/week), vitamin D insufficiency (<50 nmol/l), smoking before or during pregnancy, and the perceived need for social support. Probable depression was assessed using the Edinburgh postnatal depression scale during pregnancy (>15) and at three months postpartum (≥13). Prevalence risk ratios were calculated with Poisson regressions while adjusting for potential confounders. RESULTS: Of 535 pregnant women, 207 (39%) had zero or one risk factor, 146 (27%) had two, 119 (22%) had three, 48 (9%) had four, and 15 (3%) had ≥5 risk factors at 26-28 weeks' gestation. These six lifestyle habits contributed to 32% of the variance in depressive symptoms during pregnancy. The prevalence of being probably depressed was 6.4 (95% CI 2.1, 19.8; ptrend < 0.001) for expecting women who had ≥4 risk factors compared to women who had ≤1 risk factor. No association was observed between the number of risk factors and depressive symptoms at 3 months postpartum (ptrend = 0.746). CONCLUSION: Pregnant women with ≥4 lifestyle risk factors showed a higher prevalence of depression during pregnancy, while no associations were observed for postpartum depression. CLINICAL TRIAL REGISTRATION: This cohort is registered under the Clinical Trials identifier NCT01174875; http://www.clinicaltrials.gov/ct2/show/NCT01174875?term=GUSTO&rank=2.

Cognitive effects of split and continuous sleep schedules in adolescents differ according to total sleep opportunity.

STUDY OBJECTIVES: We compared the basic cognitive functions of adolescents undergoing split (nocturnal sleep + daytime nap) and continuous nocturnal sleep schedules when total sleep opportunity was either below or within the recommended range (i.e. 6.5 or 8 h). METHODS: Adolescent participants (age: 15-19 year) in the 8-h split (n = 24) and continuous (n = 29) sleep groups were compared with 6.5-h split and continuous sleep groups from a previous study (n = 58). These protocols involved two baseline nights (9-h time-in-bed [TIB]), 5 nights of sleep manipulation, 2 recovery nights (9-h TIB), followed by a second cycle of sleep manipulation (3 nights) and recovery (2 nights). Cognitive performance, subjective sleepiness, and mood were evaluated daily; sleep was assessed using polysomnography. RESULTS: Splitting 6.5 h of sleep with a mid-afternoon nap offered a boost to cognitive function compared to continuous nocturnal sleep. However, when total TIB across 24 h increased to 8 h, the split and continuous sleep groups performed comparably in tests evaluating vigilance, working memory, executive function, processing speed, subjective sleepiness, and mood. CONCLUSIONS: In adolescents, the effects of split sleep on basic cognitive functions vary by the amount of total sleep obtained. As long as the total sleep opportunity across 24 h is within the recommended range, students may fulfill sleep requirements by adopting a split sleep schedule consisting of a shorter period of nocturnal sleep combined with a mid-afternoon nap, without significant impact on basic cognitive functions. CLINICAL TRIAL REGISTRATION: NCT04044885.

Associations of time spent on homework or studying with nocturnal sleep behavior and depression symptoms in adolescents from Singapore.

OBJECTIVE: To investigate associations of adolescents' time spent on homework/studying with nocturnal time for sleep and depression symptoms, in a competitive academic environment. DESIGN: Cross-sectional, anonymous survey of sleep habits, school life, and health-related measures. SETTING: Eight schools in Singapore. PARTICIPANTS: Total 1225 adolescents aged 13-19 years. MEASUREMENTS: Self-reported sleep behavior and time use data were collected separately for school days and weekends. Multiple regression models were used to test covariation of time spent on homework/studying with other activities, and associations of homework/studying duration with depression symptoms. RESULTS: Time in bed for sleep and media use were inversely related with homework/studying duration on both school days and weekends, adjusting for time spent on other activities and demographic variables. Face-to-face family time and hanging out with friends were also reciprocally related with homework/studying duration on weekends. Depression scores were higher in adolescents who spent long hours on homework/studying. On school days, this was mediated by reduced time in bed for sleep. On weekends, homework/studying duration associated with depression symptoms, adjusting for time in bed and other covariates. Adolescents who spent ≥5 hours on homework/studying per day on weekends had greater symptoms of anhedonia and anxiety. CONCLUSIONS: In a competitive academic setting, adolescents who spent more time on homework/studying spent less time on sleep, media use, and social activities. Independent of effects on sleep, long hours on homework/studying on weekends may be a risk factor for depression. Reducing adolescents' workload outside of class may benefit their sleep, schoolwork-life balance, and mental well-being.

Menstrual phase-dependent differences in neurobehavioral performance: the role of temperature and the progesterone/estradiol ratio.

STUDY OBJECTIVES: Women in the luteal phase of the menstrual cycle exhibit better cognitive performance overnight than women in the follicular phase, although the mechanism is unknown. Given the link between core body temperature (CBT) and performance, one potential mechanism is the thermoregulatory role of progesterone (P4), estradiol (E2), and their ratio (P4/E2), which change across the menstrual cycle. We examined the role of P4/E2 in modulating performance during extended wake in premenopausal women. Additionally, we compared the acute effects of nighttime light exposure on performance, CBT, and hormones between the menstrual phases. METHODS: Participants were studied during a 50 h constant routine and a 6.5 h monochromatic nighttime light exposure. Participants were 16 healthy, naturally cycling women (eight follicular; eight luteal). Outcome measures included reaction time, attentional failures, self-reported sleepiness, CBT, melatonin, P4, and E2. RESULTS: As compared to women in the luteal phase, women in the follicular phase exhibited worse performance overnight. CBT was significantly associated with performance, P4, and P4/E2 but not with other sex hormones. Sex hormones were not directly related to performance. Light exposure that suppressed melatonin improved performance in the follicular phase (n = 4 per group) to levels observed during the luteal phase and increased CBT but without concomitant changes in P4/E2. CONCLUSIONS: Our results underscore the importance of considering menstrual phase when assessing cognitive performance during sleep loss in women and indicate that these changes are driven predominantly by CBT. Furthermore, this study shows that vulnerability to sleep loss during the follicular phase may be resolved by exposure to light.

Evaluation of an interactive school-based sleep education program: a cluster-randomized controlled trial.

OBJECTIVES: Shortened sleep has negative consequences on adolescents' well-being. The present study evaluated an interactive school-based sleep education program (SEP) aimed at increasing adolescent sleep duration. DESIGN AND INTERVENTION: A cluster-randomized controlled trial with 12 clusters (classes) was used. The intervention group received a SEP and the active control group received a healthy living program (HLP). Both groups underwent a 4-week class-based education program. The SEP students learned about the importance of sleep, the barriers to getting enough sleep, and how to improve their time management to increase their sleep opportunity. The HLP students learned about various health-related topics not including sleep. PARTICIPANTS: A total of 210 students (mean age = 14.04 ± 0.32 years) were randomly assigned to the SEP (n = 102) or the HLP (n = 108) group, with 6 classes per group. MEASUREMENTS: Sleep (actigraphically measured), sleep knowledge, and time usage were assessed using linear mixed models at three time points: baseline, immediately after intervention, and 1-month follow-up. RESULTS: Sleep knowledge improved at follow-up in the SEP relative to the HLP group (p = .017). Although students were receptive of the program and self-reported the intention to create more time for sleep, no changes in sleep were found following the SEP. Some benefit may have been masked by exam preparations at the follow-up evaluation. CONCLUSIONS: Sleep education alone may not be sufficient to change sleep behavior. A combination of sleep education, starting school later, and parental involvement may be needed to encourage and enable changes in adolescent sleep duration.

Antenatal sleep quality associated with perinatal outcomes in women of advanced maternal age.

OBJECTIVES: The increasing prevalence of advanced maternal age (AMA) coupled with poor sleep quality among pregnant women makes it important to study their association with perinatal outcomes. However, little is known about the interaction of AMA and maternal antenatal sleep on perinatal outcomes. Here, we examined whether associations between AMA and perinatal outcomes are modified by antenatal sleep quality. PARTICIPANTS: Data were collected from 446 women, with a singleton pregnancy and no pregnancy complications, who participated in the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort study. MEASUREMENTS: Participants completed the Pittsburgh Sleep Quality Index (PSQI) at 26-28 weeks gestation and had perinatal outcome data collected upon delivery. Interactions between AMA and maternal sleep quality on perinatal outcomes were investigated and where significant, analyses were further stratified by maternal age. All analyses were adjusted for maternal BMI at 26-28 weeks gestation, ethnicity, and maternal education. RESULTS: Neonates of mothers of AMA and poor sleep quality (PSQI score >5) had increased odds of stay in the neonatal intensive care unit (adjusted odds ratio = 3.53, 95% CI: -1.21 to 10.27) and shorter birth length (adjusted mean difference = -1.05 cm, 95% CI: -1.82 to -0.20), as compared with women of AMA and good sleep quality (PSQI score ≤5). In women <35 years, sleep quality did not associate with perinatal outcomes. CONCLUSION: Poor sleep quality in women of AMA was associated with neonatal health outcomes. Improving maternal antenatal sleep may potentially improve perinatal outcomes in offspring of women of AMA.

Using a Single Daytime Performance Test to Identify Most Individuals at High-Risk for Performance Impairment during Extended Wake.

We explored the predictive value of a neurobehavioral performance assessment under rested baseline conditions (evaluated at 8 hours awake following 8 hours of sleep) on neurobehavioral response to moderate sleep loss (evaluated at 20 hours awake two days later) in 151 healthy young participants (18-30 years). We defined each participant's response-to-sleep-loss phenotype based on the number of attentional failures on a 10-min visual psychomotor vigilance task taken at 20 hours awake (resilient: less than 6 attentional failures, n = 26 participants; non-resilient: 6 or more attentional failures, n = 125 participants). We observed that 97% of rested participants with 2 or more attentional failures (n = 73 of 151) and 100% of rested participants with 3 or more attentional failures (n = 57 of 151) were non-resilient after moderate sleep loss. Our approach can accurately identify a significant proportion of individuals who are at high risk for neurobehavioral performance impairment from staying up late with a single neurobehavioral performance assessment conducted during rested conditions. Additional methods are needed to predict the future performance of individuals who are not identified as high risk during baseline.