Memory encoding is impaired after multiple nights of partial sleep restriction

Ozone rectal insufflation mitigates chronic rapid eye movement sleep deprivation-induced cognitive impairment through inflammation alleviation and gut microbiota regulation in mice

A range of sleep disorders has the potential to adversely affect cognitive function. This study was undertaken with the objective of investigating the effects of ozone rectal insufflation (O3-RI) on cognitive dysfunction induced by chronic REM sleep deprivation, as well as elucidating possible underlying mechanisms. O3-RI ameliorated cognitive dysfunction in chronic REM sleep deprived mice, improved the neuronal damage in the hippocampus region and decreased neuronal loss. Administration of O3-RI may protect against chronic REM sleep deprivation induced cognitive dysfunction by reversing the abnormal expression of Occludin and leucine-rich repeat and pyrin domain-containing protein 3 inflammasome as well as interleukin-1β in the hippocampus and colon tissues. Moreover, the microbiota diversity and composition of sleep deprivation mice were significantly affected by O3-RI intervention, as evidenced by the reversal of the Firmicutes/Bacteroidetes abundance ratio and the relative abundance of the Bacteroides genus. In particular, the relative abundance of the Bacteroides genus demonstrated a pronounced correlation with cognitive impairment and inflammation. Our findings suggested that O3-RI can improve cognitive dysfunction in sleep deprivation mice, and its mechanisms may be related to regulating gut microbiota and alleviating inflammation and damage in the hippocampus and colon.

A systematic and meta-analytic review of the impact of sleep restriction on memory formation

Modern life causes a quarter of adults and half of teenagers to sleep for less than is recommended (Kocevska et al., 2021). Given well-documented benefits of sleep on memory, we must understand the cognitive costs of short sleep. We analysed 125 sleep restriction effect sizes from 39 reports involving 1234 participants. Restricting sleep (3-6.5 hours) compared to normal sleep (7-11 hours) negatively affects memory formation with a small effect size (Hedges' g = 0.29, 95 % CI = [0.13, 0.44]). We detected no evidence for publication bias. When sleep restriction effect sizes were compared with 185 sleep deprivation effect sizes (Newbury et al., 2021) no statistically significant difference was found, suggesting that missing some sleep has similar consequences for memory as not sleeping at all. When the analysis was restricted to post-encoding, rather than pre-encoding, sleep loss, sleep deprivation was associated with larger memory impairment than restriction. Our findings are best accounted for by the sequential hypothesis which emphasises complementary roles of slow-wave sleep and REM sleep for memory.

Melatonin ameliorates chronic sleep deprivation against memory encoding vulnerability: Involvement of synapse regulation via the mitochondrial-dependent redox homeostasis-induced autophagy inhibition

Voluntary sleep curtailment is increasingly more rampant in modern society and compromises healthy cognition, including memory, to varying degrees. However, whether memory encoding is impaired after chronic sleep deprivation (CSD) and the underlying molecular mechanisms involved remain unclear. Here, using the mice, we tested the impact of CSD on the encoding abilities of social recognition-dependent memory and object recognition-dependent memory. We found that memory encoding was indeed vulnerable to CSD, while memory retrieval remained unaffected. The hippocampal neurons of mice with memory encoding deficits exhibited significant synapse damage and hyperactive autophagy, which dissipates during regular sleep cycles. This excessive autophagy appeared to be triggered by damage to mitochondrial DNA (mtDNA), resulting from oxidative stress within the mitochondria. The relief at the behavioral and molecular biological levels can be achieved with intraperitoneal injections of the antioxidant compound melatonin. Moreover, our in vitro experiments using HT-22 cells demonstrated that oxidative stress induced by hydrogen peroxide led to oxidative damage, including mtDNA damage, and activation of autophagy. Melatonin treatment effectively countered these effects, restoring redox homeostasis and reducing excessive autophagic activity. Notably, this protective effect was not observed when melatonin was administered as a pre-treatment. Together, our findings reveal the vulnerability of memory encoding during chronic sleep curtailment, which is caused by oxidative stress and consequent enhancement of autophagy, suggest a potential therapeutic strategy for addressing these effects following prolonged wakefulness through melatonin intervention, and reiterate the significance of adequate sleep for memory formation and retention.

Interactions among neighborhood conditions, sleep quality, and episodic memory across the adult lifespan

OBJECTIVES

On average, adults racialized as non-Hispanic Black and Hispanic sleep more poorly than adults racialized as non-Hispanic White (hereafter, Black, Hispanic, White), but associations between factors that may moderate sleep-memory associations in these groups, such as neighborhood conditions, are unclear. Poorer neighborhood conditions (e.g. lower neighborhood cohesion) may be negatively associated with sleep quality and multiplicatively influence sleep-memory associations. We hypothesized lower ratings of neighborhood conditions would be associated with poorer sleep quality and moderate the association between sleep quality and episodic memory, especially in Black and Hispanic adults, who are disproportionately situated in poor neighborhood conditions.

DESIGN

Seven-hundred-thirty-six adults across the adult lifespan (27-89 years) were recruited from the northern Manhattan community as a part of the Offspring Study of Racial and Ethnic Disparities in Alzheimer's disease. Sleep quality was assessed using a modified version of the Pittsburgh Sleep Quality Index, and episodic memory was evaluated with the Buschke Selective Reminding Test. With multiple regression models, we measured associations between perceived neighborhood conditions and sleep quality and the interaction between sleep quality and neighborhood conditions on episodic memory stratified by racial/ethnic and gender identity groups.

RESULTS

Overall, poorer neighborhood conditions were associated with poorer sleep quality. In Black and Hispanic women, the sleep-memory association was moderated by neighborhood conditions. With more favorable neighborhood conditions, Black women showed an association between higher sleep quality and higher memory performance, and Hispanic women showed a protective effect of neighborhood (higher memory even when sleep quality was poor).

CONCLUSION

Poorer neighborhood experiences may contribute to poorer sleep quality across groups. In Black and Hispanic women, the association between sleep quality and episodic memory performance was dependent upon neighborhood conditions. These findings may inform tailored, structural level sleep interventions, aimed to improve neighborhood experiences and thereby sleep quality and episodic memory.

Bidirectional associations between the duration and timing of nocturnal sleep and daytime naps in adolescents differ from weekdays to weekends

STUDY OBJECTIVES

Previous studies examining bidirectional relationships between nocturnal sleep and napping have focused on sleep duration, leaving a gap in our understanding of how sleep timing contributes. Here, we assessed the duration and timing for night sleep and daytime naps, to evaluate how the previous night's sleep influences the next day's napping, and how napping influences same-night nocturnal sleep.

METHODS

We analyzed sleep diary and actigraphy data from 153 teens (males = 43.8%, mean age = 16.6 years). Participants who never napped were excluded. Nocturnal sleep-nap relationships were investigated using logistic and linear regression models separately for weekdays and weekends.

RESULTS

Participants napped an average of 2.3 times a week. 167 school day naps and 107 weekends were recorded. Naps were on average 82.12 ± 53.34 minutes and the average nap onset was 14:58 ± 3.78 hours. Their duration, start and end times did not significantly differ between weekdays and weekends. Nocturnal sleep duration did not predict next-day nap occurrence or duration. However, on school days, earlier wake times significantly increased the likelihood of napping that day, and advanced nap timing. On weekends, later bedtimes and wake times delayed nap timing. On school days, napping longer than one's average shortened nocturnal sleep whereas on weekends, waking from a nap later than one's average delayed bedtimes.

CONCLUSIONS

Early wake times increase the likelihood of napping and advance the time of a nap that day. Naps may be detrimental to the same night's sleep only if they are long and occur late, as these can delay bedtimes and shorten nocturnal sleep duration, especially on school days.

CLINICAL TRIALS

The Cognitive and Metabolic Effects of Sleep Restriction in Adolescents (NFS4), https://clinicaltrials.gov/study/NCT03333512, ID: NCT03333512. Investigating Preferred Nap Schedules for Adolescents (NFS5), https://clinicaltrials.gov/study/NCT04044885, ID: NCT04044885.

Neuroelectrophysiological alteration associated with cognitive flexibility after 24 h sleep deprivation in adolescents

The cognitive neural mechanisms by which sleep deprivation affects cognitive flexibility are poorly understood. Therefore, the study investigated the neuroelectrophysiological basis of the effect of 24 h sleep deprivation on cognitive flexibility in adolescents. 72 participants (36 females, mean age ± SD=20.46 ± 2.385 years old) participated in the study and were randomly assigned to the sleep deprivation group and control group. They were instructed to complete a task switch paradigm, during which participants' behavioral and electroencephalographic data were recorded. Behaviorally, there were significant between-group differences in accuracy. The results of event-related potential showed that the P2, N2 and P3 components had significant group effects or interaction effects. At the time-frequency level, there were statistically significant differences between the delta and theta bands. These results suggested that 24 h sleep deprivation affected problem-solving effectiveness rather than efficiency, mainly because it systematically impaired cognitive processing associated with cognitive flexibility.

Investigating the acute effect of low and moderate intensity aerobic exercise on whole-body task learning and cognition in young adults

Recent studies have shown that a single bout of exercise has acute improvements on various forms of memory, including procedural motor learning, through mechanisms such as the plasticity-promoting effect. This study aimed to examine (1) the acute effects of timing and intensity of aerobic exercise on the acquisition and retention of motor learning in healthy adults, (2) the effect of sleep quality of the night before and after acquisition on motor learning, and (3) the acute effects of low and moderate-intensity aerobic exercise on cognitive functions. Seventy-five healthy adults were divided into five groups: Two groups performed low or moderate intensity aerobic exercise before motor practice; two groups performed low or moderate intensity aerobic exercise after motor practice; the control group only did motor practice. Low- and moderate-intensity exercises consisted of 30 min of running at 57%-63% and 64%-76% of the maximum heart rate, respectively. Motor learning was assessed using a golf putting task. The sleep quality of the night before and after the acquisition was evaluated using the Richard Campbell Sleep Questionnaire. Cognitive function was assessed before and after aerobic exercise using the Paced Auditory Serial Acquisition Task test. Results indicated that all groups demonstrated acquisition, 1-day and 7-day retention at a similar level (p > 0.05). Regression analysis revealed no significant relationship between sleep quality on the night before the experimental day and total acquisition (p > 0.05). However, a positive correlation was found between the sleep quality on the night of the experimental day and both 1-day and 7-day retention (p < 0.05). A single bout of low or moderate acute exercise did not modify motor skill acquisition and retention. Other results showed the importance of night sleep quality on the retention and proved that a single bout of moderate intensity exercise was associated with improved cognitive function.

Neurocognitive Effects of Sleep Disruption in Children and Adolescents

A main childhood task is learning. In this task, the role of sleep is increasingly demonstrated. Although most literature examining this role focuses on preadolescence and middle adolescence, some studies apply napping designs in preschoolers. Studies overall conclude that without proper sleep a child's cognitive abilities suffer, but questions on how and to what extent linger. Observational studies show the hazards of potential confounders such as an individual's resilience to poor sleep as well as developmental risk factors (eg, disorders, stressors). A better understanding of cognitive sleep neuroscience may have a big impact on pediatric sleep research and clinical applications.

Sleep loss disrupts the neural signature of successful learning

Sleep supports memory consolidation as well as next-day learning. The influential "Active Systems" account of offline consolidation suggests that sleep-associated memory processing paves the way for new learning, but empirical evidence in support of this idea is scarce. Using a within-subjects (n = 30), crossover design, we assessed behavioral and electrophysiological indices of episodic encoding after a night of sleep or total sleep deprivation in healthy adults (aged 18-25 years) and investigated whether behavioral performance was predicted by the overnight consolidation of episodic associations from the previous day. Sleep supported memory consolidation and next-day learning as compared to sleep deprivation. However, the magnitude of this sleep-associated consolidation benefit did not significantly predict the ability to form novel memories after sleep. Interestingly, sleep deprivation prompted a qualitative change in the neural signature of encoding: Whereas 12-20 Hz beta desynchronization-an established marker of successful encoding-was observed after sleep, sleep deprivation disrupted beta desynchrony during successful learning. Taken together, these findings suggest that effective learning depends on sleep but not necessarily on sleep-associated consolidation.

Understanding the Need for Sleep to Improve Cognition

The restorative function of sleep is shaped by its duration, timing, continuity, subjective quality, and efficiency. Current sleep recommendations specify only nocturnal duration and have been largely derived from sleep self-reports that can be imprecise and miss relevant details. Sleep duration, preferred timing, and ability to withstand sleep deprivation are heritable traits whose expression may change with age and affect the optimal sleep prescription for an individual. Prevailing societal norms and circumstances related to work and relationships interact to influence sleep opportunity and quality. The value of allocating time for sleep is revealed by the impact of its restriction on behavior, functional brain imaging, sleep macrostructure, and late-life cognition. Augmentation of sleep slow oscillations and spindles have been proposed for enhancing sleep quality, but they inconsistently achieve their goal. Crafting bespoke sleep recommendations could benefit from large-scale, longitudinal collection of objective sleep data integrated with behavioral and self-reported data.

Impaired procedural memory in narcolepsy type 1

Objectives

Sleep enhances the consolidation of memories. Here, we investigated whether sleep‐dependent memory consolidation differs between healthy subjects and narcolepsy type 1 (NT1) patients.

Material and Methods

We recruited 18 patients with NT1 and 24 healthy controls. The consolidation of spatial (declarative memory; 2‐dimensional object location) and procedural (non‐declarative memory; finger sequence tapping) memories was examined across one night of at‐home sleep. Sleep was measured by an ambulatory sleep recording device.

Results

The overnight gain in the number of correctly recalled sequences in the finger‐tapping test was smaller for NT1 patients than healthy subjects (+8.1% vs. +23.8% from pre‐sleep learning to post‐sleep recall, p = .035). No significant group differences were found for the overnight consolidation of spatial memory. Compared to healthy subjects, the sleep of NT1 patients was significantly more fragmented and shallow. However, no significant correlations were found between sleep parameters and overnight performance changes on the memory tests in the whole group.

Conclusion

The sleep‐dependent consolidation of procedural but not spatial memories may be impaired among patients with NT1. Therefore, future studies are warranted to examine whether sleep improvement, for example, using sodium oxybate, can aid the sleep‐dependent formation of procedural memories among NT1 patients.

A collaborative approach to adopting/adapting guidelines. The Australian 24-hour movement guidelines for children (5-12 years) and young people (13-17 years): An integration of physical activity, sedentary behaviour, and sleep

Abstract

Background

In 2018, the Australian Government updated the Australian Physical Activity and Sedentary Behaviour Guidelines for Children and Young People. A requirement of this update was the incorporation of a 24-hour approach to movement, recognising the importance of adequate sleep. The purpose of this paper was to describe how the updated Australian 24-Hour Movement Guidelines for Children and Young People (5 to 17 years): an integration of physical activity, sedentary behaviour and sleep were developed and the outcomes from this process.

Methods

The GRADE-ADOLOPMENT approach was used to develop the guidelines. A Leadership Group was formed, who identified existing credible guidelines. The Canadian 24-Hour Movement Guidelines for Children and Youth best met the criteria established by the Leadership Group. These guidelines were evaluated based on the evidence in the GRADE tables, summaries of findings tables and recommendations from the Canadian Guidelines. We conducted updates to each of the Canadian systematic reviews. A Guideline Development Group reviewed, separately and in combination, the evidence for each behaviour. A choice was then made to adopt or adapt the Canadian recommendations for each behaviour or create de novo recommendations. We then conducted an online survey (n=237) along with three focus groups (n=11 in total) and 13 key informant interviews. Stakeholders used these to provide feedback on the draft guidelines.

Results

Based on the evidence from the Canadian systematic reviews and the updated systematic reviews in Australia, the Guideline Development Group agreed to adopt the Canadian recommendations and, apart from some minor changes to the wording of good practice statements, maintain the wording of the guidelines, preamble, and title of the Canadian Guidelines. The Australian Guidelines provide evidence-informed recommendations for a healthy day (24-hours), integrating physical activity, sedentary behaviour (including limits to screen time), and sleep for children (5-12 years) and young people (13-17 years).

Conclusions

To our knowledge, this is only the second time the GRADE-ADOLOPMENT approach has been used to develop movement behaviour guidelines. The judgments of the Australian Guideline Development Group did not differ sufficiently to change the directions and strength of the recommendations and as such, the Canadian Guidelines were adopted with only very minor alterations. This allowed the Australian Guidelines to be developed in a shorter time frame and at a lower cost. We recommend the GRADE-ADOLOPMENT approach, especially if a credible set of guidelines that was developed using the GRADE approach is available with all supporting materials. Other countries may consider this approach when developing and/or revising national movement guidelines.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12966-021-01236-2.

Mapping Sleep Spindle Characteristics to Vigilance Outcomes in Patients with Obstructive Sleep Apnea

Obstructive Sleep Apnea (OSA) is a sleep disorder associated with reduced vigilance. Vigilance status is often measured using the Psychomotor Vigilance Task (PVT). This paper investigates modelling strategies to map sleep spindle (Sp) characteristics to PVT metrics in patients with OSA. Sleep spindles (n=2305) were manually detected across blocks of sleep for 20 patients randomly selected from a cohort of 190 undergoing Polysomnography (PSG) for suspected OSA. Novel Sp metrics based on runs or "bursts" of Sps were used to model Sp characteristics to standardized (z) Lapse and Median Reaction Time (MdRT) scores, and to Groups based on zLapse and zMdRT scores. A model employing Sp Burst characteristics mapped to MdRT Group membership with an accuracy of 91.9%, (95% C.I. 90.8-93.0). The model had a sensitivity of 88.9%, (95% C.I. 87.5-89.0) and specificity of 89.1% (95% C.I. 87.3-90.5) for detecting patients with the lowest MdRTs in our cohort.Clinical Relevance- Based on these results it may be possible to use Sp data collected during overnight diagnostic PSG for OSA to detect patients at risk for attention deficits. This would improve triage for OSA therapy by identifying at risk patients at the time of OSA diagnosis and would remove the need to employ additional testing to assess vigilance status.

An Ergogenic Medical Education: Building Curricula to Optimize Performance and Decrease Burnout

One of the most pervasive myths in our culture today is the belief that training increases performance. When, in fact, training decreases performance. The current structure of training programs and educational curriculums provide the evidence regarding the acceptance of this belief. Intense focus is placed on the quantity of training time with little regard for additional factors. In pursuit of excellence, maximizing training opportunity and learning exposure insists upon the sacrifice of recovery time. However, recovery is the necessary training period to increase performance. In athletics, training without recovery leads to overtraining syndrome. Burnout is the non-athletic equivalency seen in under-recovered learners and workers. As demonstrated by the climbing burnout rates, the current structure of educational programs, epitomized by medical residency, perpetuates the myth that more training equals better performance. The purpose of the article does not revolve around the presentation of novel research discoveries, but it insists upon the implementation of previously established performance data in curricula development beyond athletics. The inflection and deflection points along the growth and adaptation curves can be explicitly utilized to meet the educational and professional standards set forth by educational institutions. When tracking performance as the metric, initial training stimuli creates a descending slope, e.g., "training decreases performance." The concept that training creates a negative deflection is a neglected concept in academics. By incorporating this feature into learning environments, training can transition from surviving training redundancy to thriving with an optimal work:recovery ratio.

The Relationship Between Perceived Stress and Subjective Cognitive Decline During the COVID-19 Epidemic

During the outbreak of the COVID-19 epidemic, fear of disease and its consequences, recommended lifestyle changes, and severe restrictions set by governments acted as stressors and affected people's mood, emotions, mental health, and wellbeing. Many studies conducted during this crisis focused on affective and physiological responses to stress, but few studies examined how the crisis affected cognition. The present cross-sectional study examined the relationship between physiological, affective, and cognitive responses to the epidemic. In an online survey conducted at the height of the first wave of the epidemic in Slovenia (April 15-25, 2020), 830 Slovenian residents aged 18-85 years reported the effects of stressors (confinement, problems at home, problems at work, lack of necessities, and increased workload), experienced emotions, generalized anxiety, perceived stress, changes in health, fatigue and sleep quality, and perceived changes in cognition during the epidemic. Risk factors for stress (neuroticism, vulnerability, general health, gender, and age) were also recorded. We hypothesized that stressors and stress risk factors will be related to subjective cognitive decline, with negative emotions, generalized anxiety, perceived stress, and physical symptoms acting as mediator variables. On average, the results showed a mild subjective cognitive decline during the epidemic. In structural equation modeling, 34% of its variance was predicted by the mediator variables, with negative emotions and physical symptoms having the largest contribution. Stress risk factors were predictably related to the four mediator variables. Among the stressors, confinement showed the strongest effect on the four mediator variables, implying the importance of thoughtful communication about necessary restrictive measures during emergency circumstances. The results of this study indicate that the possibility of altered cognitive function should be considered when planning work and study activities during the epidemic.

Memory performance following napping in habitual and non-habitual nappers

Study Objectives

Afternoon naps benefit memory but this may depend on whether one is a habitual napper (HN; ≥1 nap/week) or non-habitual napper (NN). Here, we investigated whether a nap would benefit HN and NN differently, as well as whether HN would be more adversely affected by nap restriction compared to NN.

Methods

Forty-six participants in the nap condition (HN-nap: n = 25, NN-nap: n = 21) took a 90-min nap (14:00–15:30 pm) on experimental days while 46 participants in the Wake condition (HN-wake: n = 24, NN-wake: n = 22) remained awake in the afternoon. Memory tasks were administered after the nap to assess short-term topographical memory and long-term memory in the form of picture encoding and factual knowledge learning respectively.

Results

An afternoon nap boosted picture encoding and factual knowledge learning irrespective of whether one habitually napped (main effects of condition (nap/wake): ps < 0.037). However, we found a significant interaction for the hippocampal-dependent topographical memory task (p = 0.039) wherein a nap, relative to wake, benefitted habitual nappers (HN-nap vs HN-wake: p = 0.003) compared to non-habitual nappers (NN-nap vs. NN-wake: p = 0.918). Notably for this task, habitual nappers’ performance significantly declined if they were not allowed to nap (HN-wake vs NN-wake: p = 0.037).

Conclusions

Contrary to concerns that napping may be disadvantageous for non-habitual nappers, we found that an afternoon nap was beneficial for long-term memory tasks even if one did not habitually nap. Naps were especially beneficial for habitual nappers performing a short-term topographical memory task, as it restored the decline that would otherwise have been incurred without a nap.

Clinical Trial Information

NCT04044885.

Anxiety in Residents in China: Prevalence and Risk Factors in a Multicenter Study

PURPOSE

To explore the prevalence of major anxiety and its associated risk factors in residents in China.

METHOD

This multicenter, cross-sectional study was conducted from December 2019 to February 2020; 1,343 residents from 8 hospitals in Northeast China were included in the final analysis (effective response rate of 86.48%). Demographic characteristics, dietary habits, life-related factors, work-related factors, and psychological characteristics were collected from participants via a self-reported questionnaire. This questionnaire measured sleep quality, physical activity, anxiety, perceived organizational support, psychological capital, and burnout. Adjusted odds ratios (ORs) and 95% confidence intervals were determined using binary logistic regression. Cutoff values and the area under the curve were calculated for risk factors using receiver operating characteristic curve analysis.

RESULTS

Of participants, 441 (32.80%) reported anxiety symptoms and 133 (9.90%) reported major anxiety symptoms. Four independent risk factors for major anxiety were identified: poor sleep quality (OR = 1.282, P < .001) and 3 dimensions of burnout: higher emotional exhaustion (OR = 1.085, P < .001), higher depersonalization (OR = 1.064, P = .002), and reduced personal accomplishment (OR = 0.951, P < .001). The optimal cutoff values for these risk factors were 7, 10, 9, and 22 scores, respectively.

CONCLUSIONS

This study found a considerable prevalence of major anxiety symptoms in residents in China and identified poor sleep quality and higher levels of burnout as having a close association with major anxiety. These findings enrich the existing literature on anxiety and demonstrate a critical need for additional studies that investigate intervention strategies to improve sleep quality and combat burnout, which could improve the mental health of residents.

Sleep after learning aids the consolidation of factual knowledge, but not relearning

Study Objectives

Sleep strengthens and reorganizes declarative memories, but the extent to which these processes benefit subsequent relearning of the same material remains unknown. It is also unclear whether sleep-memory effects translate to educationally realistic learning tasks and improve long-term learning outcomes.

Methods

Young adults learned factual knowledge in two learning sessions that were 12 h apart and separated by either nocturnal sleep (n = 26) or daytime wakefulness (n = 26). Memory before and after the retention interval was compared to assess the effect of sleep on consolidation, while memory before and after the second learning session was compared to assess relearning. A final test 1 week later assessed whether there was any long-term advantage to sleeping between two study sessions.

Results

Sleep significantly enhanced consolidation of factual knowledge (p = 0.01, d = 0.72), but groups did not differ in their capacity to relearn the materials (p = 0.72, d = 0.10). After 1 week, a numerical memory advantage remained for the sleep group but was no longer significant (p = 0.21, d = 0.35).

Conclusions

Reduced forgetting after sleep is a robust finding that extends to our ecologically valid learning task, but we found no evidence that sleep enhances relearning. Our findings can exclude a large effect of sleep on long-term memory after 1 week, but hint at a smaller effect, leaving open the possibility of practical benefits from organizing study sessions around nocturnal sleep. These findings highlight the importance of revisiting key sleep-memory effects to assess their relevance to long-term learning outcomes with naturalistic learning materials.

A daytime nap restores hippocampal function and improves declarative learning

STUDY OBJECTIVES

Daytime naps can confer benefits on subsequent declarative learning, but the physiological correlates of this improvement are less well studied. We examined learning following a daytime nap compared with an equivalent waking period using fMRI and polysomnography.

METHODS

Forty healthy young adults who slept normally the previous night encoded word pair lists in an MRI scanner at 13:00 and 16:30. Between sessions, participants either stayed awake and watched a documentary (Wake Group; N = 20) or had a 90-minute nap opportunity (Nap Group; N = 20) monitored by polysomnography. Approximately 40 minutes after completing each encoding session, memory for learned words was assessed using cued-recall.

RESULTS

A significant Session × Group interaction effect (p < 0.001) was observed in which memory was significantly improved in the Nap but not in the Wake group (p < 0.001). There was also a Session × Run × Group interaction effect in the left hippocampus (p = 0.001), whereby activation during word pair encoding increased only following the nap. Both performance improvement (rs = 0.46, p = 0.04) and nap-related increase in hippocampal activation (rs = 0.46, p = 0.04) were correlated with nap spindle count (12-15 Hz) but not with slow oscillation power (p's ≥ 0.18).

CONCLUSIONS

After a habitual nocturnal sleep, participants who had a 90-minute afternoon nap encoded word pairs better than a comparable group who stayed awake. Increases in hippocampal activation following the nap suggest restored hippocampal function. Naptime spindles may contribute to improved memory.

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.

Sleep and human cognitive development

Emerging studies across learning domains have shed light on mechanisms underlying sleep's benefits during numerous developmental periods. In this conceptual review, we survey recent studies of sleep and cognition across infancy, childhood, and adolescence. By summarizing recent findings and integrating across studies with disparate approaches, we provide a novel understanding of sleep's role in human cognitive function. Collectively, these studies point to an interrelation between brain development, sleep, and cognition. Moreover, we point to gaps in our understanding, which inform the agenda for future research in developmental and sleep science.

Splitting sleep between the night and a daytime nap reduces homeostatic sleep pressure and enhances long-term memory

Daytime naps have been linked with enhanced memory encoding and consolidation. It remains unclear how a daily napping schedule impacts learning throughout the day, and whether these effects are the same for well-rested and sleep restricted individuals. We compared memory in 112 adolescents who underwent two simulated school weeks containing 8 or 6.5 h sleep opportunities each day. Sleep episodes were nocturnal or split between nocturnal sleep and a 90-min afternoon nap, creating four experimental groups: 8 h-continuous, 8 h-split, 6.5 h-continuous and 6.5 h-split. Declarative memory was assessed with picture encoding and an educationally realistic factual knowledge task. Splitting sleep significantly enhanced afternoon picture encoding and factual knowledge under both 6.5 h and 8 h durations. Splitting sleep also significantly reduced slow-wave energy during nocturnal sleep, suggesting lower homeostatic sleep pressure during the day. There was no negative impact of the split sleep schedule on morning performance, despite a reduction in nocturnal sleep. These findings suggest that naps could be incorporated into a daily sleep schedule that provides sufficient sleep and benefits learning.

Contribution of sleep disturbances to the heterogeneity of cognitive and brain alterations in alcohol use disorder

Cognitive and brain alterations are common in alcohol use disorder and vary importantly from one patient to another. Sleep disturbances are also very frequent in these patients and remain largely neglected even though they can persist after drinking cessation. Sleep disturbances may be the consequence of specific brain alterations, resulting in cognitive impairments. But sleep disruption may also exacerbate alcohol-related brain abnormalities and cognitive deficits through common pathophysiological mechanisms. Besides, sleep disturbances seem a vulnerability factor for the development of alcohol use disorder. From a clinical perspective, sleep disturbances are known to affect treatment outcome and to increase the risk of relapse. In this article, we conducted a narrative review to provide a better understanding of the relationships between sleep disturbances, brain and cognition in alcohol use disorder. We suggest that the heterogeneity of brain and cognitive alterations observed in patients with alcohol use disorder could at least partially be explained by associated sleep disturbances. We also believe that sleep disruption could indirectly favor relapse by exacerbating neuropsychological impairments required in psychosocial treatment and for the maintenance of abstinence. Implications for clinical practice as well as perspectives for future research are proposed.

Differences in the Association of Anxiety, Insomnia and Somatic Symptoms between Medical Staff and the General Population During the Outbreak of COVID-19

BACKGROUND

During the outbreak of coronavirus disease 2019 (COVID-19), occupational differences were recognized with respect to psychological issues, but there are no reports regarding the insomnia and anxiety comorbidities and their related factors among the general public and medical staff. Our study aimed to compare the prevalence of anxiety and anxiety with insomnia, as well as the relationship between different psychological symptoms between the two groups.

METHODS

A total of 605 medical staff and 1091 public respondents were assessed through an online questionnaire survey, including the 7-item Insomnia Severity Index (ISI), the somatization subscale of Symptom Checklist 90-Revised (SCL-90-R), and the 7-item Generalized Anxiety Disorder scale (GAD-7).

RESULTS

Compared with the general public, medical staff had a higher incidence of anxiety (45.5% vs 32.4%). The incidence of insomnia in anxious participants was 52.7% in medical staff and 44.6% in the general public, and the difference was significant (p < 0.05). The GAD-7 score and somatization subscore of the SCI-90 were independently associated with insomnia among anxiety participants in both groups (all p < 0.001).

CONCLUSION

Our findings suggest that during the epidemic period of COVID-19, medical staff experienced more anxiety and anxiety with insomnia. Somatization, anxiety and insomnia are highly correlated among medical staff and the general public.

Neurocognitive Effects of Sleep Disruption in Children and Adolescents

A main childhood task is learning. In this task, the role of sleep is increasingly demonstrated. Although most literature examining this role focuses on preadolescence and middle adolescence, some studies apply napping designs in preschoolers. Studies overall conclude that without proper sleep a child's cognitive abilities suffer, but questions on how and to what extent linger. Observational studies show the hazards of potential confounders such as an individual's resilience to poor sleep as well as developmental risk factors (eg, disorders, stressors). A better understanding of cognitive sleep neuroscience may have a big impact on pediatric sleep research and clinical applications.

Newly walking infants' night sleep impacts next day learning and problem solving

Sleep is part of the process that prepares children and adults for next day cognitive activity. Insufficient or fragmented sleep has a detrimental impact on subsequent encoding (Rouleau et al., 2002) and cognitive functioning (Joo et al., 2012). However, fragmented sleep early in life is a developmental norm, limiting the extent to which conclusions derived from older populations can be generalized. To directly test the continuity of this relationship, newly-walking infants' (N=58) sleep was monitored overnight using actigraphy. The next morning they were taught a motor problem-solving task. The task required infants to navigate through a tunnel to reach a goal at the other end. We coded infants' exploratory behaviors and the extent of training required to solve the task. Using a cluster analysis that accounted for exploratory behaviors and number of training prompts, infants were sorted into three profiles: those who found the task Easy to solve, those who found it Difficult, and those who Never solved it. Wake episodes and sleep efficiency were entered as predictors of cluster membership in a multinomial logistic regression. Of the infants who ultimately solved the task, those with more wake episodes and lower sleep efficiency had more difficulty. Specifically, fragmentation appeared to negatively impact preparedness to learn. Contrary to our expectations, infants who Never solved the task had the least fragmented sleep, indicating that an optimal level of fragmentation is needed for efficient problem-solving. For infants, some level of sleep fragmentation is needed the night before learning in order to solve a task efficiently. These findings highlight the interaction between developmental domains, from sleep quality to motor experience, and their impact on infant learning in real time.

A daytime nap combined with nighttime sleep promotes learning in toddlers

Napping after learning promotes consolidation of new information during infancy. Yet, whether naps play a similar role during toddlerhood, a stage when many children are beginning to transition away from napping, is less clear. In Experiment 1, we examined whether napping after learning promotes generalization of novel category exemplars 24 h later. Young children (N = 54, age range = 29-36 months) viewed three category exemplars in different contexts from each of three categories and remained awake (No-Nap condition) or napped (Nap condition) after encoding and were then tested 24 h later. Children who napped after learning showed superior generalization 24 h later relative to children who did not nap. In a Nap-Control condition tested 4 h after awakening from a nap, children performed at the same low level as in the No-Nap condition, indicating that generalization stemmed from an additional period of nighttime sleep and not simply from a nap or increased time. In Experiment 2, we examined whether nighttime sleep is sufficient for generalization if it occurs soon after learning. An additional group of children (N = 18) learned before bedtime and were tested 4 h after waking up the next day. Children did not generalize as well as those who had a nap combined with subsequent nighttime sleep. These findings suggest that naps, when combined with a period of nighttime sleep, might help toddlers to retain newly learned information and lead to delayed benefits in generalization.

Association Between Sleep Duration and Cognitive Decline

Importance

An association between sleep duration and the trajectory of cognitive decline has not been conclusively demonstrated.

Objective

To investigate the association between sleep duration and cognitive decline by a pooled analysis of 2 nationally representative aging cohorts.

Design, Setting, and Participants

A pooled cohort study using data from waves 4 to 8 (2008-2009 to 2016-2017) in the English Longitudinal Study of Ageing and waves 1 to 3 (2011 to 2015) in the China Health and Retirement Longitudinal Study in a population-based setting. Participants were 2 randomly enrolled cohorts comprising 28 756 individuals living in England who were 50 years or older and those living in China who were 45 years or older.

Exposure

Self-reported sleep duration per night according to face-to-face interviews.

Main Outcomes and Measures

Global cognitive z scores were calculated according to immediate and delayed recall test, an animal fluency test, the serial sevens test, an intersecting pentagon copying test, and a date orientation test.

Results

Data were analyzed from 20 065 participants, including 9254 from the English Longitudinal Study of Ageing (mean [SD] age, 64.6 [9.8] years; 55.9% [5174 of 9254] women; median follow-up duration, 8 [interquartile range, 6-8] years) and 10 811 from the China Health and Retirement Longitudinal Study (mean [SD] age, 57.8 [9.0] years; 50.2% [5425 of 10 811] men; median follow-up duration, 4 [interquartile range, 4-4] years). During 100 000 person-years of follow-up, global cognitive z scores in individuals with 4 hours or less (pooled β = -0.022; 95% CI, -0.035 to -0.009 SD per year; P = .001) and 10 hours or more (pooled β = -0.033; 95% CI, -0.054 to -0.011 SD per year; P = .003) of sleep per night declined faster than in the reference group (7 hours per night) after adjusting for a number of covariates. An inverted U-shaped association between sleep duration and global cognitive decline was also observed.

Conclusions and Relevance

In this pooled cohort study, an inverted U-shaped association between sleep duration and global cognitive decline was found, indicating that cognitive function should be monitored in individuals with insufficient (≤4 hours per night) or excessive (≥10 hours per night) sleep duration. Future studies are needed to examine the mechanisms of the association between sleep duration and cognitive decline.

A daytime nap does not increase mnemonic discrimination ability

It has been proposed that sleep readies the brain for novel learning, and previous work has shown that sleep loss impairs the ability to encode new memories. In the present study, we examined if a daytime nap would increase mnemonic discrimination (MD) performance. MD is the ability to differentiate between memories that are similar but not identical. Participants performed the Mnemonic Similarity Task (MST) twice, once in the morning and once in the afternoon. The goal of this task is to distinguish stimuli that have been seen before from novel stimuli that are similar but not identical. After the morning MST, participants were randomly allocated into either a sleep or a wake group. The sleep group had a 2-hr nap opportunity, whereas the wake group spent a similar amount of time passively resting. All participants then performed a second MST in the afternoon with a novel set of images. Results did not show any support for increased MD ability after a nap. There was, however, a correlation showing that an increase in sleepiness between sessions predicted a decrease in MD performance. Future work must systematically examine how strong sleep manipulations that are needed for sleep to have an effect on encoding ability, as well as which kind of memory tasks that are sensitive to sleep manipulations. More knowledge about the relationship between sleep and the ability to differentiate similar memories from each other is important because impaired MD ability has previously been reported in various groups in which sleep disturbances are also common.

Differential effects of split and continuous sleep on neurobehavioral function and glucose tolerance in sleep-restricted adolescents

Study Objectives

Many adolescents are exposed to sleep restriction on school nights. We assessed how different apportionment of restricted sleep (continuous vs. split sleep) influences neurobehavioral function and glucose levels.

Methods

Adolescents, aged 15–19 years, were evaluated in a dormitory setting using a parallel-group design. Following two baseline nights of 9-hour time-in-bed (TIB), participants underwent either 5 nights of continuous 6.5-h TIB (n = 29) or 5-hour nocturnal TIB with a 1.5-hour afternoon nap (n = 29). After two recovery nights of 9-hour TIB, participants were sleep restricted for another three nights. Sleep was assessed using polysomnography (PSG). Cognitive performance and mood were evaluated three times per day. Oral glucose tolerance tests (OGTT) were conducted on mornings after baseline sleep, recovery sleep, and the third day of each sleep restriction cycle.

Results

The split sleep group had fewer vigilance lapses, better working memory and executive function, faster processing speed, lower level of subjective sleepiness, and more positive mood, even though PSG-verified total sleep time was less than the continuous sleep group. However, vigilance in both sleep-restricted groups was inferior to adolescents in a prior sample given 9-hour nocturnal TIB. During both cycles of sleep restriction, blood glucose during the OGTT increased by a greater amount in the split sleep schedule compared with persons receiving 6.5-hour continuous sleep.

Conclusions

In adolescents, modest multinight sleep restriction had divergent negative effects on cognitive performance and glucose levels depending on how the restricted sleep was apportioned. They are best advised to obtain the recommended amount of nocturnal sleep.

Trial registration

https://clinicaltrials.gov/ct2/show/NCT03333512

A split sleep schedule rescues short-term topographical memory after multiple nights of sleep restriction

Study Objectives

Chronic sleep restriction in adolescents is widespread, yet we know little about how to apportion the limited amount of sleep obtained to minimize cognitive impairment: should sleep occur only nocturnally, or be split across separate nocturnal and daytime nap periods? This is particularly relevant to hippocampal-dependent cognitive functions that underpin several aspects of learning.

Method

We assessed hippocampal function in four groups by evaluating short-term topographical memory with the Four Mountains Test (4MT). All participants began with 9 hours nocturnal time-in-bed (TIB) for 2 days before following different sleep schedules over the next 3 days. Each day, one group had 5 hours nocturnal TIB (5.0h; n = 30), another, 6.5 hours nocturnal TIB (6.5h; n = 29), and a third had 6.5 hours split into 5 hours nocturnal TIB and a 1.5 hour TIB daytime nap (5.0 + 1.5h; n = 29). A control group maintained 9 hours nocturnal TIB (9.0h; n = 30). The 4MT was administered mid-afternoon (1.5 hours after awakening for those who napped).

Results

Performance of the 5.0h and 6.5h nocturnal TIB groups was significantly impaired relative to the 9.0h control group. Performance of participants on the split- sleep schedule (5.0 + 1.5h) did not significantly differ from controls.

Conclusions

These findings suggest that hippocampal function is sensitive to moderate multi-night sleep restriction, but deficits can be ameliorated by splitting sleep, at least for a period after waking from a daytime nap. While this split sleep schedule should not be considered a replacement for adequate nocturnal sleep, it appears to benefit the cognitive and neurophysiological functions that underpin learning in those who are chronically sleep deprived.

Linking inhibition and anxiety symptoms following sleep restriction: The moderating role of prior sleep efficiency

Although sleep loss increases state anxiety, the effects of partial sleep restriction on specific anxiety symptoms and mechanisms that may influence this relation remain unknown. It is also unknown whether prior sleep buffers the impact of sleep restriction on anxiety symptoms. Thus, the present study examined the relations between inhibition and repetitive negative thinking (RNT), obsessions, and other OCD symptoms following sleep restriction and the moderating role of prior night's sleep efficiency. Healthy sleeping adults (n = 73) completed measures of inhibition, anxiety symptoms, and sleep before and after one night of sleep restriction (4 h between 4:00am and 8:00am). Results indicate significant associations between decreased post-sleep restriction inhibition and increased post-sleep restriction RNT and obsessions. Prior night's subjective and objective sleep efficiency significantly moderated these relations, such that the highest post-sleep restriction anxiety symptoms were reported by those with the lowest post-sleep restriction inhibition and the lowest pre-sleep restriction sleep efficiency. These findings suggest decreased inhibition may be one mechanism by which sleep loss affects anxiety, and those with worse sleep prior to acute sleep loss may be particularly vulnerable. The implications for the prevention and treatment of anxiety-related disorders characterized by intrusive cognition are discussed.

Sleep in the anxiety-related disorders: A meta-analysis of subjective and objective research

Although sleep disturbance is implicated in psychopathology, its role in anxiety-related disorders remains unclear. The present meta-analysis characterizes sleep disturbance in anxiety-related disorders collectively and individually. Subjective measures of total sleep time and sleep continuity were included with objective measures. Results indicate a large effect for increased subjective sleep disturbance (g = 2.16), medium effects for decreased total sleep time (g = -.40) and sleep continuity (g = -.49), and a small effect for decreased sleep depth (g = -.20) in anxiety-related disorders compared to healthy controls. Each anxiety-related disorder exhibited a distinct sleep disturbance pattern, suggesting that sleep may facilitate identification of unique biopsychological underpinnings. Effects were not moderated by comorbid depression and were similar in magnitude to those found for depression. Sleep disturbances, particularly decreased sleep continuity, may be a key pathology in the anxiety-related disorders that could highlight novel etiological mechanisms and intervention targets.

Are subjective sleepiness and sleep quality related to prospective memory?

Event-based prospective memory (PM) involves carrying out intentions when specific events occur and is ubiquitous in everyday life. It consists of a prospective component (remembering that something must be done) and a retrospective component (remembering what must be done and when). Subjective sleep-related variables may be related to PM performance and an attention-demanding prospective component. In two studies, the relationship of subjective sleepiness and subjective sleep quality with both PM components was investigated with a laboratory PM task and separation of its components via Bayesian multinomial processing tree modeling. In Study 1, neither component of PM was related to naturally occurring subjective sleepiness or sleep quality. In Study 2, sleepiness was experimentally increased by placing some participants in a supine body posture. Testing participants in upright vs. supine posture affected neither PM component. However, body posture moderated the relationship between subjective sleep quality and the prospective component: In supine posture, subjective sleep quality tended to be more positively related to the prospective component. Overall, neither subjective sleepiness nor subjective sleep quality alone was related to PM.

Sleep deprivation directly following eyeblink-conditioning impairs memory consolidation

The relation between sleep and different forms of memory formation continues to be a relevant topic in our daily life. Sleep has been found to affect cerebellum-dependent procedural memory formation, but it remains to be elucidated to what extent the level of sleep deprivation directly after motor training also influences our ability to store and retrieve memories. Here, we studied the effect of disturbed sleep in mice during two different time-windows, one covering the first four hours following eyeblink conditioning (EBC) and another window following the next period of four hours. Compared to control mice with sleep ad libitum, the percentage of conditioned responses and their amplitude were impaired when mice were deprived of sleep directly after conditioning. This impairment was still significant when the learned EBC responses were extinguished and later reacquired. However, consolidation of eyeblink responses was not affected when mice were deprived later than four hours after acquisition, not even when tested during a different day-night cycle for control. Moreover, mice that slept longer directly following EBC showed a tendency for more conditioned responses. Our data indicate that consolidation of motor memories can benefit from sleep directly following memory formation.

Multi-Night Sleep Restriction Impairs Long-Term Retention of Factual Knowledge in Adolescents

PURPOSE

Sleep deprivation is associated with increased forgetting of declarative memories. Sleep restriction across multiple consecutive nights is prevalent in adolescents, but questions remain as to whether this pattern of sleep impairs memory for material typically learned in the classroom and the time course of retention beyond a few days.

METHODS

Adolescents aged 15-18 years (n = 29) were given 5 hours sleep opportunity each night for 5 consecutive nights (sleep restricted group; SR), simulating a school week containing insufficient sleep. After the fourth night of restriction, participants learned detailed facts about different species of arthropod across a 6-hour period. Retention was tested 30 minutes and 3 days after learning and contrasted with a control group (n = 30) who had 9 hours sleep opportunity every night of the study. A subset of participants (SR, n = 14; control, n = 22) completed a surprise test 42 days after learning.

RESULTS

Memory was significantly impaired in the SR group relative to controls, with 26% increased forgetting at the 30-minute test (t(57) = 2.54, p = .014, d = .66), 34% at the Day 3 test (t(57) = 2.65, p = .010, d = .69), and 65% at the Day 42 test (t(34) = 3.22, p = .003, d = 1.17). Vigilance was also significantly impaired after 4 nights of restricted sleep (p < .05), but did not correlate significantly with memory (p > .05).

CONCLUSION

Long-term retention of classroom material is significantly compromised when adolescents learn after being sleep restricted, reinforcing the importance of keeping good sleep habits to optimize learning.

Does splitting sleep improve long-term memory in chronically sleep deprived adolescents?

Sleep aids the encoding and consolidation of declarative memories, but many adolescents do not obtain the recommended amount of sleep each night. After a normal night of sleep, there is abundant evidence that a daytime nap enhances the consolidation of material learned before sleep and also improves the encoding of new information upon waking. However, it remains unclear how learning is affected when sleep is split between nocturnal and daytime nap periods during a typical school week of restricted sleep. We compared long-term memory in 58 adolescents who underwent two simulated school weeks of suboptimal continuous (6.5 h nocturnal sleep opportunity) or split sleep (5 h nocturnal sleep +1.5 h daytime nap at 14:00). In the first week, participants encoded pictures in the late afternoon on Day 5 and were tested after 2-nights of recovery sleep. On 3 consecutive days in the second week, participants learned about six species of amphibians in the morning, and six different amphibians in the late afternoon. Testing was performed in the evening following a night of recovery sleep. In the first week, the split sleep group recognized more pictures. In the second week, they remembered more facts about species learned in the afternoon. Groups did not differ for species learned in the morning. This suggests that under conditions of sleep restriction, a split sleep schedule benefits learning after a nap opportunity without impairing morning learning, despite less preceding nocturnal sleep. While not replacing adequate nocturnal sleep, a split sleep schedule may be beneficial for chronically sleep restricted learners.

The impact of sleep deprivation on declarative memory

Sleep plays a crucial role in memory stabilization and integration, yet many people obtain insufficient sleep. This review assesses what is known about the level of sleep deprivation that leads to impairments during encoding, consolidation and retrieval of declarative memories, and what can be determined about the underlying neurophysiological processes. Neuroimaging studies that deprived sleep after learning have provided some of the most compelling evidence for sleep's role in the long-term reorganization of memories in the brain (systems consolidation). However, the behavioral consequences of losing sleep after learning-shown by increased forgetting-appear to recover over time and are unaffected by more common forms of partial sleep restriction across several nights. The capacity to encode new memories is the most vulnerable to sleep loss, since long-term deficits have been observed after total and partial sleep deprivation, while retrieval mechanisms are relatively unaffected. The negative impact of sleep loss on memory has been explored extensively after a night of total sleep deprivation, but further research is needed on the consequences of partial sleep loss over many days so that impairments may be generalized to more common forms of sleep loss.

Time to think: Subjective sleep quality, trait anxiety and university start time

Poor quality sleep is related to mental health and there is increasing interest in student wellbeing and mental health. The aim of the current study was to evaluate sleep quality, daytime dozing, anxiety proneness, chronotype and preferred start time in a sample of university students. A total of 546 university students (age range, 18-55) from two university located in South East England were included and completed an online survey. Participants' self-reported age, gender, year and field of study. Sleep quality, anxiety, daytime dozing, coffee/caffeine/tobacco use (coded as binary variables), preferred start time and chronotype were also recorded. Data were analysed using independent samples t-tests, chi-square, simple mediation-analyses and Analysis of Variance. Across the entire sample 46% percent of participants rated their sleep as fairly bad or very bad. Poor quality sleep was associated with significantly higher levels of anxiety which was not mediated by chronotype. Poor quality sleep is more prevalent in the first year of university and our sample endorsed a start time for university activities approximately 2 h later than currently timetabled. The current findings demonstrate that a large proportion of students are chronically sleep deprived, obtaining, on average, less than 7 h sleep per night on week days and this was more marked in first year students. In addition, we show that poor sleep is associated with increased anxiety. Based on the current evidence the authors suggest a review of current university timetabling and examination scheduling merits immediate consideration by policy makers and educators.