Paradoxical insomnia and subjective-objective sleep discrepancy: A review

The utility of wearable headband electroencephalography and pulse photoplethysmography to assess cortical and physiological arousal in individuals with stress-related mental disorders

Several stress-related mental disorders are characterised by disturbed sleep, but objective sleep biomarkers are not routinely examined in psychiatric patients. We examined the use of wearable-based sleep biomarkers in a psychiatric sample with headband electroencephalography (EEG) including pulse photoplethysmography (PPG), with an additional focus on microstructural elements as especially the shift from low to high frequencies appears relevant for several stress-related mental disorders. We analysed 371 nights of sufficient quality from 83 healthy participants and those with a confirmed stress-related mental disorder (anxiety-affective spectrum). The median value of macrostructural, microstructural (spectral slope fitting), and heart rate variables was calculated across nights and analysed at the individual level (N = 83). The headbands were accepted well by patients and the data quality was sufficient for most nights. The macrostructural analyses revealed trends for significance regarding sleep continuity but not sleep depth variables. The spectral analyses yielded no between-group differences except for a group × age interaction, with the normal age-related decline in the low versus high frequency power ratio flattening in the patient group. The PPG analyses showed that the mean heart rate was higher in the patient group in pre-sleep epochs, a difference that reduced during sleep and dissipated at wakefulness. Wearable devices that record EEG and/or PPG could be used over multiple nights to assess sleep fragmentation, spectral balance, and sympathetic drive throughout the sleep-wake cycle in patients with stress-related mental disorders and healthy controls, although macrostructural and spectral markers did not differ between the two groups.

Sleep discrepancy and cognitive function in community-dwelling older adults

This was the first study to use cluster analysis to characterise sleep discrepancy (the discordance between self-reported and objective sleep) across multiple sleep parameters, in community-dwelling older adults. For sleep efficiency, negative discrepancy (the tendency to self-report worse sleep than objectively-measured) was associated with poorer memory, independent of insomnia severity, depressive symptoms and objective sleep. This suggests a unique role for sleep discrepancy as a possible risk factor for future cognitive decline, and warrants the need for further research.

The Integration of Sleep Research Into Eating Disorders Research: Recommendations and Best Practices

OBJECTIVE

Sleep disturbance is common among individuals with eating disorders (EDs), with approximately 50% of patients with EDs reporting sleep disturbance. Sleep problems may promote, exacerbate, or maintain ED symptoms through a variety of hypothesized mechanisms, such as impaired executive function, increased negative affect, and disruptions to appetitive rhythms. Although research investigating the role of sleep in EDs is growing, the current literature suffers from methodological limitations and inconsistencies, which reduce our ability to translate findings to improve clinical practice. The purpose of this forum is to propose a coordinated approach to more seamlessly integrate sleep research into ED research with particular emphasis on best practices in the definition and assessment of sleep characteristics.

METHODS

In this article, we will describe the current status of sleep-related research and relevant gaps within ED research practices, define key sleep characteristics, and review common assessment strategies for these sleep characteristics. Throughout the forum, we also discuss study design considerations and recommendations for future research aiming to integrate sleep research into ED research.

RESULTS/DISCUSSION

Given the potential role of sleep in ED maintenance and treatment, it is important to build upon preliminary findings using a rigorous and systematic approach. Moving forward as a field necessitates a common lens through which future research on sleep and EDs may be conducted, communicated, and evaluated.

Chronotype and subjective sleep quality predict white matter integrity in young people with emerging mental disorders

Protecting brain health is a goal of early intervention. We explored whether sleep quality or chronotype could predict white matter (WM) integrity in emerging mental disorders. Young people (N = 364) accessing early-intervention clinics underwent assessments for chronotype, subjective sleep quality, and diffusion tensor imaging. Using machine learning, we examined whether chronotype or sleep quality (alongside diagnostic and demographic factors) could predict four measures of WM integrity: fractional anisotropy (FA), and radial, axial, and mean diffusivities (RD, AD and MD). We prioritised tracts that showed a univariate association with sleep quality or chronotype and considered predictors identified by ≥80% of machine learning (ML) models as 'important'. The most important predictors of WM integrity were demographics (age, sex and education) and diagnosis (depressive and bipolar disorders). Subjective sleep quality only predicted FA in the perihippocampal cingulum tract, whereas chronotype had limited predictive importance for WM integrity. To further examine links with mood disorders, we conducted a subgroup analysis. In youth with depressive and bipolar disorders, chronotype emerged as an important (often top-ranking) feature, predicting FA in the cingulum (cingulate gyrus), AD in the anterior corona radiata and genu of the corpus callosum, and RD in the corona radiata, anterior corona radiata, and genu of corpus callosum. Subjective quality was not important in this subgroup analysis. In summary, chronotype predicted altered WM integrity in the corona radiata and corpus callosum, whereas subjective sleep quality had a less significant role, suggesting that circadian factors may play a more prominent role in WM integrity in emerging mood disorders.

Exploring obstructive sleep apnea and sleep architecture in Parkinson's disease motor subtypes

INTRODUCTION

Parkinson's disease (PD) can be divided into motor subtypes: postural instability/gait difficulty (PIGD), tremor dominant, and indeterminate. This study aimed to assess differences in sleep structure and obstructive sleep apnea (OSA) between the PIGD and non-PIGD subtypes.

METHODS

PD participants with or without OSA (defined as apnea-hypopnea index (AHI) ≥ 15 events/hour on overnight polysomnography) were included. Patients were separated into two groups: PIGD and non-PIGD. Linear regression was used to explore differences in sleep, AHI, and other respiratory parameters between groups (adjusted for variables determined a priori). Logistic regression adjusted for the same variables was used to determine if the proportion of patients with OSA differed across groups. Subset analyses were performed: subset 1 excluding patients on psychoactive medication; subset 2 excluding patients taking levodopa or dopaminergic agonists (DAs) at nighttime and subset 3 excluding patients on either of the abovementioned drugs.

RESULTS

146 participants were studied. The non-PIGD group had less N3 sleep compared to the PIGD group (12.4% vs 16.9% p = 0.06), reaching significance in subsets 1 and 3. The AHI was significantly lower in the PIGD group (p = 0.047), including when medication effects were removed (p < 0.05). OSA was more frequent in the non-PIGD group, but only significantly in subset 3 (adjusted OR 0.3, p = 0.04).

CONCLUSION

OSA may be more severe in non-PIGD subtypes, and more frequent, in a subset free of psychoactive medication, and of levodopa and DAs, possibly owing to motor complications and dyskinesia. Future studies are required to confirm this.

Interventions for insomnia in cancer patients and survivors-a comprehensive systematic review and meta-analysis

BACKGROUND

Considering the persistent nature and higher prevalence of insomnia in cancer patients and survivors compared with the general population, there is a need for effective management strategies. This systematic review and meta-analysis aimed to comprehensively evaluate the available evidence for the efficacy of pharmacological and nonpharmacological interventions for insomnia in adult cancer patients and survivors.

METHODS

Following the PRISMA guidelines, we analyzed data from 61 randomized controlled trials involving 6528 participants. Interventions included pharmacological, physical, and psychological treatments, with a focus on insomnia severity and secondary sleep and non-sleep outcomes. Frequentist and Bayesian analytical strategies were employed for data synthesis and interpretation.

RESULTS

Cognitive-Behavioral Therapy for Insomnia (CBT-I) emerged as the most efficacious intervention for reducing insomnia severity in cancer survivors and further demonstrated significant improvements in fatigue, depressive symptoms, and anxiety. CBT-I showed a large postintervention effect (g = 0.86; 95% confidence interval [CI] = 0.57 to 1.15) and a medium effect at follow-up (g = 0.55; 95% CI = 0.18 to 0.92). Other interventions such as bright white light therapy, sleep medication, melatonin, exercise, mind-body therapies, and mindfulness-based therapies showed benefits, but the evidence for their efficacy was less convincing compared with CBT-I. Brief Behavioral Therapy for Insomnia showed promise as a less burdensome alternative for patients in active cancer treatment.

CONCLUSIONS

CBT-I is supported as a first-line treatment for insomnia in cancer survivors, with significant benefits observed across sleep and non-sleep outcomes. The findings also highlight the potential of less intensive alternatives. The research contributes valuable insights for clinical practice and underscores the need for further exploration into the complexities of sleep disturbances in cancer patients and survivors.

Harnessing technology to improve sleep in frontline healthcare workers: A pilot study of electronic noise-masking earbuds on subjective and objective sleep measures

Objective: This pilot study assessed the effects of electronic noise-masking earbuds on subjective sleep perception and objective sleep parameters among healthcare workers (HCWs) reporting sleep difficulties during the COVID-19 pandemic. Methods: Using a pre-post design, 77 HCWs underwent 3 nights of baseline assessment followed by a 7-night intervention period. Participants wore an at-home sleep monitoring headband to assess objective sleep measures and completed subjective self-report assessments. The difference in mean sleep measures from baseline to intervention was estimated in linear mixed models. Results: Compared to baseline assessments, HCWs reported significant improvements in sleep quality as measured by the Insomnia Severity Index (ISI) (Cohen's d = 1.74, p < 0.001) and a significant reduction in perceived sleep onset latency (SOL) during the intervention (M = 17.2 minutes, SD = 7.7) compared to baseline (M = 24.7 minutes, SD = 16.1), (Cohen's d = -0.42, p = 0.001). There were no significant changes in objective SOL (p = 0.703). However, there was a significant interaction between baseline objective SOL (<20 minutes vs >20 minutes) and condition (baseline vs intervention) (p = 0.002), such that individuals with objective SOL >20 minutes experienced a significant decrease in objective SOL during the intervention period compared to baseline (p = 0.015). Conclusions: HCWs experienced a significant improvement in perceived SOL and ISI scores after using the electronic noise-masking earbuds. Our data provide preliminary evidence for a nonpharmacological intervention to improve the sleep quality of HCWs which should be confirmed by future controlled studies.

Assessing the Real-World, Long-Term Impact of Lemborexant on Sleep Quality in a Home-Based Clinical Study

Purpose

Both subjective and objective evaluations are essential for the treatment of insomnia. Lemborexant has been shown to be effective in the long-term based solely on a subjective basis, and no long-term objective measures have been evaluated under natural sleep conditions. Small, lightweight sleep electroencephalogram (EEG) monitor was used, instead of polysomnography, to objectively evaluate sleep at home 4 and 12 weeks after lemborexant treatment.

Patients and Methods

Adults and elderly subjects with insomnia disorder, per the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, were enrolled in this open-label, single-arm, single-center trial. Objective and subjective measures of sleep were prospectively assessed. Sleep disturbance, excessive sleepiness, and depressive symptoms were assessed using questionnaires.

Results

A total of 45 subjects were screened, of which 33 were enrolled. Paired t-tests were conducted to evaluate changes in sleep variables and compared with the baseline; subjects showed significant improvements in objective sleep efficiency (SE) and subjective sleep parameters at weeks 4 and 12 following treatment with lemborexant. When baseline values were taken into account, a repeated-multivariate analysis of variance (MANOVA) revealed statistically significant changes in the objective measures. Sleep disturbance, excessive sleepiness, and depressive symptoms improved after three months of lemborexant treatment.

Conclusion

Furthermore, lemborexant therapy improved nocturnal sleep, when measured objectively using sleep EEG monitoring at home, and improved daytime sleepiness and depressive symptoms in older adults with insomnia disorder.

Sleep-Related Predictors of Risk for Alcohol Use and Related Problems in Adolescents and Young Adults

PURPOSE

Growing evidence supports sleep and circadian rhythms as influencing alcohol use and the course of alcohol use disorder (AUD). Studying sleep/circadian-alcohol associations during adolescence and young adulthood may be valuable for identifying sleep/circadian-related approaches to preventing and/or treating AUD. This paper reviews current evidence for prospective associations between sleep/circadian factors and alcohol involvement during adolescence and young adulthood with an emphasis on the effects of sleep/circadian factors on alcohol use.

SEARCH METHODS

The authors conducted a literature search in PsycInfo, PubMed, and Web of Science using the search terms "sleep" and "alcohol" paired with "adolescent" or "adolescence" or "young adult" or "emerging adult," focusing on the title/abstract fields, and restricting to English-language articles. Next, the search was narrowed to articles with a prospective/longitudinal or experimental design, a sleep-related measure as a predictor, an alcohol-related measure as an outcome, and confirming a primarily adolescent and/or young adult sample. This step was completed by a joint review of candidate article abstracts by two of the authors.

SEARCH RESULTS

The initial search resulted in 720 articles. After review of the abstracts, the list was narrowed to 27 articles reporting on observational longitudinal studies and three articles reporting on intervention trials. Noted for potential inclusion were 35 additional articles that reported on studies with alcohol-related predictors and sleep-related outcomes, and/or reported on candidate moderators or mediators of sleep-alcohol associations. Additional articles were identified via review of relevant article reference lists and prior exposure based on the authors' previous work in this area.

DISCUSSION AND CONCLUSIONS

Overall, the review supports a range of sleep/circadian characteristics during adolescence and young adulthood predicting the development of alcohol use and/or alcohol-related problems. Although sleep treatment studies in adolescents and young adults engaging in regular and/or heavy drinking show that sleep can be improved in those individuals, as well as potentially reducing alcohol craving and alcohol-related consequences, no studies in any age group have yet demonstrated that improving sleep reduces drinking behavior. Notable limitations include relatively few longitudinal studies and only two experimental studies, insufficient consideration of different assessment timescales (e.g., day-to-day vs. years), insufficient consideration of the multidimensional nature of sleep, a paucity of objective measures of sleep and circadian rhythms, and insufficient consideration of how demographic variables may influence sleep/circadian-alcohol associations. Examining such moderators, particularly those related to minoritized identities, as well as further investigation of putative mechanistic pathways linking sleep/circadian characteristics to alcohol outcomes, are important next steps.

Association of COVID-19 preventive behavior and job-related stress with the sleep quality of healthcare workers one year into the COVID-19 outbreak: a Japanese cross-sectional survey

BACKGROUND

This study aimed to evaluate the association of COVID-19 preventive behavior and job-related stress with sleep quality among healthcare workers (HCWs). We conducted a cross-sectional survey using a questionnaire at the National Center of Neurology and Psychiatry, Tokyo, Japan.

METHODS

A total of 586 participants who completed the questionnaire were eligible for the study. The Pittsburgh Sleep Quality Index was used to evaluate sleep quality. We examined the level of engagement between poor sleep and COVID-19-related infection preventive behaviors, such as avoiding closed spaces, crowded places, and close contact (three Cs), a distance of at least one meter from others, wearing a face mask regularly, washing hands regularly, and working remotely, as well as job-related stress in the work environment, exposure to patients, potential risk of infection, fear of infecting others, need for social confinement, and financial instability. We conducted a hierarchical logistic regression analysis to examine the relationship between poor sleep and COVID-19 preventive behavior, job-related stress, and other covariates, including age, sex, and the Kessler Psychological Distress Scale (K6), which was used to measure non-specific psychological distress.

RESULTS

Poor sleep was observed in 223 (38.1%) participants. Adherence to COVID-19 preventive measures was relatively high: 84.1% of participants answered "always" for wearing a face mask regularly and 83.4% for washing hands regularly. In the multivariate logistic regression analysis, stress in the work environment (odds ratio [OR] = 2.09, 95% confidence interval [CI], 1.37-3.20; p < 0.001), financial instability (OR = 1.73, 95% CI, 1.12-2.67; p < 0.05), and low adherence to working remotely (OR = 1.65, 95% CI, 1.06-2.57; p < 0.05) were independently and significantly associated with poor sleep after controlling for the covariates.

CONCLUSIONS

One year into the COVID-19 pandemic, the poor sleep rates of HCWs remained high. These results emphasize the need to protect HCWs from work environment stress and financial concerns.

Methodological approach to sleep state misperception in insomnia disorder: Comparison between multiple nights of actigraphy recordings and a single night of polysomnography recording

STUDY OBJECTIVE

To provide a comprehensive assessment of sleep state misperception in insomnia disorder (INS) and good sleepers (GS) by comparing recordings performed for one night in-lab (PSG and night review) and during several nights at-home (actigraphy and sleep diaries).

METHODS

Fifty-seven INS and 29 GS wore an actigraphy device and filled a sleep diary for two weeks at-home. They subsequently completed a PSG recording and filled a night review in-lab. Sleep perception index (subjective/objective × 100) of sleep onset latency (SOL), sleep duration (TST) and wake duration (TST) were computed and compared between methods and groups.

RESULTS

GS displayed a tendency to overestimate TST and WASO but correctly perceived SOL. The degree of misperception was similar across methods within the GS group. In contrast, INS underestimated their TST and overestimated their SOL both in-lab and at-home, yet the severity of misperception of SOL was larger at-home than in-lab. Finally, INS overestimated WASO only in-lab while correctly perceiving it at-home. While only the degree of TST misperception was stable across methods in INS, misperception of SOL and WASO were dependent on the method used.

CONCLUSIONS

We found that GS and INS exhibit opposite patterns and severity of sleep misperception. While the degree of misperception in GS was similar across methods, only sleep duration misperception was reliably detected by both in-lab and at-home methods in INS. Our results highlight that, when assessing sleep misperception in insomnia disorder, the environment and method of data collection should be carefully considered.

Latent profile of the insomnia severity index: A longitudinal study

STUDY OBJECTIVES

To identify the distinct classification of insomnia symptoms and to explore their association with sleep problems and depression.

METHODS

Latent profile analysis was used to examine patterns of insomnia symptoms in two samples. Discovery and replication samples comprised 1043 (Mean age at baseline = 18.95 ± 0.93 years, 62.2% females) and 729 (Mean age at baseline = 18.71 ± 1.02 years, 66.4% females) college students, respectively. Participants completed measures of sleep problems (insomnia symptoms, sleep quality, susceptibility to insomnia, perceived consequences of insomnia, dream recall frequency, and percentage of recurring nightmares) and other psychological variables (rumination and depression). Binary logistic regression was used to analyze the effects of different types of insomnia symptoms at baseline on sleep problems and depression two years later.

RESULTS

Four classes of insomnia symptoms were identified, and classified as "non-insomnia" (class 1, 45.7%), "mild subjective symptoms but severe subjective feelings" (class 2, 23.9%), "severe subjective symptoms but mild subjective feelings" (class 3, 22.0%), and "high insomnia risk" (class 4, 8.4%), respectively. Compared with the group classified as non-insomnia group, other classifications significantly predicted insomnia two years later, only class 4 significantly predicted depression, and class 3 significantly predicted susceptibility to insomnia, after adjusting gender, insomnia, depression, and susceptibility to insomnia at baseline.

CONCLUSIONS

The findings highlighted the importance of identifying the patterns of insomnia symptoms, and the need for tailored intervention to improve sleep problems. Additionally, when screening for insomnia symptoms, simplified screening using Insomnia Severity Index (ISI) dimensions or items should be considered.

Effects of Temperature, Duration, and Heating Height of Foot Thermal Therapy on Sleep Quality of Older Adults: A Systematic Review and Meta-Analysis

Background: Sleep disturbances, which are common problems in older adults, often lead to cognitive decline and depression and may even increase mortality risk. Foot thermal therapy is a simple and safe approach for improving sleep and is associated with relatively few side effects. However, the effect of different operations of foot thermal therapy on sleep quality in older adults is inconclusive. This study aimed to access the effects of temperature, duration, and heating height of foot thermal therapy (administered through a footbath) on the subjective and objective sleep quality of older adults. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline, eight databases were searched for all relevant articles published up to July 2023, and a rigorous systematic review and meta-analysis was conducted. This study was registered in the PROSPERO database (CRD42022383460). Inclusion criteria were: (1) participants with a mean age ≥60 years; (2) interventions that included foot thermal therapy; (3) a control group that received routine care but no thermal therapy; (4) outcome measurements that assessed sleep quality; and (5) the studies that utilized randomized controlled trials or quasi-experimental studies. Methodological quality was assessed using the Joanna Briggs Institute critical appraisal tools. The meta-analysis was performed using RevMan version 5.4. Results: A total of 11 studies were included. Foot thermal therapy before bedtime improved subjective sleep quality in older adults, with optimal parameters of 40°C temperature (standardized mean difference [SMD] = 0.66, 95% confidence interval [CI]: 0.33 to 0.99), ≤20-min duration (SMD = 0.66, 95% CI: 0.39 to 0.93), and 10 cm heating height (SMD = 0.78, 95% CI: 0.45 to 1.11). Subgroup analyses revealed that a temperature of 41°C-42°C can improve objective sleep latency (SMD = 0.54, 95% CI: 0.09 to 0.99). Conclusions: It is recommended to administer foot thermal therapy (40°C; ≤20 min; 10 cm above the ankle) to older adults 1 h before their bedtime. If they have trouble falling asleep, the temperature can be increased to 41°C-42°C.

Is it Time to Include Wearable Sleep Trackers in the Applied Psychologists' Toolbox?

Wearable sleep trackers are increasingly used in applied psychology. Particularly, the recent boom in the fitness tracking industry has resulted in a number of relatively inexpensive consumer-oriented devices that further enlarge the potential applications of ambulatory sleep monitoring. While being largely positioned as wellness tools, wearable sleep trackers could be considered useful health devices supported by a growing number of independent peer-reviewed studies evaluating their accuracy. The inclusion of sensors that monitor cardiorespiratory physiology, diurnal activity data, and other environmental signals allows for a comprehensive and multidimensional approach to sleep health and its impact on psychological well-being. Moreover, the increasingly common combination of wearable trackers and experience sampling methods has the potential to uncover within-individual processes linking sleep to daily experiences, behaviors, and other psychosocial factors. Here, we provide a concise overview of the state-of-the-art, challenges, and opportunities of using wearable sleep-tracking technology in applied psychology. Specifically, we review key device profiles, capabilities, and limitations. By providing representative examples, we highlight how scholars and practitioners can fully exploit the potential of wearable sleep trackers while being aware of the most critical pitfalls characterizing these devices. Overall, consumer wearable sleep trackers are increasingly recognized as a valuable method to investigate, assess, and improve sleep health. Incorporating such devices in research and professional practice might significantly improve the quantity and quality of the collected information while opening the possibility of involving large samples over representative time periods. However, a rigorous and informed approach to their use is necessary.

Insomnia and Alexithymia in Chinese Adolescents with Major Depressive Disorder: A Cross-Sectional Study of Sex Differences and Associations

Purpose

Insomnia is related to alexithymia in adults, but the relationship between insomnia and alexithymia in adolescents with major depressive disorder remains unclear. This study aimed to investigate the sex differences and the association between insomnia and alexithymia in adolescents with major depressive disorder.

Patients and Methods

From October 2020 to April 2022, adolescent patients with major depressive disorder were recruited from psychiatric departments of seven hospitals in Anhui Province, China. Their general demographic and clinical information were collected. The 20-item Toronto Alexithymia Scale, the Center for Epidemiologic Studies of Depression Scale, and the Insomnia Severity Index Scale were used to assess their alexithymia, depression, and insomnia symptoms, respectively. The analysis of variance (ANOVA), Student's t-test and Mann-Whitney U-test were used for continuous variables and chi-square tests for categorical variables. Pearson's correlation analysis and Spearman correlation analysis were used to examine the correlation between ISI and demographic and clinical variables. Multiple binary logistic regression analyses with the "Enter" method were carried out to explore the correlations of insomnia.

Results

The prevalence of insomnia in female adolescent patients was similar to that of male patients (χ2=1.84, p = 0.175). Compared with those without insomnia, patients with insomnia had worse family relationships (F = 7.71, p = 0.021), perceived heavier academic stress (F = 6.32, p = 0.012), more likely to take sedative-hypnotics (F = 5.51, p = 0.019), had higher levels of depression (F = 81.57, p < 0.001) and alexithymia (F = 28.57, p < 0.001). Correlation analysis showed that alexithymia was significantly associated with insomnia in adolescent patients (r = 0.360, p < 0.01). Binary logistic regression analyses showed that, alexithymia was significantly associated with insomnia in female patients (OR = 1.050, p < 0.05) but not male patients.

Conclusion

In female adolescent patients, alexithymia is a risk factor of insomnia, which is of great importance in the understanding of the psychopathological mechanisms, treatments and psychological interventions of insomnia in adolescents with major depressive disorder.

Sleep-wake state discrepancy does not impair the efficacy of cognitive behavioural therapy for insomnia: Findings from a large clinic sample

The current study determined the extent to which sleep-wake state discrepancy impairs the efficacy of cognitive behavioural therapy for insomnia in a real-world clinical sample. Sleep-wake state discrepancy occurs when there is an inconsistency between a person's subjective and objective sleep, and is a common phenomenon amongst patients with insomnia. Limited information is available on the effectiveness of cognitive behavioural therapy for insomnia in treating patients who experience significant sleep-wake state discrepancy in "real-world" samples. In the present study, all patients with insomnia received cognitive behavioural therapy for insomnia through an outpatient insomnia program (N = 386; mean age = 51.96 years, SD = 15.62; 65.97% [N = 254] female). Prior to treatment, participants completed a polysomnography sleep study and sleep diary, which was used to calculate sleep-wake state discrepancy. At pre-treatment, post-treatment and 3-month follow-up, participants completed the Insomnia Severity Index and other questionnaires, and 1 week of sleep diaries from which sleep-onset latency, wake after sleep onset and other sleep variables were calculated. There were no differences in self-reported sleep-onset latency, wake after sleep onset or Insomnia Severity Index scores at post-treatment or 3-month follow-up between quintiles of sleep-wake state discrepancy. These results indicate that sleep-wake state discrepancy at pre-treatment does not predict treatment response to cognitive behavioural therapy for insomnia. Future research could examine multi-night assessments of sleep-wake state discrepancy to determine whether variations in discrepancy may relate to pre-treatment insomnia severity and cognitive behavioural therapy for insomnia outcomes.

Subjective sleep onset latency is influenced by sleep structure and body heat loss in human subjects

The present study examined the relationship between subjective sleep onset latency (SOL), sleep structure, changes in skin and body temperature, and subjective evaluation of sleep in healthy young adults to elucidate the pathophysiological mechanisms of insomnia. A total of 28 participants (age 21.54 [0.50] years) with no sleep problems participated in a 1-h polysomnographic recording that obtained objective sleep parameters during the daytime while skin and body temperatures were recorded. The distal-proximal skin temperature gradient (DPG) was calculated. Subjective parameters, such as subjective SOL, sleep time, and restorative sleepiness, were evaluated before and after sleep. Most participants estimated their sleep latency as being longer than their actual SOL (13.7 versus 7.6 min). Objective SOL was significantly correlated with each sleep stage parameter whereas subjective SOL was negatively correlated with Stage N2 sleep duration (Rho = -0.454, p = 0.020), slow-wave activity and delta power (Rho = -0.500, p = 0.011 and Rho = -0.432, p = 0.031, respectively), and ΔDPG (the degree of reduction of heat loss before and after lights-off). Stepwise regression analysis showed that ΔDPG was the strongest predictive factor in explaining the length of subjective SOL. The degree of heat dissipation before and after lights-off contributed most to the sensation of falling asleep in healthy young adults. This finding may be helpful for elucidating the physiological mechanisms of insomnia and its treatment.

Reduced REM and N2 sleep, and lower dream intensity predict increased mind-wandering

Mind-wandering is a mental state in which attention shifts from the present environment or current task to internally driven, self-referent mental content. Homeostatic sleep pressure seems to facilitate mind-wandering as indicated by studies observing links between increased mind-wandering and impaired sleep. Nevertheless, previous studies mostly relied on cross-sectional measurements and self-reports. We aimed to combine the accuracy of objective sleep measures with the use of self-reports in a naturalistic setting in order to examine if objective sleep parameters predict the tendency for increased mind-wandering on the following day. We used mobile sleep electroencephalographic (EEG) headbands and self-report scales over 7 consecutive nights in a group of 67 healthy participants yielding ~400 analyzable nights. Nights with more wakefulness and shorter REM and slow wave sleep were associated with poorer subjective sleep quality at the intraindividual level. Reduced REM and N2 sleep, as well as less intense dream experiences, predicted more mind-wandering the following day. Our micro-longitudinal study indicates that intraindividual fluctuations in the duration of specific sleep stages predict the perception of sleep quality as assessed in the morning, as well as the intensity of daytime mind-wandering the following hours. The combined application of sleep EEG assessments and self-reports over repeated assessments provides new insights into the subtle intraindividual, night-to-day associations between nighttime sleep and the next day's subjective experiences.

Inhibitory Deficits of Insomnia Disorder: A Meta-Analysis on Event Related Potentials in Auditory Oddball Task

BACKGROUND

Despite numerous studies on auditory event-related potentials (ERPs) in insomnia disorder (ID), the results are inconsistent across different ERP components (e.g. N1, P2, P3, and N350), types of auditory stimuli (e.g. standard and deviant), and stages of sleep (e.g. wakefulness, NREM sleep, and REM sleep). In light of this variability, we conducted a systematic meta-analysis of previous auditory ERP studies in ID to provide a quantitative review of the existing literature.

METHODS

Relevant literatures were searched on the Embase, PubMed/MEDLINE, PsycINFO and Cochrane Library. A total of 12 studies comprising 497 participants were finally included in this meta-analysis. The study protocol was registered with PROSPERO under the registration number CRD42022308348.

RESULTS

We found that patients with ID have significantly decreased N1 (Hedges' g = 0.34, 95%CI [0.04, 0.65]) and P3 (Hedges'g = -1.21, 95%CI [-2.37, -0.06]) amplitudes during wakefulness. In addition, decreases in P2 (Hedges'g = -0.57, 95%CI [-0.96, -0.17]) amplitude during wakefulness and N350 (Hedges' g = 0.73, 95%CI [0.36, 1.09]) amplitude during NREM.

CONCLUSIONS

This meta-analysis represents the first systematic investigation of ERP features across different stages of sleep in individuals with ID. Our results suggest that in patients with insomnia, the absence or deficiency of arousal inhibition during the nighttime sleep initiation or maintenance process may interfere with the normal process of sleep.

Well-being therapy and sleep hygiene in a non-clinical population of adults reporting poor sleep quality and distress: A remote pilot randomized controlled study

OBJECTIVES

This pilot randomized controlled study evaluates the feasibility and preliminary efficacy of a 7-week remote intervention combining well-being therapy and sleep hygiene to improve sleep and psychological outcomes among adults reporting poor sleep and distress.

METHODS

Thirty-one participants (81% women, 40.2 ± 13.0 y, 48% racial/ethnic minority) were recruited from the community during the COVID-19 pandemic through online and local advertisement, and randomized to well-being therapy+sleep hygiene or sleep hygiene-only. Study outcomes were evaluated by self-reported questionnaires administered at baseline and post-intervention and a daily sleep diary.

RESULTS

Compared to sleep hygiene-only, well-being therapy+sleep hygiene led to greater improvements in wake after sleep onset (time-by-group interaction: 3.6 ± 1.5 min, p = .017), personal growth (β -3.0, 95%CI -5.2, -0.8, p = .01), and purpose in life (β -3.5, 95%CI -6.1, -0.9, p = .009). Anxiety, perceived stress, sleep quality, and insomnia symptoms improved similarly in both groups (between-group differences, p > .05). Improvements in sleep quality, insomnia, and sleep duration were associated with reductions in multiple measures of psychological distress (all p < .05).

CONCLUSIONS

These findings suggest that, in a non-clinical setting of individuals suffering from combined poor sleep and psychological distress, the addition of well-being therapy to sleep hygiene may provide additional benefits for sleep by promoting sleep continuity and well-being.

LPS and its relationship with subjective-objective discrepancies of sleep onset latency in patients with psychiatric disorders

Subjective-objective discrepancies in sleep onset latency (SOL), which is often observed among psychiatric patients, is attributed partly to the definition of sleep onset. Recently, instead of SOL, latency to persistent sleep (LPS), which is defined as the duration from turning out the light to the first consecutive minutes of non-wakefulness, has been utilized in pharmacological studies. This study aimed to determine the non-awake time in LPS that is most consistent with subjective sleep onset among patients with psychiatric disorders. We calculated the length of non-awake time in 30-s segments from lights-out to 0.5-60 min. The root mean square error was then calculated to determine the most appropriate length. The analysis of 149 patients with psychiatric disorders showed that the optimal non-awake time in LPS was 12 min. On the other hands, when comorbid with moderate or severe obstructive sleep apnea (OSA), the optimal length was 19.5 min. This study indicates that 12 min should be the best fit for the LPS non-awake time in patients with psychiatric disorders. When there is comorbidity with OSA, however, a longer duration should be considered. Measuring LPS minimizes discrepancies in SOL and provides important clinical information.

Sleep-wake state discrepancy among cancer survivors with insomnia symptoms

PURPOSE

To evaluate the discrepancy and correlation between sleep-wake measures (i.e., time in bed (TIB), total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO), and sleep efficiency (SE%)) reported on sleep diary and measured by actigraphy among cancer survivors with insomnia symptoms; and examine the influences of sociodemographic and clinical variables on these measurement differences.

METHODS

A heterogenous sample of cancer survivors with insomnia symptoms (n = 120; M age = 63.7 ± 10.1; female = 58.3%) was included. Seven consecutive days of sleep diary and actigraphic data were obtained along with information on demographic, sleep, and mental health symptoms. Bland-Altman plot, Pearson correlation coefficient, concordance correlation coefficient, and mixed linear model approach were used to conduct the analysis.

RESULTS

Self-reported TIB, SOL, and WASO were longer than measured by actigraphy (TIB: 8.6 min. (95% CI, 3.7, 13.5; p < .001); SOL: 14.8 min. (95% CI, 9.4, 20.2; p < .0001); and WASO: 20.7 min. (95% CI, 9.4, 20.2; p < .0001), respectively); and self-reported TST and SE% were shorter than measured by actigraphy (TST: 6.8 min. (95% CI, -18.7, 5.13); and SE%: 0.7% (95%CI, -3.0, 2.0), respectively), but were not statistically significant. Sex, higher insomnia severity, and poor sleep quality were associated with discrepancy between several sleep-wake measures.

CONCLUSION

Subjective and objective sleep-wake measures may present discrepant finding among cancer survivors with symptoms of insomnia. Future research is needed to validate appropriate sleep-wake assessment, and better understand factors that influence the discrepancy that exists between measures among this population.

CLINICAL TRIAL REGISTRATION

Clinical trials identifier: NCT03810365. Date of registration: January 14, 2019.

Objective and subjective sleep in patients with non-seasonal major depressive disorder and eveningness - Results from a randomized controlled trial of bright light therapy

STUDY OBJECTIVES

This study examines the (dis)agreement between objective and subjective sleep and their prospective changes in a randomized controlled trial of bright light therapy (BLT) in patients with major depressive disorder (MDD) and eveningness.

METHODS

A total of 93 adults were randomized to receive either 30-min daily of 10,000 lux BLT or 50lux placebo dim red light therapy (DRL group) for a total of 5 weeks. Actigraphic data were collected at the baseline and during the last week of treatment. (Dis)Concordance of diary and actigraphic sleep parameters were assessed by partial correlations and Bland-Altman plots, and the associations between these discrepancies to depression severity was assessed by linear regression models. Changes of sleep parameters were assessed by linear mixed models.

RESULTS

Significant correlations were found between subjective sleep timings and chronotype to actigraphic parameters. Discrepancies between diary- and actigraphic-measures were observed, and patients with more severe depressive symptoms were associated with a greater under-estimation of total sleep time (TST). A greater advance in the diary-based time to fall sleep and rise time were achieved in the BLT group as compared to the DRL group, while diary-based wake after sleep onset (WASO), TST and sleep efficiency (SE) comparably improved with time in both groups. There was no significant difference between the two groups in the actigraphic parameters after treatment.

CONCLUSIONS

In this study, we found that depression severity influenced subjective report of sleep. BLT led to a greater advance in subjective sleep timings when compared to the placebo group.

Near-Death Experiences and Sleep Disturbance: An Exploratory Study Using Wrist Actigraphy

ABSTRACT

Near-death experiences (NDEs) are nonordinary states of consciousness typically occurring on the brink of death. Sleep changes after NDEs have been described, including shorter sleep duration, longer sleep latency, and more sleep disturbances; however, objective verification is lacking. In this exploratory research, 57 participants took part in a 14-day actigraphy study and were assigned to three groups: those who have had an NDE ( n = 26); those who experienced a near-death event but without NDE ( n = 12); and those who had never come close to death ( n = 19). No significant differences were found between groups for actigraphy data. Paired samples t tests indicated significant differences between subjective and objective measures of sleep onset latency, sleep duration, and sleep efficiency, notably among the NDE group. Findings are indicative of the phenomenon known as sleep state misperception (SSM), which may have clinical implications for the study of NDEs and SSM.

A wearable EEG system for closed-loop neuromodulation of sleep-related oscillations

Objective.Healthy sleep plays a critical role in general well-being. Enhancement of slow-wave sleep by targeting acoustic stimuli to particular phases of delta (0.5-2 Hz) waves has shown promise as a non-invasive approach to improve sleep quality. Closed-loop stimulation during other sleep phases targeting oscillations at higher frequencies such as theta (4-7 Hz) or alpha (8-12 Hz) could be another approach to realize additional health benefits. However, systems to track and deliver stimulation relative to the instantaneous phase of electroencephalogram (EEG) signals at these higher frequencies have yet to be demonstrated outside of controlled laboratory settings.Approach.Here we examine the feasibility of using an endpoint-corrected version of the Hilbert transform (ecHT) algorithm implemented on a headband wearable device to measure alpha phase and deliver phase-locked auditory stimulation during the transition from wakefulness to sleep, during which alpha power is greatest. First, the ecHT algorithm is implementedin silicoto evaluate the performance characteristics of this algorithm across a range of sleep-related oscillatory frequencies. Secondly, a pilot sleep study tests feasibility to use the wearable device by users in the home setting for measurement of EEG activity during sleep and delivery of real-time phase-locked stimulation.Main results.The ecHT is capable of computing the instantaneous phase of oscillating signals with high precision, allowing auditory stimulation to be delivered at the intended phases of neural oscillations with low phase error. The wearable system was capable of measuring sleep-related neural activity with sufficient fidelity for sleep stage scoring during the at-home study, and phase-tracking performance matched simulated results. Users were able to successfully operate the system independently using the companion smartphone app to collect data and administer stimulation, and presentation of auditory stimuli during sleep initiation did not negatively impact sleep onset.Significance.This study demonstrates the feasibility of closed-loop real-time tracking and neuromodulation of a range of sleep-related oscillations using a wearable EEG device. Preliminary results suggest that this approach could be used to deliver non-invasive neuromodulation across all phases of sleep.

Investigating sleep quality and sleep hygiene awareness among Chinese adults: an association and network analysis study

PURPOSE

The relationships between sleep quality and sleep hygiene awareness in the Chinese population were unclear. We aimed to investigate the associations and related factors between sleep quality and sleep hygiene awareness in adults and to identify the most central domain for sleep quality using network analysis.

METHODS

A cross-sectional survey was conducted from April 22 to May 5, 2020. Adults (18 years old or above) who had access to smartphones were invited to participate in this survey. The Pittsburg Sleep Quality Index (PSQI) and the Sleep Hygiene Awareness and Practice Scale (SHAPS) were used to evaluate the sleep quality and sleep hygiene awareness of the participants. Propensity score matching (PSM) was used as sensitivity analysis to reduce the confounding effects. Multiple logistic regression was performed to evaluate the associations. The R packages "bootnet" and "qgraph" were used to estimate the connection and calculate the network centrality indices between good and poor sleepers.

RESULTS

In total, 939 respondents were included in the analysis. Of them, 48.8% (95% CI: 45.6-52.0%) were identified as poor sleepers. Participants with nervous system diseases, psychiatric diseases, and psychological problems were more likely to have poor sleep quality. The notion that using sleep medication regularly was beneficial to sleep was associated with poor sleep quality. Similarly, the notion that waking up at the same time each day disrupted sleep was also associated with poor sleep quality. The findings were consistent before and after PSM. Subjective sleep quality was the most central domain for sleep quality in good and poor sleepers.

CONCLUSION

Poor sleep quality was positively associated with certain sleep hygiene notions in Chinese adults. Effective measures such as self-relief, sleep hygiene education, and cognitive behavioral treatment may have been needed to improve sleep quality, especially during the COVID-19 outbreak.

A useful tool or a new challenge? Hand-wrist-worn sleep trackers in patients with insomnia

Consumer sleep wearables are increasingly popular, even among patients with sleep problems. However, the daily feedback provided by these devices could exacerbate sleep-related worry. To investigate this issue, 14 patients received a self-help guide booklet to improve sleep and wore the sleep tracker Fitbit Inspire 2 on their non-dominant hand for 4 weeks, while a control group of 12 patients only kept a handwritten sleep diary. All patients completed questionnaires at a primary care centre's first and final visit to assess general anxiety, sleep quality, sleep reactivity to stress, and quality of life. Our analysis showed that sleep quality, sleep reactivity to stress, and quality of life improved significantly for all patients between the first and final visit (p < 0.05). However, there were no significant differences between the Fitbit and control groups. Using sleep diary-derived estimates from the first and last week, we found that the control group but not the Fitbit group, increased their average time asleep each night and sleep efficiency (p < 0.05). However, these differences were primarily driven by baseline differences between the two groups. Our findings suggest that using wearables does not necessarily exacerbate sleep worries among people with insomnia.

Does providing feedback and guidance on sleep perceptions using sleep wearables improve insomnia? Findings from "Novel Insomnia Treatment Experiment": a randomized controlled trial

STUDY OBJECTIVES

Insomnia is a disorder diagnosed based on self-reported sleep complaints. Differences between self-reported and sensor-based sleep parameters (sleep-wake state discrepancy) are common but not well-understood in individuals with insomnia. This two-arm, parallel-group, single-blind, superiority randomized-controlled trial examined whether monitoring sleep using wearable devices and providing support for interpretation of sensor-based sleep data improved insomnia symptoms or impacted sleep-wake state discrepancy.

METHODS

A total of 113 (age M = 47.53; SD = 14.37, 64.9% female) individuals with significant insomnia symptoms (Insomnia Severity Index(ISI) ≥10) from the community were randomized 1:1 (permuted block randomization) to receive 5 weeks (1) Intervention (n = 57): feedback about sensor-based sleep (Fitbit and EEG headband) with guidance for data interpretation and ongoing monitoring, and (2) Control (n = 56): sleep education and hygiene. Both groups received one individual session and two check-in calls. The ISI (primary outcome), sleep disturbance (SDis), sleep-related impairment (SRI), depression, and anxiety were assessed at baseline and post-intervention.

RESULTS

In total, 103 (91.2%) participants completed the study. Intention-to-treat multiple regression with multiple imputations showed that after controlling for baseline values, compared to the Control group (n = 51), the Intervention group (n = 52) had lower ISI (p = .011, d = 0.51) and SDis (p = .036, d = 0.42) post-intervention, but differences in SRI, depression, anxiety, and sleep-wake state discrepancy parameters (total sleep time, sleep onset latency, and wake after sleep onset) were not meaningful (P-values >.40).

CONCLUSIONS

Providing feedback and guidance about sensor-based sleep parameters reduced insomnia severity and sleep disturbance but did not alter sleep-wake state discrepancy in individuals with insomnia more than sleep hygiene and education. The role of sleep wearable devices among individuals with insomnia requires further research.

CLINICAL TRIAL REGISTRATION

The Novel Insomnia Treatment Experiment (NITE): the effectiveness of incorporating appropriate guidance for sleep wearables in users with insomnia. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=378452, Australia New Zealand Clinical Trials Registry: ACTRN12619001636145.

The REM microarousal and REM duration as the potential indicator in paradoxical insomnia

OBJECTIVE

Although paradoxical insomnia is a prevalent subtype of chronic insomnia, the etiology of it is unclear. Contrary to complaints of little or no sleep, polysomnography (PSG) findings show that paradoxical insomnia patients have near normal sleep macrostructure. The purpose of this study is to determine the changes of microstructure and explore the etiology of paradoxical insomnia.

METHODS

The PSG findings of 89 paradoxical insomnia patients were compared with those of 41 gender balanced healthy controls without sleep complaints. All subjects underwent nocturnal PSG recordings. Conventional PSG measures and microarousals were quantified and statistically analyzed. Receiver operating characteristic curve and correlation analysis were used to evaluate the potential of REM sleep microarousals and REM duration as indicators of paradoxical insomnia.

RESULTS

Compared with the controls, paradoxical insomnia patients had no significant differences in sleep macrostructures. Statistical analysis showed that non-rapid eye movement (NREM) microarousals revealed no significant differences between paradoxical insomnia patients and controls. Noticeably, more spontaneous microarousals appeared in rapid eye movement (REM) stage for paradoxical insomnia patients. Based on receiver operating characteristic curve (ROC), the optimal cutoff value of REM sleep microarousals could predict paradoxical insomnia. Furthermore, a positive correlation between microarousals in REM sleep and the duration of REM sleep was presented in paradoxical insomnia patients.

CONCLUSIONS

The frequency of REM microarousals and the duration of REM sleep could reflect the real sleep state of paradoxical insomnia patients. That suggested PSG investigation extended to microarousal could be helpful to understand the etiology in paradoxical insomnia.

Insomnia with objective, but not subjective, short sleep duration is associated with increased risk of incident hypertension: the Sleep Heart Health Study

STUDY OBJECTIVES

Insomnia with objective short sleep duration has been associated with higher risk of cardiometabolic morbidity. In this study, we examined the association between insomnia with objective short sleep duration, also based on subjective sleep duration, with incident hypertension in the Sleep Heart Health Study.

METHODS

We analyzed data from 1,413 participants free of hypertension or sleep apnea at baseline from the Sleep Heart Health Study, with a median follow-up duration of 5.1 years. Insomnia symptoms were defined based on difficulty falling asleep, difficulty returning to sleep, early morning awakening, or sleeping pill use more than half the days in a month. Objective short sleep duration was defined as polysomnography-measured total sleep time < 6 hours. Incident hypertension was defined based on blood pressure measures and/or use of antihypertensive medications at follow-up.

RESULTS

Individuals with insomnia who slept objectively < 6 hours had significantly higher odds of incident hypertension compared to normal sleepers who slept ≥ 6 hours (odds ratio = 2.00, 95% confidence interval = 1.09-3.65) or < 6 hours (odds ratio = 2.00, 95% confidence interval = 1.06-3.79) or individuals with insomnia who slept ≥ 6 hours (odds ratio = 2.79, 95% confidence interval = 1.24-6.30). Individuals with insomnia who slept ≥ 6 hours or normal sleepers who slept < 6 hours were not associated with increased risk of incident hypertension compared to normal sleepers who slept ≥ 6 hours. Finally, individuals with insomnia who self-reported sleeping < 6 hours were not associated with significantly increased odds of incident hypertension.

CONCLUSIONS

These data further support that the insomnia with objective short sleep duration phenotype based on objective, but not subjective measures, is associated with increased risk of developing hypertension in adults.

CITATION

Dai Y, Chen B, Chen L, et al. Insomnia with objective, but not subjective, short sleep duration is associated with increased risk of incident hypertension: the Sleep Heart Health Study. J Clin Sleep Med. 2023;19(8):1421-1428.

Spotlight on Sleep Stage Classification Based on EEG

The recommendations for identifying sleep stages based on the interpretation of electrophysiological signals (electroencephalography [EEG], electro-oculography [EOG], and electromyography [EMG]), derived from the Rechtschaffen and Kales manual, were published in 2007 at the initiative of the American Academy of Sleep Medicine, and regularly updated over years. They offer an important tool to assess objective markers in different types of sleep/wake subjective complaints. With the aims and advantages of simplicity, reproducibility and standardization of practices in research and, most of all, in sleep medicine, they have overall changed little in the way they describe sleep. However, our knowledge on sleep/wake physiology and sleep disorders has evolved since then. High-density electroencephalography and intracranial electroencephalography studies have highlighted local regulation of sleep mechanisms, with spatio-temporal heterogeneity in vigilance states. Progress in the understanding of sleep disorders has allowed the identification of electrophysiological biomarkers better correlated with clinical symptoms and outcomes than standard sleep parameters. Finally, the huge development of sleep medicine, with a demand for explorations far exceeding the supply, has led to the development of alternative studies, which can be carried out at home, based on a smaller number of electrophysiological signals and on their automatic analysis. In this perspective article, we aim to examine how our description of sleep has been constructed, has evolved, and may still be reshaped in the light of advances in knowledge of sleep physiology and the development of technical recording and analysis tools. After presenting the strengths and limitations of the classification of sleep stages, we propose to challenge the "EEG-EOG-EMG" paradigm by discussing the physiological signals required for sleep stages identification, provide an overview of new tools and automatic analysis methods and propose avenues for the development of new approaches to describe and understand sleep/wake states.

Subtypes of insomnia revealed by the heterogeneity of neuroanatomical patterns: a structural MRI study

The current conflicting neuroimaging findings of insomnia disorder (ID) may be attributed to heterogeneity in ID. The present study aims to clarify the high heterogeneity in ID and examine the objective neurobiological subtypes of ID by using a novel machine learning method based on gray matter volumes (GMVs). We recruited 56 patients with ID and 73 healthy controls (HCs). The T1-weighted anatomical images were obtained for each participant. We investigated whether the ID has higher interindividual heterogeneity in GMVs. Then, we used a heterogeneous machine learning algorithm by discriminative analysis (HYDRA) to identify subtypes of ID with features of brain regional GMVs. We found that patients with ID have higher interindividual variability than HCs. HYDRA identified two distinct and reliable neuroanatomical subtypes of ID. Two subtypes showed significantly different aberrance in GMVs compared with HCs. Specifically, subtype 1 exhibited widespread decreased GMVs in some brain regions, including the right inferior temporal gyrus, left superior temporal gyrus, left precuneus, right middle cingulate, and right supplementary motor area. Subtype 2 only demonstrated increased GMVs in the right superior temporal gyrus. Additionally, the GMVs of altered brain regions in subtype 1 were significantly correlated with daytime functioning, but in subtype 2, they were significantly correlated with sleep disturbance. These results explain conflicting neuroimaging findings and propose a potential objective neurobiological classification contributing to ID's precise clinical diagnosis and treatment. DATA AND CODE AVAILABILITY: The source and means of obtaining the data used in the study have been described fully in the Methods and Materials section. The codes and data in this study are available upon a reasonable request to the corresponding author.

Discriminating Paradoxical and Psychophysiological Insomnia Based on Structural and Functional Brain Images: A Preliminary Machine Learning Study

Insomnia disorder (ID) is a prevalent mental illness. Several behavioral and neuroimaging studies suggested that ID is a heterogenous condition with various subtypes. However, neurobiological alterations in different subtypes of ID are poorly understood. We aimed to assess whether unimodal and multimodal whole-brain neuroimaging measurements can discriminate two commonly described ID subtypes (i.e., paradoxical and psychophysiological insomnia) from each other and healthy subjects. We obtained T1-weighted images and resting-state fMRI from 34 patients with ID and 48 healthy controls. The outcome measures were grey matter volume, cortical thickness, amplitude of low-frequency fluctuation, degree centrality, and regional homogeneity. Subsequently, we applied support vector machines to classify subjects via unimodal and multimodal measures. The results of the multimodal classification were superior to those of unimodal approaches, i.e., we achieved 81% accuracy in separating psychophysiological vs. control, 87% for paradoxical vs. control, and 89% for paradoxical vs. psychophysiological insomnia. This preliminary study provides evidence that structural and functional brain data can help to distinguish two common subtypes of ID from each other and healthy subjects. These initial findings may stimulate further research to identify the underlying mechanism of each subtype and develop personalized treatments for ID in the future.

Sleep Quality Disturbances Are Associated with White Matter Alterations in Veterans with Post-Traumatic Stress Disorder and Mild Traumatic Brain Injury

Sleep disturbances are strongly associated with mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD). PTSD and mTBI have been linked to alterations in white matter (WM) microstructure, but whether poor sleep quality has a compounding effect on WM remains largely unknown. We evaluated sleep and diffusion magnetic resonance imaging (dMRI) data from 180 male post-9/11 veterans diagnosed with (1) PTSD (n = 38), (2) mTBI (n = 25), (3) comorbid PTSD+mTBI (n = 94), and (4) a control group with neither PTSD nor mTBI (n = 23). We compared sleep quality (Pittsburgh Sleep Quality Index, PSQI) between groups using ANCOVAs and calculated regression and mediation models to assess associations between PTSD, mTBI, sleep quality, and WM. Veterans with PTSD and comorbid PTSD+mTBI reported poorer sleep quality than those with mTBI or no history of PTSD or mTBI (p = 0.012 to <0.001). Poor sleep quality was associated with abnormal WM microstructure in veterans with comorbid PTSD+mTBI (p < 0.001). Most importantly, poor sleep quality fully mediated the association between greater PTSD symptom severity and impaired WM microstructure (p < 0.001). Our findings highlight the significant impact of sleep disturbances on brain health in veterans with PTSD+mTBI, calling for sleep-targeted interventions.

Comparison of the treatment effectiveness between lemborexant and zolpidem tartrate extended-release for insomnia disorder subtypes defined based on polysomnographic findings

STUDY OBJECTIVES

Patients with chronic insomnia may respond differently to therapeutic modalities. This study examined differences in response of individuals with 2 insomnia phenotypes-short sleep duration (I-SSD; < 6 hours) and normal sleep duration (I-NSD; ≥ 6 hours) determined by polysomnography-to treatment with lemborexant and zolpidem tartrate extended-release 6.25 mg (zolpidem ER), compared with placebo.

METHODS

Study E2006-G000-304 (Study 304; SUNRISE-1; NCT02783729) was a global, randomized, double-blind, placebo, and active comparator-controlled, parallel-group study comparing lemborexant 5 and 10 mg in individuals aged ≥ 55 years with insomnia disorder. In this analysis, changes in subjective (self-reported) variables based on sleep diaries and objective variables based on polysomnographs were assessed after 1-month administration of study drugs. Data from participants with I-SSD and I-NSD were compared.

RESULTS

In the I-SSD subgroup, both lemborexant doses provided significant benefit for sleep-onset latency (SOL), total sleep time (TST), and wake after sleep onset (WASO) vs placebo; zolpidem ER also provided significant benefit for TST and WASO, but not SOL, on both measures vs placebo. In the I-NSD subgroup, lemborexant and zolpidem ER provided significant benefit for TST and WASO vs placebo objectively but not subjectively; both doses of lemborexant provided significant benefit for SOL vs placebo subjectively, but not objectively.

CONCLUSIONS

Both drugs, but lemborexant more consistently, showed subjective and objective benefits compared with placebo in participants with insomnia with objective short sleep duration. However, neither lemborexant nor zolpidem provided consistent benefits for participants with normal sleep duration on sleep-onset and sleep maintenance variables.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Study of the Efficacy and Safety of Lemborexant in Subjects 55 Years and Older With Insomnia Disorder (SUNRISE 1); URL: https://clinicaltrials.gov/ct2/show/record/NCT02783729; Identifier: NCT02783729.

CITATION

Inoue Y, Nishida M, Kubota N, et al. Comparison of the treatment effectiveness between lemborexant and zolpidem tartrate extended-release for insomnia disorder subtypes defined based on polysomnographic findings. J Clin Sleep Med. 2023;19(3):519-528.

Nonsuicidal self-injury, sleep quality, and shame response to a laboratory stress task

OBJECTIVE

Nonsuicidal self-injury (NSSI) frequently functions to regulate shame-based emotions and cognitions in the context of interpersonal stress. The present study sought to examine how sleep quality (SQ) may influence this process in a laboratory setting.

METHODS

Participants included 72 adults (Mage  = 24.28; 36 with a lifetime history of NSSI) who completed a self-report measure of prior month SQ and engaged in a modified Trier social stress task (TSST). State shame ratings were collected immediately before and following the TSST, as well as 5 min post-TSST, to allow for the measurement of shame reactivity and recovery.

RESULTS

No significant results emerged for NSSI history and SQ as statistical predictors of shame reactivity. However, NSSI history was significantly associated with heightened shame intensity during the recovery period of the task, and this was moderated by SQ. Simple slopes analyses revealed a conditional effect whereby poorer SQ (1SD above the mean) was associated with greater intensity of shame during recovery, but only for those with a history of NSSI.

CONCLUSION

Poor SQ may contribute to worrisome emotional responses to daytime stressors in those at risk for NSSI.

Effects of Continuous Positive Airway Pressure on Sleep State Misperception in Patients With Obstructive Sleep Apnea

BACKGROUND

Little is known regarding the effects of continuous positive airway pressure (CPAP) on sleep misperception in obstructive sleep apnea (OSA).

METHODS

Sleep state perception was measured by subtracting the objective total sleep time from the subjective sleep duration. Sleep underestimation and overestimation were defined as ± 60 minutes sleep perception. Insomnia and depressive symptoms were assessed using questionnaires. Finally, nonparametric statistical analyses were performed.

RESULTS

Of the 339 patients with OSA included in the study, 90 (26.5%) and 45 (13.3%) showed sleep underestimation and overestimation, respectively. Overall, a significant underestimation of sleep was noted during CPAP titration comparing to a diagnostic PSG (P < 0.001). OSA patients with insomnia or depressive symptoms did not show any changes in sleep perception between diagnostic and CPAP titration studies, whereas those without insomnia or depressed mood showed significantly underestimated sleep duration during CPAP titration. Patients with OSA and either underestimated or overestimated misperception showed perceptual improvements during CPAP titration regardless of the presence of insomnia or depressive symptoms. However, of 204 patients with normal sleep perception, 138 (67.6%) and 10 (4.9%) had underestimation and overestimation of sleep during CPAP titration.

CONCLUSION

CPAP titration may improve sleep perception with moderate to severe OSA who have sleep misperception. However, CPAP titration may result in sleep misperception especially underestimation of sleep in those who have normal sleep perception.

The Virtual Sleep Lab-A Novel Method for Accurate Four-Class Sleep Staging Using Heart-Rate Variability from Low-Cost Wearables

Sleep staging based on polysomnography (PSG) performed by human experts is the de facto "gold standard" for the objective measurement of sleep. PSG and manual sleep staging is, however, personnel-intensive and time-consuming and it is thus impractical to monitor a person's sleep architecture over extended periods. Here, we present a novel, low-cost, automatized, deep learning alternative to PSG sleep staging that provides a reliable epoch-by-epoch four-class sleep staging approach (Wake, Light [N1 + N2], Deep, REM) based solely on inter-beat-interval (IBI) data. Having trained a multi-resolution convolutional neural network (MCNN) on the IBIs of 8898 full-night manually sleep-staged recordings, we tested the MCNN on sleep classification using the IBIs of two low-cost (<EUR 100) consumer wearables: an optical heart rate sensor (VS) and a breast belt (H10), both produced by POLAR®. The overall classification accuracy reached levels comparable to expert inter-rater reliability for both devices (VS: 81%, κ = 0.69; H10: 80.3%, κ = 0.69). In addition, we used the H10 and recorded daily ECG data from 49 participants with sleep complaints over the course of a digital CBT-I-based sleep training program implemented in the App NUKKUAA™. As proof of principle, we classified the IBIs extracted from H10 using the MCNN over the course of the training program and captured sleep-related changes. At the end of the program, participants reported significant improvements in subjective sleep quality and sleep onset latency. Similarly, objective sleep onset latency showed a trend toward improvement. Weekly sleep onset latency, wake time during sleep, and total sleep time also correlated significantly with the subjective reports. The combination of state-of-the-art machine learning with suitable wearables allows continuous and accurate monitoring of sleep in naturalistic settings with profound implications for answering basic and clinical research questions.

Wearable and mobile technology to characterize daily patterns of sleep, stress, presleep worry, and mood in adolescent insomnia

OBJECTIVES

Characterizing daily patterns of sleep, stress, presleep worry, and mood in adolescents with and without insomnia symptomatology.

DESIGN

Two months of continuous wearable tracking and daily diary ratings.

SETTING

Free-living conditions.

PARTICIPANTS

Ninety-three adolescents (59 girls; 16-19 years old) with (N = 47; 26 with clinical and 21 with sub-clinical) and without (N = 46; control) DSM-5 insomnia symptomatology.

MEASUREMENTS

Fitbit Charge 3 tracked sleep, heart rate, and steps. Evening electronic diaries collected ratings of daily stress, presleep worry, and mood.

RESULTS

While sleep duration (control: 6.88 ± 1.41 hours; insomnia: 6.92 ± 1.28 hours), architecture, timing, and night-to-night variability were similar between groups, the insomnia group reported higher levels of stress and worry, being mainly related to "school". At the intraindividual level, stress and worry predicted shorter sleep duration and earlier wake up times, which, in turn, predicted higher stress the following day. Moreover, higher-than-usual stress predicted higher sleep-time heart rate, with a more consistent effect in adolescents with insomnia. Results were overall consistent after controlling for covariates and several robustness checks.

CONCLUSIONS

There is a bidirectional relationship between daily stress and sleep, with daily stress negatively impacting sleep, which in turn leads to more stress in adolescents with and without insomnia symptoms. Findings also highlight the complexity of insomnia in adolescence, in which the core clinical features (perceived sleep difficulties) and the critical factors (stress/worry) implicated in the pathophysiology of the disorder are not necessarily reflected in objective sleep indicators.

Post-Approval Research in Drug Development: Priorities and Practices

A prescriber might ask if a new medication is a good option for use in the patients he or she sees in clinic, with their particular blends of demographic and comorbid clinical characteristics. Is this medicine more effective, safe, tolerable, or affordable than the options used in the past? A payer may ask if the new medication offers a more effective, cost-efficient, or convenient alternative to those treatments already being covered. These are the types of questions that are often difficult to answer on the basis of the clinical trials used to support a medication's initial approval, which are generally designed to evaluate a medication's efficacy, safety, and tolerability in narrowly defined patient populations. Consequently, in order to answer the questions most relevant to key stakeholders (i.e., regulators, patients, and clinicians), it is important to continue to examine a medication's impact and characteristics after it has received regulatory approval. Such studies vary in their purpose, scope, and methodology. In this chapter, we review the types of questions most likely to be investigated after regulatory approval, the methods generally used to investigate them, and the characteristics typically considered when prioritizing the allocation of resources.

Emerging applications of objective sleep assessments towards the improved management of insomnia

Self-reported sleep difficulties are the primary concern associated with diagnosis and treatment of chronic insomnia. This said, in-home sleep monitoring technology in combination with self-reported sleep outcomes may usefully assist with the management of insomnia. The rapid acceleration in consumer sleep technology capabilities together with their growing use by consumers means that the implementation of clinically useful techniques to more precisely diagnose and better treat insomnia are now possible. This review describes emerging techniques which may facilitate better identification and management of insomnia through objective sleep monitoring. Diagnostic techniques covered include insomnia phenotyping, better detection of comorbid sleep disorders, and identification of patients potentially at greatest risk of adverse outcomes. Treatment techniques reviewed include the administration of therapies (e.g., Intensive Sleep Retraining, digital treatment programs), methods to assess and improve treatment adherence, and sleep feedback to address concerns about sleep and sleep loss. Gaps in sleep device capabilities are also discussed, such as the practical assessment of circadian rhythms. Proof-of-concept studies remain needed to test these sleep monitoring-supported techniques in insomnia patient populations, with the goal to progress towards more precise diagnoses and efficacious treatments for individuals with insomnia.

Exploring Predictors of Sleep State Misperception in Women with Posttraumatic Stress Disorder

OBJECTIVES

Insomnia is a common symptom of posttraumatic stress disorder (PTSD) that is resistant to first-line cognitive behavioral interventions. However, research suggests that, among individuals with PTSD, self-reported sleep impairment is typically more severe than what is objectively observed, a phenomenon termed sleep state misperception. Relatively little research has examined which individuals with PTSD are most likely to exhibit sleep state misperception. This study explored clinical predictors of sleep state misperception in a sample of 43 women with PTSD and clinically significant sleep impairment.

METHOD

During a baseline assessment, participants' PTSD symptoms were assessed using a clinical interview and their sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI). Objective sleep, self-reported sleep, and PTSD symptoms were then assessed over a 1-week period using actigraphy and daily diaries.

RESULTS

Consistent with previous research, women in the study exhibited total sleep time (TST), sleep efficiency (SE), and sleep onset latency (SOL) sleep state misperception. For TST and SE, but not SOL, discrepancies between actigraphy and the PSQI were associated with each clinician-rated PTSD symptom cluster, whereas discrepancies between actigraphy and daily diary were only associated with clinician-rated reexperiencing symptoms. The only self-reported PTSD symptom that was uniquely associated with sleep state misperception was nightmares. This association was no longer significant after controlling for sleep-related anxiety.

CONCLUSIONS

Results suggest that women with more severe reexperiencing symptoms of PTSD, particularly nightmares, may be more likely to exhibit TST and SE sleep state misperception, perhaps due to associated sleep-related anxiety.

Sleep and day-to-day PTSD symptom variability: an ecological momentary assessment and actigraphy monitored study in trauma-exposed young adults

BACKGROUND

Disrupted sleep and post-traumatic stress disorder (PTSD) are bi-directionally linked and have been found to mutually reinforce each other on a day-to-day basis. However, most of the previous research has focused on subjective measures of sleep only.

OBJECTIVE

Here, we investigated the temporal relationship between sleep and PTSD symptoms using both subjective (sleep diary) and objective measures of sleep (actigraphy).

METHODS

Forty-one non-treatment seeking, trauma exposed young adults (age M = 24.68, SD = 8.15) with a range of PTSD symptom severities (PTSS, 0-53 on PCL-5) were recruited. Participants completed two surveys per day over four weeks to measure day-time PTSD symptoms (i.e. PTSS and number of intrusions) and night-time sleep subjectively, while wearing an actigraphy watch to measure sleep objectively.

RESULTS

Linear mixed models revealed that subjectively reported sleep disruptions were associated with elevated next-day PTSS and increasing number of intrusive memories both within and between participants. Similar results were found for daytime PTSD symptoms on night-time sleep. However, these associations were not found using objective sleep data. Exploratory moderator analyses including sex (male vs. female) found that these associations differed in strength between sexes but were generally in the same direction.

DISCUSSION

These results were in line with our hypothesis with regards to the sleep diary (subjective sleep), but not actigraphy (objective sleep). Several factors which have implications on both PTSD and sleep, such as the COVID-19 pandemic and/ or sleep-state misperception, may be potential reasons behind those discrepancies. However, this study had limited power and needs to be replicated in larger samples. Nonetheless, these results add to the current literature about the bi-directional relationship between sleep and PTSD and have clinical implications for treatment strategies.

Sex differences in the effect of subjective sleep on fear conditioning, extinction learning, and extinction recall in individuals with a range of PTSD symptom severity

Sleep has been found to play a key role in fear conditioning, extinction learning and extinction recall, and sleep disturbances are linked to many mental disorders including post-traumatic stress disorder (PTSD). Previous studies examining associations between sleep and fear or extinction processes primarily focused on objectively measured sleep architecture. Little research has so far focused on subjective sleep measures and particularly in clinical populations, which often experience subjectively poor sleep, including PTSD. Here we investigated whether subjective sleep disturbance, sleep onset latency, wake after sleep onset or sleep efficiency were related to fear conditioning, extinction learning or extinction recall in a large sample of individuals with a range of PTSD symptom severity (n = 248). Overall, we did not find that subjective sleep was associated with fear conditioning or extinction processes. However, exploratory analyses examining the moderating effect of sex found that shorter sleep onset latency and greater sleep efficiency were associated with improved extinction recall in women with higher PTSD symptom severity. This suggests that less time falling asleep and longer time asleep while in bed may be protective in highly symptomatic women against the commonly observed impaired extinction recall in PTSD. More studies are needed to explore sex-specific effects further.

The association between subjective-objective discrepancies in sleep duration and mortality in older men

A discrepancy in subjective and objective estimations of sleep duration, which often diverge, could have long-term adverse effects on health outcomes in older adults. Using data from 2674 older adult men (≥ 65 years of age) of the Osteoporotic Fractures in Men Sleep Study, we assessed the longitudinal association between misperception index (MI), calculated as MI = (objective sleep duration - subjective sleep duration)/objective sleep duration, and all-cause mortality. During the follow-up with a mean (standard deviation) of 10.8 (4.2) years, 1596 deaths were observed. As a continuous variable, MI showed a linear relationship with all-cause mortality after adjusting for multiple covariates, including polysomnography-measured objective sleep duration [fully adjusted hazard ratio (HR), 0.69; 95% confidence interval [CI], 0.56-0.84]. As a categorical variable, the lowest MI quartile (vs. the interquartile MI range) was associated with increased mortality (fully adjusted HR, 1.28; 95% CI, 1.12-1.46), whereas the highest MI quartile was not associated with mortality (fully adjusted HR, 0.97; 95% CI, 0.85-1.11). The subjective overestimation of sleep duration may be a risk factor for all-cause mortality in older men. Future studies should examine why subjective overestimation of sleep duration is associated with all-cause mortality from a physiological perspective.

White matter microstructure and sleep-wake disturbances in individuals at ultra-high risk of psychosis

Aim

White matter changes in individuals at ultra-high risk for psychosis (UHR) may be involved in the transition to psychosis. Sleep-wake disturbances commonly precede the first psychotic episode and predict development of psychosis. We examined associations between white matter microstructure and sleep-wake disturbances in UHR individuals compared to healthy controls (HC), as well as explored the confounding effect of medication, substance use, and level of psychopathology.

Methods

Sixty-four UHR individuals and 35 HC underwent clinical interviews and diffusion weighted imaging. Group differences on global and callosal mean fractional anisotropy (FA) was tested using general linear modeling. Sleep-wake disturbances were evaluated using the subjective measures disturbed sleep index (DSI) and disturbed awakening index (AWI) from the Karolinska Sleep Questionnaire, supported by objective sleep measures from one-night actigraphy. The primary analyses comprised partial correlation analyses between global FA/callosal FA and sleep-wake measures. Secondary analyses investigated multivariate patterns of covariance between measures of sleep-wake disturbances and FA in 48 white matter regions of interest using partial least square correlations.

Results

Ultra-high risk for psychosis individuals displayed lower global FA (F = 14.56, p < 0.001) and lower callosal FA (F = 11.34, p = 0.001) compared to HC. Subjective sleep-wake disturbances were significantly higher among the UHR individuals (DSI: F = 27.59, p < 0.001, AWI: F = 36.42, p < 0.001). Lower callosal FA was correlated with increased wake after sleep onset (r = -0.34, p = 0.011) and increased sleep fragmentation index (r = -0.31, p = 0.019) in UHR individuals. Multivariate analyses identified a pattern of covariance in regional FA which were associated with DSI and AWI in UHR individuals (p = 0.028), but not in HC. Substance use, sleep medication and antipsychotic medication did not significantly confound these associations. The association with objective sleep-wake measures was sustained when controlling for level of depressive and UHR symptoms, but symptom level confounded the covariation between FA and subjective sleep-wake measures in the multivariate analyses.

Conclusion

Compromised callosal microstructure in UHR individuals was related to objectively observed disruptions in sleep-wake functioning. Lower FA in ventrally located regions was associated with subjectively measured sleep-wake disturbances and was partly explained by psychopathology. These findings call for further investigation of sleep disturbances as a potential treatment target.

The underestimation of sleep duration phenotype is associated with better treatment response to cognitive behavior therapy for insomnia in patients with chronic insomnia: a preliminary study

STUDY OBJECTIVES

To examine treatment response to cognitive behavior therapy for insomnia (CBT-I) in patients with chronic insomnia with and without underestimation of sleep duration.

METHODS

We studied 41 patients with chronic insomnia who had received 5-week CBT-I. Self-reported and objective sleep were assessed with sleep diary and actigraphy, respectively. Sleep perception was calculated as self-reported total sleep time/objective total sleep time. The underestimation of sleep duration group was defined based on sleep perception less than the median of the overall sample (85%). Insomnia Severity Index was used to assess the severity of insomnia.

RESULTS

The total scores of Insomnia Severity Index decreased significantly after CBT-I in both groups with and without underestimation of sleep duration. Compared to pretreatment, self-reported sleep efficiency increased and total wake time decreased after CBT-I, while the magnitude of changes in sleep efficiency (d = 1.40 vs d=0.81, interaction P = .016) and total wake time (d = -1.82 vs d = -0.85, interaction P < .001) were larger in the underestimation of sleep duration group . Furthermore, self-reported sleep onset latency (interaction P = .520) and wake after sleep onset (interaction P = .052) decreased in the underestimation of sleep duration group (all P < .05), but not in patients without underestimation of sleep duration. Linear regressions showed that lower sleep perception at baseline predicted greater increase in self-reported sleep efficiency (β = -0.99, P < .001) and total sleep time (β = -0.51, P = .006) and greater decrease in self-reported total wake time (β=1.22, P = .023) after CBT-I after adjusting for confounders.

CONCLUSIONS

The current preliminary study suggests that sleep perception moderates the self-reported CBT-I effects on chronic insomnia: the phenotype of underestimation of sleep duration is associated with a better response to CBT-I, especially in self-reported sleep parameters.

CITATION

Sun Q, Dai Y, Chen B, et al. The underestimation of sleep duration phenotype is associated with better treatment response to cognitive behavior therapy for insomnia in patients with chronic insomnia: a preliminary study. J Clin Sleep Med. 2022;18(10):2443-2450.

Sleep-dependent memory consolidation in breast cancer: Use of a virtual reality prospective memory task

Background

Previous studies have revealed both sleep alterations and prospective memory (PM) impairments in breast cancer (BC) patients. PM refers to memory of intended actions and is crucial for daily living tasks and treatment compliance. As sleep is known to favor memory consolidation, one may expect that changes in sleep quality related to BC would have an impact on PM performance. This study aimed at assessing sleep-dependent consolidation of intentions using an ecological, virtual reality-based PM task in BC patients not treated with chemotherapy.

Materials and methods

Thirty-seven early stages BC patients and 21 healthy controls (HC) participated in this study. PM was assessed using a virtual reality task, during which participants learnt a list of intentions and recalled them after a retention interval filled with a day awake or a night of sleep monitored by polysomnography. Sleep spindles and slow waves, brain oscillations involved in sleep-dependent memory consolidation, were quantified automatically using the Aseega software (Physip). Subjective sleep disturbances and markers of quality of life (psychological distress, fatigue, and well-being) were assessed by questionnaires.

Results

Greater PM performance was observed after sleep than after an equivalent period of daytime wakefulness for both groups (HC and BC). PM performance after sleep did not differ significantly between groups. Yet, BC patients reported greater sleep disturbances than HC which were related with poorer intentions retrieval, greater psychological distress, fatigue and poorer well-being. The frequency of spindles was higher and the amplitude of slow waves lower in BC patients compared to HC. However, no significant association was observed between polysomnography parameters and PM scores in the whole sample of participants.

Conclusion

Although subtle changes in brain oscillations involved in sleep-dependent memory consolidation were observed, these changes did not significantly impair overnight PM consolidation in BC patients. Nevertheless, poorer PM performance was associated with greater sleep complaints which in turn were related to poorer quality of life. Overall, these data suggest that sleep-dependent PM consolidation mechanisms are not altered in early stages BC patients not treated with chemotherapy. Further investigations are needed to understand the association between markers of quality of life and sleep-dependent memory consolidation.

Adaptive Solutions to the Problem of Vulnerability During Sleep

Sleep is a behavioral state whose quantity and quality represent a trade-off between the costs and benefits this state provides versus the costs and benefits of wakefulness. Like many species, we humans are particularly vulnerable during sleep because of our reduced ability to monitor the external environment for nighttime predators and other environmental dangers. A number of variations in sleep characteristics may have evolved over the course of human history to reduce this vulnerability, at both the individual and group level. The goals of this interdisciplinary review paper are (1) to explore a number of biological/instinctual features of sleep that may have adaptive utility in terms of enhancing the detection of external threats, and (2) to consider relatively recent cultural developments that improve vigilance and reduce vulnerability during sleep and the nighttime. This paper will also discuss possible benefits of the proposed adaptations beyond vigilance, as well as the potential costs associated with each of these proposed adaptations. Finally, testable hypotheses will be presented to evaluate the validity of these proposed adaptations.