Sleepiness as motivation: a potential mechanism for how sleep deprivation affects behavior

Prior-Night Sleep Predicts Next-Day Sedentary Behavior as a Function of Work Duration in Public Safety Telecommunicators

Public safety telecommunicators are at significant risk for obesity and other health conditions, which can likely be attributed to high-intensity job functions that occur in seated positions for long work hours. However, the interactions between these variables, as well as the role of recovery sleep, remains underexplored. We hypothesized that work duration would moderate the daily relationship between prior-night sleep and next day sedentary behavior. To test this hypothesis, actigraphic estimates of sleep and activity were gathered in 47 public safety telecommunicators over an average of 11 days (n = 525 cases). Results indicated that participants spent more time sedentary when they had less efficient, prior-night sleep in combination with both longer shifts or longer-than-usual same-day shifts. Wake time after sleep onset and total sleep time were positively associated with more next-day sedentary behavior, but only when working fewer hours. These findings suggest that public safety telecommunicators engage in compensatory, behavioral sleep patterns that are consistent with chronic insomnia and affected by both cumulative and daily work duration. Taken together, these results provide strong proof-of-concept that sleep health promotion and insomnia intervention might decrease sedentary behavior.

The new science of sleep: From cells to large-scale societies

In the past 20 years, more remarkable revelations about sleep and its varied functions have arguably been made than in the previous 200. Building on this swell of recent findings, this essay provides a broad sampling of selected research highlights across genetic, molecular, cellular, and physiological systems within the body, networks within the brain, and large-scale social dynamics. Based on this raft of exciting new discoveries, we have come to realize that sleep, in this moment of its evolution, is very much polyfunctional (rather than monofunctional), yet polyfunctional for reasons we had never previously considered. Moreover, these new polyfunctional insights powerfully reaffirm sleep as a critical biological, and thus health-sustaining, requisite. Indeed, perhaps the only thing more impressive than the unanticipated nature of these newly emerging sleep functions is their striking divergence, from operations of molecular mechanisms inside cells to entire group societal dynamics.

Insomnia symptom severity and dynamics of arousal-related symptoms across the day

Arousal is a central component of many emotional symptoms and can contribute to insomnia. Here we assessed how the timing and fluctuating nature of arousal-related symptoms over the course of the day relate to insomnia symptom severity. In this study, 361 participants (M age = 31.9 years, 282 women, 77 men, 2 non-binary individuals) completed the Insomnia Severity Index to assess severity of insomnia symptoms, followed by repeated ratings of anxiety or nervousness, stress, sleepiness, and feeling down via their mobile phone between ~08:00 hours and 00:00 hours across 1 day. Measures of dynamics included: mean levels across the day; variation (standard deviation); instability (mean squared successive differences); and resistance to change/inertia (first-order autocorrelation). Time-of-day patterns were modelled using generalized additive mixed effects models. Insomnia symptom severity (mean Insomnia Severity Index = 9.1, SD = 5.2, range 0-25) was associated with higher mean levels of all arousal-related symptoms, and increased instability and variation throughout the day in anxiety or nervousness, stress, and feeling down. Resistance to change (inertia) was not associated with insomnia symptom severity. Generalized additive mixed effects analyses showed that while individuals with more severe insomnia symptoms had elevated symptoms across the entire day, they were especially more anxious or nervous and sleepy in the early morning (~08:00 hours), anxious or nervous, stressed and sleepy in the late afternoon/early evening (~16:00 hours-21:00 hours), and anxious or nervous and stressed in the late evening (~22:00 hours). Remarkably, higher arousal occurred in the presence of high subjective sleepiness. Together these results indicate that insomnia symptom severity is associated with problems with daytime and evening arousal regulation.

Physical Activity After Heart Surgery: Associations With Psychosocial and Sleep Factors

BACKGROUND

Heart surgery is an effective intervention for managing heart disease, the leading cause of death globally. After surgery, physical activity is key to improving patients' quality of life and decreasing mortality, but patients are frequently physically inactive after heart surgery.

OBJECTIVE

This cross-sectional pilot study aimed to examine how psychosocial and sleep factors influenced physical activity in patients after heart surgery. The mediating role of sleep factors between psychosocial factors and physical activity was also examined.

METHODS

Thirty-three patients who had undergone heart surgery were recruited. Psychosocial and sleep factors and physical activity were measured using an online survey and a wrist-worn ActiGraph for 7 days and nights.

RESULTS

The participants had heart surgery an average of about 7 years previously. They exceeded the recommended 150 minutes per week of moderate-intensity physical activity for Americans; however, 64% of them showed poor sleep quality (Pittsburgh Sleep Quality Index >5). Higher anxiety and depressive symptoms, lower self-efficacy, and greater sleep disturbances were associated with lower physical activity. Moreover, self-efficacy, sleep duration, sleep disturbance, sleep efficiency, and wake after sleep onset were predictors for physical activity. No mediating role of sleep factors was observed between psychosocial factors and physical activity.

CONCLUSIONS

Psychosocial and sleep factors should be considered when developing and implementing physical activity strategies for patients after heart surgery. Researchers should examine the relationships among the study variables with larger samples of postsurgical cardiac patients during different periods after heart surgery.

Human Prosocial Preferences Are Related to Slow-Wave Activity in Sleep

Prosocial behavior is crucial for the smooth functioning of the society. Yet, individuals differ vastly in the propensity to behave prosocially. Here, we try to explain these individual differences under normal sleep conditions without any experimental modulation of sleep. Using a portable high-density EEG, we measured the sleep data in 54 healthy adults (28 females) during a normal night's sleep at the participants' homes. To capture prosocial preferences, participants played an incentivized public goods game in which they faced real monetary consequences. The whole-brain analyses showed that a higher relative slow-wave activity (SWA, an indicator of sleep depth) in a cluster of electrodes over the right temporoparietal junction (TPJ) was associated with increased prosocial preferences. Source localization and current source density analyses further support these findings. Recent sleep deprivation studies imply that sleeping enough makes us more prosocial; the present findings suggest that it is not only sleep duration, but particularly sufficient sleep depth in the TPJ that is positively related to prosociality. Because the TPJ plays a central role in social cognitive functions, we speculate that sleep depth in the TPJ, as reflected by relative SWA, might serve as a dispositional indicator of social cognition ability, which is reflected in prosocial preferences. These findings contribute to the emerging framework explaining the link between sleep and prosocial behavior by shedding light on the underlying mechanisms.

How emotions impact sleep: A quantitative review of experiments

Although sleep and emotional processes are recognized as mutually dependent, the causal impact of emotions on sleep has been comparatively neglected. To appraise evidence for the causal influence of emotions on sleep, a meta-analysis of the existing experimental literature evaluated the strength, form, and context of experimental effects of emotion inductions on sleep parameters (k = 31). Quality of experiments was evaluated, and theoretically-relevant features were extracted and examined as moderating factors of observed effects (i.e., sleep parameter, design, sleep context, types of emotion inductions and emotions). Random-effect models were used to aggregate effects for each sleep parameter, while-mixed effect models examined moderators. There was a significant impact of emotion inductions on delayed sleep onset latency (D = 3.36 min, 95%CI [1.78, 4.94], g = 0.53), but not other parameters. There was little evidence of publication bias regarding sleep-onset latency effect, the studies overall were heterogeneous, sometimes of limited methodological quality, and could only detect moderate-to-large impacts. The findings supported the hypothesis that negative emotions delayed sleep onset, but evidence regarding other sleep parameters was inconclusive. The results call for more targeted investigation to disambiguate distinct features of emotions and their import for sleep.

Fundamentals of sleep regulation: Model and benchmark values for fractal and oscillatory neurodynamics

Homeostatic, circadian and ultradian mechanisms play crucial roles in the regulation of sleep. Evidence suggests that ratios of low-to-high frequency power in the electroencephalogram (EEG) spectrum indicate the instantaneous level of sleep pressure, influenced by factors such as individual sleep-wake history, current sleep stage, age-related differences and brain topography characteristics. These effects are well captured and reflected in the spectral exponent, a composite measure of the constant low-to-high frequency ratio in the periodogram, which is scale-free and exhibits lower interindividual variability compared to slow wave activity, potentially serving as a suitable standardization and reference measure. Here we propose an index of sleep homeostasis based on the spectral exponent, reflecting the level of membrane hyperpolarization and/or network bistability in the central nervous system in humans. In addition, we advance the idea that the U-shaped overnight deceleration of oscillatory slow and fast sleep spindle frequencies marks the biological night, providing somnologists with an EEG-index of circadian sleep regulation. Evidence supporting this assertion comes from studies based on sleep replacement, forced desynchrony protocols and high-resolution analyses of sleep spindles. Finally, ultradian sleep regulatory mechanisms are indicated by the recurrent, abrupt shifts in dominant oscillatory frequencies, with spindle ranges signifying non-rapid eye movement and non-spindle oscillations - rapid eye movement phases of the sleep cycles. Reconsidering the indicators of fundamental sleep regulatory processes in the framework of the new Fractal and Oscillatory Adjustment Model (FOAM) offers an appealing opportunity to bridge the gap between the two-process model of sleep regulation and clinical somnology.

The dark side of mobile work during non-work hours: moderated mediation model of presenteeism through conservation of resources lens

Owing to the development of Information and Communication Technology (ICT) and the inevitability of telecommuting in the COVID-19 environment, the boundary between working and non-working hours has become blurred. mWork, that is, ICT-based off-hour work, which has increased through the pandemic, affects employees' work attitudes, such as presenteeism. Hence, we designed a study to investigate the antecedents and mechanisms of employee presenteeism from the perspective of the conservation of resources theory. We supported our hypothesis using a sample of 325 Korean office workers obtained through three rounds of time-delay surveys. The results show that presenteeism is higher among employees with high mWork. In addition, employees' mWork increases sleep deprivation and presenteeism, and the exchange ideology of employees reinforces the positive effect of sleep deprivation on presenteeism. Additionally, the higher the level of exchange ideology, the stronger the mediating effect of mWork on presenteeism through sleep deprivation. This study verified the conservation of resources theory by identifying the mechanism by which mWork affects an employee's life, which in turn affects their work, and provides practical implications for managing productivity loss due to presenteeism.

A real-world study of quality of life following treatment with xylometazoline hydrochloride in individuals with common cold

BACKGROUND

The common cold is a frequent, acute, and mild upper respiratory human disease. Nasal congestion has been considered the most bothersome symptom in the common cold, impacting quality of life (QoL). Topical decongestants containing steroids benefit QoL in allergic rhinitis, but no published research has assessed the impact of topical decongestants on QoL in the common cold.

OBJECTIVE

To evaluate the effects of xylometazoline hydrochloride 0.1% (Otrivin, GSK Consumer Healthcare SARL, Switzerland) for up to 7 days on QoL in participants with nasal congestion associated with the common cold.

DESIGN

This was a decentralized, longitudinal, open-label study.

METHODS

The study enrolled 136 participants (⩾18 years) with early symptoms of the common cold, of which 102 were included in the modified intention-to-treat (mITT) population. Within 24 h of study product receipt, participants confirmed a 'plugged nose' and ⩾1 other common cold symptom. Primary endpoints were Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21) total score, total and individual symptom scores, and total QoL score. Secondary endpoints were additional QoL scores. Exploratory and post hoc analyses included median days to resolution for each QoL factor and analyses of five QoL categories.

RESULTS

Consistent improvements in symptoms and QoL were seen in the mITT population. From day 1, improvements were seen in the 'plugged nose' symptom (p = 0.0023), WURSS-21 total QoL score, and all individual QoL scores (p < 0.0001 for all). After the last dose needed, significant improvements were seen in sleep quality (73%), vitality (76%), physical activity (71%), social activity (80%), and sensation (81%). No serious or unexpected adverse events were reported.

CONCLUSION

This study is the first to demonstrate in a real-life setting that treating nasal congestion in adults with xylometazoline hydrochloride 0.1% during the common cold positively impacts QoL factors relevant to daily living [Otrivin: Quality of Life (QoL) Impact in a Real-World Setting; https://clinicaltrials.gov/study/NCT05556148].

Assessing 'readiness' by tracking fluctuations in daily sleep duration and their effects on daily mood, motivation, and sleepiness

STUDY OBJECTIVES

Consumer sleep trackers issue daily guidance on 'readiness' without clear empirical basis. We investigated how self-rated mood, motivation, and sleepiness (MMS) levels are affected by daily fluctuations in sleep duration, timing, and efficiency and overall sleep regularity. We also determined how temporally specific these associations are.

METHODS

119 healthy university students (64 female, mean age = 22.54 ± 1.74 years) wore a wearable sleep tracker and undertook twice-daily smartphone-delivered ecological momentary assessment of mood, motivation, and sleepiness at post-wake and pre-bedtime timings for 2-6 weeks. Naps and their duration were reported daily. Nocturnal sleep on 2471 nights were examined using multilevel models to uncover within-subject and between-subject associations between sleep duration, timing, efficiency, and nap duration on following day MMS ratings. Time-lagged analyses examined the temporal specificity of these associations. Linear regression models investigated associations between MMS ratings and sleep variability, controlling for sleep duration.

RESULTS

Nocturnal sleep durations were short (6.03 ± 0.71 h), and bedtimes were late (1:42AM ± 1:05). Within-subjects, nocturnal sleep longer than a person's average was associated with better mood, higher motivation, and lower sleepiness after waking. Effects of such longer sleep duration lingered for mood and sleepiness till the pre-bedtime window (all Ps < .005) but did not extend to the next day. Between-subjects, higher intraindividual sleep variability, but not sleep duration, was associated with poorer mood and lower motivation after waking. Longer average sleep duration was associated with less sleepiness after waking and lower motivation pre-bedtime (all Ps < .05). Longer naps reduced post-nap sleepiness and improved mood. Controlling for nocturnal sleep duration, longer naps also associated with lower post-waking sleepiness on the following day.

CONCLUSIONS

Positive connections between nocturnal sleep and nap duration with MMS are temporally circumscribed, lending credence to the construction of sleep-based, daily 'readiness' scores. Higher sleep duration variability lowers an individual's post waking mood and motivation.

CLINICAL TRIAL ID

ClinicalTrials.gov NCT04880629.

Disturbed sleep and patterns of psychiatric symptoms and function in a school-based sample of adolescents

BACKGROUND

Sleep problems are common in adolescence and often related to psychopathology and impaired functioning. However, most studies have used summative scores, and little is known about how adolescents with disrupted sleep perceive their specific symptoms and dysfunctions. This study explored differences in levels of psychiatric symptoms and functional ability between Swedish adolescents with and without self-reported disturbed sleep in a school-based sample.

METHODS

Swedish adolescents (n = 618, mean age 15.7+/-1.9yrs) answered the PROMIS pediatric measures for fatigue, anxiety, depression, pain interference, anger, physical activity and peer and family relationships. Logistic regression analyses were performed to assess differences between respondents with and without disturbed sleep.

RESULTS

Disturbed sleep was associated with higher levels of symptoms of fatigue, anxiety, depression, anger and pain interference, as well as lower functional abilities in terms of physical activity and peer- and family relationships. Adolescents reporting disturbed sleep generally displayed a pattern of impaired executive functioning, internal emotional distress and school- and sleep related worry and dysfunction, as compared to physical disability, aggressive behavior, stress and generalized worry.

CONCLUSIONS

The present study adds to the understanding of how disturbed sleep and specific psychiatric symptoms and functional ability are interrelated, which may also have clinical implications.

The Impact of Sleep Deprivation on Brain Networks in Response to Social Evaluation Tasks

Sleep loss may lead to negative bias during social interaction. In the current study, we conducted a revised social evaluation task experiment to investigate how sleep deprivation influences the self-referential and cognitive processes of social feedback. The experiment consisted of a first impression task and a social feedback task. Seventy-eight participants completed the first impression task and were divided into normal and poor sleep groups. The results of an independent samples t-test showed that participants who slept worse were less likely to socialize with others but did not evaluate others as less attractive. Afterward, 22 of the participants from the first impression task were recruited to complete the social feedback task during functional magnetic resonance imaging (fMRI) on the mornings following two different sleep conditions at night: one night of normal sleep and one night of sleep deprivation. The results of this within-subject design study showed that participants who experienced the latter condition showed increased activation within the default mode network (i.e. superior parietal lobule, precuneus, inferior parietal lobule, inferior temporal gyrus, and medial frontal gyrus) and anterior cingulate cortex (ACC) and stronger negative insula functional connectivity (FC) with the precuneus to negative feedback than positive feedback. The altered activation and behavioral pattern may indicate a negative bias for social cues. However, stronger negative coupling may indicate stronger cognitive control, which may protect against potential damage to self-concept. Our study suggested that sleep impairs most social functions, but may protect against impairment of important ones, such as self-concept.

Utilizing EEG and fNIRS for the detection of sleep-deprivation-induced fatigue and its inhibition using colored light stimulation

Drowsy driving is a common, but underestimated phenomenon in terms of associated risks as it often results in crashes causing fatalities and serious injuries. It is a challenging task to alert or reduce the driver's drowsy state using non-invasive techniques. In this study, a drowsiness reduction strategy has been developed and analyzed using exposure to different light colors and recording the corresponding electrical and biological brain activities. 31 subjects were examined by dividing them into 2 classes, a control group, and a healthy group. Fourteen EEG and 42 fNIRS channels were used to gather neurological data from two brain regions (prefrontal and visual cortices). Experiments shining 3 different colored lights have been carried out on them at certain times when there is a high probability to get drowsy. The results of this study show that there is a significant increase in HbO of a sleep-deprived participant when he is exposed to blue light. Similarly, the beta band of EEG also showed an increased response. However, the study found that there is no considerable increase in HbO and beta band power in the case of red and green light exposures. In addition to that, values of other physiological signals acquired such as heart rate, eye blinking, and self-reported Karolinska Sleepiness Scale scores validated the findings predicted by the electrical and biological signals. The statistical significance of the signals achieved has been tested using repeated measures ANOVA and t-tests. Correlation scores were also calculated to find the association between the changes in the data signals with the corresponding changes in the alertness level.

Effects of Acute Sleep Loss on Physical Performance: A Systematic and Meta-Analytical Review

BACKGROUND

Sleep loss may influence subsequent physical performance. Quantifying the impact of sleep loss on physical performance is critical for individuals involved in athletic pursuits.

DESIGN

Systematic review and meta-analysis.

SEARCH AND INCLUSION

Studies were identified via the Web of Science, Scopus, and PsycINFO online databases. Investigations measuring exercise performance under 'control' (i.e., normal sleep, > 6 h in any 24 h period) and 'intervention' (i.e., sleep loss, ≤ 6 h sleep in any 24 h period) conditions were included. Performance tasks were classified into different exercise categories (anaerobic power, speed/power endurance, high-intensity interval exercise (HIIE), strength, endurance, strength-endurance, and skill). Multi-level random-effects meta-analyses and meta-regression analyses were conducted, including subgroup analyses to explore the influence of sleep-loss protocol (e.g., deprivation, restriction, early [delayed sleep onset] and late restriction [earlier than normal waking]), time of day the exercise task was performed (AM vs. PM) and body limb strength (upper vs. lower body).

RESULTS

Overall, 227 outcome measures (anaerobic power: n = 58; speed/power endurance: n = 32; HIIE: n = 27; strength: n = 66; endurance: n = 22; strength-endurance: n = 9; skill: n = 13) derived from 69 publications were included. Results indicated a negative impact of sleep loss on the percentage change (%Δ) in exercise performance (n = 959 [89%] male; mean %Δ =  - 7.56%, 95% CI - 11.9 to - 3.13, p = 0.001, I2 = 98.1%). Effects were significant for all exercise categories. Subgroup analyses indicated that the pattern of sleep loss (i.e., deprivation, early and late restriction) preceding exercise is an important factor, with consistent negative effects only observed with deprivation and late-restriction protocols. A significant positive relationship was observed between time awake prior to the exercise task and %Δ in performance for both deprivation and late-restriction protocols (~ 0.4% decrease for every hour awake prior to exercise). The negative effects of sleep loss on different exercise tasks performed in the PM were consistent, while tasks performed in the AM were largely unaffected.

CONCLUSIONS

Sleep loss appears to have a negative impact on exercise performance. If sleep loss is anticipated and unavoidable, individuals should avoid situations that lead to experiencing deprivation or late restriction, and prioritise morning exercise in an effort to maintain performance.

Self-reported sleepiness associates with greater brain and cortical volume and lower prevalence of ischemic covert brain infarcts in a community sample

STUDY OBJECTIVES

We evaluated if self-reported sleepiness was associated with neuroimaging markers of brain aging and ischemic damage in a large community-based sample.

METHODS

Participants from the Framingham Heart Study Offspring cohort (n = 468, 62.5 ± 8.7 years old, 49.6%M) free of dementia, stroke, and neurological diseases, completed sleep questionnaires and polysomnography followed by magnetic resonance imaging (MRI), 3 years later on average. We used linear and logistic regression models to evaluate the associations between Epworth Sleepiness Scale (ESS) scores and total brain, cortical and subcortical gray matter, and white matter hyperintensities volumes, and the presence of covert brain infarcts.

RESULTS

Higher sleepiness scores were associated with larger total brain volume, greater cortical gray matter volume, and a lower prevalence of covert brain infarcts, even when adjusting for a large array of potential confounders, including demographics, sleep profiles and disorders, organic health diseases, and proxies for daytime cognitive and physical activities. Interactions indicated that more sleepiness was associated with larger cortical gray matter volume in men only and in APOE ε4 noncarriers, whereas a trend for smaller cortical gray matter volume was observed in carriers. In longitudinal analyses, those with stable excessive daytime sleepiness over time had greater total brain and cortical gray matter volumes, whereas baseline sleepiness scores were not associated with subsequent atrophy or cognitive decline.

CONCLUSION

Our findings suggest that sleepiness is not necessarily a marker of poor brain health when not explained by diseases or sleep debt and sleep disorders. Rather, sleepiness could be a marker of preserved sleep-regulatory processes and brain health in some cases.

The influence of sleep and movement on mental health and life satisfaction during the transition to parenthood

OBJECTIVES

This study assessed whether sleep and physical activity impact mental health and life satisfaction across the transition to parenthood. This study assessed the impact of parenthood on mental health of new parents and parents expecting their second child, and whether change in mental health occurred dyadically across couples.

DESIGN

Longitudinal 12-month study.

PARTICIPANTS

One hundred and fifty-seven couples (N = 314) between the ages of 25 and 40, who were not expecting to have a child (n = 102), expecting their first child (n = 136), or expecting their second child (n = 76) were recruited.

MEASUREMENTS

Participants completed measures at baseline, 6 months, and 12 months. Sleep was assessed with how often participants met sleep guidelines (7-9 hours). Physical activity was measured objectively via accelerometers. Mental health was measured using 6 items from the short form-12 Quality of Life Survey. Life satisfaction was assessed with the Satisfaction with Life Scale (5 items).

RESULTS

Mental health was not predicted by physical activity but was predicted by sleep. Sleep at 6 months was positively related to mental health at 6 months (β = 0.156, p < .001), and sleep at 12 months was positively related to mental health at 12 months (β = 0.170, p < .001). The change in mental health did not occur dyadically: mental health increased for women but not for men across groups. Mental health was positively related to life satisfaction at 6 months (β = 0.338, p < .001) and 12-months (β = 0.277, p < .001).

CONCLUSIONS

For new and established parents, getting sufficient sleep plays an important role in mental health and, in turn, life satisfaction.

Sleepy and Secluded: Sleep Disturbances are Associated With Connectedness in Early Adolescent Social Networks

Studies in adults suggest that sleep disturbances predict poorer socioemotional skills and impaired social interactions. However, little is known regarding how sleep disturbances are associated with social processes during adolescence, a period when both sleep neurobiology and social relationships are undergoing dramatic developmental changes. The current study examined associations among sleep disturbances and peer connectedness in a sample of middle-school students (N = 213, 11-15 years old, 57% female) using a social network approach. Findings suggested that youth with greater sleep disturbances reported having fewer social connections, were rated as a social connection by fewer peers, and were less likely to have reciprocated nominations, even after controlling for sociodemographic characteristics and mental health symptoms.

Sleep loss impairs cognitive performance and alters song output in Australian magpies

Sleep maintains optimal brain functioning to facilitate behavioural flexibility while awake. Owing to a historical bias towards research on mammals, we know comparatively little about the role of sleep in facilitating the cognitive abilities of birds. We investigated how sleep deprivation over the full-night (12 h) or half-night (6 h) affects cognitive performance in adult Australian magpies (Cracticus tibicen), relative to that after a night of undisturbed sleep. Each condition was preceded and followed by a baseline and recovery night of sleep, respectively. Prior to each treatment, birds were trained on an associative learning task; on the day after experimental treatment (recovery day), birds were tested on a reversal learning task. To glean whether sleep loss affected song output, we also conducted impromptu song recordings for three days. Ultimately, sleep-deprived magpies were slower to attempt the reversal learning task, less likely to perform and complete the task, and those that did the test performed worse than better-rested birds. We also found that sleep-deprived magpies sang longer yet fewer songs, shifted crepuscular singing to mid-day, and during the post-recovery day, song frequency bandwidth narrowed. These results collectively indicate that sleep loss impairs motivation and cognitive performance, and alters song output, in a social adult songbird.

How Sleep-Deprived People See and Evaluate Others' Faces: An Experimental Study

BACKGROUND

Acute sleep loss increases the brain's reactivity toward positive and negative affective stimuli. Thus, despite well-known reduced attention due to acute sleep loss, we hypothesized that humans would gaze longer on happy, angry, and fearful faces than neutral faces when sleep-deprived. We also examined if facial expressions are differently perceived after acute sleep loss.

METHODS

In the present, within-subjects study, 45 young adults participated in one night of total sleep deprivation and one night with an 8-hour sleep opportunity. On the morning after each night, an eye tracker was used to measure participants' time spent fixating images of happy, angry, fearful, and neutral faces. Participants also evaluated faces' attractiveness, trustworthiness, and healthiness on a 100-mm visual analog scale.

RESULTS

Following sleep loss, participants struggled more fixating the faces than after sleep. The decrease in total fixation duration ranged from 6.3% to 10.6% after sleep loss (P<0.001). Contrary to our hypothesis, the reduction in total fixation duration occurred irrespective of the displayed emotion (P=0.235 for sleep*emotion interaction) and was also present for the upper (P<0.001) but not the lower part of the faces (except for the lower part of angry faces). Overall, faces were evaluated as less trustworthy (-2.6 mm) and attractive (-3.6 mm) after sleep loss (p<0.05).

DISCUSSION

Facial expressions are crucial for social interactions. Thus, spending less time fixating on faces after acute sleep loss may come along with several problems for social interactions, eg, inaccurate and delayed judgment of the emotional state of others. In addition, more negative social impressions of others may lead to social withdrawal in sleep-deprived humans.

Impact of total sleep deprivation and related mood changes on approach-avoidance decisions to threat-related facial displays

STUDY OBJECTIVES

Total sleep deprivation is known to have significant detrimental effects on cognitive and socio-emotional functioning. Nonetheless, the mechanisms by which total sleep loss disturbs decision-making in social contexts are poorly understood. Here, we investigated the impact of total sleep deprivation on approach/avoidance decisions when faced with threatening individuals, as well as the potential moderating role of sleep-related mood changes.

METHODS

Participants (n = 34) made spontaneous approach/avoidance decisions in the presence of task-irrelevant angry or fearful individuals, while rested or totally sleep deprived (27 h of continuous wakefulness). Sleep-related changes in mood and sustained attention were assessed using the Positive and Negative Affective Scale and the psychomotor vigilance task, respectively.

RESULTS

Rested participants avoided both fearful and angry individuals, with stronger avoidance for angry individuals, in line with previous results. On the contrary, totally sleep deprived participants favored neither approach nor avoidance of fearful individuals, while they still comparably avoided angry individuals. Drift-diffusion models showed that this effect was accounted for by the fact that total sleep deprivation reduced value-based evidence accumulation toward avoidance during decision making. Finally, the reduction of positive mood after total sleep deprivation positively correlated with the reduction of fearful display avoidance. Importantly, this correlation was not mediated by a sleep-related reduction in sustained attention.

CONCLUSIONS

All together, these findings support the underestimated role of positive mood-state alterations caused by total sleep loss on approach/avoidance decisions when facing ambiguous socio-emotional displays, such as fear.

Interindividual differences in energy intake after sleep restriction: The role of personality and implicit attitudes toward food

Sleep restriction (SR) often leads to an increase in energy intake (EI). However, large variability in EI after SR is often observed, which suggests that individual characteristics may affect food intake. The objective of this study was to explore the influence of characteristics generally associated with risk-taking (sensitivity to reward and personality traits: impulsiveness, sensation seeking) and implicit attitudes toward food on EI after sleep loss. 17 subjects completed the NEO-PI-3, an Implicit Association Test measuring implicit attitudes towards healthy and unhealthy foods, and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire. 24h Ad libitum EI was assessed following a habitual sleep night, a 50% SR with an advanced wake time, and a 50% SR with a delayed bedtime. Changes in EI between each SR condition and the control condition (ΔEI) were calculated for each subject. Despite no changes in overall EI between sleep conditions, results showed large interindividual variations (-669 to +899 kcal) across SR conditions. Regression modeling showed that a lower sensation seeking and higher favorable implicit attitudes towards unhealthy food were significantly associated with increased ΔEI in the advanced wake time condition. For the delayed bedtime, lower sensation seeking was associated with increased ΔEI while controlling for age, sex, REM sleep, and implicit attitudes. These results suggest that certain personality traits and implicit attitudes toward food are associated with changes in EI after sleep loss.

Awareness of sleepiness: Temporal dynamics of subjective and objective sleepiness

We systematically examined the temporal relationships between subjective sleepiness and both physiological drowsiness and performance impairment in a controlled laboratory setting. Eighteen healthy young adults (8 women; M_AGE  = 21.44 ± 3.24 years) underwent 40 hr of extended wakefulness, completing a bihourly Karolinska Sleepiness Scale (KSS) and 10-min Psychomotor Vigilance Task (PVT). Microsleeps and slow eye movements (SEMs) were scored during the PVT. KSS scores increased 3 hr prior to performance impairment (p < .001) and 4-6 hr prior to physiological sleepiness (p < .001). There were strong within-subject correlations between KSS and PVT lapses (r = 0.75, p < .001) and physiological drowsiness (r > 0.60, p < .001). Between-subjects product-moment correlations were more modest but showed a significant positive increase across time awake, suggesting that subjective sleepiness and objective outcomes were more tightly correlated after sleep loss. Cross-correlations showed significant positive correlations at 0-lag (p < .034); however, a high proportion of participants showed maximal correlations at positive lags, suggesting KSS was associated with future objective impairment. Within individuals, subjective sleepiness was highly correlated with objective impairment, between-subject correlations were more modest, possibly due to interindividual vulnerability to sleep loss. These results suggest that subjective sleepiness represents an inbuilt early warning system for subsequent drowsiness and performance impairment.

Sleepiness is a signal to go to bed: data and model simulations

Study Objectives

Assess the validity of a subjective measure of sleepiness as an indicator of sleep drive by quantifying associations between intraindividual variation in evening sleepiness and bedtime, sleep duration, and next morning and subsequent evening sleepiness, in young adults.

Methods

Sleep timing and sleepiness were assessed in 19 students in late autumn and late spring on a total of 771 days. Karolinska Sleepiness Scales (KSS) were completed at half-hourly intervals at fixed clock times starting 4 h prior to participants’ habitual bedtime, and in the morning. Associations between sleepiness and sleep timing were evaluated by mixed model and nonparametric approaches and simulated with a mathematical model for the homeostatic and circadian regulation of sleepiness.

Results

Intraindividual variation in evening sleepiness was very large, covering four or five points on the 9-point KSS scale, and was significantly associated with subsequent sleep timing. On average, a one point higher KSS value was followed by 20 min earlier bedtime, which led to 11 min longer sleep, which correlated with lower sleepiness next morning and the following evening. Associations between sleepiness and sleep timing were stronger in early compared to late sleepers. Model simulations indicated that the directions of associations between sleepiness and sleep timing are in accordance with their homeostatic and circadian regulation, even though much of the variance in evening sleepiness and details of its time course remain unexplained by the model.

Conclusion

Subjective sleepiness is a valid indicator of the drive for sleep which, if acted upon, can reduce insufficient sleep.

Age- and gender-associated differences in the sleepy brain's electroencephalogram

Background. With the eyes closed, an increase in sleepiness is associated with a decrease of spectral electroencephalographic (EEG) power in the high-frequency rage (i.e. alpha activity) and an increase of the power in the low-frequency range (i.e. theta activity). It has been suggested that the changes in the high- and low-frequency ranges might determine the two (earlier and later) drowsiness stages that precede sleep onset, respectively.Objective. We tested whether such spectral EEG signatures of sleepiness vary with age or gender.Approach. The EEG signal was recorded at 2 h intervals in 48 volunteers (15-67 years, 27 females) deprived of sleep between Friday evening and Sunday evening. The EEG signatures of sleepiness were calculated by expressing each EEG spectrum as a deviation from the initial (Friday evening) EEG spectrum.Main results. An age- and gender-specific variation was found in the signatures. Only the pattern of age-associated variation changed with an increase in the sleepiness level. A two-stage response to the increase of sleepiness was confirmed, but only in younger study participants. Subjective sleepiness was associated with neither age nor gender.Significance. In sleep-deprivation research, accounting for age- and gender-specific variations in the spectral EEG measures of drowsiness might be recommended. The results did not reveal any disturbance of the motivational function of subjective sleepiness in older study participants.

Sleep and social relationships in healthy populations: A systematic review

Over the past decade, research linking sleep and social relationships has burgeoned. Researchers across the globe are trying to understand whether the quality and quantity of our social relationships matter for sleep, and vice versa. We conducted a systematic review of the literature, identifying over 200 relevant articles examining sleep and social relationships in healthy populations. Here, we summarize our findings by reviewing 1) links between sleep and broad social ties across the lifespan, and 2) links between sleep and specific social relationships identified in the literature search, including romantic relationships, family relationships, and work relationships. Taken together, the literature provides evidence that the quality and presence of social relationships, especially our closest relationships, play a role in how we sleep. Likewise, sleep appears to influence our social bonds. However, the majority of work is correlational, limiting conclusions about the directionality of these effects. We conclude by synthesizing the findings, considering the limitations of the present literature, and identifying key future directions for this emerging area of research.

Changes in Subjective Motivation and Effort During Sleep Restriction Moderate Interindividual Differences in Attentional Performance in Healthy Young Men

PURPOSE

The effects of sleep restriction on subjective alertness, motivation, and effort vary among individuals and may explain interindividual differences in attention during sleep restriction. We investigated whether individuals with a greater decrease in subjective alertness or motivation, or a greater increase in subjective effort (versus other participants), demonstrated poorer attention when sleep restricted.

PARTICIPANTS AND METHODS

Fifteen healthy men (M±SD, 22.3±2.8 years) completed a study with three nights of 10-hour time in bed (baseline), five nights of 5-hour time in bed (sleep restriction), and two nights of 10-hour time in bed (recovery). Participants completed a 10-minute psychomotor vigilance task (PVT) of sustained attention and rated alertness, motivation, and effort every two hours during wake (range: 3-9 administrations on a given day). Analyses examined performance across the study (first two days excluded) moderated by per-participant change in subjective alertness, motivation, or effort from baseline to sleep restriction. For significant interactions, we investigated the effect of study day² (day*day) on the outcome at low (mean-1 SD) and high (mean+1 SD) levels of the moderator (N = 15, all analyses).

RESULTS

False starts increased across sleep restriction in participants who reported lower (mean-1 SD) but not preserved (mean+1 SD) motivation during sleep restriction. Lapses increased across sleep restriction regardless of change in subjective motivation, with a more pronounced increase in participants who reported lower versus preserved motivation. Lapses increased across sleep restriction in participants who reported higher (mean+1 SD) but not preserved (mean-1 SD) effort during sleep restriction. Change in subjective alertness did not moderate the effects of sleep restriction on attention.

CONCLUSION

Vigilance declines during sleep restriction regardless of change in subjective alertness or motivation, but individuals with reduced motivation exhibit poorer inhibition. Individuals with preserved subjective alertness still perform poorly during sleep restriction, while those reporting additional effort demonstrate impaired vigilance.

Quality of life and procrastination in post-H1N1 narcolepsy, sporadic narcolepsy and idiopathic hypersomnia, a Swedish cross-sectional study

OBJECTIVE/BACKGROUND

A cross-sectional study of health-related quality of life (HRQoL), procrastination and the relation to sleepiness, depression and fatigue in post-H1N1 narcolepsy type 1 (NT1), sporadic NT1 and idiopathic hypersomnia (IH).

PATIENTS/METHODS

Participants with NT1 and IH were enrolled from the Department of Neurology, Sahlgrenska University Hospital in Gothenburg (Sweden). All participants completed questionnaires about medication, employment, studies, transfer income, sleepiness, HRQoL, depression, fatigue and three questionnaires for procrastination.

RESULTS

Post-H1N1, sporadic NT1 and IH all scored higher than healthy controls on Epworth Sleepiness Scale (ESS), Patient Health Questionnaire (PHQ-9) and Fatigue Severity Scale (FSS), whereas EQ-5D-5L index and VAS was lower than for healthy individuals, but with no difference between groups. Post-H1N1 NT1 had a larger proportion of participants prescribed with sodium oxybate (44% vs. 9%, p = 0.003) and dexamphetamine (62% vs. 17%, p = 0.03) compared to sporadic NT1. The latter also in significantly higher doses than in sporadic NT1 (46 ± 12 vs. 25 ± 10 and 47.5 ± 21 mg, p < 0.0001). Post-H1N1 NT1 also had significantly higher scores on Pure Procrastination Scale (PPS), Irrational Procrastination Scale (IPS) and Susceptibility to Temptation Scale (STS), indicating a higher degree of procrastination. Multivariate analysis showed that depression, and to some extent fatigue, were predictors in NT1 for both HRQoL and procrastination.

CONCLUSIONS

The results show that health-related quality of life is impaired and tendency to procrastinate is higher in patients suffering from NT1 and both attributes can in part be explained by depressive symptoms. These findings highlight the impact of symptoms other than sleep and wakefulness regulation in patients with NT1.

Sleepiness, sleep duration, and human social activity: An investigation into bidirectionality using longitudinal time-use data

Daytime sleepiness impairs cognitive ability, but recent evidence suggests it is also an important driver of human motivation and behavior. We aimed to investigate the relationship between sleepiness and a behavior strongly associated with better health: social activity. We additionally aimed to investigate whether a key driver of sleepiness, sleep duration, had a similar relationship with social activity. For these questions, we considered bidirectionality, time of day, and differences between workdays and days off. Over 3 wk, 641 working adults logged their behavior every 30 min, completed a sleepiness scale every 3 h, and filled a sleep diary every morning (rendering >292,000 activity and >70,000 sleepiness datapoints). Using generalized additive mixed-effect models, we analyzed potential nonlinear relationships between sleepiness/sleep duration and social activity. Greater sleepiness predicted a substantial decrease in the probability of social activity (odds ratio 95% CI = 0.34 to 0.35 for days off), as well as a decreased duration of such activity when it did occur. These associations appear especially robust on days off and in the evenings. Social duration moderated the typical time-of-day pattern of sleepiness, with, for example, extended evening socializing associated with lower sleepiness. Sleep duration did not robustly predict next-day social activity. However, extensive social activity (>5 h) predicted up to 30 min shorter subsequent sleep duration. These results indicate that sleepiness is a strong predictor of voluntary decreases in social contact. It is possible that bouts of sleepiness lead to social withdrawal and loneliness, both risk factors for mental and physical ill health.