Sleep stage physiology, mood, and vigilance responses to total sleep deprivation in healthy 80-year-olds and 20-year-olds

Unraveling the interplay of circadian rhythm and sleep deprivation on mood: A Real-World Study on first-year physicians

The interplay between circadian rhythms, time awake, and mood remains poorly understood in the real-world. Individuals in high-stress occupations with irregular schedules or nighttime shifts are particularly vulnerable to depression and other mood disorders. Advances in wearable technology have provided the opportunity to study these interactions outside of a controlled laboratory environment. Here, we examine the effects of circadian rhythms and time awake on mood in first-year physicians using wearables. Continuous heart rate, step count, sleep data, and daily mood scores were collected from 2,602 medical interns across 168,311 days of Fitbit data. Circadian time and time awake were extracted from minute-by-minute wearable heart rate and motion measurements. Linear mixed modeling determined the relationship between mood, circadian rhythm, and time awake. In this cohort, mood was modulated by circadian timekeeping (p<0.001). Furthermore, we show that increasing time awake both deteriorates mood (p<0.001) and amplifies mood's circadian rhythm nonlinearly. These findings demonstrate the contributions of both circadian rhythms and sleep deprivation to underlying mood and show how these factors can be studied in real-world settings using Fitbits. They underscore the promising opportunity to harness wearables in deploying chronotherapies for psychiatric illness.

Memory load of information encoded amplifies the magnitude of hindsight bias

Our recollections tend to become more similar to the correct information when we recollect an initial response using the correct information, known as the hindsight bias. This study investigated the effect of memory load of information encoded on the hindsight bias's magnitude. We assigned participants (N = 63) to either LOW or HIGH conditions, in which they answered 20 or 50 questions, which were their initial responses. Then, they memorized and remembered the correct information. They finally recollected the initial responses. Twenty of the fifty questions in the HIGH condition were identical to those in the LOW condition. We used the answers to these 20 common questions in LOW and HIGH conditions to examine the effect of the memory load of information encoded, defined as the number of correct answers to remember (i.e., 20 or 50) on the hindsight bias. Results indicated that the magnitude of the hindsight bias was more prominent in the HIGH than the LOW condition, suggesting that the memory load amplifies the hindsight bias's magnitude. This finding also implies that controlling the memory load of information encoded when learning correct information could mitigate the hindsight bias. We expect these findings to have practical implications in occupational settings where hindsight bias could lead to critical errors such as financial losses or medical problems.

An experimental test of the effects of acute sleep deprivation on affect and avoidance

BACKGROUND AND OBJECTIVES

Avoidance and sleep have been identified as mechanisms involved in the development and maintenance of many mental health disorders. However, there has been little research into the relation between sleep and avoidance.

METHODS

To address this, a randomized controlled experiment using behavioral and self-report measures of affect and avoidance was conducted. Compared to a control group, we hypothesized that sleep-deprived individuals would demonstrate increased negative, and decreased positive, affectivity, more avoidance behavior toward a negatively valenced stimulus, as well as increased self-reported avoidance. Fifty-two healthy individuals ages 18-30 years old were randomly assigned to a full night of sleep deprivation or normal sleep. They completed a baseline and post-manipulation behavioral avoidance task (BAT) using a disgusting stimulus and self-reports of avoidance and state affect.

RESULTS

Repeated measures ANOVAs demonstrated negative affectivity and self-reported avoidance increased, and positive affectivity decreased, from pre-to post-manipulation in the sleep loss condition as expected. However, there were no effects of sleep deprivation on avoidance behaviors.

LIMITATIONS

This study emphasized internal validity over generalizability. Additionally, the at-home sleep deprivation limited researcher control over the overnight activities of participants.

CONCLUSIONS

Results replicate prior work on the affective consequences of sleep deprivation and highlight a discrepancy between the effect of sleep deprivation on behavioral avoidance toward a specific stimulus compared to self-reported cognitive and social avoidance behaviors.

The effect of auditory stimulation using delta binaural beat for a better sleep and post-sleep mood: A pilot study

Background

Although previous evidence confirms the effects of sleep deprivation on mental health and wellbeing, due to the interaction effects of sleep and mood on each other, the influence of sleep improvement has received less attention.

Objective

This study aimed to find whether binaural beat technology can enhance sleep quality and thus post-sleep mood.

Methods

Twenty healthy students participated in this pilot study. All subjects were investigated for two weeks (a baseline week and an experimental week). In the first week, there was no intervention, but in the second week, all subjects were exposed to a 90 min binaural beat in the delta frequency range. The individuals’ sleep was monitored for two weeks using a sleep diary form, and a Profile of Mood State questionnaire was employed to assess their mood at the end of the first and second weeks.

Results

Auditory stimulation with delta binaural beat enhanced sleep parameters such as sleep failure, the number of awakenings, real duration of sleep, sleep quality, and feeling following the waking of the individuals. Finally, students’ moods improved by reducing anxiety and anger, but other mood parameters did not indicate a significant difference.

Conclusion

The findings of this study confirmed that auditory stimulation with a delta binaural beat seems to be a low-cost and alternative method for medicine and other treatment methods with side effects.

Application

This study demonstrates the use of technology with a neuroergonomics approach to improve sleep and mood disorders.

Sleep in Normal Aging, Homeostatic and Circadian Regulation and Vulnerability to Sleep Deprivation

In the context of geriatric research, a growing body of evidence links normal age-related changes in sleep with many adverse health outcomes, especially a decline in cognition in older adults. The most important sleep alterations that continue to worsen after 60 years involve sleep timing, (especially early wake time, phase advance), sleep maintenance (continuity of sleep interrupted by numerous awakenings) and reduced amount of sigma activity (during non-rapid eye movement (NREM) sleep) associated with modifications of sleep spindle characteristics (density, amplitude, frequency) and spindle-Slow Wave coupling. After 60 years, there is a very clear gender-dependent deterioration in sleep. Even if there are degradations of sleep after 60 years, daytime wake level and especially daytime sleepiness is not modified with age. On the other hand, under sleep deprivation condition, older adults show smaller cognitive impairments than younger adults, suggesting an age-related lower vulnerability to extended wakefulness. These sleep and cognitive age-related modifications would be due to a reduced homeostatic drive and consequently a reduced sleep need, an attenuation of circadian drive (reduction of sleep forbidden zone in late afternoon and wake forbidden zone in early morning), a modification of the interaction of the circadian and homeostatic processes and/or an alteration of subcortical structures involved in generation of circadian and homeostatic drive, or connections to the cerebral cortex with age. The modifications and interactions of these two processes with age are still uncertain, and still require further investigation. The understanding of the respective contribution of circadian and homeostatic processes in the regulation of neurobehavioral function with aging present a challenge for improving health, management of cognitive decline and potential early chronobiological or sleep-wake interventions.

Differential interactions of age and sleep deprivation in driving and spatial perception by male drivers in a virtual reality environment

We determined the effects of age and sleep deprivation on driving and spatial perception in a virtual reality environment. Twenty-two young (mean age: 22 years, range: 18-35) and 23 old (mean age: 71 years, range: 65-79) participants were tested after a normal night of sleep and a night of sleep deprivation. The participants drove a virtual car while responding to uni- and bilateral visual and auditory stimuli. Driving errors (crossing the lane borders), reaction times and accuracy to visual and auditory stimuli, performance in psychological tests, and subjective driving ability and tiredness were measured. Age had no effect on the number of driving errors, whereas sleep deprivation increased significantly especially the number of left lane border crossings. Age increased the number of stimulus detection errors, while sleep deprivation increased the number of errors particularly in the young and in the auditory modality as response omissions. Age and sleep deprivation together increased the number of response omissions in both modalities. Left side stimulus omissions suggest a bias to the right hemispace. The subjective evaluations were consistent with the objective measures. The psychological tests were more sensitive to the effects of age than to those of sleep deprivation. Driving simulation in a virtual reality setting is sensitive in detecting the effects of deteriorating factors on both driving and simultaneous spatial perception.

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.

Positive effect of timed blue-enriched white light on sleep and cognition in patients with mild and moderate Alzheimer's disease

Conflicting results have been reported regarding the effectiveness of light treatment (LT) in patients with Alzheimer's disease (AD). We investigated the effectiveness of blue-enriched white LT on sleep, cognition, mood and behavior in patients with mild and moderate AD. The treatment group (n = 14) sat about 60 cm away from a small (136 × 73 × 16 mm) LED light box for 1 h each morning for 2 weeks. The control group (n = 11) wore dark, blue-attenuating sunglasses during the 1 h exposures. The morning light started 9-10 h after each individual's dim light melatonin onset (DLMO). Assessments were done at baseline (T0), immediate post-treatment (T1), and 4 weeks after the end of the 2 weeks of LT (T2). Sleep was measured by actigraphy. Blue-enriched LT had a significantly better effect on the Pittsburgh Sleep Quality Index at T2 compared to blue-attenuated LT, and a trend of better effectiveness on total sleep time at T2. There was a significant increase in Mini-Mental State Examination score at T2 after blue-enriched LT than that at T0. Our findings suggest that morning blue-enriched LT has a benefit in improving sleep and cognitive function in AD patients.

The age differences of sleep disruption on mood states and memory performance

Objectives: In the present study, we explored the age differences of mood states and memory performance between younger and older adults after one night of sleep disruption.Method: Twenty-nine younger adults and 30 older adults completed mood states assessments and memory tasks before and after sleep disruption. Participants' sleep was disrupted by periodical phone calls once per hour. Sleep parameters of baseline sleep and disrupted sleep were recorded by actigraphy.Results: Regarding the mood states, older adults were less affected than younger adults, more tolerant of sleep disruption. With respect to memory, younger adults showed increased memory performance after nocturnal sleep, even if this sleep was disrupted. In contrast, older adults' sleep-related memory consolidation was impaired.Conclusion: Periodic sleep disruption for one night resulted in impaired function of older adults' sleep-related memory consolidation and younger adults' mood states. These findings shed light on the understanding of sleep function on memory and emotion. Specifically, sleep disruption might be one of the reasons for older adults' memory decline and it might also be one of the causes for younger adults' emotion disorders. Further investigations on the relationship between sleep disruption, cognitive performance and emotional well-being are needed to find potential ways to prevent and treat the sleep-related neuropsychological impairments in both younger and older adults.

Young adults are more vulnerable to chronic sleep deficiency and recurrent circadian disruption than older adults

More than a third of US adults report fewer than 6 hours of sleep a night, making chronic sleep restriction a growing public health concern. Sleep curtailment is associated with an increase in industrial accidents, motor vehicle accidents, medical and other occupational errors. Young adults are more vulnerable to acute sleep deprivation than older adults, but less is known about how young vs. older adults respond to the more commonly experienced chronic sleep restriction. To test the hypothesis that young adults are more vulnerable to chronic sleep loss than older adults, we compared data from young and older adults who underwent three weeks of chronic sleep restriction (equivalent to 5.6 hours/24 hours) combined with recurrent circadian disruption in an experiment that enabled us to separate the influences of the sleep-wake homeostatic process, the circadian timing system, and the chronic sleep deficit. We found that while young and older adults reported similar levels of subjective sleepiness, objective measures of sleepiness revealed that young adults were more vulnerable and had more attentional failures than the older adults. These results have important public health implications, particularly related to prevention of sleep-related motor vehicle crashes in young drivers. Further research is needed to understand the neurobiological basis of these age-related differences.

Pleasure: The missing link in the regulation of sleep

Although largely unrecognized by sleep scholars, sleeping is a pleasure. This report aims first, to fill the gap: sleep, like food, water and sex, is a primary reinforcer. The levels of extracellular mesolimbic dopamine show circadian oscillations and mark the "wanting" for pro-homeostatic stimuli. Further, the dopamine levels decrease during waking and are replenished during sleep, in opposition to sleep propensity. The wanting of sleep, therefore, may explain the homeostatic and circadian regulation of sleep. Accordingly, sleep onset occurs when the displeasure of excessive waking is maximal, coinciding with the minimal levels of mesolimbic dopamine. Reciprocally, sleep ends after having replenished the limbic dopamine levels. Given the direct relation between waking and mesolimbic dopamine, sleep must serve primarily to gain an efficient waking. Pleasant sleep (i.e. emotional sleep), can only exist in animals capable of feeling emotions. Therefore, although sleep-like states have been described in invertebrates and primitive vertebrates, the association sleep-pleasure clearly marks a difference between the sleep of homeothermic vertebrates and cool blooded animals.

Sex differences in age-related changes in the sleep-wake cycle

Age-related changes in sleep and circadian regulation occur as early as the middle years of life. Research also suggests that sleep and circadian rhythms are regulated differently between women and men. However, does sleep and circadian rhythms regulation age similarly in men and women? In this review, we present the mechanisms underlying age-related differences in sleep and the current state of knowledge on how they interact with sex. We also address how testosterone, estrogens, and progesterone fluctuations across adulthood interact with sleep and circadian regulation. Finally, we will propose research avenues to unravel the mechanisms underlying sex differences in age-related effects on sleep.

Sleep Loss and Affective Functioning: More Than Just Mood

Empirical evidence supports an intimate link between sleep and affective functioning. While the bidirectional relationship between sleep duration and mood is well documented, limited research targets other aspects of affective functioning, such as emotion and emotion regulation, or considers their interrelationships. The present review summarizes research examining the relationship between sleep and emotion, emotion regulation, and mood, and presents a theoretical model representing the relationships between these constructs. Disruptions to sleep and mood may trigger and maintain a negative cascade, leading to more entrenched sleep problems and psychopathology. Given that insufficient sleep is a widespread phenomenon, understanding the interrelationships between sleep and affective functioning has implications for both public health and clinical practice.

Sleep continuity is positively correlated with sleep duration in laboratory nighttime sleep recordings

Sleep duration varies widely across individuals and appears to be trait-like. Differences in the stability of underlying sleep processes may underlie this phenomenon. To investigate underlying mechanisms, we examined the relationship between sleep duration and sleep continuity in baseline polysomnography (PSG) recordings from three independently collected datasets: 1) 134 healthy controls (ages 37 ± 13 years) from the São Paulo Epidemiologic Sleep Study, who spent one night in a sleep laboratory, 2) 21 obstructive sleep apnea (OSA) patients who were treated with continuous positive airway pressure for at least 2 months (45 ± 12 years, respiratory disturbance index <15), who spent one night in a sleep laboratory with previous experience of multiple PSG studies, and 3) 62 healthy controls (28 ± 6 years) who, as part of larger experiments, spent 2 consecutive nights in a sleep laboratory. For each dataset, we used total sleep time (TST) to separate subjects into those with shorter sleep (S-TST) and those with longer sleep (L-TST). In all three datasets, survival curves of continuous sleep segments showed greater sleep continuity in L-TST than in S-TST. Correlation analyses with TST as a continuous variable corroborated the results; and the results also held true after controlling for age. There were no significant differences in baseline waking performance and sleepiness between S-TST and L-TST. In conclusion, in both healthy controls and treated OSA patients, sleep continuity was positively correlated with sleep duration. These findings suggest that S-TST may differ from L-TST in processes underlying sleep continuity, shedding new light on mechanisms underlying individual differences in sleep duration.

Effects of partial sleep deprivation on reaction time in anesthesiologists

BACKGROUND

Fatigue in anesthesiologists may have implications that extend beyond individual well-being.

AIM

The aim of the present study was to evaluate the impact of sleep deprivation on the reaction time in anesthesiologists either after an overnight call or regular working hours. Moderation of this effect by coping strategies was observed.

METHODS

Psychomotor vigilance test was used to assess reaction time in 23 anesthesiologists at two time-points: (i) on a regular non-call day and (ii) after a 17-h in-house call. Student's paired t-test was used to compare Psychomotor Vigilance Task data at these two moments. Change score regression was performed to determine the association between coping strategies, assessed using the Coping Strategy Indicator instrument, and decline in reaction time after night call.

RESULTS

Twenty-one colleagues completed the psychomotor vigilance test measurements after two decided to end their participation for personal reasons. Post-call psychomotor vigilance test mean reaction time decreased by an average of 31.2 ms (95% CI: 0.5, 61.9; P = 0.047) when compared to regular day. Reliance on specific coping mechanisms, indicated by Coping Strategy Indicator scale scores, included problem-solving (28 ± 4), followed by seeking social support (23 ± 5) and avoidance (19 ± 4). The change score regression model (r² = 0.48) found that greater reliance on avoidance was associated with greater increase in reaction time after night call.

CONCLUSION

Reaction time increased considerably in anesthesiologists after a night call duty. Greater subjective reliance on avoidance as a coping strategy was associated with greater deterioration in performance.

Sleep-related vehicle crashes on low speed roads

BACKGROUND

Very little is known about the characteristics of sleep related (SR) crashes occurring on low speed roads compared with current understanding of the role of sleep in crashes occurring on high speed roads e.g. motorways. To address this gap, analyses were undertaken to identify the differences and similarities between (1) SR crashes occurring on roads with low (≤60km/h) and high (≥100km/h) speed limits, and (2) SR crashes and not-SR crashes occurring on roads with low speed limits.

METHOD

Police reports of all crashes occurring on low and high speed roads over a ten year period between 2000 and 2009 were examined for Queensland, Australia. Attending police officers identified all crash attributes, including 'fatigue/fell asleep', which indicates that the police believe the crash to have a causal factor relating to falling asleep, sleepiness due to sleep loss, time of day, or fatigue. Driver or rider involvement in crashes was classified as SR or not-SR. All crash-associated variables were compared using Chi-square tests (Cramer's V=effect size). A series of logistic regression was performed, with driver and crash characteristics as predictors of crash category. A conservative alpha level of 0.001 determined statistical significance.

RESULTS

There were 440,855 drivers or riders involved in a crash during this time; 6923 (1.6%) were attributed as SR. SR crashes on low speed roads have similar characteristics to those on high speed roads with young (16-24y) males consistently over represented. SR crashes on low speed roads are noticeably different to not-SR crashes in the same speed zone in that male and young novice drivers are over represented and outcomes are more severe. Of all the SR crashes identified, 41% occurred on low speed roads.

CONCLUSION

SR crashes are not confined to high speed roads. Low speed SR crashes warrant specific investigation because they occur in densely populated areas, exposing a greater number of people to risk and have more severe outcomes than not-SR crashes on the same low speed roads.

Age-Related Reduction of Recovery Sleep and Arousal Threshold in Drosophila

STUDY OBJECTIVES

Physiological studies show that aging affects both sleep quality and quantity in humans, and sleep complaints increase with age. Along with knowledge about the negative effects of poor sleep on health, understanding the enigmatic relationship between sleep and aging is important. Because human sleep is similar to Drosophila (fruit fly) sleep in many ways, we addressed the effects of aging on sleep in this model organism.

METHODS

Baseline sleep was recorded in five different Drosophila genotypes raised at either 21°C or 25°C. The amount of sleep recovered was then investigated after a nighttime of sleep deprivation (12 h) and after chronic sleep deprivation (3 h every night for multiple nights). Finally, the effects of aging on arousal, namely, sensitivity to neuronal and mechanical stimuli, were studied.

RESULTS

We show that fly sleep is affected by age in a manner similar to that of humans and other mammals. Not only do older flies of several genotypes have more fragmented sleep and reduced total sleep time compared to young flies, but older flies also fail to recover as much sleep after sleep deprivation. This suggests either lower sleep homeostasis and/or a failure to properly recover sleep. Older flies also show a decreased arousal threshold, i.e., an increased response to neuronal and mechanical wake-promoting stimuli. The reduced threshold may either reflect or cause the reduced recovery sleep of older flies compared to young flies after sleep deprivation.

CONCLUSIONS

Further studies are certainly needed, but we suggest that the lower homeostatic sleep drive of older flies causes their decreased arousal threshold.

Has adult sleep duration declined over the last 50+ years?

The common assumption that population sleep duration has declined in the past few decades has not been supported by recent reviews, which have been limited to self-reported data. The aim of this review was to assess whether there has been a reduction in objectively recorded sleep duration over the last 50+ years. The literature was searched for studies published from 1960 to 2013, which assessed objective sleep duration (total sleep time (TST)) in healthy normal-sleeping adults. The search found 168 studies that met inclusion criteria, with 257 data points representing 6052 individuals ages 18-88 y. Data were assessed by comparing the regression lines of age vs. TST in studies conducted between 1960 and 1989 vs. 1990-2013. Weighted regression analyses assessed the association of year of study with age-adjusted TST across all data points. Regression analyses also assessed the association of year of study with TST separately for 10-y age categories (e.g., ages 18-27 y), and separately for polysomnographic and actigraphic data, and for studies involving a fixed sleep schedule and participants' customary sleep schedules. Analyses revealed no significant association of sleep duration with study year. The results are consistent with recent reviews of subjective data, which have challenged the notion of a modern epidemic of insufficient sleep.

The effect of partial sleep deprivation on computer-based measures of fitness to drive

PURPOSE

Using a partial sleep deprivation paradigm, the aim of the study was to investigate the sensitivity of a computer-based test battery of fitness to drive to detect impairments related to sleepiness.

METHODS

Forty-seven healthy subjects (34 females, mean age 26.0 ± 6.8 years) participated in a counterbalanced within-subject design of two conditions: (i) normal night sleep and (ii) partial sleep deprivation (PSD) with 4 h time in bed. For the assessment of fitness to drive, we used a validated traffic psychological test battery. Moreover, well-established measures of sleepiness highly responsive to sleep deprivation were applied: the Karolinska Sleepiness Scale (KSS), pupillography (Pupil Unrest Index (PUI) as physiological sleepiness indicator) and two sustained attention tasks (psychomotor Vigilance Task and Mackworth Clock Test).

RESULTS

Subjective and physiological sleepiness were significantly increased after PSD, accompanied by large (d > 1.50 for KSS) and medium (d = 0.55 for PUI) effect sizes. Sleepiness-related performance decrements were found in both sustained attention tasks (d = 0.59-0.77). Assessing driving-related ability, PSD induced decrements only in the test domain Reaction Test (reaction time d = 0.54 and motor time d = 0.45). All other subtests-as well as the overall judgement of fitness to drive-were not significantly affected by PSD.

CONCLUSION

In contrast to established tests of sustained attention and subjective sleepiness, computer-based test batteries of fitness to drive might lack sensitivity to core aspects of sleepiness as they mainly consist of short and stimulating subtests. Therefore, tasks that require sustained attention should be an essential part of traffic psychological test batteries when sleepiness is a potential issue.

Sleep, cognition, and normal aging: integrating a half century of multidisciplinary research

Sleep is implicated in cognitive functioning in young adults. With increasing age, there are substantial changes to sleep quantity and quality, including changes to slow-wave sleep, spindle density, and sleep continuity/fragmentation. A provocative question for the field of cognitive aging is whether such changes in sleep physiology affect cognition (e.g., memory consolidation). We review nearly a half century of research across seven diverse correlational and experimental domains that historically have had little crosstalk. Broadly speaking, sleep and cognitive functions are often related in advancing age, though the prevalence of null effects in healthy older adults (including correlations in the unexpected, negative direction) indicates that age may be an effect modifier of these associations. We interpret the literature as suggesting that maintaining good sleep quality, at least in young adulthood and middle age, promotes better cognitive functioning and serves to protect against age-related cognitive declines.

Total sleep deprivation decreases flow experience and mood status

BACKGROUND

The purpose of this study was to examine the effect of sleep deprivation on flow experience.

METHODS

Sixteen healthy male volunteers of mean age 21.4±1.59 (21-24) years participated in two experimental conditions, ie, sleep-deprivation and normal sleep. In the sleep-deprived condition, participants stayed awake at home for 36 hours (from 8 am until 10 pm the next day) beginning on the day prior to an experimental day. In both conditions, participants carried out a simple reaction time (psychomotor vigilance) task and responded to a questionnaire measuring flow experience and mood status.

RESULTS

Flow experience was reduced after one night of total sleep deprivation. Sleep loss also decreased positive mood, increased negative mood, and decreased psychomotor performance.

CONCLUSION

Sleep deprivation has a strong impact on mental and behavioral states associated with the maintenance of flow, namely subjective well-being.

The fatigued anesthesiologist: A threat to patient safety?

Universally, anesthesiologists are expected to be knowledgeable, astutely responding to clinical challenges while maintaining a prolonged vigilance for administration of safe anesthesia and critical care. A fatigued anesthesiologist is the consequence of cumulative acuity, manifesting as decreased motor and cognitive powers. This results in impaired judgement, late and inadequate responses to clinical changes, poor communication and inadequate record keeping. With rising expectations and increased medico-legal claims, anesthesiologists work round the clock to provide efficient and timely services, but are the "sleep provider" in a sleep debt them self? Is it the right time to promptly address these issues so that we prevent silent perpetuation of problems pertinent to anesthesiologist's health and the profession. The implications of sleep debt on patient safety are profound and preventive strategies are quintessential. Anesthesiology governing bodies must ensure requisite laws to prevent the adverse outcomes of sleep debt before patient care is compromised.

Reduced slow-wave rebound during daytime recovery sleep in middle-aged subjects

Cortical synchronization during NREM sleep, characterized by electroencephalographic slow waves (SW <4Hz and >75 µV), is strongly related to the number of hours of wakefulness prior to sleep and to the quality of the waking experience. Whether a similar increase in wakefulness length leads to a comparable enhancement in NREM sleep cortical synchronization in young and older subjects is still a matter of debate in the literature. Here we evaluated the impact of 25-hours of wakefulness on SW during a daytime recovery sleep episode in 29 young (27y ±5), and 34 middle-aged (51y ±5) subjects. We also assessed whether age-related changes in NREM sleep cortical synchronization predicts the ability to maintain sleep during daytime recovery sleep. Compared to baseline sleep, sleep efficiency was lower during daytime recovery sleep in both age-groups but the effect was more prominent in the middle-aged than in the young subjects. In both age groups, SW density, amplitude, and slope increased whereas SW positive and negative phase duration decreased during daytime recovery sleep compared to baseline sleep, particularly in anterior brain areas. Importantly, compared to young subjects, middle-aged participants showed lower SW density rebound and SW positive phase duration enhancement after sleep deprivation during daytime recovery sleep. Furthermore, middle-aged subjects showed lower SW amplitude and slope enhancements after sleep deprivation than young subjects in frontal and prefrontal derivations only. None of the SW characteristics at baseline were associated with daytime recovery sleep efficiency. Our results support the notion that anterior brain areas elicit and may necessitate more intense recovery and that aging reduces enhancement of cortical synchronization after sleep loss, particularly in these areas. Age-related changes in the quality of wake experience may underlie age-related reduction in markers of cortical synchronization enhancement after sustained wakefulness.

The prefrontal model revisited: double dissociations between young sleep deprived and elderly subjects on cognitive components of performance

STUDY OBJECTIVES

The prefrontal model suggests that total sleep deprivation (TSD) and healthy aging produce parallel cognitive deficits. Here we decompose global performance on two common tasks into component measures of specific cognitive processes to pinpoint the source of impairments in elderly and young TSD participants relative to young controls and to each other.

SETTING

The delayed letter recognition task (DLR) was performed in 3 studies. The psychomotor vigilance task (PVT) was performed in 1 of the DLR studies and 2 additional studies.

SUBJECTS

For DLR, young TSD (n=20, age=24.60 ± 0.62 years) and young control (n=17, age=24.00 ± 2.42); elderly (n=26, age=69.92 ± 1.06). For the PVT, young TSD (n=18, age=26.65 ± 4.57) and young control (n=16, age=25.19 ± 2.90); elderly (n=21, age=71.1 ± 4.92).

MEASUREMENTS AND RESULTS

Both elderly and young TSD subjects displayed impaired reaction time (RT), our measure of global performance, on both tasks relative to young controls. After decomposing global performance on the DLR, however, a double dissociation was observed as working memory scanning speed was impaired only in elderly subjects while other components of performance were impaired only by TSD. Similarly, for the PVT a second double dissociation was observed as vigilance impairments were present only in TSD while short-term response preparation effects were altered only in the elderly.

CONCLUSIONS

The similarity between TSD and the elderly in impaired performance was evident only when examining global RT. In contrast, when specific cognitive components were examined double dissociations were observed between TSD and elderly subjects. This demonstrates the heterogeneity in those cognitive processes impaired in TSD versus the elderly.

Changes in structural aspects of mood during 39-66 h of sleep loss using matched controls

A number of studies have described mood change during sleep loss in the laboratory, however, an understanding of fluctuations in structural aspects of mood under such conditions is lacking. Sixty-two healthy young adults completed one of three possible conditions: one (n = 20) or two (n = 23) nights of sleep loss or the control condition which consisted of one (n = 9) or two (n = 10) nights of 9 h time in bed. The Mood Scale II was completed every two waking hours and data were analysed in terms of the frequency and intensity of mood reports. Overall, sleep loss conditions were associated with significantly less frequent happiness and activation and more frequent fatigue reports (p < 0.001). Intensity was also significantly reduced for activation and happiness, and increased for depression, anger and fatigue (p < 0.05). Interestingly, there were no significant differences in anger following two nights in the laboratory with or without sleep. Further, two nights in the lab with normal sleep was associated with significant increases in depression intensity (p < 0.05). Findings support the hypothesis of a mood regulatory function of sleep and highlight the relative independence of frequency and intensity and of positive and negative mood dimensions. Findings also suggest that the laboratory environment, in the absence of sleep loss, may have a significant negative impact on mood.

The impact of a single 24 h working day on cognitive and psychomotor performance in staff anaesthesiologists

BACKGROUND AND OBJECTIVE

The profession of anaesthesiologist is demanding and potentially hazardous. Extended work shifts combined with intensive work load may adversely affect physicians' performance. The aim of this study was to explore the impact of a single in-hospital 24 h shift on the cognitive and psychomotor performance of anaesthesiologists in a surgical emergency department.

METHODS

Following ethical and institutional approval, 11 staff anaesthesiologists [six men, five women, age 48 (35-50), years of experience 17 (7-20), median (range)] successfully completed the study protocol. Four computer-generated psychological tests (CRD, Complex Reactionmeter Drenovac, Croatia) consisting of light signal position discrimination (CRD 311), simple visual orientation (CRD 21), simple arithmetic operations (CRD 11), and complex psychomotor coordination (CRD 411) were used to measure objective parameters of cognitive and psychomotor performance at four time points (D1 = 8:00 a.m., D2 = 3:00 p.m., D3 = 11:00 p.m.; and D4 = 7:00-8:00 a.m. next day) during the 24 h working day. The control testing on an ordinary working day was performed at two time points (C1 = 8:00 a.m., C2 = 3:00 p.m.). Three parameters were recorded: total test solving time (TTST), total variability, and total number of errors for all four tests.

RESULTS

TTST was significantly impaired during the 24 h shift in all tests, and TTST was prolonged in CRD 21 test at different time points from 1.6 +/- 1.4 to 5.5 +/- 1.6 s compared with the control (F = 6.39, P = 0.001). The reaction times were prolonged from 1.3 +/- 1.8 to 5.4 +/- 1.2 s (F = 3.49, P = 0.009) in CRD 311, from 3.8 +/- 9.0 to 34.3 +/- 5.8 s (F = 5.05, P = 0.002) in CRD 11 TTST, and from 0.8 +/- 3.0 to 16.3 +/- 8.6 s (F = 2.67, P = 0.034) in CRD 411. Total variability was significantly altered during the 24 h shift only in CRD 411 (F = 2.63, P = 0.036). There was no difference in the total number of errors between the 24 h shift and the ordinary working day.

CONCLUSION

Anaesthesiologists' 24 h working day in the emergency department altered cognitive and psychomotor function in comparison with ordinary working days. Speed, reliability and mental endurance (measured by TTST) were significantly impaired in all four tests. Stability and reaction time (measured by total variability) were only slightly impaired. Paradoxically, attention and alertness (measured by total number of errors) were not adversely affected. In conclusion, anaesthesiologists' psychomotor performance was impaired during the single 24 h shift.

Hypersomnolence and Accidents in Truck Drivers: A Cross‐Sectional Study

Truck drivers are more likely to suffer severe injury and death due to certain truck driving characteristics. Identifying and preventing factors associated with accidents in this population is important to minimize damage and improve road safety. Excessive daytime sleepiness is a major public health problem, leading to impaired cognitive function, reduced alertness, and increased risk of motor vehicle crashes. The aim of this cross-sectional study was to determine the prevalence and predictors of hypersomnolence (defined as an Epworth Sleepiness Scale score greater than 10) among truck drivers. Three hundred male truck drivers were studied. Quality of sleep was assessed by the Pittsburgh Sleep Quality Index, and the association between demographic, clinical, and occupational data with excessive sleepiness was analyzed. The mean daily sleep duration was 5.6+/-1.3 h, and poor quality of sleep was found in 46.3% of the individuals. Hypersomnolence was found in 46% of the drivers and was associated with younger age, snoring, and working >10 h without rest. A positive correlation between hypersomnolence and previous accidents was detected (p=0.005). These results show that sleep deprivation and hypersomnolence are frequent among truck drivers. The treatment of sleep-disordered breathing and the implementation of educational programs, particularly targeting younger drivers and promoting increased awareness of the deleterious effects of sleep loss and work overload, may help to reduce hypersomnolence and accidents among truck drivers.

Subjective well-being is modulated by circadian phase, sleep pressure, age, and gender

Subjective well-being largely depends on mood, which shows circadian rhythmicity and can be linked to rhythms in many physiological circadian markers, such as melatonin and cortisol. In healthy young volunteers mood is influenced by an interaction of circadian phase and the duration of time awake. The authors analyzed this interaction under differential sleep pressure conditions to investigate age and gender effects on subjective well-being. Sixteen healthy young (8 women, 8 men; 20-35 years) and 16 older volunteers (8 women, 8 men; 55-75 years) underwent a 40-h sleep deprivation (high sleep pressure) and a 40-h nap protocol (low sleep pressure) in a balanced crossover design under constant routine conditions. Mood, tension, and physical comfort were assessed by visual analogue scales during scheduled wakefulness, and their average formed a composite score of well-being. Significant variations in well-being were determined by the factors "age," "sleep pressure," and "circadian phase." Well-being was generally worse under high than low sleep pressure. Older volunteers felt significantly worse than the young under both experimental conditions. Significant interactions were found between "sleep pressure" and "age," and between "sleep pressure" and "gender." This indicated that older volunteers and women responded with a greater impairment in well-being under high compared with low sleep pressure. The time course of well-being displayed a significant circadian modulation, particularly in women under high sleep pressure conditions. The results demonstrate age- and/or gender-related modifications of well-being related to sleep deprivation and circadian phase and thus point to specific biological components of mood vulnerability.

Olfactory Discrimination and Transient Mood Change in Young Men and Women: Variation by Season, Mood State, and Time of Day

Odor performance varies by clinical state and gender, though little is known about its variation by season or time of day. Many odors, including lavender, induce transient mood changes. This study explored discrimination differences between various lavender oil blends and their effects on transient mood in the morning and evening in depressed and nondepressed adults. We also determined seasonal influences on these measures. A total of 169 subjects, 98 women and 71 men (mean age +/- SD, 19.3 +/- 1.6 y) participated, with different subjects studied at different times of the year. The Beck Depression Inventory (BDI) classified subjects as depressed (score > or =10; N= 57) or nondepressed (score <10; N= 112). In the discrimination test, subjects compared pairs of two different lavender oil blends or a control. Transient change in mood was assessed by the Profile of Mood States (POMS) after each trial of five lavender blends interspersed by three control odors. Tests were conducted in the morning (08:00-10:00 h) and evening (18:00-20:00h). In all subjects, discrimination was significantly better for some odor pairs than for others, thus demonstrating test specificity. Discrimination was better overall in the fall than winter/spring and better in depressed than nondepressed subjects for specific odor pairs. No significant gender or time-of-day differences in discriminability were detected. There were, however, significant group differences in transient mood profiles. Current depressed state affected mood response, with lavender increasing anger in depressed subjects only. In addition, depressed subjects and men, whether or not depressed, exhibited diurnal mood variation, with better mood in the evening; the former group also showed more evening energy. All subjects were more confused in the morning than evening. Season also affected transient mood; winter/spring-tested subjects reported more vigor than fall-tested subjects. In addition, summer-tested subjects showed more tension in the morning, whereas fall-tested subjects showed the opposite pattern in the evening. In all subjects, lavender increased fatigue, tension, confusion, and total mood disturbance, and it decreased vigor. The study showed that both chronobiological (seasonal and time-of-day) and clinical factors modify discrimination and mood response to odors. Brief lavender odor presentation may serve as a nonphotic method for altering mood in young depressed and nondepressed adults particularly during the fall, a time of heightened discriminability.

Age‐related Changes in the Circadian and Homeostatic Regulation of Human Sleep

The reduction of electroencephalographic (EEG) slow-wave activity (SWA) (EEG power density between 0.75-4.5 Hz) and spindle frequency activity, together with an increase in involuntary awakenings during sleep, represent the hallmarks of human sleep alterations with age. It has been assumed that this decrease in non-rapid eye movement (NREM) sleep consolidation reflects an age-related attenuation of the sleep homeostatic drive. To test this hypothesis, we measured sleep EEG characteristics (i.e., SWA, sleep spindles) in healthy older volunteers in response to high (sleep deprivation protocol) and low sleep pressure (nap protocol) conditions. Despite the fact that the older volunteers had impaired sleep consolidation and reduced SWA levels, their relative SWA response to both high and low sleep pressure conditions was similar to that of younger persons. Only in frontal brain regions did we find an age-related diminished SWA response to high sleep pressure. On the other hand, we have clear evidence that the circadian regulation of sleep during the 40 h nap protocol was changed such that the circadian arousal signal in the evening was weaker in the older study participants. More sleep occurred during the wake maintenance zone, and subjective sleepiness ratings in the late afternoon and evening were higher than in younger participants. In addition, we found a diminished melatonin secretion and a reduced circadian modulation of REM sleep and spindle frequency-the latter was phase-advanced relative to the circadian melatonin profile. Therefore, we favor the hypothesis that age-related changes in sleep are due to weaker circadian regulation of sleep and wakefulness. Our data suggest that manipulations of the circadian timing system, rather than the sleep homeostat, may offer a potential strategy to alleviate age-related decrements in sleep and daytime alertness levels.

Healthy older adults better tolerate sleep deprivation than young adults

OBJECTIVES

To determine whether healthy aging is associated with increased sleepiness and whether healthy older adults experience more sleepiness when acutely sleep deprived.

DESIGN

A 5-day inpatient circadian rhythm-sleep study consisting of 3 baseline nights followed by an extended 26-hour wake episode under constant conditions.

SETTING

Intensive Physiological Monitoring Unit, General Clinical Research Center, Brigham and Women's Hospital.

PARTICIPANTS

Thirty-seven healthy participants without medical, psychological, or sleep disorders: 26 young (7 women, 19 men; mean age 21.9 +/- 3.3, range 18-29) and 11 "young-old" adults (3 women, 8 men; mean age 68.1 +/- 3.6, range 65-76).

INTERVENTION

An extended 26-hour wake episode under constant conditions.

MEASUREMENTS

Electroencephalographic-verified wakefulness, slow eye movements, sustained attention, subjective sleepiness.

RESULTS

During the first 16 hours corresponding to the usual waking day, both groups rated themselves as alert and had similar levels of vigilance and little evidence of sleepiness. As the wake episode continued, the older subjects were less impaired, showing faster reaction times, fewer performance lapses and attentional failures, and less frequent unintentional sleep episodes than the younger subjects.

CONCLUSION

This small study suggests that excessive sleepiness is not normal in healthy older adults. Symptoms of excessive sleepiness in this population, including reliance on caffeine to maintain alertness, should be evaluated and treated. Further study is needed to determine whether daytime sleepiness in middle-old (75-84 years) and old-old (> or = 85) adults is normal or is instead associated with sleep restriction, undiagnosed sleep disorders, medication side effects, mood disorders, or other medical disorders that disrupt sleep.

Are personality dimensions associated with sleep length in a large nationally representative sample?

OBJECTIVES

The purpose of this hypothesis-generating study was to determine whether personality domains and specific personality traits are uniquely associated with sleep duration using data obtained from the National Comorbidity Survey (NCS).

METHODS

Using trained interviewers, we administered to the 5877 noninstitutionalized adults living in the United States the Composite International Diagnostic Interview (World Health Organization. Composite International Diagnostic Interview. Geneva, Switzerland: WHO, 1990) to assess for any DSM-III-R psychiatric diagnoses, and they completed self-report measures of personality and sleep. This was a secondary data analysis using information from a large existing public use data set (NCS-part II). The NCS-part II was an epidemiologic survey based on a stratified multistage area probability method with a response rate of 82.4%.

RESULTS

Using a multivariate logistic regression technique, we found significant and positive associations between short sleep (defined as <or=6 hours of sleep per 24-hour period) and self-criticism (odds ratio [OR] = 1.36), the presence of a medical condition (OR = 1.35), neuroticism (OR = 1.30), and the use of sedating medication in the past 12 months (OR = 1.26). Significant and positive associations were found for long sleep (defined as >or=9 hours per 24 hour period) and a diagnosis of dysthymia (OR = 1.52), the use of a sedating medication in the past 12 months (OR = 1.52), emotional reliance on another person (OR = 1.37), employment status (OR = 1.31), and marital status (OR = 1.20).

CONCLUSIONS

Findings suggest that personality, even after controlling for psychiatric and medical conditions, is associated with sleep length and may be an additional factor to consider when assessing any individual patient.

Does hormone therapy affect attention and memory in sleep-deprived women?

OBJECTIVES

To evaluate whether hormone therapy (HT) modifies cognitive performance during sleep deprivation in postmenopausal women. Comparison was made with a group of young women.

METHODS

Participants included 26 postmenopausal women (age 58-72 years, 16 HT users, 10 non-users), 11 young women (age 20-26 years). They spent four consecutive nights in the sleep laboratory. Cognitive tests of attention, working memory, and verbal episodic memory were carried out after the baseline night, 25-h sleep deprivation, and recovery night.

RESULTS

Sleep deprivation impaired performance in all groups. It was manifested either as delayed practice effect or deteriorated performance (p < 0.05). In simple reaction time and 10-choice reaction time, non-users and young maintained their performance, whereas HT users suffered a minor impairment (p < 0.01). In other measurements, there was no interaction of group and condition. In 10-choice reaction time and vigilance, postmenopausal women made fewer errors and omissions than the young (p < 0.05). For most tasks, all groups showed improvement after one recovery night.

CONCLUSIONS

HT had a minor adverse effect on cognitive performance during sleep deprivation. Attention and memory deteriorated similarly in postmenopausal and young women, despite the lower initial performance level of postmenopausal women. One night of sleep ensured recovery in most tasks.

Relationships between affect, vigilance, and sleepiness following sleep deprivation

This pilot study examined the relationships between the effects of sleep deprivation on subjective and objective measures of sleepiness and affect, and psychomotor vigilance performance. Following an adaptation night in the laboratory, healthy young adults were randomly assigned to either a night of total sleep deprivation (SD group; n = 15) or to a night of normal sleep (non-SD group; n = 14) under controlled laboratory conditions. The following day, subjective reports of mood and sleepiness, objective sleepiness (Multiple Sleep Latency Test and spontaneous oscillations in pupil diameter, PUI), affective reactivity/regulation (pupil dilation responses to emotional pictures), and psychomotor vigilance performance (PVT) were measured. Sleep deprivation had a significant impact on all three domains (affect, sleepiness, and vigilance), with significant group differences for eight of the nine outcome measures. Exploratory factor analyses performed across the entire sample and within the SD group alone revealed that the outcomes clustered on three orthogonal dimensions reflecting the method of measurement: physiological measures of sleepiness and affective reactivity/regulation, subjective measures of sleepiness and mood, and vigilance performance. Sleepiness and affective responses to sleep deprivation were associated (although separately for objective and subjective measures). PVT performance was also independent of the sleepiness and affect outcomes. These findings suggest that objective and subjective measures represent distinct entities that should not be assumed to be equivalent. By including affective outcomes in experimental sleep deprivation research, the impact of sleep loss on affective function and their relationship to other neurobehavioral domains can be assessed.

An assessment of the relevance of laboratory and motorcycling tests for investigating time of day and sleep deprivation influences on motorcycling performance

The aim of this study was to assess time of day and sleep deprivation impacts on motorcycling performance taking into consideration key variables, such as reaction time, motor coordination and vigilance that are principally involved in a riding task. Eight subjects participated in different tests sessions planned at 06:00 and 18:00h after a normal night's sleep and after a night of total sleep deprivation. During each session all subjects completed "laboratory" and "motorcycling" tests that were designed to assess each of the variables tested. As classically observed in sport performance, motorcycling performance demonstrates a time of day fluctuation by increasing from 06:00 to 18:00h during the day after a normal night's sleep. For each variable tested, the effects of sleep deprivation depend on the design of the test conditions. Thus, the data collected in laboratory specific conditions are more affected than those noted in arranged motorcycling situations. Taking into account that the sample size used in this study was limited, which may limit the results interpretations, these discrepancies suggest that during complex tasks, compensation mechanisms may be set up between different resources so as to maintain a good level of performance.

Travel Recommendations for Older Adults

Older age is an important factor in preparing travelers owing not only to physiologic changes and the increased probability of underlying medical conditions and prescription medications but also to immune status with regard to naturally acquired immunity versus immunization for vaccine-preventable diseases. Cardiovascular events (including myocardial infarctions and cerebrovascular accidents) account for most deaths abroad, followed by injuries. To plan for healthy travel, international travelers should be advised to seek care at least 4 to 6 weeks before departure. Travel medicine is a dynamic field because conditions worldwide are subject to rapid change. Clinicians must maintain a current base of knowledge if they will be regularly advising travelers or must set a threshold for referral to a travel medicine specialist.

Effects of obstructive sleep apnea on cognitive function: a comparison between younger and older OSAS patients

BACKGROUND AND PURPOSE

Patients with obstructive sleep apnea syndrome (OSAS) present cognitive deficits similar to those observed with aging. The aim of the study was to assess the effects of age on cognitive functions in OSAS patients. It was hypothesized that older OSAS patients will exhibit significant cognitive dysfunction relative to younger OSAS patients and controls.

PATIENTS AND METHODS

Younger and older OSAS patients were compared to younger and older control subjects (age cut-off set at 50 yrs). Participants underwent a polysomnographic (PSG) and neuropsychological evaluation. Variables were analyzed by two-way analyses of variance (ANOVAs) with two factors: Group (control and OSAS) and Age (younger and older). Additionally, we evaluated the contribution of attentional deficits to cognitive dysfunction for each subgroup of patients by using Spearman correlation coefficients.

RESULTS

No Group-by-Age interaction was found for any neuropsychological variables (p<0.05). However, main Group and Age effects were found. Correlations indicated that attentional deficits contributed importantly to a poorer cognitive performance in younger OSAS patients only (p<0.01).

CONCLUSIONS

Our results are in agreement with those of the literature for both OSAS-related and aging-related cognitive deficits but did not demonstrate that age interacts with the effects of the OSAS condition to make those cognitive deficits worse.

Circadian rhythms in cognitive performance: Methodological constraints, protocols, theoretical underpinnings

The investigation of time-of-day effects on cognitive performance began in the early days of psychophysiological performance assessments. Since then, standardised, highly controlled protocols (constant routine and forced desynchrony) and a standard performance task (psychomotor vigilance task) have been developed to quantify sleep-wake homeostatic and internal circadian time-dependent effects on human cognitive performance. However, performance assessment in this field depends on a plethora of factors. The roles of task difficulty, task duration and complexity, the performance measure per se, practice effects, inter-individual differences, and ageing are all relevant aspects. Therefore, well-defined theoretical approaches and standard procedures are needed for tasks pinpointing higher cortical functions along with more information about time-dependent changes in the neural basis of task performance. This promises a fascinating challenge for future research on sleep-wake related and circadian aspects of different cognitive domains.