Effects of six weeks of chronic sleep restriction with weekend recovery on cognitive performance and wellbeing in high-performing adults

Chronic sleep loss is associated with escalating declines in vigilant attention across days of sleep restriction. However, studies exceeding two weeks of chronic sleep loss are scarce, and the cognitive performance outcomes assessed are limited. We assessed the effects of six weeks of chronic sleep restriction on a range of cognitive domains in 15 high-performing individuals (38.5±8.2 years, 6 women) confined to small space in groups of four. Sleep opportunities were limited to 5h on weekdays and 8h on weekends. Individual sleep/wake patterns were recorded with actigraphy. Neurobehavioral performance was assessed in evenings with Cognition, a computerized battery of ten tests assessing a range of cognitive domains. There were some small to moderate effects of increasing sleep debt relative to pre-mission baseline, with decreases in accuracy across cognitive domains (standardized β=0.121, p=0.001), specifically on tests of spatial orientation (β=0.289, p=0.011) and vigilant attention (β=0.688, p<0.001), which were not restored by two nights of weekend recovery sleep. Cognitive and subjective decrements occurred despite occasional daytime napping in breach of study protocol, evening testing around the circadian peak, and access to caffeine before 14:00. Sensorimotor speed, spatial learning and memory, working memory, abstraction and mental flexibility, emotion identification, abstract reasoning, cognitive throughput and risk decision making were not significantly affected by sleep debt. Taken together with modest lower subjective ratings of happiness and healthiness, these findings underline the importance of sufficient sleep, on both an acute and chronic basis, for performance in selected cognitive domains and subjective wellbeing in operationally-relevant environments.

0105 Working Memory Impairment Due to Chronic Sleep Restriction, Dose Response to Recovery and Re-Exposure

Introduction

Chronic sleep restriction negatively effects working memory. Recovery sleep following sleep restriction partially restores working memory performance. This study examines the impact of chronic sleep restriction and subsequent recovery sleep dose on the N-Back Task (N-Back), a valid measure of working memory.

Methods

N=223 participants (29.9±6.9 years; 48.4% female), completed two baseline nights of 8h time in bed (TIB), followed by five nights of 4h TIB, and were then randomized to a sleep dose of 0, 2, 4, 6, 8, 10, or 12 h TIB. A subset of participants (n=73) were re-exposed to another five nights of 4h TIB. Participants completed the three versions of the N-Back (i.e. 1-Back, 2-Back, and B-back) every two hours during wakefulness and daily averages were computed. Mixed effects and linear regression models were used to assess the impact of sleep restriction and the sleep dose response on percent correct on the N-Back corrected for baseline.

Results

N=219 participants had valid working memory data. The 2-Back (β =-4.5%; P&lt;0.0001) and the 3-Back (β =-12.5%; P&lt;0.0001) were more difficult than the 1-Back. Working memory performance declined across days of sleep restriction for all N-Backs: 1-Back (β =-1.10%; P&lt;0.0001), 2-Back (β =-0.99%; P&lt;0.0001), and 3-Back (β =-1.10%; P&lt;0.0001). The sleep dose analysis revealed a positive association with N-Back performance for all N-Back versions, 1-Back (β =0.99%; P=0.0002), 2-Back (β =1.46%; P&lt;0.0001), and 3-Back (β =1.43%; P&lt;0.0001). Re-exposure to only one night of 4h TIB following recovery sleep resulted in performance decrements equal to performance prior to recovery sleep for all N-Back versions (Ps&gt;0.41).

Conclusion

These data indicate that working memory is adversely impacted by sleep restriction, and that sufficient recovery sleep, possibly across consecutive days, is necessary to maintain optimal working memory performance.

Support

Funded by National Institute of Health NIH R01NR004281 and National Space and Biomedical Research Institute NSRBI NCC 5–98

0291 Recovery Sleep Alleviates Mood Disturbance Following Chronic Sleep Restriction, Albeit Transiently and in a Dose-Dependent Manner

Introduction

Fatigue is one contributor to mood disturbance observed following sleep restriction; however, the contribution of other factors remains unclear. This study examined contributions to mood disturbance resulting from sleep restriction beyond that of fatigue, evaluated the benefit of recovery sleep, and assessed whether recovery sleep buffered the re-emergence of mood disturbance upon re-exposure to sleep restriction.

Methods

N=223 healthy participants (48% female; n=108) approximately 30-years-old (SD=6.89, range=22–45 years) completed two baseline nights of 8h time in bed (TIB), followed by five nights of 4h TIB, and were then then randomized to one of 7 sleep recovery opportunities (i.e., 0, 2, 4, 6, 8, 10, or 12 hours TIB). Following the sleep period, a subset of participants (n=72) were re-exposed to five consecutive nights of 4h TIB. The profile of mood states (POMS) was completed every 2h during wakefulness and daily averages were calculated. The POMS total mood disturbance (TMD) score without the fatigue subscale (i.e., mood disturbance = TMD - fatigue) was the primary outcome to isolate changes in mood disturbance beyond fatigue. Individual growth curve models were applied to the trajectory of mood disturbance. General linear models were used to evaluate the dose-response function of mood disturbance after recovery sleep.

Results

Mood disturbance (absent the POMS fatigue scale) increased with each day of sleep restriction (β=1.550 per day; P&lt;0.0001), and decreased with longer recovery sleep durations in a dose-dependent manner (β=-1.614 for every 2h increase; P&lt;0.0001). The benefits of recovery sleep were abated by the second night of 4h sleep during re-exposure, where mood disturbance was slightly higher than that observed before recovery, but this difference was not statistically significant (β=0.046; P=0.85).

Conclusion

The study findings suggest that fatigue is not the only contributor to mood disturbance following sleep restriction. Recovery sleep attenuates mood disturbance in a dose-dependent manner, albeit transiently. Candidate pathways linking sleep restriction and mood include the immune system and the dynamics of sleep physiology.

Support

This work was funded by National Institute of Health NIH R01NR004281 and National Space and Biomedical Research Institute NSRBI NCC 5–98.

0196 Differences in Sleep Duration and Alertness Among Internal Medicine Interns Comparing Intensive Care Unit to General Medicine Rotations: A Secondary Analysis of the ICOMPARE Trial

Introduction

Little is known about the impact of specific rotations on medical residents’ sleep. The purpose of this analysis was to examine the difference in sleep duration and alertness among internal-medicine resident interns during intensive care unit (ICU) compared to general medicine (GM) rotations.

Methods

This is a secondary report of a randomized non-inferiority trial of 63 United States internal-medicine residency programs. Programs were assigned to either standard duty-hour (80h workweek/16h shifts) or flexible (80h workweek/no shift-length limit) policies. Interns were followed for 2 weeks during either a GM or ICU rotation. The primary outcome was sleep duration/24h (actigraphy). Secondary outcomes were sleepiness (Karolinska Sleepiness Scale [KSS]) and alertness (number of Brief Psychomotor Vigilance Test [PVT-B] lapses). Data were averaged across days (thirteen 24-hour periods). Linear mixed-effect models with random program intercept were used to determine the association between each outcome by rotation, controlling for age, sex, and policy followed.

Results

N=386 interns were included (mean age 27.9±2.1y, 194 (50.3%) males), with n=261 (67.6%) in GM, and n=125 (32.4%) in ICU. Average sleep duration was 7.00±0.08h and 6.84±0.10h for GM and ICU respectively (p=.09; 95%CI -0.02;0.33h). Percent of days with self-reports of excessive sleepiness were significantly more likely for ICU vs GM from 12am-6am (ICU: 20.2%; GM: 12.5%) and 6am-12pm (ICU: 20.5%; GM: 14.3%). GM had significantly more days with no excessive sleepiness (GM: 40.5%; ICU: 28.1%). Average KSS was 4.8±0.1 for both GM and ICU (p=.60; 95%CI -0.18;0.32). Average number of PVT-B lapses were 5.5±0.5 and 5.7±0.7 for GM and ICU respectively (p=.83; 95%CI -1.48;1.18 lapses). There were no significant differences in PVT-B response speed or false starts between rotations.

Conclusion

Interns in ICU may experience more excessive sleepiness compared to GM interns, especially in early morning hours. However, sleep duration and alertness were not significantly different between rotations.

Support

Funded by the National Heart, Lung, and Blood Institute and American Council for Graduate Medical Education

0304 Greater Slow-Wave Activity is Associated with Deteriorating Mood Across Sleep Restriction

Introduction

Mood progressively deteriorates over consecutive days of sleep restriction. The neurobiological processes active during sleep that influence the risk of mood disturbance are unknown. This study investigated the relationships between physiological sleep parameters (i.e., slow-wave activity (SWA), slow-wave energy (SWE), rapid eye-movement (REM) sleep duration and latency), and self-reported measures of mood across sleep restriction.

Methods

N=181 healthy participants (48.1% female; 30±6.8 yrs) had valid polysomnography (PSG) and mood data. The study design included two baseline nights (8h time in bed [TIB]) followed by five nights of 4h TIB. PSG (EEG derivations C3-A2, Fz-A1, O2-A1) was collected on the second baseline night (B2), first night of 4h TIB (SR1), and the fifth night of 4h TIB (SR5). The Profile of Mood States was assayed on days following PSG. Power spectral analysis for SWE and SWA was conducted (delta power; band: 0.5-4.5 Hz). General linear regression models were used to independently assess the slope of SWE, SWA, percent REM of total sleep time (TST), and REM latency on mood disturbance across sleep restriction.

Results

At baseline, higher SWE (unadjusted; r=0.21; P=0.004) and SWA (unadjusted; r=0.19; P=0.007) were associated with greater mood disturbance; these relations were attenuated when adjusted for age and sex. No relation was found between mood and REM latency or REM percent of TST. The slope of mood disturbance from B2 to SR5 was associated with greater percentage increases in C3 SWA on SR5 relative to B2 (β=0.039; P=0.008); this association was not observed for SWE (β=-0.016; P=0.48). The slope of REM latency and REM percent of TST were not associated with the slope of mood disturbance.

Conclusion

Our results indicate that greater SWA due to sleep restriction was associated with greater mood disturbance, suggesting that less SWA may confer resilience to mood disturbances resulting from sleep restriction.

Support

This work was supported by National Institute of Health NIH R01NR004281 and National Space and Biomedical Research Institute NSRBI NCC 5-98.

0300 The Circadian Timing of Sleep Affects the Rate of Accumulation of Neurobehavioral Impairment Across Days of Sleep Restriction

Introduction

Chronic restriction of nighttime sleep to less than ~8h/day leads to build-up of neurobehavioral impairment across days. Although it is known that sleep loss effects depend on the circadian timing of sleep, it is not known how the timing of restricted sleep influences the accumulation of neurobehavioral impairment over days. Here we studied the accumulation of impairment across days of restricted sleep placed in the morning or afternoon.

Methods

N=71 healthy young adults (39% female; ages 21-45y, mean±SD: 27.9±6.6y) completed a 14-day laboratory study. After two baseline days with nighttime sleep (8h TIB: 23:30-07:30), subjects were randomized to 10 consecutive days of A) morning sleep at 4h, 6h, or 8h TIB ending at 11:30 each day (n=18, 8, 8, respectively), or B) afternoon sleep at 4h, 6h, or 8h TIB ending at 19:30 each day (n=13, 17, 7, respectively). Subjects were tested on the 10min psychomotor vigilance test (PVT) every ~2 hours during scheduled wakefulness. Daily averages for PVT lapses (RTs&gt;500ms) observed between 2h and 14h after awakening were analyzed with non-linear mixed-effects regression to investigate differences in the neurobehavioral impairment build-up rate between sleep restriction conditions.

Results

Afternoon sleep conditions showed a significant sleep dose-response effect (p&lt;0.001), with the fastest accrual of PVT performance deficits across days in the 4h condition, and slow-to-negligible accumulation (p=0.36) of PVT performance deficits in the 8h condition. However, morning sleep resulted in no significant sleep dose-response effect (p=0.96). All 3 morning sleep doses displayed negligible (p≥0.12) accumulation of impairment across days.

Conclusion

In this sample of young adults, sleep dosages ending in the morning (at 11:30) appear to provide considerable protection against cumulative performance deficits from sleep restricted to 4h-6h/day over 10 days, suggesting that the afternoon circadian promotion of wakefulness can sustain behavioral alertness even over multiple days of repeated sleep restriction.

Support

NIH grants R01-NR04281 and M01-RR00040

0261 A Randomized Trial on The Effects of Standard and Flexible Duty-Hour Rules on Intern Sleep and Alertness

Introduction

Duty hour regulations affect resident sleep, education, and patient care in complex ways. We performed a national cluster-randomized trial (iCOMPARE) in 63 internal medicine residency programs comparing the effects of the 2011 duty-hour standards to a more flexible set of duty hour rules characterized by maintaining an 80-hour workweek but without limits on shift length or mandatory time off between shifts, relative to patient mortality, intern educational outcomes, and intern sleep and alertness.

Methods

In the sleep and alertness sub-study, sleep duration and morning sleepiness and alertness were assessed with actigraphy, the Karolinska Sleepiness Scale, and a 3-minute Psychomotor Vigilance Test (PVT-B) for 14 days in 193 interns from 6 standard programs and 205 interns from 6 flexible programs.

Results

During the 14-day study periods, interns in standard and flexible programs averaged 7.03h sleep/24h (95% confidence interval [CI] 6.78h, 7.27h) and 6.85h sleep/24h (95% CI 6.61h, 7.10h), respectively. Sleep duration (difference between arms of -0.17h/24h; 1-sided lower 95% confidence limit -0.45h; NIM -0.5h; P=0.02 for noninferiority) and KSS sleepiness (difference 0.12 points; 1-sided upper 95% confidence limit 0.31 points; NIM 1 point; P&lt;0.001) were noninferior in flexible versus standard programs. We could not establish noninferiority for PVT-B alertness (difference -0.3 lapses; 1-sided upper 95% confidence limit 1.6 lapses; NIM 1 lapse; P=0.10). Based on analyses by shift type, sleep duration was 1.77h shorter on days when interns in flexible programs finished an overnight shift relative to a regular day shift (p&lt;.001), with significant decreases in subjective and objective alertness, and frequent reports of excessive sleepiness, especially between 12am and 6am.

Conclusion

There were no signs of relevant chronic sleep loss across shifts in interns in flexible programs relative to their standard program counterparts. Interns were able to compensate for the sleep lost during extended overnight shifts by increasing sleep duration on nights prior to day shifts, night shifts, and days off. Increased sleepiness and reduced alertness of interns following extended overnight shifts need to be mitigated and suggest a role for fatigue-risk management programs.

Support

Supported by NHLBI grants U01HL125388 and U01HL126088 and grants from the ACGME.

0390 Associations of the Neighborhood Built Environment with Adolescent Sleep Outcomes

Introduction

Over 75% of U.S. high school students obtain insufficient amounts of sleep. Identification of modifiable environmental determinants of adolescent sleep is needed to inform interventions and public health strategies, yet little is known about the influence of the built environment on adolescent sleep. We examined associations of the built environment with objectively-measured adolescent sleep outcomes.

Methods

In this longitudinal, prospective study, we used actigraphy to assess sleep outcomes for 14 days each in 8th grade and 9th grade: duration (hours/night), onset (hours from 00:00), offset (hours from 00:00), and sleeping &gt;8 hours. Home addresses were linked to built environment exposures based on half-mile Euclidian buffers (overall/human-made sound levels, percent tree canopy cover, street density, intersection density) and census block group (population density, housing density). Mixed-effects linear (sleep duration, onset, offset) and logistic (&gt;8 hours) regression estimated associations of each built environment measure with sleep outcomes, adjusting for sex, race, parent education, household income, grade and weeknight status (school or non-school night).

Results

Among 108 adolescents - 53% female and 25% Black - providing 2,388 nights of sleep data across 8th and 9th grades, a 1-standard deviation increase in neighborhood sound (overall and human-made) associated with 11 minutes later sleep onset (β=0.19; 95% CI: 0.01, 0.38) and 20% lower odds of sleeping for &gt;8 hours (OR=0.80, 95% CI: 0.62, 1.02). A 1-standard deviation increase in neighborhood tree canopy cover associated with 11 minutes earlier sleep onset (β= -0.19, 95% CI: -0.35, -0.03) and 7 minutes earlier sleep offset (β= -0.12, 95% CI: -0.23, -0.02). No associations were observed for “density based” exposures.

Conclusion

Higher tree canopy cover associated with more favorable sleep timing while higher neighborhood sound level associated with later timing of sleep onset. These modifiable neighborhood built environment factors should be considered when intervening to support healthier sleep among adolescents.

Support

NIH/NHLBI K01HL123612 (JM) and Sleep Research Society Foundation and K23HD094905 (AAW)

0952 Parent-Child Perceptions About Healthy Sleep Promotion in a Mobile Health Sleep Extension Intervention

Introduction

Over half of school-aged children sleep insufficiently and sleep promoting interventions are urgently needed. To effectively promote pediatric sleep health, it is critical to obtain feedback from youth and their families about acceptable intervention strategies. This qualitative study examined perceptions about healthy sleep promotion in parent-child dyads participating in a mobile health sleep extension intervention.

Methods

A total of 26 parent-child dyads (child mean age 11 years, SD = 0.67; 46% non-Latinx White; 19% Black) participated in a mobile intervention to extend child sleep duration over 11 weeks (2-week baseline; 7-week intervention; 2-week follow-up). Participants wore a FitBit during the study, were provided with a sleep duration goal, and received general sleep health-promoting electronic messages using the University of Pennsylvania’s Way to Health platform. Following the intervention, parents and their children separately completed a semi-structured telephone interview to capture perceptions of the intervention strategies. Three coders developed a codebook using an inductive approach to identify emergent themes and conducted coding in NVivo.

Results

Emergent themes fell into domains of intervention acceptability/feasibility and barriers. Mobile messaging about the child’s sleep duration goal was well-received, although child participants in particular desired more personalized messaging, with sleep promotion targeted to their specific sleep habits. Parents and children both discussed ancillary benefits to intervention participation, including an enhanced focus on sleep. Barriers to sleep extension during the intervention and maintenance of any gains post-intervention were related to: competing child academic, social, and extracurricular demands; family factors (work schedules; family rules and norms); and the challenges of limiting ubiquitous electronic devices.

Conclusion

Despite high parent-child acceptability of a mobile child sleep extension intervention, individual and contextual barriers may limit long-term adherence. Tailoring healthy sleep messages to target these factors could improve sustained benefits to child sleep.

Support

Sleep Research Society Foundation and K23HD094905 (AAW); NIH/NCATS UL1TR001878 (JAM and DFD) and K01HL123612 (JAM).

0292 Baseline Pro-Inflammatory Cytokine and Cortisol Levels Differentially Predict Mood Disturbance and Working Memory Deficits Induced by Chronic Sleep Restriction

Introduction

Sleep restriction disturbs mood, impairs neurocognitive performance, and elevates proinflammatory cytokine levels. However, whether basal inflammation influences mood and neurocognitive performance across sleep restriction is unknown. This study examines whether baseline IL-6, cortisol, and TNF-α levels predict the deterioration of mood and working memory performance across sleep restriction.

Methods

N=124 healthy participants (52% female; n=64), 22–45 years of age, had valid protein, mood, and working memory data. The study included two baseline nights (8h time in bed [TIB]) followed by five nights of 4h TIB. Venous blood was collected on the second baseline day and IL-6, cortisol, and TNF-α levels were measured via commercially available ELISA assays. The profile of mood states (POMS) and the digit span test (DST) were completed every 2h during wakefulness and daily averages were computed. Mixed-effects multi-level models, adjusted for baseline, evaluated the main effect of IL-6, cortisol, and TNF-α levels on the POMS and DST independently and examined the trajectory of POMS and DST by the interaction of protein levels and day of sleep restriction.

Results

At baseline, IL-6, cortisol, and TNF-α levels were not associated with POMS or DST. There was a main effect of IL-6, but not cortisol or TNF-α, levels on mood disturbance (β=3.811; P=0.015); IL-6 levels did not predict the trajectory of mood across sleep restriction (β=0.187; P=0.57). Higher baseline cortisol levels predicted increasing mood disturbance across days (β=-1.329; P&lt;0.0001). Higher baseline TNF-α levels predicted degrading DST performance across days (β=-0.313; P=0.020). Higher IL-6 (β=-0.246; P=0.010) and lower cortisol (β=0.185; P=0.037) levels also predicted degrading DST performance across days.

Conclusion

The study findings suggest that basal inflammatory cytokine and cortisol levels are implicated in the individual risk of mood disturbance and working memory deficits resulting from chronic sleep restriction and highlight the need to consider biological processes and phenotypes together.

Support

This work was supported by National Institute of Health NIH R01NR004281 and National Space and Biomedical Research Institute NSRBI NCC 5–98.

520-d Isolation and confinement simulating a flight to Mars reveals heightened immune responses and alterations of leukocyte phenotype

During interplanetary exploration, chronic stress caused by long term isolation and confinement in the spacecraft is one of the major concerns of physical and psychological health of space travelers. And for human on Earth, more and more people live in an isolated condition, which has become a common social problem in modern western society. Collective evidences have indicated prolonged chronic stress could bring big influence to human immune function, which may lead to a variety of health problems. However, to what extent long-term isolation can affect the immune system still remains largely unknow. A simulated 520-d Mars mission provided an extraordinary chance to study the effect of prolonged isolation. Six healthy males participated in this mission and their active neuroendocrine and immune conditions were studied with saliva and blood samples from all participants on chosen time points during the isolation period. As a typical neuroendocrine parameter, stress hormone cortisol was measured in the morning saliva samples. Immune phenotype changes were monitored through peripheral leukocyte phenotype analysis. Using an ex vivo viral infection simulation assay we assessed the immune response changes characterized by the ability to produce representative endogenous pro-inflammatory cytokines. The results of this study revealed elevated cortisol levels, increased lymphocyte amount and heightened immune responses, suggesting that prolonged isolation acting as chronic stressors are able to trigger leukocyte phenotype changes and poorly controlled immune responses.

Sleep loss reduces diurnal rhythm amplitude of leptin in healthy men

The aim of the current study was to investigate the effects of sleep loss on the diurnal rhythm of circulating leptin levels. An indwelling forearm catheter was used to sample blood at 90-min intervals for a total of 120 h, which included 88 h of sustained sleeplessness, in 10 healthy men. The diurnal amplitude of leptin was reduced during total sleep deprivation and returned toward normal during the period of recovery sleep. This finding provides evidence that sleep influences the nocturnal leptin profile, and may have implications for the understanding of the role of sleep in metabolic regulation and the aetiologies of obesity and the night eating syndrome.

Caffeine eliminates psychomotor vigilance deficits from sleep inertia

STUDY OBJECTIVES

This study sought to establish the effects of caffeine on sleep inertia, which is the ubiquitous phenomenon of cognitive performance impairment, grogginess and tendency to return to sleep immediately after awakening.

DESIGN

28 normal adult volunteers were administered sustained low-dose caffeine or placebo (randomized double-blind) during the last 66 hours of an 88-hour period of extended wakefulness that included seven 2-hour naps during which polysomnographical recordings were made. Every 2 hours of wakefulness, and immediately after abrupt awakening from the naps, psychomotor vigilance performance was tested.

SETTING

N/A.

PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

In the placebo condition, sleep inertia was manifested as significantly impaired psychomotor vigilance upon awakening from the naps. This impairment was absent in the caffeine condition. Caffeine had only modest effects on nap sleep.

CONCLUSIONS

Caffeine was efficacious in overcoming sleep inertia. This suggests a reason for the popularity of caffeine-containing beverages after awakening. Caffeine's main mechanism of action on the central nervous system is antagonism of adenosine receptors. Thus, increased adenosine in the brain upon awakening may be the cause of sleep inertia.

Neuroimmunologic aspects of sleep and sleep loss

The complex and intimate interactions between the sleep and immune systems have been the focus of study for several years. Immune factors, particularly the interleukins, regulate sleep and in turn are altered by sleep and sleep deprivation. The sleep-wake cycle likewise regulates normal functioning of the immune system. Although a large number of studies have focused on the relationship between the immune system and sleep, relatively few studies have examined the effects of sleep deprivation on immune parameters. Studies of sleep deprivation's effects are important for several reasons. First, in the 21st century, various societal pressures require humans to work longer and sleep less. Sleep deprivation is becoming an occupational hazard in many industries. Second, to garner a greater understanding of the regulatory effects of sleep on the immune system, one must understand the consequences of sleep deprivation on the immune system. Significant detrimental effects on immune functioning can be seen after a few days of total sleep deprivation or even several days of partial sleep deprivation. Interestingly, not all of the changes in immune physiology that occur as a result of sleep deprivation appear to be negative. Numerous medical disorders involving the immune system are associated with changes in the sleep-wake physiology--either being caused by sleep dysfunction or being exacerbated by sleep disruption. These disorders include infectious diseases, fibromyalgia, cancers, and major depressive disorder. In this article, we will describe the relationships between sleep physiology and the immune system, in states of health and disease. Interspersed will be proposals for future research that may illuminate the clinical relevance of the relationships between sleeping, sleep loss and immune function in humans.

Sustained attention performance during sleep deprivation: evidence of state instability

Nathaniel Kleitman was the first to observe that sleep deprivation in humans did not eliminate the ability to perform neurobehavioral functions, but it did make it difficult to maintain stable performance for more than a few minutes. To investigate variability in performance as a function of sleep deprivation, n = 13 subjects were tested every 2 hours on a 10-minute, sustained-attention, psychomotor vigilance task (PVT) throughout 88 hours of total sleep deprivation (TSD condition), and compared to a control group of n = 15 subjects who were permitted a 2-hour nap every 12 hours (NAP condition) throughout the 88-hour period. PVT reaction time means and standard deviations increased markedly among subjects and within each individual subject in the TSD condition relative to the NAP condition. TSD subjects also had increasingly greater performance variability as a function of time on task after 18 hours of wakefulness. During sleep deprivation, variability in PVT performance reflected a combination of normal timely responses, errors of omission (i.e., lapses), and errors of commission (i.e., responding when no stimulus was present). Errors of omission and errors of commission were highly intercorrelated across deprivation in the TSD condition (r = 0.85, p = 0.0001), suggesting that performance instability is more likely to include compensatory effort than a lack of motivation. The marked increases in PVT performance variability as sleep loss continued supports the "state instability" hypothesis, which posits that performance during sleep deprivation is increasingly variable due to the influence of sleep initiating mechanisms on the endogenous capacity to maintain attention and alertness, thereby creating an unstable state that fluctuates within seconds and that cannot be characterized as either fully awake or asleep.

Absence of diurnal variation of C-reactive protein concentrations in healthy human subjects

BACKGROUND

The concentration of C-reactive protein (CRP) in otherwise healthy subjects has been shown to predict future risk of myocardial infarction and stroke. CRP is synthesized by the liver in response to interleukin-6, the serum concentration of which is subject to diurnal variation.

METHODS

To examine the existence of a time-of-day effect for baseline CRP values, we determined CRP concentrations in hourly blood samples drawn from healthy subjects (10 males, 3 females; age range, 21-35 years) during a baseline day in a controlled environment (8 h of nighttime sleep).

RESULTS

Overall CRP concentrations were low, with only three subjects having CRP concentrations >2 mg/L. Comparison of raw data showed stability of CRP concentrations throughout the 24 h studied. When compared with cutoff values of CRP quintile derived from population-based studies, misclassification of greater than one quintile did not occur as a result of diurnal variation in any of the subjects studied. Nonparametric ANOVA comparing different time points showed no significant differences for both raw and z-transformed data. Analysis for rhythmic diurnal variation using a method fitting a cosine curve to the group data was negative.

CONCLUSIONS

Our data show that baseline CRP concentrations are not subject to time-of-day variation and thus help to explain why CRP concentrations are a better predictor of vascular risk than interleukin-6. Determination of CRP for cardiovascular risk prediction may be performed without concern for diurnal variation.

Soluble TNF-alpha receptor 1 and IL-6 plasma levels in humans subjected to the sleep deprivation model of spaceflight

BACKGROUND

The extent to which sleep loss may predispose astronauts to a state of altered immunity during extended space travel prompts evaluation with ground-based models.

OBJECTIVE

We sought to measure plasma levels of selected cytokines and their receptors, including the putative sleep-regulation proteins soluble TNF-alpha receptor (sTNF-alpha R) I and IL-6, in human subjects undergoing 2 types of sleep deprivation during environmental confinement with performance demands.

METHODS

Healthy adult men (n = 42) were randomized to schedules that varied in severity of sleep loss: 4 days (88 hours) of partial sleep deprivation (PSD) involving two 2-hour naps per day or 4 days of total sleep deprivation (TSD). Plasma samples were obtained every 6 hours across 5 days and analyzed by using enzyme-linked immunoassays for sTNF-alpha RI, sTNF-alpha RII, IL-6, soluble IL-2 receptor, IL-10, and TNF-alpha.

RESULTS

Interactions between the effects of time and sleep deprivation level were detected for sTNF-alpha RI and IL-6 but not for sTNF-alpha RII, soluble IL-2 receptor, IL-10, and TNF-alpha. Relative to the PSD condition, subjects in the TSD condition had elevated plasma levels of sTNF-alpha RI on day 2 (P =.04), day 3 (P =.01), and across days 2 to 4 of sleep loss (P =.01) and elevated levels of IL-6 on day 4 (P =.04).

CONCLUSIONS

Total sleep loss produced significant increases in plasma levels of sTNF-alpha RI and IL-6, messengers that connect the nervous, endocrine, and immune systems. These changes appeared to reflect elevations of the homeostatic drive for sleep because they occurred in TSD but not PSD, suggesting that naps may serve as the basis for a countermeasures approach to prolonged spaceflight.

Commentary: future considerations for models of human neurobehavioral function

Modeling human neurobehavioral functions has the goal of identifying work-rest schedules that are safer and more productive. The models of Folkard et al. and of Jewett and Kronauer illustrate excellent progress toward this goal. Examination of these models reveals four additional areas that need to be addressed to facilitate continued development of accurate models of neurobehavioral functions. (1) The choice of neurobehavioral metrics may have a significant influence on model development. The lack of correlation among different neurobehavioral measures may make comparisons of models difficult. Many neurobehavioral measures are confounded by secondary and random error variance that can lead to model distortion. Although different models may ultimately be required for different neurobehavioral functions, measures that have been extensively validated to be sensitive to circadian variation and sleep loss should take priority in model development. (2) Because error variance in neurobehavioral outcomes can be substantial in uncontrolled environments, model validation should proceed from controlled laboratory protocols to real-world scenarios. Once validated, the ability of a model to predict field data can be tested. (3) While neurobehavioral models have been developed to predict behavior over time (i.e., within-subjects), to be useful in the real world, models will also ultimately have to provide estimates of between-subject variation in vulnerability to neurobehavioral dysfunction during night work or sleep loss (e.g., younger versus older workers). (4) Finally, to be theoretically accurate and practically useful, models of human neurobehavioral functions should be able to predict both cumulative effects (i.e., across days or weeks) and the influence of countermeasures (e.g., light, naps, caffeine).

A comparative model: reaction time performance in sleep-disordered breathing versus alcohol-impaired controls

OBJECTIVES/HYPOTHESIS

Patients with sleep-disordered breathing have reaction time deficits that may lead to catastrophic accidents and loss of life. Although safety guidelines do not exist for unsafe levels of sleepiness, they have been established for unsafe levels of alcohol consumption. Since reaction time performance is altered in both, we prospectively used seven measures of reaction time performance as a comparative model in alcohol-challenged normal subjects with corresponding measures in subjects with sleep-disordered breathing.

STUDY DESIGN

Institutional Review Board-approved, nonrandomized prospective controlled study.

METHODS

Eighty healthy volunteers (29.1+/-7.5 y of age, 56.3% female subjects) performed four reaction time trials using a psychomotor test at baseline and at three subsequent rising alcohol-influenced time points. The same test without alcohol was given to 113 subjects (47.2+/-10.8 y of age, 19.3% female subjects) with mild to moderate sleep-disordered breathing.

RESULTS

Mean blood alcohol concentrations (BACs) in the alcohol-influenced subjects at baseline and three trials were 0, 0.057, 0.080, and 0.083 g/dL. The sleep-disordered subjects had mean respiratory disturbance indices of 29.2 events per hour of sleep. On all seven reaction time measures, their performance was worse than that of the alcohol subjects when BACs were 0.057 g/dL. For three of the measures, the sleep-disordered subjects performed as poorly as or worse than the alcohol subjects when alcohol levels were 0.080 g/dL. These results could not be explained by sex or age differences.

CONCLUSION

The data demonstrate that sleep-disordered subjects in this study (with a mean age of 47 y) with mild to moderate sleep-disordered breathing had worse test reaction time performance parameters than healthy, nonsleepy subjects (with a mean age of 29 y) whose BAC is illegally high for driving a commercial motor vehicle in California. This comparative model points out the potential risks of daytime sleepiness in those with sleep-disordered breathing relative to a culturally accepted standard of impairment.

Time-on-task decrements in "steer clear" performance of patients with sleep apnea and narcolepsy

Loss of attention with time-on-task reflects the increasing instability of the waking state during performance in experimentally induced sleepiness. To determine whether patients with disorders of excessive sleepiness also displayed time-on-task decrements indicative of wake state instability, visual sustained attention performance on "Steer Clear," a computerized simple RT driving simulation task, was compared among 31 patients with untreated sleep apnea, 16 patients with narcolepsy, and 14 healthy control subjects. Vigilance decrement functions were generated by analyzing the number of collisions in each of six four-minute periods of Steer Clear task performance in a mixed-model analysis of variance and linear regression equations. As expected, patients had more Steer Clear collisions than control subjects (p=0.006). However, the inter-subject variability in errors among the narcoleptic patients was four-fold that of the apnea patients, and 100-fold that of the controls volunteers; the variance in errors among untreated apnea patients was 27-times that of controls. The results of transformed collision data revealed main effects for group (p=0.006), time-on-task (p=0.001), and a significant interaction (p=0.022). Control subjects showed no clear evidence of increasing collision errors with time-on-task (adjusted R2=0.22), while apnea patients showed a trend toward vigilance decrement (adjusted R2=0.42, p=0.097), and narcolepsy patients evidenced a robust linear vigilance decrement (adjusted R2=0.87, p=0.004). The association of disorders of excessive somnolence with escalating time-on-task decrements makes it imperative that when assessment of neurobehavioral performance is conducted in patients, it involves task durations and analyses that will evaluate the underlying vulnerability of potentially sleepy patients to decrements over time in tasks that require sustained attention and timely responses, both of which are key components in safe driving performance.

Rapid eye movement sleep changes during the adaptation night in combat veterans with posttraumatic stress disorder

BACKGROUND

Hyperarousal in posttraumatic stress disorder (PTSD) is manifested during sleep as well as waking. Elevated rapid eye movement sleep (REMS) phasic activity, likely signifying central nervous system alerting, has been identified in PTSD. The authors reasoned that PTSD compared to control subjects would show particularly increased REMS phasic activity on the first night of polysomnography, with adaptation to a novel environment.

METHODS

First-night polysomnograms of 17 veterans with PTSD were compared with those of 11 control subjects. Sleep was also studied in subsets of both groups over two nights.

RESULTS

On the first night, the PTSD subjects had a higher density of rapid eye movements in the first REMS period. This measure was increased on the first compared to the second night, but there was no interaction effect between night and group.

CONCLUSIONS

REMS changes are again demonstrated in veterans with PTSD. Introduction to a novel environment activated a REMS phasic process, but not differentially in PTSD compared to control subjects.

Dose-response relationship between sleep duration and human psychomotor vigilance and subjective alertness

Although it has been well documented that sleep is required for human performance and alertness to recover from low levels after prolonged periods of wakefulness, it remains unclear whether they increase in a linear or asymptotic manner during sleep. It has been postulated that there is a relation between the rate of improvement in neurobehavioral functioning and rate of decline of slow-wave sleep and/or slow-wave activity (SWS/SWA) during sleep, but this has not been verified. Thus, a cross-study comparison was conducted in which dose-response curves (DRCs) were constructed for Stanford Sleepiness Scale (SSS) and Psychomotor Vigilance Task (PVT) tests taken at 1000 hours by subjects who had been allowed to sleep 0 hours, 2 hours, 5 hours or 8 hours the previous night. We found that the DRCs to each PVT metric improved in a saturating exponential manner, with recovery rates that were similar [time constant (T) approximately 2.14 hours] for all the metrics. This recovery rate was slightly faster than, though not statistically significantly different from, the reported rate of SWS/SWA decline (T approximately 2.7 hours). The DRC to the SSS improved much more slowly than psychomotor vigilance, so that it could be fit equally well by a linear function (slope = -0.26) or a saturating exponential function (T = 9.09 hours). We conclude that although SWS/SWA, subjective alertness, and a wide variety of psychomotor vigilance metrics may all change asymptotically during sleep, it remains to be determined whether the underlying physiologic processes governing their expression are different.

Flight controller alertness and performance during spaceflight shiftwork operations

Decreased alertness and performance associated with fatigue, sleep loss, and circadian disruption are issues faced by a diverse range of shiftwork operations personnel. During Space Transportation System (STS) operations, Mission Operations Directorate (MOD) personnel provide 24-hr. coverage of critical tasks. A joint NASA Johnson Space Center and NASA Ames Research Center project was undertaken to examine these issues in flight controllers during MOD shiftwork operations. An initial operational test of procedures and measures was conducted during the STS-53 mission in December 1992. The study measures included a Background Questionnaire, a subjective daily logbook completed on a 24-hour basis (to report sleep patterns, work periods, etc.), and an 8 minute performance and mood test battery administered at the beginning, middle, and end of each shift period. Seventeen flight controllers representing the 3 Orbit shifts participated. The initial results clearly support the need for further data collection during other STS missions to document baseline levels of alertness and performance during MOD shiftwork operations. Countermeasure strategies specific to the MOD environment are being developed to minimize the adverse effects of fatigue, sleep loss, and circadian disruption engendered by shiftwork operations. These issues are especially pertinent for the night shift operations and the acute phase advance required for the transition of day shift personnel into the night for shuttle launch. Implementation and evaluation of the countermeasure strategies to maximize alertness and performance is planned. As STS missions extend to further EDO (extended duration orbiters), and timelines and planning for 24-hour Space Station operations continue, alertness and performance issues related to sleep and circadian disruption will remain highly relevant in the MOD environment.

Rotating shiftwork schedules: can we enhance physician adaptation to night shifts?

OBJECTIVES

To evaluate the effectiveness of a broad, literature-based night shiftwork intervention for enhancement of emergency physicians' (EPs') adaptation to night rotations.

METHODS

A prospective, double-blind, active placebo-controlled study was conducted on 6 attending physicians in a university hospital ED. Three data sets were collected under the following conditions: baseline, after active placebo intervention, and after experimental intervention. In each condition, data were collected when the physicians worked both night and day shifts. Measurements included ambulatory polysomnographic recordings of the main sleep periods, objective performance tests administered several times during the subjects' shifts, and daily subjective ratings of the subjects' sleep, moods, and intervention use.

RESULTS

The subjects slept an average of 5 hr 42 min across all conditions. After night shifts, the subjects slept significantly less than they did after day shifts (5 hr 13 min vs 6 hr 20 min; p < 0.05). The physicians' vigilance reaction times and times for intubation of a mannequin were significantly slower during night shifts than they were during day shifts (p = 0.007 and p < 0.04, respectively), but performances on ECG analysis did not significantly differ between night and day shifts. Mood ratings were significantly more negative during night shifts than they were during day shifts (more sluggish p < 0.04, less motivated p < 0.03, and less clear thinking p < 0.04). The strategies in the experimental intervention were used 85% of the time according to logbook entries. The experimental and active placebo interventions did not significantly improve the physician's performance, or mood on the night shift, although the subjects slept more after both interventions.

CONCLUSIONS

Although the experimental intervention was successfully implemented, it failed to significantly improve attending physicians' sleep, performance, or mood on night shifts. A decrease in speed of intubation, vigilance reaction times, and subjective alertness was evident each time the physicians rotated through the night shift. These findings plus the limited sleep across all conditions and shifts suggest that circadian-mediated disruptions of waking neurobehavioral functions and sleep deprivation are problems in EPs.

Self-hypnosis training as an adjunctive treatment in the management of pain associated with sickle cell disease

A cohort of patients with sickle cell disease, consisting of children, adolescents, and adults, who reported experiencing three or more episodes of vaso-occlusive pain the preceding year, were enrolled in a prospective two-period treatment protocol. Following a 4-month conventional treatment baseline phase, a supplemental cognitive-behavioral pain management program that centered on self-hypnosis was implemented over the next 18 months. Frequency of self-hypnosis group straining sessions began at once per week for the first 6 months, became biweekly for the next 6 months, and finally occurred once every third week for the remaining 6 months. Results indicate that the self-hypnosis intervention was associated with a significant reduction in pain days. Both the proportion of "bad sleep" nights and the use of pain medications also decreased significantly during the self-hypnosis treatment phase. However, participants continued to report disturbed sleep and to require medications on those days during which they did experience pain. Findings further suggest that the overall reduction in pain frequency was due to the elimination of less severe episodes of pain. Non-specific factors may have contributed to the efficacy of treatment. Nevertheless, the program clearly demonstrates that an adjunctive behavioral treatment for sickle cell pain, involving patient self-management and regular contact with a medical self-hypnosis team, can be beneficial in reducing recurrent, unpredictable episodes of pain in a patient population for whom few safe, cost-effective medical alternatives exist.

An instrument to measure functional status outcomes for disorders of excessive sleepiness

This article reports the development of the functional outcomes of sleep questionnaire (FOSQ). This is the first self-report measure designed to assess the impact of disorders of excessive sleepiness (DOES) on multiple activities of everyday living. Three samples were used in the development and psychometric analyses of the FOSQ: Sample 1 (n = 153) consisted of individuals seeking medical attention for a sleep problem and persons of similar age and gender having no sleep disorder; samples 2 (n = 24) and 3 (n = 51) were composed of patients from two medical centers diagnosed with obstructive sleep apnea (OSA). Factor analysis of the FOSQ yielded five factors: activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcome. Internal reliability was excellent for both the subscales (alpha = 0.86 to alpha = 0.91) and the total scale (alpha = 0.95). Test-retest reliability of the FOSQ yielded coefficients ranging from r = 0.81 to r = 0.90 for the five subscales and r = 0.90 for the total measure. The FOSQ successfully discriminated between normal subjects and those seeking medical attention for a sleep problem (T157 = -5.88, p = 0.0001). This psychometric evaluation of the FOSQ demonstrated parameters acceptable for its application in research and in clinical practice to measure functional status outcomes for persons with DOES. Thus, the FOSQ can be used to determine how disorders of excessive sleepiness affect patients' abilities to conduct normal activities and the extent to which these abilities are improved by effective treatment of DOES.

Night-to-night variability in CPAP use over the first three months of treatment

The purpose of this study was to examine the relationship between night-to-night variability and nightly duration of continuous positive airway pressure (CPAP) therapy over the first 9 weeks of treatment and to determine when patients begin to establish a nonadherent pattern of use. Data were analyzed from a study of daily CPAP use covertly monitored in 32 diagnosed patients with obstructive sleep apnea (OSA) using a microprocessor monitor encased in a CPAP machine. Patterns of CPAP use were bimodal, based on the frequency of nightly use. Approximately half the subjects were consistent users of CPAP, applying it > 90% of the nights for an average of 6.22 +/- 1.21 hours per night, while the other half comprised intermittent users who had a wide range of daily use averaging 3.45 +/- 1.94 hours per night on the nights CPAP was used. The percent of days skipped was significantly correlated with decreased nightly duration (rho = -0.73, p < 0.0001). Analysis of the night-to-night pattern of use revealed that the two groups differed significantly in the nightly duration of CPAP use by the fourth day of treatment (p = 0.001). Exploration of factors that potentially differentiate the two groups revealed no reliable predictors. However, intermittent users continued to report significantly greater OSA symptoms (snoring, snorting, and apnea) posttreatment, suggesting that they continued to experience sleep disordered breathing.

Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night

To determine whether a cumulative sleep debt (in a range commonly experienced) would result in cumulative changes in measures of waking neurobehavioral alertness, 16 healthy young adults had their sleep restricted 33% below habitual sleep duration, to an average 4.98 hours per night [standard deviation (SD) = 0.57] for seven consecutive nights. Subjects slept in the laboratory, and sleep and waking were monitored by staff and actigraphy. Three times each day (1000, 1600, and 2200 hours) subjects were assessed for subjective sleepiness (SSS) and mood (POMS) and were evaluated on a brief performance battery that included psychomotor vigilance (PVT), probed memory (PRM), and serial-addition testing, Once each day they completed a series of visual analog scales (VAS) and reported sleepiness and somatic and cognitive/emotional problems. Sleep restriction resulted in statistically robust cumulative effects on waking functions. SSS ratings, subscale scores for fatigue, confusion, tension, and total mood disturbance from the POMS and VAS ratings of mental exhaustion and stress were evaluated across days of restricted sleep (p = 0.009 to p = 0.0001). PVT performance parameters, including the frequency and duration of lapses, were also significantly increased by restriction (p = 0.018 to p = 0.0001). Significant time-of-day effects were evident in SSS and PVT data, but time-of-day did not interact with the effects of sleep restriction across days. The temporal profiles of cumulative changes in neurobehavioral measures of alertness as a function of sleep restriction were generally consistent. Subjective changes tended to precede performance changes by 1 day, but overall changes in both classes of measure were greatest during the first 2 days (P1, P2) and last 2 days (P6, P7) of sleep restriction. Data from subsets of subjects also showed: 1) that significant decreases in the MSLT occurred during sleep restriction, 2) that the elevated sleepiness and performance deficits continued beyond day 7 of restriction, and 3) that recovery from these deficits appeared to require two full nights of sleep. The cumulative increase in performance lapses across days of sleep restriction correlated closely with MSLT results (r = -0.95) from an earlier comparable experiment by Carskadon and Dement (1). These findings suggest that cumulative nocturnal sleep debt had a dynamic and escalating analog in cumulative daytime sleepiness and that asymptotic or steady-state sleepiness was not achieved in response to sleep restriction.

Neurobehavioral consequences of arousals

The neurobehavioral deficits of obstructive sleep apnea syndrome (OSAS) are often attributed to the rate of respiratory disturbance or rate of arousals during sleep. However, sleep disordered breathing is also associated with other changes in sleep infrastructure that may account for cumulative waking deficits. This was illustrated in polysomnographic data from 1,521 patients with OSAS where increasing arousal indices were associated with increased duration of stage 1 sleep and concomitant reduction in total sleep time. Similar results have been found in paradigms in which sleep was experimentally fragmented in healthy individuals. It appears that chronic fragmentation of sleep, whether by apneas or acoustic stimuli, leads to cumulative homeostatic pressure for sleep, which may explain a number of phenomenon characteristic of both untreated OSAS patients and experimentally fragmented sleepers: (1) increased arousal threshold, (2) rapid return to sleep after arousal, (3) fewer awakenings over time, (4) increased sleep inertia on awakenings, (5) increased amnesia for arousals, and (6) daytime sleepiness. Elevated homeostatic drive for sleep appears to be a function of both the frequency of arousals within a night and the chronicity of sleep fragmentation across nights, neither of which have been adequately modeled in experimental studies of healthy subjects.

Memory liabilities associated with hypnosis: does low hypnotizability confer immunity?

Retrospective analyses of data from the authors' program of research on hypnosis and memory are presented, with special emphasis on effects observed among low hypnotizable individuals. In Experiment 1, participants completed seven forced-recall trials in an attempt to remember a series of pictures that had been shown 1 week earlier. For half the participants, the middle five trials were carried out using hypnotic procedures; the remaining participants performed all recall attempts in a motivated waking condition. Hypnosis failed to enhance correct recall for either high or low hypnotizable participants beyond the hypermnesia and reminiscence effects associated with repeated retrieval attempts over time. However, whereas high hypnotizable participants produced substantial numbers of confident recall errors (i.e., intrusions) independent of the use of hypnosis, low hypnotizable participants exposed to hypnotic procedures reported significantly more intrusions than their counterparts in the waking condition. In Experiment 2, participants were asked to identify whether specific recollections, reported during two forced-interrogatory recall tests conducted 1 week earlier, had originated in the first or second of those tests. A general bias to misattribute previously reported recollections to the first of two recall occasions was observed; however, the effect was greatest among low hypnotizables who had undergone the second recall attempt in hypnosis. The findings imply that highly hypnotizable individuals are not unique in their vulnerability to distortions of memory induced by hypnotic techniques. Individuals of lesser hypnotic capacity also manifest memory alterations when exposed to such procedures.

Total sleep deprivation and the thyroid axis: effects of sleep and waking activity

BACKGROUND

Circadian and sleep components modulate anterior pituitary release of thyrotropin (TSH), the chemical substance regulating the thyroid hormones, thyroxine (T4), and triiodothyronine (T3). The present study examined TSH, T4, and T3 concentrations across the wake-sleep boundary time (2300-0130 hours) before, during, and after a 64-h sleep deprivation paradigm. Additionally, adrenocorticotropic hormone (ACTH) and cortisol were measured as an index of hypothalamic-pituitary-adrenal axis activation. Activity levels and ratings of effort required to perform cognitive tasks were also incorporated to evaluate physical and cognitive load, respectively, across the study period. Assessing the combined effects of activity and sleep deprivation on thyroid hormone economy is relevant to the relationship of high physical and/or cognitive performance demands during sleep deprivation inherent in extended military operations and space exploration.

METHODS

There were 12 healthy subjects who were monitored during a 2-d baseline period, 3 d of total sleep deprivation, and 2 nights of recovery sleep. Serum samples were collected at 2300 hours and 0130 hours across the entire study period, and measured for TSH, T4, T3, and glucocorticoids.

RESULTS

Change scores evaluated at the wake-sleep boundary time demonstrated significant inhibitory effects of sleep on thyroid hormone measures. As expected, sleep deprivation was associated with elevated TSH. However, sleep deprivation also significantly increased circulating levels of T3 at 2300 hours and T4 concentration change scores (2300-0130 hours). Glucocorticoid levels did not track thyroid hormone changes. Physical activity remained constant while subjective ratings of effort to perform cognitive tasks increased significantly during sleep deprivation.

CONCLUSION

Compared to sleep deprivation studies under constant conditions reporting no change in peripheral T4 and T3 levels, the present study suggests activity level, including cognitive effort to perform, during total sleep deprivation may produce substantive changes in the thyroid axis.

Psychosocial and immune effects of self-hypnosis training for stress management throughout the first semester of medical school

This study was a 19-week prospective conducted to determine the effectiveness of a self-hypnosis/relaxation intervention to relieve symptoms of psychological distress and moderate immune system reactivity to examination stress in 35 first-year medical students. Twenty-one subjects were randomly selected for training in the use of self-hypnosis as a coping skill and were encouraged to practice regularly and to maintain daily diary records related to mood, sleep, physical symptoms, and frequency of relaxation practice. An additional 14 subjects received no explicit training in stress-reduction strategies, but completed similar daily diaries. Self-report psychosocial and symptom measures, as well as blood draws, were obtained at four time points: orientation, late semester, examination period, and postsemester recovery. It was found that significant increases in stress and fatigue occurred during the examination period, paralleled by increases in counts of B lymphocytes and activated T lymphocytes, PHA-induced and PWM-induced blastogenesis, and natural killer cell (NK) cytotoxicity. No immune decreases were observed. Subjects in the self-hypnosis condition reported significantly less distress and anxiety than their nonintervention counterparts, but the two groups did not differ with respect to immune function. Nevertheless, within the self-hypnosis group, the quality of the exercises (ie, relaxation ratings) predicted both the number of NK cells and NK activity. It was concluded that stress associated with academic demands affects immune function, but immune suppression is not inevitable. Practice of self-hypnosis reduces distress, without differential immune effects. However, individual responses to the self-hypnosis intervention appear to predict immune outcomes.

Characteristics of crashes attributed to the driver having fallen asleep

While it has been known for some time that crashes can result from the driver falling asleep at the wheel, this issue has received less attention in traffic safety programs than the role of alcohol or speed of the vehicle. The present study was done to investigate the characteristics of crashes attributed to the driver being asleep. The study utilized the database at the Highway Safety Research Center at the University of North Carolina that is based on the uniform crash reporting system in that state. Over the years 1990-1992, inclusive, there were 4333 crashes in which the driver was judged to be asleep but not intoxicated. The crashes were primarily of the drive-off-the-road type (78% of the total) and took place at higher speeds (62% in excess of 50 mph). The fatality rate was of similar magnitude to that in alcohol-related crashes with fatalities in 1.4% of such crashes (alcohol crashes had fatalities in 2.1%). The crashes occurred primarily at two times of day--during the nighttime period of increased sleepiness (midnight to 7.00 a.m.) and during the mid-afternoon "siesta" time of increased sleepiness (3.00 p.m.). These crashes occurred predominately in young people. Fifty-five percent of these were in individuals 25 years of age or younger, with a peak age of occurrence at age 20 years. Sleepiness may play a role in crashes other than those attributed by the police to the driver being asleep. Determining the magnitude of this role is a challenge to the traffic safety community.

An overview of sleepiness and accidents

This paper reviews the association between neurobiologically-based sleepiness/fatigue and human-error related accidents. It concludes that fatigue contributes to human error and accidents in technology-rich, industrialized societies in terms of human, environmental and economic impacts. The cultural utilization of time as expressed in 24-h work operations, combined with the widespread use of automation, will continue to escalate in the next century, further increasing the risks of fatigue-related accidents, as more people conduct vigilance-based activities at times other than the traditional daytime work hours. Fatigue management and prevention of fatigue-related catastrophes need to become a sustained priority for government, industries, labour, and the public. Scientific data are urgently needed on the most likely areas in which sleepiness-related performance failures contribute to accidents, and on the effectiveness of a wide range of potentially useful countermeasures.

Review of regulations and guidelines for commercial and noncommercial drivers with sleep apnea and narcolepsy

Studies show that persons with sleep disorders, such as sleep apnea and narcolepsy, have an increased incidence of automobile accidents. The goal of this study was to review any regulations or guidelines dealing with fitness to drive of persons with sleep disorders in all the 50 states and countries around the world. Several authorities in the United States and abroad in fact have produced guidelines or regulations stating that certain of these persons are not fit to drive. As of March 1994, only four states in the United States (Maryland, North Carolina, Oregon and Utah) had guidelines for narcolepsy, while two had guidelines for both narcolepsy and sleep apnea (California and Texas). In Maine, guidelines had been proposed for sleep apnea. In contrast, almost all Canadian provinces have guidelines for both sleep apnea and narcolepsy, as does the United Kingdom. There are, however, considerable variations in the nature of the regulations used in different states, Canadian provinces and countries. These variations are not based on scientific data. Currently the impact of these regulations on crash rates or on the practice of sleep medicine has not been assessed.

A survey screen for prediction of apnea

Questionnaire data from patients presenting at three sleep disorders centers were used to develop and assess a screening tool for sleep apnea based on the reporting of the frequency of various symptoms of sleep apnea and other sleep disorders plus age, body mass index (BMI) and gender. Patients were not specifically referred for suspicion of sleep apnea. Separate factor analyses of survey responses from 658, 193 and 77 respondents from the first, second and third sites, respectively, each yielded four orthogonal factors, one of which accounted for all the questions concerned with the frequency of disordered breathing during sleep. The survey was shown to be reliable in a subset of patients from one of the sites (test-retest correlation = 0.92). Survey data were then compared to a clinical measure of sleep apnea (respiratory disturbance index) obtained from polysomnography. A multivariable apnea risk index including survey responses, age, gender and BMI was estimated using multiple logistic regression in a total sample of 427 respondents from two of the sites. Predictive ability was assessed using receiver operating characteristic (ROC) curves. The area under the ROC curve was 0.79 (p < 0.0001). For BMI alone, it was 0.73, and for an index measuring the self-report of the frequency of apnea symptoms, it was 0.70. The multivariable apnea risk index has potential utility in clinical settings.

Motor dysfunction during sleep in posttraumatic stress disorder

A subjective disturbance of sleep, including the occurrence of repetitive, stereotypical anxiety dreams, is characteristic of posttraumatic stress disorder (PTSD). The phenomenology of the PTSD anxiety dream has seemed most consistent with an underlying rapid eye movement (REM) sleep dysfunction. However, motor behavior reportedly can accompany PTSD dreams, and normal REM sleep typically involves a nearly total paralysis of the body musculature. As a means of understanding this discrepancy, anterior tibialis muscle activity during sleep was studied in a group of Vietnam combat veterans with current PTSD and in an age-matched normal control group. The PTSD subjects had a higher percentage of REM sleep epochs with at least one prolonged twitch burst; they also were more likely to have periodic limb movements in sleep, during nonrapid eye movement sleep. Both these forms of muscle activation also have been observed in REM behavior disorder (RBD), a parasomnia characterized by the actual enactment of dream sequences during REM sleep. The identification of RBD-like signs in PTSD adds to the evidence for a fundamental disturbance of REM sleep phasic mechanisms in PTSD.

Leukocytosis and natural killer cell function parallel neurobehavioral fatigue induced by 64 hours of sleep deprivation

The hypothesis that sleep deprivation depresses immune function was tested in 20 adults, selected on the basis of their normal blood chemistry, monitored in a laboratory for 7 d, and kept awake for 64 h. At 2200 h each day measurements were taken of total leukocytes (WBC), monocytes, granulocytes, lymphocytes, eosinophils, erythrocytes (RBC), B and T lymphocyte subsets, activated T cells, and natural killer (NK) subpopulations (CD56/CD8 dual-positive cells, CD16-positive cells, CD57-positive cells). Functional tests included NK cytotoxicity, lymphocyte stimulation with mitogens, and DNA analysis of cell cycle. Sleep loss was associated with leukocytosis and increased NK cell activity. At the maximum sleep deprivation, increases were observed in counts of WBC, granulocytes, monocytes, NK activity, and the proportion of lymphocytes in the S phase of the cell cycle. Changes in monocyte counts correlated with changes in other immune parameters. Counts of CD4, CD16, CD56, and CD57 lymphocytes declined after one night without sleep, whereas CD56 and CD57 counts increased after two nights. No changes were observed in other lymphocyte counts, in proliferative responses to mitogens, or in plasma levels of cortisol or adrenocorticotropin hormone. The physiologic leukocytosis and NK activity increases during deprivation were eliminated by recovery sleep in a manner parallel to neurobehavioral function, suggesting that the immune alterations may be associated with biological pressure for sleep.

Rapid eye movement sleep disturbance in posttraumatic stress disorder

The subjective sleep disturbance in posttraumatic stress disorder (PTSD), including the repetitive, stereotypical anxiety dream, suggests dysfunctional rapid eye movement (REM) sleep mechanisms. The polysomnograms of a group of physically healthy combat veterans with current PTSD were compared with those of an age-appropriate normal control group. Tonic and phasic REM sleep measures in the PTSD subjects were elevated on the second night of recorded sleep. Increased phasic REM sleep activity persisted in the PTSD group on the subsequent night. During the study, an anxiety dream occurred in a PTSD subject in REM sleep. The results are consistent with the view that a dysregulation of the REM sleep control system, particularly phasic event generation, may be involved in the pathogenesis of PTSD. The finding of a specific disturbance of sleep unique to PTSD may have significant implications for the design of effective treatments for PTSD.

Effects of one night without nasal CPAP treatment on sleep and sleepiness in patients with obstructive sleep apnea

Nasal continuous positive airway pressure (CPAP) has become the nonsurgical treatment of choice for obstructive sleep apnea syndrome (OSAS). Recent evidence suggests that intermittent use of CPAP by patients is more common than nightly compliance. To determine the consequences of intermittent CPAP use, in terms of a return of sleep-disordered breathing and daytime hypersomnolence, 15 OSAS subjects were evaluated at three times: (1) before CPAP treatment (pretreatment), (2) after 30 to 237 days posttreatment during a night of CPAP use (on CPAP), and (3) during a night without CPAP (off CPAP). Evaluations of sleep-disordered breathing and three domains of hypersomnolence, physiologic sleep tendency, subjective sleepiness, and performance, were accomplished with the respiratory disturbance index (RDI), multiple sleep latency test (MSLT), Stanford sleepiness scale (SSS), and psychomotor vigilance task (PVT), respectively. CPAP use was encouraged and monitored from pretreatment to post-treatment by daily diaries for most subjects and an electronic device for a subset of subjects. As expected, CPAP eliminated apneas and hypopneas, and following the on CPAP night, there were statistically significant improvements in objective measures of sleepiness (MSLT and PVT). Subjective measures of sleepiness and fatigue also showed improvement. Sleeping without CPAP for one night reversed virtually all of the sleep and daytime alertness gains derived from sleeping with CPAP. This occurred despite a statistically significant reduction in the RDI on the night off CPAP (M = 36.8, SD = 28.0 events/h) relative to the pretreatment night (M = 56.6, SD = 24.8 events/h), which may be due to a lessening of the edema of the upper airway following CPAP use.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective measurement of patterns of nasal CPAP use by patients with obstructive sleep apnea

Obstruction of the upper airway during sleep (OSAS) is widely treated by having patients self-administer nasal continuous positive airway pressure (CPAP). To obtain objective evidence of the patterns of CPAP use, information was gathered from two urban sites on 35 OSAS patients who were prescribed CPAP for a total of 3,743 days. Patients were given CPAP machines that contained a microprocessor and monitor that measured actual pressure at the mask for every minute of each 24-h day for an average of 106 days per patient. They were not aware of the monitor inside the CPAP machines. Monitor output was compared with patients' diagnostic status, pretreatment clinical and demographic characteristics, and follow-up self-reports of CPAP use, problems, side effects, and aspects of daytime fatigue and sleepiness. Patients attempted to use CPAP an average of 66 +/- 37% of the days monitored. When CPAP was used, the mean duration of use was 4.88 +/- 1.97 h. However, patients' reports of the duration of CPAP use overestimated actual use by 69 +/- 110 min (p < 0.002). Both frequency and duration of CPAP use in the first month reliably predicted use in the third month (p < 0.0001). Although the majority (60%) of patients claimed to use CPAP nightly, only 16 of 35 (46%) met criteria for regular use, defined by at least 4 h of CPAP administered on 70% of the days monitored. Relative to less regular users, these 16 patients had more years of education (p = 0.05), and were more likely to work in professional occupations.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluating hypnotic memory enhancement (hypermnesia and reminiscence) using multitrial forced recall

Two experiments investigated whether hypnosis enhances memory retrieval per se or merely increases a person's willingness to report recollections. Both experiments assessed immediate and delayed (i.e., 1 week) recall for pictorial stimuli. In Experiment 1, following an initial waking baseline recall, subjects of high or low hypnotic ability completed a series of recall trials conducted either in hypnosis or in the walking condition. The classic hypermnesia effect was obtained, but with no supplemental contribution of hypnosis. In Experiment 2, hypnosis was introduced only after 6 waking-recall trials. Hypnosis again failed to enhance retrieval of new correct items, although it increased the production of new incorrect recall among hypnotizable individuals. The findings provide no evidence for alleged hypermnesic properties of hypnosis.