Beyond the symptom: the biology of fatigue

A workshop titled "Beyond the Symptom: The Biology of Fatigue" was held virtually September 27-28, 2021. It was jointly organized by the Sleep Research Society and the Neurobiology of Fatigue Working Group of the NIH Blueprint Neuroscience Research Program. For access to the presentations and video recordings, see: https://neuroscienceblueprint.nih.gov/about/event/beyond-symptom-biology-fatigue. The goals of this workshop were to bring together clinicians and scientists who use a variety of research approaches to understand fatigue in multiple conditions and to identify key gaps in our understanding of the biology of fatigue. This workshop summary distills key issues discussed in this workshop and provides a list of promising directions for future research on this topic. We do not attempt to provide a comprehensive review of the state of our understanding of fatigue, nor to provide a comprehensive reprise of the many excellent presentations. Rather, our goal is to highlight key advances and to focus on questions and future approaches to answering them.

Development of a Definition of Postacute Sequelae of SARS-CoV-2 Infection

Importance

SARS-CoV-2 infection is associated with persistent, relapsing, or new symptoms or other health effects occurring after acute infection, termed postacute sequelae of SARS-CoV-2 infection (PASC), also known as long COVID. Characterizing PASC requires analysis of prospectively and uniformly collected data from diverse uninfected and infected individuals.

Objective

To develop a definition of PASC using self-reported symptoms and describe PASC frequencies across cohorts, vaccination status, and number of infections.

Design, Setting, and Participants

Prospective observational cohort study of adults with and without SARS-CoV-2 infection at 85 enrolling sites (hospitals, health centers, community organizations) located in 33 states plus Washington, DC, and Puerto Rico. Participants who were enrolled in the RECOVER adult cohort before April 10, 2023, completed a symptom survey 6 months or more after acute symptom onset or test date. Selection included population-based, volunteer, and convenience sampling.

Exposure

SARS-CoV-2 infection.

Main Outcomes and Measures

PASC and 44 participant-reported symptoms (with severity thresholds).

Results

A total of 9764 participants (89% SARS-CoV-2 infected; 71% female; 16% Hispanic/Latino; 15% non-Hispanic Black; median age, 47 years [IQR, 35-60]) met selection criteria. Adjusted odds ratios were 1.5 or greater (infected vs uninfected participants) for 37 symptoms. Symptoms contributing to PASC score included postexertional malaise, fatigue, brain fog, dizziness, gastrointestinal symptoms, palpitations, changes in sexual desire or capacity, loss of or change in smell or taste, thirst, chronic cough, chest pain, and abnormal movements. Among 2231 participants first infected on or after December 1, 2021, and enrolled within 30 days of infection, 224 (10% [95% CI, 8.8%-11%]) were PASC positive at 6 months.

Conclusions and Relevance

A definition of PASC was developed based on symptoms in a prospective cohort study. As a first step to providing a framework for other investigations, iterative refinement that further incorporates other clinical features is needed to support actionable definitions of PASC.

Monitoring sleep using smartphone data in a population of college students

Sleep is fundamental to all health, especially mental health. Monitoring sleep is thus critical to delivering effective healthcare. However, measuring sleep in a scalable way remains a clinical challenge because wearable sleep-monitoring devices are not affordable or accessible to the majority of the population. However, as consumer devices like smartphones become increasingly powerful and accessible in the United States, monitoring sleep using smartphone patterns offers a feasible and scalable alternative to wearable devices. In this study, we analyze the sleep behavior of 67 college students with elevated levels of stress over 28 days. While using the open-source mindLAMP smartphone app to complete daily and weekly sleep and mental health surveys, these participants also passively collected phone sensor data. We used these passive sensor data streams to estimate sleep duration. These sensor-based sleep duration estimates, when averaged for each participant, were correlated with self-reported sleep duration (r = 0.83). We later constructed a simple predictive model using both sensor-based sleep duration estimates and surveys as predictor variables. This model demonstrated the ability to predict survey-reported Pittsburgh Sleep Quality Index (PSQI) scores within 1 point. Overall, our results suggest that smartphone-derived sleep duration estimates offer practical results for estimating sleep duration and can also serve useful functions in the process of digital phenotyping.

Sleep and circadian informatics data harmonization: a workshop report from the Sleep Research Society and Sleep Research Network

The increasing availability and complexity of sleep and circadian data are equally exciting and challenging. The field is in constant technological development, generating better high-resolution physiological and molecular data than ever before. Yet, the promise of large-scale studies leveraging millions of patients is limited by suboptimal approaches for data sharing and interoperability. As a result, integration of valuable clinical and basic resources is problematic, preventing knowledge discovery and rapid translation of findings into clinical care. To understand the current data landscape in the sleep and circadian domains, the Sleep Research Society (SRS) and the Sleep Research Network (now a task force of the SRS) organized a workshop on informatics and data harmonization, presented at the World Sleep Congress 2019, in Vancouver, Canada. Experts in translational informatics gathered with sleep research experts to discuss opportunities and challenges in defining strategies for data harmonization. The goal of this workshop was to fuel discussion and foster innovative approaches for data integration and development of informatics infrastructure supporting multi-site collaboration. Key recommendations included collecting and storing findable, accessible, interoperable, and reusable data; identifying existing international cohorts and resources supporting research in sleep and circadian biology; and defining the most relevant sleep data elements and associated metadata that could be supported by early integration initiatives. This report introduces foundational concepts with the goal of facilitating engagement between the sleep/circadian and informatics communities and is a call to action for the implementation and adoption of data harmonization strategies in this domain.

0609 Sleep Stabilization in Prehypertensive/Hypertensive Patients

Introduction

Variable sleep/wake patterns have been linked to increased cardiometabolic risk. The current project investigates the effects of using sleep hygiene interventions to stabilize sleep timing in prehypertensive/hypertensive patients. Growing evidence supports the importance of regularizing sleep timing in improving cardiovascular health, and we believe that using sleep hygiene techniques to stabilize sleep may reduce these risks.

Methods

As part of a larger study, fifty-three participants (55.5 ± 1.4 years; 51% male) completed sleep diaries during 3 study periods. The first period (S1) was a baseline control, the second period (S2) was a 4-week wait-list control condition, and the third period (S3) was an 8-week randomly assigned intervention that used sleep hygiene approaches and scheduling to stabilize sleep timing or stabilize and lengthen sleep. Currently, we are still blind to condition; however, because both conditions involve sleep stabilization, an analysis using linear mixed models was used to assess change in the variability of total sleep time (SDTST), wake up time (SDWUT), and fall asleep time (SDFAT) across the 3 study periods.

Results

There was a significant decrease in SDTST variability (standard deviation) at post-intervention (S3) compared to S2 (p<0.01) and S1 (p<0.01). There was also a significant decrease in SDWUT variability at post-intervention (S3) compared to S2 (p<0.01) and S1 (p<0.01). There was a trend towards a significantly decreased SDFAT at S3 compared to S2 (p=0.057), but there was a significant decrease in SDFAT variability during S3 compared to S1 (p<0.01).

Conclusion

These data suggest that we were able to utilize sleep hygiene interventions to decrease the variability in total sleep time, wake-up time and fall asleep time. When we unblind we will report on if we were able to increase and lengthen the sleep period for those in the sleep extension condition.

Support (If Any)

NIH (R01HL125379 to Dr. Janet Mullington), Harvard Catalyst, Harvard Clinical and Translational Science Center (UL1TR001102)

0087 Feasibility of examining component-specific effects of yogic breathing on self-report sleep metrics: A three-arm pilot RCT

Introduction

Mind-body interventions (MBIs) continue to receive widespread interest for improving sleep disturbances. This study investigated the feasibility of using an automated electronic survey system in REDCap in the context of a fully remote clinical trial study to produce detailed measures of participant adherence, daily sleep quality, and associations with physiological outcomes captured by wearable devices.

Methods

Eighteen healthy participants (age 18-30 yrs, 12 female) were randomized to one of three 8-week long interventions: slow-paced breathing (SPB, N=5, 24.6 ± 2.1 years, 4 female), mindfulness (M, N=6, 23.7 ± 3.7 years, 4 female), or yogic breathing (SPB+M, N=7, 24.3 ± 3.1 years). Participants completed two weeks of daily sleep logs along with the Pittsburgh Sleep Quality Index (PSQI) prior to a virtual laboratory visit, which consisted of a 60-min intervention-specific training, including a 20-min guided practice, and subsequent tasks including experimental stress induction. Participants were then instructed to repeat their assigned intervention practice daily, selecting either the same or a similar guided audio as their initial training. After an initial video check-in appointment, participants received regular visual feedback of their data and completed weekly check-ins with the study team to improve adherence. At the end of the intervention period, participants again completed daily sleep logs and the PSQI, in addition to other outcome measures and a virtual laboratory visit. Data were analyzed using linear mixed models.

Results

Sleep log adherence was over 90% in all three groups. The groups were successfully distinguishable based on HRV-derived breathing and mindfulness ratings. For the SBP+M group only, there was a trend of reduced sleep onset latency (SOL, p=.093) and a significant increase in sleep efficiency (SE, p=.025). There were no significant changes in PSQI or other sleep log measures. More detailed analysis of timecourse across these measures is ongoing.

Conclusion

These findings support feasibility for a fully remote, semi-automated clinical trial study assessing component-specific effects of these MBIs on sleep in generally healthy young adults. Research evaluating MBIs for sleep in both clinical and nonclinical populations would benefit from similar study designs to examine intervention-specific components while increasing both scalability and quality control.

Support (If Any)

Pilot Research Grant, Osher Center for Integrative Medicine of Harvard Medical School and Brigham & Women’s Hospital; National Institutes of Health (5T32HL007901-22)

0103 Feasibility of examining component-specific effects of yogic breathing on heart rate variability during sleep: A three-arm pilot RCT

Introduction

Wearable devices and mind-body interventions (MBIs) continue to receive widespread interest as tools for improving sleep. This study investigated the feasibility of using an automated electronic survey system and wearable heart rate (HR) monitor in the context of a fully remote clinical trial study to produce detailed measures of participant adherence, daily sleep quality, and associations with physiological outcomes captured by wearable devices.

Methods

Eighteen healthy participants (age 18-30yrs, 12 female) were randomized to one of three 8-week long interventions: slow-paced breathing (SPB, N=5, 24.6 ± 2.1 years, 4 female), mindfulness (M, N=6, 23.7 ± 3.7 years, 4 female), or yogic breathing (SPB+M, N=7, 24.3 ± 3.1 years). Participants completed two weeks of daily sleep logs prior to a virtual laboratory visit, consisting of a 60-min intervention-specific training with 20-min guided practice, and subsequent tasks including experimental stress induction. Participants started a 24-hour HR recording using a Polar H10 chest strap on the night prior. Then, participants were instructed to repeat their assigned intervention practice daily, using a guided audio similar to their initial training, while concurrently recording HR data and completing a detailed practice log. HR interbeat interval data were examined with spectral analysis using full spectrograms for inspection of timecourse and frequency-specific patterns in both the nocturnal recordings and daily practice sessions.

Results

Participants completed an average of 75% of daily practice sessions across the 8-week intervention period (SPB: 77%, M: 65%, SPB+M: 77%). An automated procedure was developed to analyze and visualize the timecourse of HRV-derived breathing patterns in the 754 completed practice sessions and 36 nocturnal recordings. The three groups were then successfully distinguishable based on breathing rates and mindfulness questionnaires. Nocturnal HR recordings demonstrated visually identifiable patterns of interindividual variability and intraindividual consistency. Statistical analysis is ongoing to further characterize these patterns.

Conclusion

These findings support feasibility for a fully remote, semi-automated clinical trial study assessing component-specific effects of these MBIs on sleep, including detailed spectral analysis of high-quality HR data. Future studies would benefit from examining scalability of this type of study design with wearable physiology in both clinical and nonclinical populations.

Support (If Any)

Pilot Research Grant, Osher Center for Integrative Medicine of Harvard Medical School and Brigham & Women’s Hospital; National Institutes of Health (5T32HL007901-22)

0287 Effects of Sleep Restriction and Recovery on the Capacity of Glucocorticoids to Inhibit Inflammatory Marker Expression in Human Monocytes

Introduction

Chronic low-grade systemic inflammation is involved in the pathogenesis of many human diseases. Common sleep patterns of restricting sleep during weekdays and catching up on sleep over the weekend induce inflammatory upregulation that may not resolve following weekend recovery sleep. We hypothesize that this sleep pattern leads to an inflammatory imbalance of markers regulating inflammatory homeostasis, including inflammatory markers (eg, interleukin-6 (IL-6) and cyclooxygenase 2 (COX-2)) and markers of counter-inflammation (eg, glucocorticoids (GCs)). The enzyme COX-2 is involved in prostaglandin synthesis and is the target of pain-relieving nonsteroidal anti-inflammatory drugs (NSAIDs). GCs are used in the treatment of many inflammatory diseases, including severe acute infection with SARS-CoV-2. We investigated if sleep restriction impairs the capacity of GCs to inhibit inflammatory COX-2 expression in a preliminary dataset.

Methods

The present preliminary dataset (N=6, 2F/4M) derives from an ongoing randomized controlled within-subjects trial consisting of three 11-day in-hospital protocols (2 restricted sleep arms, 1 control sleep arm). The ongoing study is blinded for administration of placebo or aspirin under sleep restriction. Under restricted sleep conditions, 2 nights of baseline sleep (8h/night) were followed by 5 nights of restricted sleep (4h/night), concluding with 3 nights of recovery sleep (8h/night). In the control condition, participants could sleep 8h/night throughout the entire protocol. Blood samples were taken after baseline sleep, after 5 nights of restricted or control sleep, and after 2 nights of recovery sleep. Data were analyzed using generalized linear mixed models.

Results

Sleep restriction was associated with decreased capacity of GCs to inhibit COX-2 expression in monocytes (p<.01) and has the expected inflammatory effect on IL-6 production in monocytes (p<.01). Moreover, sleep restriction has lasting inflammatory effects as shown in increased inflammation following 2 nights of recovery sleep (p<.01).

Conclusion

In conclusion, the present preliminary analysis suggests that in patients treated with GCs, sleep restriction potentially reduces their effectiveness in controlling inflammation, thus contributing to increased inflammation-related morbidity. Sample collection and data analysis is ongoing.

Support (If Any)

NIH/NHLBI R01-HL136310; NIH/NCRR UL1-RR02758, M01-RR01032; German Research Foundation (DFG) EN1291/1-1.

Abstract P207: Sleep Hygiene As An Intervention To Improve Autonomic Function

Introduction: Insufficient sleep is associated with increased heart rate (HR) and blood pressure (BP). Exaggerated cardiovascular reactivity to the cold pressor test (CPT) has been linked to an increased incidence of hypertension. This project investigates the effects of improved sleep hygiene on autonomic function at rest and in response to CPT. We hypothesize a decrease in BP and HR at rest, and attenuated BP and HR response during CPT.

Methods: Fifty participants (59.8 ± 1.5 years; 31 women) completed 3 overnight in-hospital stays in which they had continuous ECG and beat-to-beat BP monitoring. The first stay (S1) was a baseline control; the second stay (S2) was a 4-week wait-list control; the third stay (S3) followed an 8-week randomly assigned intervention that used sleep hygiene approaches along with scheduling to either A) stabilize sleep timing, or B) stabilize and extend the bed period. This study is still ongoing, so we are blind to the specific arm that the participants were randomized to. During each stay, autonomic testing was performed about four hours after the participant awoke, including a 5-minute resting period where breathing was controlled (BL), a 3-minute resting period where breathing was not controlled (CPT BL), and 2-minute CPT when participants then submerged their hand in 3°C water. Linear mixed models analyzing the changes in HR and systolic BP (SBP) across the three stays were used.

Results: During the 5-minute BL, HR did not significantly decrease from S1 to S2 (p=.310) but did significantly decrease by 2 bpm from S2 to S3 (p=.006). SBP decreased by 7 mmHg from S1 to S2 (p=.022) but did not significantly decrease from S2 to S3 (p=.907). During CPT in all stays, HR and SBP significantly increased compared to CPT BL (p<0.05). There was a significant stay x test interaction effect in HR (interaction, p=.042), but not in SBP (interaction p=.361).

Conclusion: While we are still blind to condition, both arms actively improve sleep hygiene. These preliminary data suggest that stabilization of sleep timing and possibly duration, has a positive impact on autonomic function as seen through the decreases in HR at rest and during CPT.

Abstract P208: Raas And Markers Of Renal Function In Response To Sleep Hygiene Interventions

Introduction: Recent epidemiologic studies report that shorter sleep duration is associated with a rapid decline in renal function. This project investigated the effects of 8 weeks of sleep hygiene interventions on the renin-angiotensin-aldosterone system (RAAS) regulation and markers of renal function. Accumulating evidence suggests that sleep plays an important role in blood pressure (BP) regulation. While BP is influenced by renal function, it is not known if improving sleep hygiene may support regulation of the RAAS.

Methods: Fifty participants (59.8 ± 1.5 years; 31 women) completed 3 overnight in-hospital stays: baseline (S1), pre-intervention (S2) following a 4-week wait-list evaluation phase from S1 and post-intervention (S3). During S2, participants with elevated BP (BP>120/80 to <160/100) were randomly assigned to two sleep hygiene conditions where in both conditions, the sleep period was stabilized, but in one it was also lengthened. As the study is still ongoing, we remain blind to which condition participants were randomized to. Morning and evening plasma renin activity (PRA), urinary albumin, creatinine, and serum cystatin C levels were measured from all three stays. Albumin-to-creatinine ratio (ACR) and estimated glomerulus filtration rate (eGFR) were calculated.

Results: There was a significant decrease of night PRA at post-intervention (S3) compared to S2 (p<0.05) and S1 (p<0.05). However, morning PRA did not show any changes throughout the stays (p=0.3). The urinary ACR obtained from evening urine samples did not show significant changes (p=0.66). In addition, serum cystatin C levels measured from evening blood draws and the eGFR did not show significant changes (p=0.21 and p=0.18, respectively).

Conclusion: The sleep hygiene approach to improving sleep was associated with blunted PRA levels in the evening. When unblinded we will report on whether increasing the sleep period was more effective than stabilizing circadian placement of sleep, alone.

125 Increased plasma renin activity during wake in a repetitive sleep restriction protocol

Introduction

Insufficient sleep is associated with an increased risk of hypertension. It is well established that long-term BP regulation is modulated by the renin-angiotensin-aldosterone system (RAAS) and chronic kidney disease is a strong independent risk factor for development of cardiovascular disease. This study investigated the biomarkers of RAAS and renal function during repetitive exposures to controlled, experimental sleep restriction (SR). We hypothesized an upregulation of RAAS and increased markers of impaired renal function.

Methods

Twenty-one healthy participants (11 women, average age 31±2 years) completed the 22-day in-hospital SR protocol: permitted 4h of sleep/night from 0300-0700 for 3 nights followed by a recovery sleep, repeated 4 times. Blood samples were collected and plasma renin activity (PRA) was assessed in the morning (7:05am) and in the evening before bedtime (22:45pm) at baseline, experimental days (3rd day of each of the 4 blocks), and recovery. Urinary albumin to creatinine ratio (ACR) was measured from 24-h urinary collection at baseline, first and fourth SR blocks. Estimated glomerulus filtration rate (eGFR) was calculated based on the serum cystatin C levels at baseline and last block of SR.

Results

Percent change of evening PRA significantly increased during 4 blocks of SR and recovery (SR effect p=0.039), but not morning PRA (SR effect p=0.34). Specifically, evening PRA increased up to 98.4% in the first (p&lt;0.01), 61.3% in the second (p=0.04) SR blocks, and 57.5% (p=0.05) in recovery. Urinary ACR showed no significant changes during first or fourth SR blocks (SR effect p=0.28). In addition, eGFR did not change in the fourth SR block compared to BL (paired t-test, p=0.27).

Conclusion

We did not see increased markers of impaired renal function (ACR or eGFR). Rather, short-term repetitive exposures to SR significantly increased percent change of PRA measured before bedtime, and evening PRA did not return to BL level during recovery. Our results suggested that sleep deficiency may contribute to hypertension through upregulation of RAAS during wake time.

Support (if any)

SRSF (CDA to Huan Yang), NIH (R01HL106782 to Dr. Janet Mullington), Harvard Catalyst, Harvard Clinical and Translational Science Center (UL1TR001102).

072 Sleep Spindle Harmonics in Insomnia

Introduction

Prior research has reported NREM spectral EEG differences between individuals with insomnia and good-sleeper controls, including elevated high-frequency EEG power (beta/gamma bands, ~16-50Hz) and, to a lesser extent, elevations in sleep spindle parameters. However, the mechanisms driving these differences remain unclear. Harmonics have been observed in EEG data as spectral peaks at multiples of a fundamental frequency associated with an event (e.g., for a 14Hz spindle, the 2nd harmonic is expected to be a peak at 28Hz). Thus far, there has been very limited application of this idea of spectral harmonics to sleep spindles, even though these patterns can indeed be seen in some existing literature. We sought to build on this literature to apply spectral harmonic analysis to better understand differences between insomnia and good sleepers.

Methods

15 individuals with insomnia disorder (DSM-5 criteria, 13 female, age 18–32 years) and 15 good-sleeper controls (matched for sex, age, and BMI) completed an overnight polysomnography recording in the laboratory and subsequent daytime testing. Insomnia diagnosis was determined by a board-certified sleep specialist, and exclusion criteria included psychiatric history within past 6 months, other sleep disorders, significant medical conditions, and medications with significant effects on inflammation, autonomic function, or other psychotropic effects.

Results

Consistent with prior studies, we found elevated sleep spindle density and fast sigma power (14-16Hz). Despite no difference in beta or gamma band power when averaged across NREM sleep, time-frequency analysis centered on the peaks of detected spindles revealed a phasic elevation in spectral power surrounding the 28Hz harmonic peak in the insomnia group, especially for spindles coupled with slow waves. We also observed an overall pattern of time-locked delay in the 28Hz harmonic peak, occurring approximately 40 msec after spindle peaks. Furthermore, we observed a 42Hz ‘3rd harmonic’ peak, not yet predicted by the existing modeling work, which was also elevated for insomnia.

Conclusion

In conjunction with existing mathematical modeling work that has linked sleep spindle harmonic peaks with thalamic relay nuclei as the primary generators of this EEG signature, these findings may enable novel insights into specific thalamocortical mechanisms of insomnia and non-restorative sleep.

Support (if any)

NIH 5T32HL007901-22

061 Sleep Hygiene as an Intervention to Lower Blood Pressure

Introduction

Insufficient sleep has been shown to increase the risk of a person developing hypertension. Impaired baroreflex sensitivity (BRS) is one of the known underlying mechanisms involved that is responsible for increasing blood pressure (BP). This project investigates the relationship between sleep, BRS, and BP during Valsalva’s Maneuver (VM).

Methods

Fifty participants (59.8 ± 1.5 years; 31 women) completed 3 overnight in-hospital stays. The first stay (S1) was a baseline control; the second stay (S2) followed a 4-week wait-list control condition; the third stay (S3) followed an 8-week randomly assigned intervention that used sleep hygiene approaches and scheduling to either A) stabilize sleep timing, or B) stabilize and extend the bed period. The study is still ongoing, and we are blind to whether participants were randomized to arm A or B of the study. A linear regression model analyzing the R-R Interval (RRI) and corresponding systolic BP was used to calculate the BRS function and the maximum change in SBP (BPMax) during Early Phase II (EPII) of VM.

Results

There was an increasing BRS trend across the three stays during EPII (p=.051). There was no significant increase between S1 and S2 (p=.876), but BRS significantly increased following 8 weeks of intervention at S3 compared to S1 (p=0.033) and S2 (p=0.037). There was also a significant decrease in BPMax across the three stays during EPII (p&lt;.001). There was no significant decrease in EPII BPMax between S1 and S2 (p=.325), but BPMax significantly decreased in S3 compared to S1 (p&lt;0.001) and S2 (p=0.002).

Conclusion

While we are still blind to condition, both conditions are considered active as they both involve stabilizing the sleep period using sleep hygiene. These preliminary data suggest that stabilization of sleep timing and possibly duration, has a positive impact on BP regulation.

Support (if any)

NIH (R01HL125379 to Dr. Janet Mullington), Harvard Catalyst, Harvard Clinical and Translational Science Center (UL1TR001102).

129 Greater NREM Sleep Rebound in Response to Experimental Sleep Disturbance Associated with Higher Inflammatory Resolution in Humans

Introduction

Sleep disturbances deteriorate immune function by not only affecting pro-inflammatory pathways, but also inflammatory resolution pathways, which actively terminate inflammation. It is assumed that slow wave sleep (SWS) amount and slow wave activity (SWA) convey the immune-supportive functions of sleep. We investigated whether changes in SWS induced by experimental sleep disturbance followed by recovery sleep predict changes in inflammatory resolution mediators.

Methods

The randomized controlled within-subjects trial (N=24, 20-42 years, 12 women) consisted of two 19-day in-hospital protocols (experimental sleep disturbance/control). After three nights of baseline sleep (8h/night), participants in the experimental sleep disturbance condition were exposed to three cycles of three nights of disturbed sleep (delayed sleep-onset, hourly sleep disruption, advanced sleep-offset) followed by one night of 8h-recovery sleep. The protocol ended with three nights of recovery sleep. In the control condition, participants had uninterrupted sleep (8h/night). Sleep (PSG) and resolvin lipid mediators in plasma (1100h, LC-MS/MS) were assessed at baseline, during the last cycle of sleep disturbance, and during/after the first and third night of final recovery sleep. Data were analyzed using generalized linear mixed models and Pearson/Spearman correlations.

Results

As expected, SWS amount decreased during experimental sleep disturbance and increased during the first recovery sleep night (p&lt;.001). Similarly, resolvin (Rv) D2 and RvD3 decreased during sleep disturbance and RvD2 increased with subsequent recovery sleep (p&lt;.001). The SWS response did not correlate with the resolvin response to sleep disturbance or to recovery sleep. However, the NREM sleep response correlated with the resolvin response during the third recovery sleep night, i.e., a greater NREM response was associated with a greater RvD2 and RvD3 response (r=.68, p=.002; r=.58, p=.012). In contrast, a greater REM sleep response was associated with a lower resolvin response (r=−.63, p=.005; r=−.66, p=.003).

Conclusion

These data suggest that during recovery from sleep disturbance, NREM rather than REM sleep promotes inflammatory resolution, thereby acting as the sleep state that protects against low-grade systemic inflammation, which has been frequently observed as a consequence of sleep disturbances. Analysis whether SWA is related to inflammatory resolution is in progress.

Support (if any)

NIH/NINDS R01-NS091177; NIH/NCRR UL1-RR02758, M01-RR01032; German Research Foundation (DFG) EN1291/1-1.

Abstract P017: Increased Sodium Excretion And Urinary Output During Acute Human Sleep Deprivation

Introduction: Insufficient sleep contributes to an increased risk (e.g. ~60%) of hypertension. While BP is influenced by renal regulation of sodium and water, the underlying mechanism involved the modulation of renin-angiotensin-aldosterone-system (RAAS) by sleep deprivation is unknown. This project investigated the RAAS regulation of water and salt balance (e.g. urine output, sodium excretion) during prolonged sleep deprivation in humans.

Methods: Twenty-six subjects (35±1 yrs; 9 women) completed a highly controlled 7-day in hospital study. They were randomly assigned to an 88-h total sleep deprivation (TSD; N=17) condition or an 8-h/night sleep control (SC; N=9) condition. Twenty-four-hour urinary output was collected from baseline (Day 2) to recovery (Day 7). Water and sodium intake were controlled and data were collected. The 24-h sodium excretion value (mmol) was calculated by multiplying the concentrations of sodium in the urine by the urinary volume. Frequent blood samples were collected throughout the experimental period in this study.

Results: There was a significant interaction effect of TSD on sodium excretion and urinary output (condition x day, p<0.05). Both TSD and SC groups showed continuous increases in sodium excretion during experimental period compared to baseline (p<0.05). The increases in TSD were significantly higher compared to SC (condition x day, p<0.05). In addition, there was a dose dependent effect of TSD on sodium excretion (i.e. p<0.05 for 48-h TSD compared to 24-h TSD). Diet and fluid intake were controlled and there was no interaction effect for TSD on 24-h water intake or oral sodium intake (condition x day, p>0.05). Urinary output significantly increased from baseline, to 24-h and 72-h (p<0.05) during TSD, but remained at baseline levels throughout days in SC group. Preliminary plasma renin activity analyses (assays ongoing) showed a decreasing statistical trend during TSD compared to baseline (p=0.058).

Conclusion: Prolonged TSD significantly increases sodium excretion and urinary output from the body compared to control group, despite similar water and sodium intake levels between two groups. In addition, the increases of sodium excretion are also dose dependent during TSD.

0058 Effects of Acute Total Sleep Deprivation on Human Plasma N-glycans

Introduction

There is a need for a novel biomarker that can be used to measure sleep sufficiency as it pertains to fitness for duty. As glycans (polysaccharides) are known to be involved in modifying protein effectiveness, we are exploring these as biomarkers that may be sensitive to differences between sleep deprivation and normal healthy adult sleep duration. We have measured one major class of glycans, called N-glycans, which are covalently linked to asparagine residues of polypeptide chains of membrane-bound and secreted proteins. We compared the plasma N-glycan profiles of participants before and after they participated in a total sleep deprivation protocol.

Methods

10 healthy participants (6 male, 4 female) aged 30–44 went through 88 hours of total sleep deprivation. Hourly blood draws were taken via forearm catheter throughout the protocol. N-glycan analysis was performed using plasma samples collected at 17:35 prior to the first night of sleep deprivation and at 17:35 following 82.5 hours of continuous wakefulness. N-glycans were first cleaved from peptides and isolated from plasma, and profiles were then measured using Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) mass spectrometry.

Results

66 N-glycans were observed in our profiles. Of these, the relative abundance of 17 N-glycans were significantly different following sleep deprivation (paired t-test, 13 with p&lt;0.05, 4 with p&lt;0.01). In each case, the relative abundance was lower in the sleep deprivation time point. We found two structures, Hex6HexNAc5NeuAc3 and Hex7HexNAc6NeuAc2, which were also significant in one of our previous chronic sleep restriction protocols.

Conclusion

While we observed that many N-glycans decreased in relative abundance, it is unclear whether these changes represent a shift in glycan synthesis or result from decreased expression of the proteins they are bound to. Our next steps involve exploring the functions of the proteins associated with Hex6HexNAc5NeuAc3 and Hex7HexNAc6NeuAc2, and measuring their expression levels.

Support

NIH/HL75501; NIH/National Center for Research Resources UL1-RR02758 and M01-RR01032 to the Harvard Clinical and Translational Science Center.

High School Start Times and the Impact on High School Students: What We Know, and What We Hope to Learn

STUDY OBJECTIVES

Several organizations have provided recommendations to ensure high school starts no sooner than 08:30. However, although there are plausible biological reasons to support such recommendations, published recommendations have been based largely on expert opinion and a few observational studies. We sought to perform a critical review of published evidence regarding the effect of high school start times on sleep and other relevant outcomes.

METHODS

We performed a broad literature search to identify 287 candidate publications for inclusion in our review, which focused on studies offering direct comparison of sleep time, academic or physical performance, behavioral health measures, or motor vehicular accidents in high school students. Where possible, outcomes were combined for meta-analysis.

RESULTS

After application of study criteria, only 18 studies were suitable for review. Eight studies were amenable to meta-analysis for some outcomes. We found that later school start times, particularly when compared with start times more than 60 min earlier, are associated with longer weekday sleep durations, lower weekday-weekend sleep duration differences, reduced vehicular accident rates, and reduced subjective daytime sleepiness. Improvement in academic performance and behavioral issues is less established.

CONCLUSIONS

The literature regarding effect of school start time delays on important aspects of high school life suggests some salutary effects, but often the evidence is indirect, imprecise, or derived from cohorts of convenience, making the overall quality of evidence weak or very weak. This review highlights a need for higher-quality data upon which to base important and complex public health decisions.

Repeating patterns of sleep restriction and recovery: Do we get used to it?

Despite its prevalence in modern society, little is known about the long-term impact of restricting sleep during the week and 'catching up' on weekends. This common sleep pattern was experimentally modeled with three weeks of 5 nights of sleep restricted to 4h followed by two nights of 8-h recovery sleep. In an intra-individual design, 14 healthy adults completed both the sleep restriction and an 8-h control condition, and the subjective impact and the effects on physiological markers of stress (cortisol, the inflammatory marker IL-6, glucocorticoid receptor sensitivity) were assessed. Sleep restriction was not perceived to be subjectively stressful and some degree of resilience or resistance to the effects of sleep restriction was observed in subjective domains. In contrast, physiological stress response systems remain activated with repeated exposures to sleep restriction and limited recovery opportunity. Morning IL-6 expression in monocytes was significantly increased during week 2 and 3 of sleep restriction, and remained increased after recovery sleep in week 2 (p<0.05) and week 3 (p<0.09). Serum cortisol showed a significantly dysregulated 24h-rhythm during weeks 1, 2, and 3 of sleep restriction, with elevated morning cortisol, and decreased cortisol in the second half of the night. Glucocorticoid sensitivity of monocytes was increased, rather than decreased, during the sleep restriction and sleep recovery portion of each week. These results suggest a disrupted interplay between the hypothalamic-pituitary-adrenal and inflammatory systems in the context of repeated exposure to sleep restriction and recovery. The observed dissociation between subjective and physiological responses may help explain why many individuals continue with the behavior pattern of restricting and recovering sleep over long time periods, despite a cumulative deleterious physiological effect.

Short-term exenatide treatment leads to significant weight loss in a subset of obese women without diabetes

OBJECTIVE

To investigate the effect of treatment with the glucagon-like peptide 1 receptor agonist exenatide on weight loss and metabolic parameters in obese nondiabetic women.

RESEARCH DESIGN AND METHODS

Forty-one obese women (aged 48 ± 11 years and BMI 33.1 ± 4.1 kg/m(2)) participated in a 35-week randomized, double-blind, placebo-controlled, crossover study, including two 16-week treatment periods separated by a 3-week washout period. There was no lifestyle intervention. The primary outcome was change in body weight.

RESULTS

Subjects treated with exenatide lost an average of 2.49 ± 0.66 kg compared with a 0.43 ± 0.63 kg weight gain during placebo treatment. Weight loss with exenatide treatment was noted at 2 weeks. The degree of weight loss could be stratified. A total of 30% of subjects were high responders who lost ≥5% body weight (-7.96 ± 0.52%), 39% were moderate responders who lost <5% body weight (-2.43 ± 0.45%), and 31% were nonresponders who gained weight (1.93 ± 0.53%). Waist circumference also decreased significantly with exenatide treatment. Subjects experienced more nausea during exenatide treatment compared with placebo, but the severity decreased over time and did not correlate with weight loss.

CONCLUSIONS

Short-term exenatide treatment was associated with modest weight loss and decreased waist circumference in a cohort of obese nondiabetic women. A subset of individuals demonstrated robust weight loss that was detected very early in the course of treatment.

[Experimental studies on the interaction between sleep and the immune system in humans]

Sleepiness and increased sleep pressure are typical symptoms of inflammation and infection. Moreover, it is a pre-scientific belief that sleep supports host defense. The present paper summarizes the experimental evidence regarding the interaction between sleep and the immune system in humans. Sleep-wake behavior is very sensitive to experimental host defense activation, for example, by bacterial endotoxin. When the injection of endotoxin is accompanied by fever and a prominent neuroendocrine activation, sleep continuity will be disturbed. When the production of inflammatory cytokines is stimulated by smaller amounts of endotoxin, but no fever and no neuroendocrine activation are apparent, the nonREM-sleep amount will increase. This is possibly due to changes in the biological activity of the tumor necrosis factor-alpha (TNF-alpha) system. Besides their important function in sleep regulation during acute immune response, cytokines also seem to be involved in physiological sleep regulation, although there still is not very much data on this issue. So far, it remains largely unknown whether or not sleep supports host defense. In humans, for example, acute sleep deprivation up to 55 hours has only minor effects on endotoxin-induced host responses. In contrast, there is preliminary and yet inconsistent evidence that sleep deprivation might impair antibody formation in response to viral challenges.

The endotoxin-induced increase of cytokines is followed by an increase of cortisol relative to dehydroepiandrosterone (DHEA) in healthy male subjects

Dehydroepiandrosterone (DHEA) and DHEA sulphate (DHEAS) inhibit T-helper lymphocyte type 2 immune reactions and exert anti-inflammatory effects in some chronic inflammatory diseases. Both DHEA and, in particular, DHEAS levels are dramatically decreased in chronic inflammatory diseases whereas cortisol levels remain stable or are elevated. However, the time course of cortisol relative to DHEA production is not known. We tested whether administration of endotoxin to healthy male subjects can induce an early predominance of cortisol relative to DHEA and DHEAS. It is demonstrated that endotoxin induces a dose-dependent increase of cortisol in relation to DHEA (no effect at 0.2 ng endotoxin/kg body weight (b.w.), clear effect at 0.4 and 0.8 ng/kg b.w., p<0.05) and DHEAS (tested at 0.4 ng/kg b.w., P=0.014). The increase of cortisol relative to DHEA appears 4 h after endotoxin injection and 2 h after a strong increase of interleukin (IL)-6 relative to tumour necrosis factor (TNF). In addition, an increase of cortisol relative to 17OH-progesterone was observed. The ratio of serum IL-6/TNF was positively correlated with the ratio of serum cortisol/DHEA (R(Rank)=0.472, P=0.041) and serum cortisol/17OH-progesterone (R(Rank)=0.514, P=0.048). In conclusion, dissociation of cortisol relative to DHEA, DHEAS or 17OH-progesterone appears very early during a systemic inflammatory response which is associated with an increase of IL-6 relative to TNF. As in chronic inflammatory diseases, during an acute inflammatory response with endotoxin, these physiological hormone changes are probably necessary to achieve adequate cortisol levels at the expense of adrenal androgens.

Impaired circadian waking arousal in narcolepsy-cataplexy

The 24-hour sleep/wake distributions of untreated patients with narcolepsy-cataplexy and matched normal habitual nappers were compared using home ambulatory monitoring. Subjects followed their usual sleep patterns including, for the habitual nappers, a self-selected daytime nap. There were no differences in 24-hour totals of sleep between groups other than a small increase in SWS in narcolepsy. Narcolepsy showed greater amounts of day sleep (stages 2, SWS, REM and total sleep) and less night sleep (stage 2, total sleep). Data were collapsed into 5 min epochs and entered into a matrix. The data in the two groups were then "wrapped" (re-aligned) around the 24 hours with phase 0 as each of the times of: evening sleep onset, onset of SWS, mid-point of night sleep and moment of morning awakening. In habitual nappers alignment beginning at morning wake-up produced the highest amplitude, least temporal dispersion and greatest kurtosis of daytime sleep (naps). The 24-hour sleep/wake distribution curves of both subject groups (data aligned at morning wake-up) based on collapsed data into 5 min bins then underwent curve fitting using 15th order polynomial regression. As with visual analyses of the raw data, the curve fits confirmed that the peak in daytime sleep propensity in narcoleptics was earlier by about 40 (2.66 hours). It was concluded that decreased daytime amplitude of a circadian arousal system was the most parsimonious explanation for the increased amount, broader temporal distribution and relative phase advance of day sleep in narcolepsy and that, as well, such a mechanism could explain a number of other features of the disease.

Experimental immunomodulation, sleep, and sleepiness in humans

Infection, inflammation, and autoimmune processes are accompanied by serious disturbances of well-being, psychosocial functioning, cognitive performance, and behavior. Here we review those studies that have investigated the effects of experimental immunomodulation on sleep and sleepiness in humans. In most of these studies bacterial endotoxin was injected intravenously to model numerous aspects of infection including the release of inflammatory cytokines. These studies show that human sleep-wake behavior is very sensitive to host defense activation. Small amounts of endotoxin, which affect neither body temperature nor neuroendocrine systems but slightly stimulate the secretion of inflammatory cytokines, promote non-rapid-eye-movement sleep amount and intensity. Febrile host responses, in contrast, go along with prominent sleep disturbances. According to present knowledge tumor necrosis factor-alpha (TNF-alpha) is most probably a key mediator of these effects, although it is likely that disturbed sleep during febrile host responses involves endocrine systems as well. There is preliminary evidence from human studies suggesting that inflammatory cytokines such as TNF-alpha not only mediate altered sleep-wake behavior during infections, but in addition are involved in physiological sleep regulation and in hypnotic effects of established sedating drugs.

Changes in dehydroepiandrosterone (DHEA) and DHEA-sulfate plasma levels during experimental endotoxinemia in healthy volunteers

Dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEA-S) have immunomodulatory effects in vitro and in vivo. Additionally, their plasma levels are altered during chronic infection and inflammation. However, it remains unknown whether these steroids are involved in early host responses to infection in humans. We examined DHEA and DHEA-S levels during experimental endotoxinemia, a well established pathophysiological model of bacterial infections in humans. Purified Salmonella abortus equi endotoxin (0.2, 0.4, or 0.8 ng/kg body weight) was injected in a single-blind, placebo-controlled experiment to 17 healthy male volunteers. During the following 12 h, rectal temperature and the plasma levels of ACTH, cortisol, DHEA, DHEA-S, interleukin 6, and tumor necrosis factor alpha were determined. Confirming earlier studies, temperature and cytokine levels showed monophasic, dose-dependent increases in response to endotoxin. In contrast, endocrinological effects of endotoxin showed a complex, biphasic pattern: cortisol levels were not affected by 0. 2 ng/kg but significantly increased during the first 6 h following 0. 4 and 0.8 ng/kg endotoxin, whereas ACTH and DHEA levels were significantly enhanced during the first 6 h following 0.8 ng/kg only. ACTH, DHEA, and cortisol secretion was blunted 6-12 h following 0.8 ng/kg. DHEA-S levels were unaffected during the first 6 h following all dosages, but between 6-12 h after injection they were significantly increased following 0.2 ng/kg, unaffected by 0.4 ng/kg, and significantly decreased following 0.8 ng/kg endotoxin. The present results suggest that similarly to glucocorticoids, the adrenal androgens DHEA and DHEA-S play an important role during early host responses to bacterial infections in humans.

Dose-dependent effects of endotoxin on human sleep

The role of the central nervous system in the host response to infection and inflammation and modulation of these responses by the hypothalamic-pituitary-adrenal system are well established. In animals, activation of host defense mechanisms increases non-rapid eye movement (NREM) sleep amount and intensity, which, in turn, are thought to support host defense, or the body's ability to defend itself against challenges to its immune system. In humans, the evidence is conflicting. Therefore, we investigated the effects of three placebo-controlled doses of endotoxin on host response, including nocturnal sleep in healthy volunteers. Administered before nocturnal sleep onset, endotoxin dose dependently increased rectal temperature, heart rate, and the plasma levels of tumor necrosis factor (TNF)-alpha, soluble TNF receptors, interleukin (IL)-1 receptor antagonist, IL-6, and cortisol. The lowest dose reliably increased circulating levels of cytokines and soluble cytokine receptors, but it did not affect rectal temperature, heart rate, or cortisol. This subtle host defense activation increased deep NREM sleep amount, often referred to as slow-wave sleep (stages 3 and 4), and intensity (delta power). Conversely, the highest dose of endotoxin disrupted sleep. Whereas it is well established that the endocrine and thermoregulatory systems are very sensitive to endotoxin, this study shows that human sleep-wake behavior is even more sensitive to activation of host defense mechanisms.

Effects of granulocyte colony-stimulating factor on night sleep in humans

Numerous animal studies suggest that cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) mediate increased sleep amount and intensity observed during infection and are, moreover, involved in physiological sleep regulation. In humans the role of cytokines in sleep-wake regulation is largely unknown. In a single-blind, placebo-controlled study, we investigated the effects of granulocyte colony-stimulating factor (G-CSF, 300 microgram sc) on the plasma levels of cytokines, soluble cytokine receptors, and hormones as well as on night sleep. G-CSF did not affect rectal temperature or the plasma levels of cortisol and growth hormone but did induce increases in the plasma levels of IL-1 receptor antagonist and both soluble TNF receptors within 2 h after injection. In parallel, the amount of slow-wave sleep and electroencephalographic delta power were reduced, indicating a lowered sleep intensity. We conclude that G-CSF suppresses sleep intensity via increased circulating amounts of endogenous antagonists of IL-1beta and TNF-alpha activity, suggesting that these cytokines are involved in human sleep regulation.

Effects of clozapine on in vitro immune parameters: a longitudinal study in clozapine-treated schizophrenic patients

Clozapine is an atypical antipsychotic agent with immunomodulatory properties. We hypothesized that in vitro immune parameters of peripheral blood mononuclear cells (PBMC) are affected in the course of clozapine treatment and that clozapine per se, added in vitro to PBMC cultures of clozapine-treated patients, exerts differential effects in the timecourse of treatment in vivo. We measured proliferation and cytokine secretion of PBMC, serum autoantibodies, and immunoglobulin levels in 17 patients before and during the first 6 weeks of clozapine treatment. Independent of clozapine dosage and rectal temperature, clozapine treatment in vivo suppressed proliferation and shedding of sIL-2r by PBMC, and the addition of clozapine in vitro induced, relative to unstimulated conditions, PBMC proliferation and secretion of IL-6 and sIL-2r. Serum IgG levels were increased; whereas, autoantibody pattern was unaffected. Thus, clozapine treatment and the addition of clozapine in vitro exert differential effects on various in vitro immune parameters independent of clozapine dosage and rectal temperature in the course of treatment.

Endotoxin-induced changes in sleep and sleepiness during the day

Sleepiness is a common symptom of infectious diseases. However, the peculiarities and causes of impaired vigilance during host defense activation are largely unknown. It has been shown earlier that mild host defense activation by endotoxin does not affect daytime sleepiness and non-rapid eye movement (NREM) sleep in humans. In the present study we investigated the effects of a more intensive stimulation of the host defense by Salmonella abortus equi endotoxin (0.8 ng/kg), administered 12 h following host response priming by granulocyte colony-stimulating factor (300 micrograms s.c.), on daytime sleep and sleepiness in a placebo-controlled design in ten healthy men. Six equidistant polysomnographically monitored naps were scheduled across the day and the time course of subjective sleepiness was assessed. Endotoxin induced prominent increases in rectal temperature, and in the plasma levels of tumor necrosis factor-alpha, interleukin-6, interleukin-1 receptor antagonist, and cortisol. In the first nap, 1 h following endotoxin administration, total sleep time and NREM sleep stage 2 were reduced, whereas wakefulness and sleep onset latency were increased. Following this nap sleepiness transiently increased peaking prior to the second nap. However, this nap and the following ones were not influenced by endotoxin. These results suggest that prominent host defense activation reduces daytime NREM sleep and increases sleepiness. One cause of daytime sleepiness during infections may be prior sleep disruption and this kind of sleepiness may not necessarily be associated with an increased sleep pressure.

In vivo and in vitro immune variables in patients with narcolepsy and HLA-DR2 matched controls

We investigated cytokine levels (interleukin [IL]-1beta, IL-1ra, IL-2, IL-6, tumor necrosis factor [TNF]-alpha, TNF-beta) in plasma and secreted by mitogen-stimulated blood monocytes and lymphocytes; T-cell subsets; and natural killer cell activity in patients with narcolepsy and in human leukocyte antigen (HLA)-DR2 matched controls. The only significant finding was higher IL-6 secretion by monocytes of patients than by those of the HLA-DR2-positive controls. In conclusion, we found no major abnormalities of T-cell function in patients with narcolepsy, but slight alterations of monocyte function deserving further investigation.

Plasma levels of cytokines and soluble cytokine receptors during treatment with haloperidol

OBJECTIVE

Clozapine increases the levels of cytokines and soluble cytokine receptors. The authors investigated whether haloperidol has similar effects.

METHOD

Rectal temperature, white blood cell counts, and plasma levels of cytokines and soluble cytokine receptors were assessed before and during 6 weeks of haloperidol treatment in 10 psychiatric patients.

RESULTS

Haloperidol at mean doses of 7.0 mg/day (SD = 3.4), 6.9 mg/day (SD = 3.4), and 5.0 mg/day (SD = 3.1) at the end of the 1st, 2nd, and 6th weeks of treatment, respectively, did not affect rectal temperature, white blood cell counts, or plasma level of interleukin-1 receptor antagonist, interleukin-6, tumor necrosis factor-alpha (TNF-alpha), soluble TNF receptor p55 or p75, or soluble interleukin-2 receptor.

CONCLUSIONS

Haloperidol is unlikely to confound the results of studies investigating disease-related alterations in the levels of a broad range of cytokines and soluble cytokine receptors in schizophrenia.

REM sleep disinhibition at sleep onset: a comparison between narcolepsy and depression

Shortened REM latency and increased REM density are frequently observed in both narcolepsy and depression, suggesting a common mechanism of REM sleep disinhibition in these disorders. We compared night sleep recordings of 24 depressive and 24 narcoleptic patients. The amount of REM sleep and REM density did not differ between the patient groups; however, REM latency distributions differed significantly. Whereas in narcoleptic patients REM episodes started either immediately at sleep onset or following at least 60 min of non-REM sleep, in depressives two thirds of REM latencies were in the range from 1 to 60 min. In narcoleptic patients, short as compared to long REM latencies were associated with longer total sleep time, greater sleep efficiency, reduced amounts of wakefulness, and increased amounts of slow-wave sleep. In depressive subjects the reverse pattern was seen. We conclude that a common mechanism of REM sleep disinhibition in narcolepsy and depression is very unlikely.

Effects of clozapine on sleep: a longitudinal study

Polysomnographic studies on the effects of clozapine, an atypical antipsychotic agent with strong sedative properties, on night sleep report inconsistent results. Most of these studies did not include baseline recordings and were not controlled for clozapine-induced fever, which is known to alter nocturnal sleep. We conducted a 2-week longitudinal polysomnographic investigation in 10 long-term drug-free schizophrenic patients prior to and at the end of the first and second weeks of clozapine treatment. Rectal temperature was measured daily and patients with fever (> 37.9 degrees C) were excluded. Clozapine significantly improved sleep continuity. In addition, non-rapid eye movement (NREM) sleep and in particular stage 2 sleep increased significantly, while the amounts of stage 4 and slow-wave sleep decreased significantly. Clozapine increased significantly REM density, but it did not affect the amount of REM sleep. We conclude that in patients who do not experience clozapine-induced fever, clozapine has strong sleep consolidating effects resulting from an increase in stage 2 NREM sleep.

The influence of clozapine treatment on plasma granulocyte colony-stimulating (G-CSF) levels

The antipsychotic drug clozapine frequently induces transient increases in white blood cell counts that have been found to be sensitive, but non-specific, predictors of subsequent life-threatening agranulocytosis. Granulocyte colony-stimulating factor (G-CSF) is an endogenous hematopoietic growth factor that plays a pivotal role in granulopoiesis. In addition, G-CSF has successfully been used to treat clozapine-induced agranulocytosis. We performed a longitudinal investigation of the plasma levels of G-CSF in 20 schizophrenic patients during six weeks of clozapine treatment. Clozapine transiently increased plasma G-CSF levels in 55% of the subjects studied. This effect was most prominent at the end of the second week of treatment. Increased G-CSF levels were accompanied by increased granulocyte and monocyte counts, increased rectal temperature and increased plasma levels of other cytokines and cytokine receptors. The results presented suggest that G-CSF is involved in clozapine-induced increases in granulocyte counts seen early during treatment. Like granulocytosis, granulocytopenia is known to occur in conjunction with increased systemic G-CSF levels. Therefore, we hypothesize that a persistent increase along with a decline in white cell counts following an early spike during clozapine treatment might predict the occurrence of agranulocytosis.

Diurnal variations in the human host response to endotoxin

To investigate diurnal variations in the host response to endotoxin, Salmonella abortus equi endotoxin (0.8 ng/kg) was given intravenously to healthy men in a placebo-controlled design at 0900 or 1900 h. The time course of rectal temperature and the plasma levels of tumor necrosis factor- alpha (TNF-alpha), interleukin-6 (IL-6), adrenocorticotropic hormone (ACTH), and cortisol were monitored for 11 h following the injections. The time of day did not affect the endotoxin-induced increase in plasma TNF-alpha or IL-6. However, subjects who received endotoxin in the evening, when endogenous glucocorticoid levels were low, showed about twice the increases in rectal temperature and plasma ACTH and cortisol levels as those who received endotoxin in the morning, when endogenous glucocorticoid levels were high. These results demonstrate diurnal variations in the human susceptibility to endotoxin that may be due to a suppression of the biologic effects of TNF-alpha and IL-6 by endogenous glucocorticoids.