Comparing Sleep‐Loss Sleepiness and Sleep Inertia: Lapses Make the Difference

To compare the behavioral effects of sleep‐loss sleepiness (performance impairment due to sleep loss) and sleep inertia (period of impaired performance that follows awakening), mean response latencies and number of lapses from a visual simple reaction‐time task were analyzed. Three experimental conditions were designed to manipulate sleepiness and sleep‐inertia levels: uninterrupted sleep, partial sleep reduction, and total sleep deprivation. Each condition included two consecutive nights (the first always a night of uninterrupted sleep, and the second either a night of uninterrupted sleep, a night when sleep was reduced to 3 h, or a night of total sleep deprivation), as well as two days in which performance was assessed at 10 different time points (08:00, 08:30, 09:00, 09:30, 10:00, 11:00, 14:00, 17:00, 20:00, and 23:00 h). From 08:00 to 09:00 h, reaction times in the partial sleep‐reduction and total sleep‐deprivation conditions were at a similar level and were slower than those observed in the uninterrupted sleep condition. In the same time period, the frequency of lapses in the total sleep‐deprivation condition was higher than in the partial sleep‐reduction condition, while this latter condition never differed from the uninterrupted sleep condition. The results indicate that both sleep inertia and sleep‐loss sleepiness lead to an increase in response latencies, but only extreme sleepiness leads to an increase in lapse frequency. We conclude that while reaction times slow as a result of both sleep inertia and sleep‐loss sleepiness, lapses appear to be a specific feature of sleep‐loss sleepiness.     

Sleep on the Job Partially Compensates for Sleep Loss in Night‐Shift Nurses

Nursing personnel in Brazil are usually submitted to fixed 12 h shifts with no consecutive working days or nights. Moonlighting is common in this group, with a consequent increase in the number of working hours. The possibility of sleeping on the job during the night shift in the studied hospitals had already been described. The present study aims to analyze whether the time devoted to daily activities (sleep, rest, leisure, housework, commuting, personal needs, care of children or other people, non‐paid work, and study) is related to the number of worked hours and to nap‐taking during the night shift. The field study took place at two public hospitals in Rio de Janeiro, Brazil. Workers filled out a structured form on time devoted to the above‐mentioned activities for at least four consecutive days. The time devoted to sleep was analyzed according to its occurrence at home or on the job. Workers were classified according to the number of jobs (one job/two jobs) and the time dedicated to work according to the median of the whole series (below the median/above the median). All workers who had at least one working night were analyzed as to nap‐taking on the job. They were classified according to the sleep occurrence during the night shift—the sleep group and the non‐sleep group, both of which were compared to daytime workers. Statistical treatment of data included non‐parametrical procedures. The study group comprised 144 workers (mean age: 35.7±10.5 years old; 91% women; 78% nurse assistants, the remainder registered nurses). They recorded their daily activities for 4–11 days; 829 cumulative days were analyzed for the whole group. A total of 165 working nights were analyzed; sleep or rest occurred during 112 (68%) of them, with mean sleep/rest duration of 141±86 min. Time devoted to sleep and leisure varied according to the number of working hours, being significantly reduced in those submitted to longer work hours (p<0.001 and p=0.002, respectively). Results close to significance point to a reduction in the time dedicated to housework among workers with long work hours (p=0.053). The time spent on sleep/rest per working night did not differ according to the number of worked hours (p=0.490). A tendency was observed for those who have two jobs to devote more time to sleep/rest on the job (p=0.058). The time of personal needs was significantly lower among those who did not sleep on the job as compared to day workers (p=0.036). The total sleep time was significantly lower among those who did not sleep on the job, as compared to day workers and to those who slept on the job (p=0.004 and p=0.05, respectively). As to home sleep length, workers who slept and those who did not sleep on the job were similar and slept significantly less than exclusively daytime workers (p<0.001 and p=0.002, respectively). Sleeping on the job during the night shift seems to partially compensate for the shorter sleep at home among night workers and may play a beneficial effect in coping with two jobs.     

TNF-α and Temporal Changes in Sleep Architecture in Mice Exposed to Sleep Fragmentation

TNF-α plays critical roles in host-defense, sleep-wake regulation, and the pathogenesis of various disorders. Increases in the concentration of circulating TNF-α after either sleep deprivation or sleep fragmentation (SF) appear to underlie excessive daytime sleepiness in patients with sleep apnea (OSA). Following baseline recordings, mice were subjected to 15 days of SF (daily for 12 h/day from 07.00 h to 19.00 h), and sleep parameters were recorded on days1, 7 and 15. Sleep architecture and sleep propensity were assessed in both C57BL/6J and in TNF-α double receptor KO mice (TNFR KO). To further confirm the role of TNF-α, we also assessed the effect of treatment with a TNF- α neutralizing antibody in C57BL/6J mice. SF was not associated with major changes in global sleep architecture in C57BL/6J and TNFR KO mice. TNFR KO mice showed higher baseline SWS delta power. Further, following 15 days of SF, mice injected with TNF-α neutralizing antibody and TNFR KO mice showed increased EEG SWS activity. However, SWS latency, indicative of increased propensity to sleep, was only decreased in C57BL/6J, and was unaffected in TNFR KO mice as well as in C57BL/6J mice exposed to SF but treated with TNF-α neutralizing antibody. Taken together, our findings show that the excessive sleepiness incurred by recurrent arousals during sleep may be due to activation of TNF-alpha-dependent inflammatory pathways, despite the presence of preserved sleep duration and global sleep architecture.     

Melanopsin as a Sleep Modulator: Circadian Gating of the Direct Effects of Light on Sleep and Altered Sleep Homeostasis in Opn4?/? Mice

Light influences sleep and alertness either indirectly through a well-characterized circadian pathway or directly through yet poorly understood mechanisms. Melanopsin (Opn4) is a retinal photopigment crucial for conveying nonvisual light information to the brain. Through extensive characterization of sleep and the electrocorticogram (ECoG) in melanopsin-deficient (Opn4^−/−) mice under various light–dark (LD) schedules, we assessed the role of melanopsin in mediating the effects of light on sleep and ECoG activity. In control mice, a light pulse given during the habitual dark period readily induced sleep, whereas a dark pulse given during the habitual light period induced waking with pronounced theta (7–10 Hz) and gamma (40–70 Hz) activity, the ECoG correlates of alertness. In contrast, light failed to induce sleep in Opn4^−/− mice, and the dark-pulse-induced increase in theta and gamma activity was delayed. A 24-h recording under a LD 1-h∶1-h schedule revealed that the failure to respond to light in Opn4^−/− mice was restricted to the subjective dark period. Light induced c-Fos immunoreactivity in the suprachiasmatic nuclei (SCN) and in sleep-active ventrolateral preoptic (VLPO) neurons was importantly reduced in Opn4^−/− mice, implicating both sleep-regulatory structures in the melanopsin-mediated effects of light. In addition to these acute light effects, Opn4^−/− mice slept 1 h less during the 12-h light period of a LD 12∶12 schedule owing to a lengthening of waking bouts. Despite this reduction in sleep time, ECoG delta power, a marker of sleep need, was decreased in Opn4^−/− mice for most of the (subjective) dark period. Delta power reached after a 6-h sleep deprivation was similarly reduced in Opn4^−/− mice. In mice, melanopsin''s contribution to the direct effects of light on sleep is limited to the dark or active period, suggesting that at this circadian phase, melanopsin compensates for circadian variations in the photo sensitivity of other light-encoding pathways such as rod and cones. Our study, furthermore, demonstrates that lack of melanopsin alters sleep homeostasis. These findings call for a reevaluation of the role of light on mammalian physiology and behavior.     

Morphofunctional Analysis of Effect of Short-Term Sleep Deprivation on the Wakefulness–Sleep Cycle in Young and Adult Rats

The work presents comparative data on changes of neurophysiological, time characteristics of the wakefulness–sleep cycle (WSC) and morphofunctional state of neurosecretory cells in supraoptic nucleus of the hypothalamus, which develop under influence of a 6-h long sleep deprivation in adult and one-month old rats. It is shown that the rebound of sleep develops in adult animals with a delay, after the 3rd hour and is characterized by a moderate increase of portions of slow-wave (SSP) and fast-wave (FSP) sleep phases in WSC and by a decrease of the wakefulness portion. Morphological analysis of the hypothalamus nonapeptidergic system has revealed a rise of content of neurosecretory material in fibers of supraoptic nucleus cells an in area of supraoptic-pituitary tract, as well as marked hyperemia that indicates activation of processes of secretion of neurohormones into the general blood flow; these reactions are similar to reactions of this system to stress. In rat pups the sleep rebound develops in 0.5 h after the end of the deprivation procedure and is characterized by more pronounced, statistically significant changes in WSC. Individual WSC become very short and almost all of them are completed with episodes of FSP. A statistically significant rise of power of the -wave band in electrogram spectra of hippocampus and somatosensory cortex in SSP, whereas peak of the activity in FSP is shifted to -waves. Ratios of SSP and FSP to wakefulness in individual WSC in mature animals increase after the deprivation 1.53 and 1.85 times, while they are elevated in one-month old animals 5.25 and 6.75 times, respectively. The obtained morphofunctional data allow believing that deprivation is the stress factor of low intensity for adult animals, whereas it may be considered as the stress action of intermediate and even high intensity for rat pups, which changes essentially the interrelations in WSC. Participation of central mechanisms of regulation of sleep and vigilance, which provide processes of compensation of damaging action of deprivation on WSC in the maturing animals, is discussed.     

Does Sleep Really Influence Face Recognition Memory?

Mounting evidence implicates sleep in the consolidation of various kinds of memories. We investigated the effect of sleep on memory for face identity, a declarative form of memory that is indispensable for nearly all social interaction. In the acquisition phase, observers viewed faces that they were required to remember over a variable retention period (0–36 hours). In the test phase, observers viewed intermixed old and new faces and judged seeing each before. Participants were classified according to acquisition and test times into seven groups. Memory strength (d′) and response bias (c) were evaluated. Substantial time spent awake (12 hours or more) during the retention period impaired face recognition memory evaluated at test, whereas sleep per se during the retention period did little to enhance the memory. Wakefulness during retention also led to a tightening of the decision criterion. Our findings suggest that sleep passively and transiently shelters face recognition memory from waking interference (exposure) but does not actively aid in its long-term consolidation.     

An Examination of Adult Women’s Sleep Quality and Sleep Routines in Relation to Pet Ownership and Bedsharing

ABSTRACT

People in many parts of the world commonly share their beds not only with human partners but also with dogs and cats. Self-report and actigraphy data have shown that sleeping with an adult human partner has both positive and negative impacts on human sleep, but there has been little exploration of the impacts that pets have on human sleep quality. We collected survey data online from 962 adult women living in the United States to investigate relationships between pet ownership and human sleep. Fifty-five percent of participants shared their bed with at least one dog and 31% with at least one cat. In addition, 57% of participants shared their bed with a human partner. Our findings did not show a strong relationship between pet ownership status or bedsharing conditions and sleep quality as assessed by the Pittsburgh Sleep Quality Index (PSQI), although according to this measure, a high percentage of study participants did experience sleep quality deficits. It is possible that pet ownership contributed to the high global PSQI scores we observed, especially since all but 7% of participants resided with dogs and/or cats. Other measures included in this study indicate that dogs and cats, and where they sleep, may indeed affect sleep habits and perceptions of sleep quality. Dog owners had earlier bedtimes and wake times than individuals who had cats but no dogs. Compared with human bed partners, dogs who slept in the owner’s bed were perceived to disturb sleep less and were associated with stronger feelings of comfort and security. Conversely, cats who slept in their owner’s bed were reported to be equally as disruptive as human partners, and were associated with weaker feelings of comfort and security than both human and dog bed partners. Follow-up research is necessary to determine if pet owners’ perceptions of pets’ impacts on their sleep align with objective measures of sleep quality.     

Longer Sleep – Slimmer Kids: The ENERGY-Project

Background

Few studies have differentiated between weekday and weekend day sleep duration in their association with indicators of weight status in children. Therefore, we examined the association of week and weekend day sleep duration with indicators of body composition in 10–12 year old European school children.

Methods and Findings

Multi-level linear regression analysis was performed to examine the association between parent-reported week and weekend day sleep duration and objectively assessed child BMI and WC, adjusting for socio-demographic variables and energy balanced related behaviours EBRBs (i.e. dietary, physical and sedentary behaviour). Compared to sleeping 10 hrs/night or more, sleeping on average less than 10 hrs/night during weekdays was associated with higher BMI (for example, B = 0.86 and CI = [0.27;1.45] when sleeping ≤7 hrs) and WC (for example, B = 1.99 and CI = [0.32;3.65] when sleeping ≤7 hrs). Sleeping 9 hrs/night during weekend days, but not ≤8 hrs, was associated with higher WC (B = 0.66; CI = [0.04;1.28]) compared to sleeping more than 10 hrs/night. Average (week and weekend) sleep duration less than 10 hrs/night was associated with higher values for BMI (B = 0.98; CI = [0.24;1.73] and WC (B = 2.35; CI = [0.08;4.31]).

Conclusions

Weekday sleep duration seems more strongly associated with body composition in European school children than weekend day sleep duration. Promoting adequate sleep duration may contribute to healthy weight in children.     

Are Individuals' Nighttime Sleep Characteristics Prior to Shift‐Work Exposure Predictive for Parameters of Daytime Sleep after Commencing Shift Work?

This study aimed to examine prospectively whether individual nighttime sleep characteristics at baseline (prior to shift‐work exposure) are related to parameters of daytime sleep after commencing shift work. A longitudinal field study was carried out with novice police officers of the Dutch Police Force. A total of 26 subjects were examined at baseline before they entered shift work and re‐examined during follow‐up sessions after four and twelve months of shift‐work exposure. Wrist actigraphy and sleep diaries were used to study nocturnal sleep at baseline and daytime sleep after night shifts during follow‐up sessions. As outcome variables, estimated total sleep time, sleep efficiency, and subjective sleep quality were analyzed. Daytime total sleep time showed a 66 min decline during the first year of shift‐work exposure. Systematic inter‐individual differences were observed for daytime total sleep time and subjective sleep quality (explaining 53% and 38% of the variance, respectively), suggesting potential predictability of these sleep parameters. Although no predictors were found for daytime total sleep time, the subjective quality of nighttime sleep before the onset of shift work predicted 40% of the variance in the subjective quality of daytime sleep after commencing shift work. Follow‐up studies may reveal whether the subjective quality of baseline nighttime sleep also predicts long‐term overall tolerance for shift work.     

Galanin Neurons Unite Sleep Homeostasis and α2-Adrenergic Sedation

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β Oscillation during Slow Wave Sleep and Rapid Eye Movement Sleep in the Electroencephalogram of a Transgenic Mouse Model of Huntington’s Disease

Study objectives

To search for early abnormalities in electroencephalogram (EEG) during sleep which may precede motor symptoms in a transgenic mouse model of hereditary neurodegenerative Huntington’s disease (HD).

Design

In the R6/1 transgenic mouse model of HD, rhythmic brain activity in EEG recordings was monitored longitudinally and across vigilance states through the onset and progression of disease.

Measurements and results

Mice with chronic electrode implants were recorded monthly over wake-sleep cycles (4 hours), beginning at 9–11 weeks (presymptomatic period) through 6–7 months (symptomatic period). Recording data revealed a unique β rhythm (20–35 Hz), present only in R6/1 transgenic mice, which evolves in close parallel with the disease. In addition, there was an unusual relationship between this β oscillation and vigilance states: while nearly absent during the active waking state, the β oscillation appeared with drowsiness and during slow wave sleep (SWS) and, interestingly, strengthened rather than dissipating when the brain returned to an activated state during rapid eye movement (REM) sleep.

Conclusions

In addition to providing a new in vivo biomarker and insight into Huntington''s disease pathophysiology, this serendipitous observation opens a window onto the rarely explored neurophysiology of the cortico-basal ganglia circuit during SWS and REM sleep.     

Is Obstructive Sleep Apnea Associated with Cardiovascular and All-Cause Mortality?

Background

Studies have reported inconsistent findings regarding the association between obstructive sleep apnea (OSA) and future risks of cardiovascular and all-cause mortality. We conducted a meta-analysis to investigate whether OSA is an independent predictor for future cardiovascular and all-cause mortality using prospective observational studies.

Methods

Electronic literature databases (Medline and Embase) were searched for prospective observational studies published prior to December 2012. Only observational studies that assessed baseline OSA and future risk of cardiovascular and all-cause mortality were selected. Pooled hazard risk (HR) and corresponding 95% confidence intervals (CI) were calculated for categorical risk estimates. Subgroup analyses were based on the severity of OSA.

Results

Six studies with 11932 patients were identified and analyzed, with 239 reporting cardiovascular mortality, and 1397 all-cause mortality. Pooled HR of all-cause mortality was 1.19 (95% CI, 1.00 to 1.41) for moderate OSA and 1.90 (95% CI, 1.29 to 2.81) for severe OSA. Pooled HR of cardiovascular mortality was 1.40 (95% CI, 0.77 to 2.53) for moderate OSA and 2.65 (95% CI, 1.82 to 3.85) for severe OSA. There were no differences in cardiovascular mortality in continuous positive airway pressure (CPAP) treatment compared with healthy subjects (HR 0.82; 95% CI, 0.50 to 1.33).

Conclusions

Severe OSA is a strong independent predictor for future cardiovascular and all-cause mortality. CPAP treatment was associated with decrease cardiovascular mortality.     

Shift Work and Inter‐Individual Differences in Sleep and Sleepiness

Inter‐individual differences in tolerance for shift work have been studied primarily in terms of external factors affecting alertness on the job or the ability to rest and sleep while at home. However, there is increasing evidence that neurobiological factors play a role as well, particularly the major processes involved in the regulation of sleep and wakefulness. These include a sleep homeostatic process seeking to balance wakefulness and sleep and a circadian process seeking to promote wakefulness during the day and sleep during the night. Shift work is associated with a temporal misalignment of these two endogenous processes. During nightwork, this misalignment makes it difficult to stay awake during the nightshift and sleep during the day. However, inter‐individual variability in the processes involved in sleep/wake regulation is substantial. Recent studies have demonstrated the existence of inter‐individual differences in vulnerability to cognitive deficits from sleep loss. Moreover, these inter‐individual differences were shown to constitute a trait. Interestingly, self‐evaluations of sleepiness did not correspond well with the trait inter‐individual variability in objective levels of performance impairment during sleep deprivation. Perhaps because of this discrepancy, in operational settings, the inter‐individual differences in vulnerability to sleep loss do not appear to be limited due to self‐selection mechanisms. Indeed, even among a highly select group of active‐duty jet fighter pilots flying a series of simulated night missions, systematic inter‐individual differences in performance impairment from sleep loss were still observed. There are significant personal and economic consequences to human error and accidents caused by performance deficits due to sleep loss. It is important, therefore, to study the inter‐individual differences in the regulation of sleep and wakefulness in the work environment so that cognitive impairment during shift work may be better anticipated and prevented.