Effects Of Sleep Restriction Research Articles

Immature sleep pattern in newborn rats when dams encountered sleep restriction during pregnancy

There is a growing realization that proper sleep during pregnancy is essential for the health of the mother and the offspring. However, there are no reports on the effects of maternal sleep restriction on the sleep-wake profiles of newborns. So, this study was conducted to evaluate the effects of sleep restriction during the third term of pregnancy on the sleep-wake profiles of neonates born to them. The female pregnant Wistar rats were sleep restricted for 5 h/day on gestational days 15–20 by gentle handling. Sleep-wake profiles of the pups born to them and to the control rats were recorded on postnatal days 1–21. Pups of sleep restricted dams had higher active sleep (AS) and lower quiet sleep (QS) as well as wakefulness. Higher ratio of AS to QS, longer duration of sleep cycles, lesser bout frequency and reduced EEG delta power were also observed in these pups, all of which indicated brain immaturity. All these signs of delayed maturation, usually found in premature babies, were observed in the pups of sleep restricted mothers, who had longer gestation period. This report not only shows the importance of sleep during pregnancy, but it also suggests that neonatal sleep monitoring can be used as a tool for early assessment of retarded brain development.

Neurophysiological differences in the adolescent brain following a single night of restricted sleep – A 7T fMRI study

Sleep deprivation in youth has garnered international attention in recent years, as correlational studies have demonstrated significant relationships between lack of sleep and detrimental behavioral and academic outcomes. However, no study to date has systematically examined the neurophysiological consequences of a single night of sleep restriction (i.e., 4 h) in adolescents using ultra-high field functional neuroimaging. Much of what we know regarding the neural consequences of sleep deprivation has come from the adult literature, and among those studies, the majority use region of interest (ROI) approaches, thus disregarding the dynamic mechanisms that may subserve the behavioral effects of sleep restriction. Leveraging a crossover within-subjects design, we demonstrate that pivotal brain regions involved in the default mode and limbic regulatory centers have disrupted functioning following a night of restricted sleep compared to a night of “normal sleep”. Specifically, a normal night (i.e., 8 h) of sleep led to increased global and local efficiency of bilateral amygdala, and less efficiency in the posterior cingulate, as measured by graph theory, compared to a night of sleep restriction. Furthermore, aberrant functional connectivity patterns were identified in key fronto-limbic circuitry, suggesting a potential pathophysiological mechanism underlying the widespread effects of sleep deprivation in youth.

Five Nights of Sleep Restriction Attenuates Microvascular Endothelial Function

Adequate sleep is requisite for optimal physiological function, including microvascular endothelial function. Short‐term sleep restriction (5 hours/night) negatively alters glucose metabolism and may also impair microvascular endothelial function via increased sympathetic nervous system activity and inflammatory pathways. The cutaneous microvasculature represents an accessible, well‐described vascular bed to non‐invasively assess the effects of sleep restriction on microvascular function. Our objective was to evaluate cutaneous microvascular endothelial function during baseline sleep replete conditions (10 hours/night time in bed), after 5 nights of sleep restriction (5 hours/night), and again after 2 nights of recovery sleep repletion. This was part of the Sleep Restriction Study (PI: Chang), an 11‐day inpatient study that took place in the Penn State University Clinical Research Center, during which diet and physical activity were controlled. Eight young, healthy men (23.3 ± 3.4 years) participated in the study. Cutaneous microvascular function was measured utilizing a standardized local skin heating protocol to induce endothelial nitric oxide‐synthase‐dependent vasodilation during all three study phases (baseline, sleep restricted, recovery). Red cell flux (laser Doppler flowmetry) was continuously measured on the ventral forearm at thermoneutral temperature (33 °C) and throughout local heating 0.5°C·5 s−1 to 42 °C until a stable (20 min) plateau had been reached. Red cell flux was normalized to cutaneous vascular conductance (CVC: flux·MAP−1) and expressed as a percentage of maximum CVC (43°C: %CVCmax). Compared to the baseline sleep replete state, the response to local heating was attenuated by 10% after 5 nights of sleep restriction (baseline: 89.2 ± 2.0, restricted: 80.4 ± 3.0 %CVCmax; p=0.045) and fully recovered after 2 nights of recovery sleep (88.7 ± 1.8 %CVCmax; p=0.99 compared to baseline). Maximum CVC was not affected by sleep restriction (all p>0.05). These results suggest that 5 nights of sleep restriction impairs microvascular endothelial function, likely through attenuated nitric oxide‐dependent vasodilation, but that 2 nights of recovery sleep restores microvascular endothelial function in young, healthy men.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Sleep restriction and cognitive load affect performance on a simulated marksmanship task.

Sleep restriction degrades cognitive and motor performance, which can adversely impact job performance and increase the risk of accidents. Military personnel are prone to operating under sleep restriction, and previous work suggests that military marksmanship may be negatively affected under such conditions. Results of these studies, however, are mixed and have often incorporated additional stressors (e.g. energy restriction) beyond sleep restriction. Moreover, few studies have investigated how the degree of difficulty of a marksmanship task impacts performance following sleep restriction. The purpose of the current experiment was to study the effects of sleep restriction on marksmanship while minimizing the potential influence of other forms of stress. A friend-foe discrimination challenge with greater or lesser degrees of complexity (high versus low load) was used as the primary marksmanship task. Active duty Soldiers were recruited, and allowed 2h of sleep every 24h over a 72-h testing period. Marksmanship tasks, cognitive assessment metrics and the NASA-Task Load Index were administered daily. Results indicated that reaction times to shoot foe targets and signal friendly targets slowed over time. In addition, the ability to correctly discriminate between friend and foe targets significantly decreased in the high-cognitive-load condition over time despite shot accuracy remaining stable. The NASA-Task Load Index revealed that, although marksmanship performance degraded, participants believed their performance did not change over time. These results further characterize the consequences of sleep restriction on marksmanship performance and the perception of performance, and reinforce the importance of adequate sleep among service members when feasible.

Sleep restriction increased murine melanoma lung metastasis formation by reducing the number of cytotoxic cells and inducing a suppressive tumor microenvironment

Sleep restriction (SR) is an increasing condition in the modern society, and it leads to higher production of stress hormones in humans and rodents. These hormones, at high concentrations, can change many aspects of the immune system, including the production of antibodies, cytokine profiles, cell trafficking, among others, providing the development of diseases, like cancer. The aim of this study was to analyze the effects of sleep restriction (SR) in the development of melanoma lung metastases in male C57BL/6. To this, mice were inoculated with B16F10 in the lateral tail vein (day 0). In the next day (day 1), mice were submitted to sleep restriction (SR) by the modified multiple platforms method. At days 2, 7, 14 and 21, control and SR mice (5 per day, per group) were euthanized, the lung metastases were counted and tumor microenvironment cells were analyzed by flow cytometry. Results shown that, in SR mice, tumor appeared earlier and more lung metastatic colonies were formed. Cytotoxic NK and CD8 T cells were reduced and the ratio between effector and regulatory T cells were smaller in sleep restricted mice in day 14. The same results were observed when the ratio IFN-gamma/Il-4 and IFN-gamma/IL-10 were analyzed. Together, these data suggest that sleep restriction induced a suppressive tumor microenvironment and impaired anti- tumor effector cells infiltration, thus favoring rapid tumor installation and growth.

Sex hormones play a role in vulnerability to sleep loss on emotion processing tasks

The central aim of this study was to investigate hormones as a predictor of individual vulnerability or resiliency on emotion processing tasks following one night of sleep restriction. The restriction group was instructed to sleep 3a.m.–7a.m. (13 men, 13 women in follicular phase, 10 women in luteal phase of menstrual cycle), and a control group slept 11p.m.–7a.m. (12 men, 12 follicular women, 12 luteal women). Sleep from home was verified with actigraphy. Saliva samples were collected on the evening prior to restriction, and in the morning and afternoon following restriction, to measure testosterone, estradiol, and progesterone. In the laboratory, event-related potentials (ERPs) were recorded during presentation of images and faces to index neural processing of emotional stimuli. Compared to controls, sleep-restricted participants had a larger amplitude Late Positive Potential (LPP) ERP to positive vs neutral images, reflecting greater motivated attention towards positive stimuli. Sleep-restricted participants were also less accurate categorizing sad faces and exhibited a larger N170 to sad faces, reflecting greater neural reactivity. Sleep-restricted luteal women were less accurate categorizing all images compared to control luteal women, and progesterone was related to several outcomes. Morning testosterone in men was lower in the sleep-restricted group compared to controls; lower testosterone was associated with lower accuracy to positive images, a greater difference between positive vs neutral LPP amplitude, and lower accuracy to sad and fearful faces. In summary, women higher in progesterone and men lower in testosterone were more vulnerable to the effects of sleep restriction on emotion processing tasks. This study highlights a role for sex and sex hormones in understanding individual differences in vulnerability to sleep loss.

The effect of sleep restriction on empathy for pain: An fMRI study in younger and older adults

Age and sleep both affect emotional functioning. Since sleep patterns change over the lifespan, we investigated the effects of short sleep and age on empathic responses. In a randomized cross-over experimental design, healthy young and older volunteers (n = 47 aged 20–30 years and n = 39 aged 65–75 years) underwent functional magnetic resonance imaging (fMRI) after normal sleep or night sleep restricted to 3 hours. During fMRI, participants viewed pictures of needles pricking a hand (pain) or Q-tips touching a hand (control), a well-established paradigm to investigate empathy for pain. There was no main effect of sleep restriction on empathy. However, age and sleep interacted so that sleep restriction caused increased unpleasantness in older but not in young participants. Irrespective of sleep condition, older participants showed increased activity in angular gyrus, superior temporal sulcus and temporo-parietal junction compared to young. Speculatively, this could indicate that the older individuals adopted a more cognitive approach in response to others’ pain. Our findings suggest that caution in generalizability across age groups is needed in further studies of sleep on social cognition and emotion.

Sleep restriction induced energy, methylation and lipogenesis metabolic switches in rat liver.

Sleep curtailment is ubiquitous in modern day society. Sleep debt is associated with maladaptive physiological changes that can lead to cardiometabolic and neuropsychiatric pathologies. Recent literature has shown the effects of sleep restriction (SR) on systemic metabolic profiles in biofluids, implying that tissue-specific metabolomes are impacted by SR. To test this hypothesis, we assessed hepatic metabolic profiles of rats after 5days of SR using UPLC-MS based metabolomics analysis and gene expression analysis. Our data suggests distinctive effects of SR on the liver metabolic profile of rats compared to forced-activity control animals. We observed specific impacts of SR on NAD metabolism through NAD accumulation and upregulation of Nampt, the rate determining step of NAD salvage. Additional multi-omic changes were observed in methionine metabolism, with an elevated SAM:SAH ratio under SR. This effect on one carbon metabolism is indicative of increased methylation potential. Changes in TCA cycle intermediates and ATP-citrate lyase (Acly) gene expression were observed that may be related to altered circulatory lipid profiles previously reported documenting the chrono-metabolic connection. Taken together with previous investigations, these observations are consistent with a model of decreased TCA activity with concomitant increase in lipogenesis induced by SR. These tissue-specific mechanistic insights into metabolic effects of SR provide a springboard to future metabolic intervention studies.

0071 ROLE OF SLEEP RESTRICTION IN ADIPOCYTE INSULIN SENSITIVITY DURING AN INTRAVENOUS GLUCOSE TOLERANCE TEST IN HEALTHY ADULT MEN

Sleep restriction, or chronic partial sleep loss, increases obesity and diabetes risk by disrupting glucose metabolism and reducing whole-body insulin sensitivity without a compensatory increase in insulin secretion. Healthy adipocytes suppress hormone sensitive lipase (HSL) activity in response to insulin, which severely limits non-esterified fatty acid (NEFA) release. Elevated overnight NEFA levels are correlated with the reduction in insulin sensitivity that occurs in sleep restriction. Additionally, subcutaneous adipose biopsies from sleep-restricted subjects have reduced pAKT, evidence that sleep restriction decreases insulin sensitivity in adipocytes. The objective of this pilot study was to extend previous findings of the effects of sleep restriction on plasma glucose to mechanistic shifts within adipocyte metabolism. Subjects (20–35 y/o) were enrolled in an 11-day in-lab protocol; light exposure, activity, temperature, and diet were carefully controlled. An intravenous glucose tolerance test (IVGTT) was performed at three time points: after three nights of baseline sleep (10 hrs/night), after five nights of sleep restriction (5 hrs/night), and after two nights of recovery sleep (10 hrs/night). NEFA were quantified (Wako Diagnostics) and parameters describing NEFA kinetics (i.e. rate of NEFA production, utilization, suppression threshold) in the Boston and Moate minimal model were calculated using WinSAAM Compartmental Modeling software. Five subjects completed the sleep restriction protocol; one did not complete IVGTT procedures for safety reasons. Preliminary results from four subjects show the fractional rate of NEFA utilization was increased by 0.024 [0.009, 0.039] min-1 in the restricted condition (p=0.008). Restriction also increased the modifier of the inhibitory effect of remote glucose on NEFA production by 4.3 fold [1.2, 15.9] from baseline (p=0.04). Sleep restriction induces symmetrical changes in both glucose and lipid markers of insulin sensitivity in vivo. Preliminary evidence indicates that NEFA rate of utilization is increased in response to sleep restriction. In the context of whole-body metabolism, this indicates a shift in Randle cycle fuel selection by metabolic tissues. Additionally, a greater concentration of glucose was required to initiate NEFA suppression, evidence that sleep restriction functionally impairs HSL activity. UL1TR000127 (Chang PI) T32GM108563 (to KMN; Korzick PI).

0056 EFFECTS OF PRIOR SLEEP DURATION AND AGE ON WAKING ALPHA ELECTROENCEPHALOGRAM POWER IN EARLY ADOLESCENCE

In the waking electroencephalogram (EEG), alpha frequency power increases when eyes are closed, and this increase is diminished following sleep deprivation. Our current longitudinal study varies time in bed (TIB) to determine changes in sleep need across adolescence. Here we report the effects of sleep restriction and age on waking alpha power in early adolescence. Seventy seven children, age 9.85 to 14.0 years (mean=12.2, sd=1.2) at the time of first recording, were studied in the first year of this ongoing longitudinal study. A laboratory day of performance and sleepiness testing follows four nights with TIB restricted to 7, 8.5 or 10 hours. Each participant completed all three sleep schedules. Laboratory days entailed 4 test sessions, every 2 hours starting at 0900. Each test session includes recording of waking EEG: 3 minutes with eyes open, followed by 2 minutes eyes closed, followed by 2 minutes eyes open, followed by 2 minutes eyes closed. EEG recorded from O1 and O2 was analyzed with FFT on 5 second artifact free epochs. Following the 7 h TIB schedule, O1 alpha power with eyes open (57 µV2) increased (by 114 µV2) when eyes were closed (p<0.0001). This eyes closed effect increased by 12 µV2 for each additional hour of nighttime TIB (p=0.0002). There was no age effect on eyes open alpha, on the eyes closed effect, or on the TIB x eyes closed interaction (p>0.4 for all). Results for O2 EEG were similar. In young adolescents, sleep restriction diminishes the eyes closed increase in waking alpha EEG power. This finding raises the possibility that alpha power is a sensitive indicator of sleep recovery and encourages further study over a wider age range and sleep durations. The absence of an age effect contrasts starkly with MSLT findings from the same subjects where sleep extension provided a much stronger decrease in sleep likelihood in younger subjects. R01HL116490.

Increased energy intake following sleep restriction in men and women: A one‐size‐fits‐all conclusion?

ObjectiveWe assessed the degree of inter-individual responses in energy intake (EI) to an imposed sleep restriction versus habitual sleep duration protocol. We also investigated participant (age, sex, ethnicity and BMI) and study (study site, protocol order) characteristics as potential contributors to the variance in EI responses to sleep restriction between individuals.MethodsData from two randomized crossover trials were combined. All participants (n = 43; age: 31±7 years, BMI: 23±2 kg/m2) were free of medical/sleep conditions, non-smokers, reported not performing shift work, and having an average sleep duration of 7–9h/night. Ad libitum, 24h EI was objectively-assessed following sleep restriction (3.5–4h in bed/night) and habitual sleep (7–9h in bed/night) conditions.ResultsLarge inter-individual variations in EI change (ΔEI) between restricted and habitual sleep conditions were noted (−813 to 1437 kcal/day). Only phase order was associated with ΔEI (β = −568 kcal/day, 95% CI for β = −921 to −215 kcal; P = 0.002); participants randomized to the habitual sleep condition first had greater increases in EI when sleep was restricted (P = 0.01).ConclusionsLarge inter-individual variations in ΔEI following sleep restriction were noted, suggesting that not all individuals were negatively impacted by the effects of sleep restriction.

Assessing the benefits of napping and short rest breaks on processing speed in sleep-restricted adolescents.

Achievement-oriented adolescents often study long hours under conditions of chronic sleep restriction, adversely affecting cognitive function. Here, we studied how napping and rest breaks (interleaved off-task periods) might ameliorate the negative effects of sleep restriction onprocessing speed. Fifty-seven healthy adolescents (26 female, age=15-19years) participated in a 15-day live-in protocol. All participants underwent sleep restriction (5h time-in-bed), but were then randomized into two groups: one of these groups received a daily 1-h nap opportunity. Data from seven of the study days (sleep restriction days 1-5, and recovery days 1-2) are reported here. The Blocked Symbol Decoding Test, administered once a day, was used to assess time-on-task effects and the effects of rest breaks on processing speed. Controlling for baseline differences, participants who took a nap demonstrated faster speed of processing and greater benefit across testing sessions from practice. These participants were also affected significantly less by time-on-task effects. In contrast, participants who did not receive a nap benefited more from the rest breaks that were permitted between blocks of the test. Our results indicate that napping partially reverses the detrimental effects of sleep restriction on processing speed. However, rest breaks have a greater effect as a countermeasure against poor performance when sleep pressure is higher. These data add to the growing body of evidence showing the importance of sleep for good cognitive functioning in adolescents, and suggest that more frequent rest breaks might be important insituations where sleep loss is unavoidable.

Effect of shortened sleep on energy expenditure, core body temperature, and appetite: a human randomised crossover trial

The effects of sleep restriction on energy metabolism and appetite remain controversial. We examined the effects of shortened sleep duration on energy metabolism, core body temperature (CBT), and appetite profiles. Nine healthy men were evaluated in a randomised crossover study under two conditions: a 3.5-h sleep duration and a 7-h sleep duration for three consecutive nights followed by one 7-h recovery sleep night. The subjects’ energy expenditure (EE), substrate utilisation, and CBT were continually measured for 48 h using a whole-room calorimeter. The subjects completed an appetite questionnaire every hour while in the calorimeter. Sleep restriction did not affect total EE or substrate utilisation. The 48-h mean CBT decreased significantly during the 3.5-h sleep condition compared with the 7-h sleep condition (7-h sleep, 36.75 ± 0.11 °C; 3.5-h sleep, 36.68 ± 0.14 °C; p = 0.016). After three consecutive nights of sleep restriction, fasting peptide YY levels and fullness were significantly decreased (p = 0.011), whereas hunger and prospective food consumption were significantly increased, compared to those under the 7-h sleep condition. Shortened sleep increased appetite by decreasing gastric hormone levels, but did not affect EE, suggesting that greater caloric intake during a shortened sleep cycle increases the risk of weight gain.

The Impact of Sleep Restriction on Contributions and Punishment: First Evidence

We implement a one-week partial sleep restriction protocol to investigate the effect of sleep deprivation on joint production in a standard voluntary contributions mechanism (VCM) experiment. Additionally, the effect of sleep restriction on an individual's likelihood of sending costly peer punishment is examined. Actigraphy sleep monitoring watches are used to validate that our random assignment to sleep restricted (SR) and well-rested (WR) conditions generates significant differences in both objective nightly sleep duration and subject sleepiness. Using multiple measures of sleep restriction, and non-parametric as well as regression analysis, we find that when punishment is not available, sleep restriction does not affect the contributions made to joint production. When punishment is available, we find weak evidence that SR subjects contribute more than WR subjects, but there is no evidence that SR and WR subjects differ in the amount they punish others. However, we also find that SR subject contributions are significantly more sensitive to the introduction of peer punishment. SR subject punishment decisions may also be more sensitive to the deviation of their contributions from other group members' contributions and more sensitive to having received punishment themselves. Our results have implications for understanding how the norm enforcement availability may differentially impact individuals depending on their current sleep state.

The effects of sleep restriction and sleep deprivation in producing false memories

False memory has been claimed to be the result of an associative process of generalisation, as well as to be representative of memory errors. These can occur at any stage of memory encoding, consolidation, or retrieval, albeit through varied mechanisms. The aim of this paper is to experimentally determine: (i) if cognitive dysfunction brought about by sleep loss at the time of stimulus encoding can influence false memory production; and (ii) whether this relationship holds across sensory modalities. Subjects undertook both the Deese-Roedigger-McDermott (DRM) false memory task and a visual task designed to produce false memories. Performance was measured while subjects were well-rested (9h Time in Bed or TIB), and then again when subjects were either sleep restricted (4h TIB for 4 nights) or sleep deprived (30h total SD). Results indicate (1) that partial and total sleep loss produced equivalent effects in terms of false and veridical verbal memory, (2) that subjects performed worse after sleep loss (regardless of whether this was partial or total sleep loss) on cued recognition-based false and veridical verbal memory tasks, and that sleep loss interfered with subjects’ ability to recall veridical, but not false memories under free recall conditions, and (3) that there were no effects of sleep loss on a visual false memory task. This is argued to represent the dysfunction and slow repair of an online verbal associative process in the brain following inadequate sleep.

Increased Sleep Depth in Developing Neural Networks: New Insights from Sleep Restriction in Children.

Brain networks respond to sleep deprivation or restriction with increased sleep depth, which is quantified as slow-wave activity (SWA) in the sleep electroencephalogram (EEG). When adults are sleep deprived, this homeostatic response is most pronounced over prefrontal brain regions. However, it is unknown how children’s developing brain networks respond to acute sleep restriction, and whether this response is linked to myelination, an ongoing process in childhood that is critical for brain development and cortical integration. We implemented a bedtime delay protocol in 5- to 12-year-old children to obtain partial sleep restriction (1-night; 50% of their habitual sleep). High-density sleep EEG was assessed during habitual and restricted sleep and brain myelin content was obtained using mcDESPOT magnetic resonance imaging. The effect of sleep restriction was analyzed using statistical non-parametric mapping with supra-threshold cluster analysis. We observed a localized homeostatic SWA response following sleep restriction in a specific parieto-occipital region. The restricted/habitual SWA ratio was negatively associated with myelin water fraction in the optic radiation, a developing fiber bundle. This relationship occurred bilaterally over parieto-temporal areas and was adjacent to, but did not overlap with the parieto-occipital region showing the most pronounced homeostatic SWA response. These results provide evidence for increased sleep need in posterior neural networks in children. Sleep need in parieto-temporal areas is related to myelin content, yet it remains speculative whether age-related myelin growth drives the fading of the posterior homeostatic SWA response during the transition to adulthood. Whether chronic insufficient sleep in the sensitive period of early life alters the anatomical generators of deep sleep slow-waves is an important unanswered question.

Sleep Restriction Impairs Vocabulary Learning when Adolescents Cram for Exams: The Need for Sleep Study.

The ability to recall facts is improved when learning takes place at spaced intervals, or when sleep follows shortly after learning. However, many students cram for exams and trade sleep for other activities. The aim of this study was to examine the interaction of study spacing and time in bed (TIB) for sleep on vocabulary learning in adolescents. In the Need for Sleep Study, which used a parallel-group design, 56 adolescents aged 15-19 years were randomly assigned to a week of either 5 h or 9 h of TIB for sleep each night as part of a 14-day protocol conducted at a boarding school. During the sleep manipulation period, participants studied 40 Graduate Record Examination (GRE)-type English words using digital flashcards. Word pairs were presented over 4 consecutive days (spaced items), or all at once during single study sessions (massed items), with total study time kept constant across conditions. Recall performance was examined 0 h, 24 h, and 120 h after all items were studied. For all retention intervals examined, recall of massed items was impaired by a greater amount in adolescents exposed to sleep restriction. In contrast, cued recall performance on spaced items was similar between sleep groups. Spaced learning conferred strong protection against the effects of sleep restriction on recall performance, whereas students who had insufficient sleep were more likely to forget items studied over short time intervals. These findings in adolescents demonstrate the importance of combining good study habits and good sleep habits to optimize learning outcomes.

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.

The effects of sleep restriction and altered sleep timing on energy intake and energy expenditure

Experimental evidence suggests that sleep restriction increases energy intake (EI) and may alter energy expenditure (EE). However, it is unknown whether the timing of a sleep restriction period impacts EI and EE the following day. Hence, we examined the effects of sleep restriction with an advanced wake-time or delayed bedtime on next day EI and EE. Twelve men and 6 women (age: 23±4years, body fat: 18.8±10.1%) participated in 3 randomized crossover sessions: control (habitual bed- and wake-times), 50% sleep restriction with an advanced wake-time and 50% sleep restriction with a delayed bedtime. Outcome variables included sleep architecture (polysomnography), EI (food menu), total EE and activity times (accelerometry). Carbohydrate intake was greater on day 2 in the delayed bedtime vs. control session (1386±513 vs. 1579±571kcal; P=0.03). Relative moderate-intensity physical activity (PA) time was greater in the delayed bedtime session vs. control and advanced wake-time sessions on day 1 (26.6±19.9 vs. 16.1±10.6 and 17.5±11.8%; P=0.01), whereas vigorous-intensity PA time was greater following advanced wake-time vs. delayed bedtime on day 1 (2.7±3.0 vs. 1.3±2.4%; P=0.004). Greater stage 1 sleep (β=110kcal, 95% CI for β=42 to 177kcal; P=0.004), and a trend for lower REM sleep (β=−20kcal, 95% CI for β=−41 to 2kcal; P=0.07), durations were associated with greater EI between sleep restriction sessions. These findings suggest that the timing of a sleep restriction period impacts energy balance parameters. Additional studies are needed to corroborate these findings, given the increasing prevalence of shift workers and incidences of sleep disorders and voluntary sleep restriction.

Cognitive Performance, Sleepiness, and Mood in Partially Sleep Deprived Adolescents: The Need for Sleep Study.

To investigate the effects of sleep restriction (7 nights of 5 h time in bed [TIB]) on cognitive performance, subjective sleepiness, and mood in adolescents. A parallel-group design was adopted in the Need for Sleep Study. Fifty-six healthy adolescents (25 males, age = 15-19 y) who studied in top high schools and were not habitual short sleepers were randomly assigned to Sleep Restriction (SR) or Control groups. Participants underwent a 2-w protocol consisting of 3 baseline nights (TIB = 9 h), 7 nights of sleep opportunity manipulation (TIB = 5 h for the SR and 9 h for the control groups), and 3 nights of recovery sleep (TIB = 9 h) at a boarding school. A cognitive test battery was administered three times each day. During the manipulation period, the SR group demonstrated incremental deterioration in sustained attention, working memory and executive function, increase in subjective sleepiness, and decrease in positive mood. Subjective sleepiness and sustained attention did not return to baseline levels even after 2 recovery nights. In contrast, the control group maintained baseline levels of cognitive performance, subjective sleepiness, and mood throughout the study. Incremental improvement in speed of processing, as a result of repeated testing and learning, was observed in the control group but was attenuated in the sleep-restricted participants, who, despite two recovery sleep episodes, continued to perform worse than the control participants. A week of partial sleep deprivation impairs a wide range of cognitive functions, subjective alertness, and mood even in high-performing high school adolescents. Some measures do not recover fully even after 2 nights of recovery sleep. A commentary on this article appears in this issue on page 497.