Sleep-wake Patterns Research Articles

Predictive Factors of Toddlers' Sleep and Parental Stress.

Background: Although most infants consolidate their sleep habits during the first year of life, for many children, sleep is described as disrupted during toddlerhood. Along with individual child variables such as temperamental characteristics, parenting behaviors play a key role in determining children’s sleep–wake patterns. The aims of the current study were to evaluate the relationship among toddlers’ sleep quality, emotion regulation, bedtime routines, parental bedtime involvement, parental perceived social support and stress, and to integrate a novel combination of the aforementioned dimensions into predictive models of toddlers’ sleep quality and parental stress. Methods: One hundred and sixty parents with 2–3-year-old children filled out the following self-report questionnaires: the Parent–Child Sleep Interaction Scale; the Emotion Regulation Checklist; the Social Provisions Scale; and an ad-hoc questionnaire to assess parental involvement in everyday and bedtime care for children. Three multiple regression analyses were conducted by regressing maternal and paternal parenting stress and infant’s quality sleep onto the independent variables described above. Results: Toddlers’ emotion regulation and parental psychosocial functioning were related to parental stress. Toddlers’ night awakenings and the time required by toddlers to fall asleep were related to parental distress. Conclusions: The findings evidenced the bidirectional associations among the studied variables, highlighting the protective role of social support in reducing parenting stress and of paternal bedtime involvement in improving toddlers’ sleep quality.

Sleep-wake behaviors exhibited by shift workers in normal operations and predicted by a biomathematical model of fatigue.

To compare rail workers' actual sleep-wake behaviors in normal operations to those predicted by a biomathematical model of fatigue (BMMF). To determine whether there are group-level residual sources of error in sleep predictions that could be modeled to improve group-level sleep predictions. The sleep-wake behaviors of 354 rail workers were examined during 1,722 breaks that were 8-24 h in duration. Sleep-wake patterns were continuously monitored using wrist-actigraphy and predicted from the work-rest schedule using a BMMF. Rail workers' actual and predicted sleep-wake behaviors were defined as split-sleep (i.e. ≥2 sleep periods in a break) and consolidated-sleep (i.e. one sleep period in a break) behaviors. Sleepiness was predicted from the actual and predicted sleep-wake data. Consolidated-sleep behaviors were observed during 1,441 breaks and correctly predicted during 1,359 breaks. Split-sleep behaviors were observed during 280 breaks and correctly predicted during 182 breaks. Predicting the wrong type of sleep-wake behavior resulted in a misestimation of hours of sleep during a break. Relative to sleepiness predictions derived from actual sleep-wake data, predicting the wrong type of sleep-wake behavior resulted in a misestimation of sleepiness predictions during the subsequent shift. All workers with the same work-rest schedule have the same predicted sleep-wake behaviors; however, these workers do not all exhibit the same sleep-wake behaviors in real-world operations. Future models could account for this group-level residual variance with a new approach to modeling sleep, whereby sub-group(s) may be predicted to exhibit one of a number of sleep-wake behaviors.

Clinical Implications of Fetal Heart Rate Interpretation Based on Underlying Physiology.

Understanding the physiology of fetal oxygenation and various influences on fetal heart rate control supports nurses, midwives, and physicians in interpreting and managing electronic fetal heart rate tracings during labor and birth. Maternal oxygenation, placental circulation and exchange, umbilical blood flow and fetal circulation affect fetal oxygenation, which is reflected in observed fetal heart rate patterns. Fetal heart control is further influenced by the central and autonomic nervous systems, baroreceptors, chemoreceptors, humoral factors, sleep-wake patterns, breathing movements, medications, painful stimuli, sound and vibrations, and temperature. Knowledge of the physiologic basis for fetal heart rate pattern characteristics guides interventions to improve fetal oxygenation when indicated. A review and update on clinical implications of fetal heart rate pattern interpretation based on underlying physiology is presented.

Activation of Preoptic GABAergic or Glutamatergic Neurons Modulates Sleep-Wake Architecture, but Not Anesthetic State Transitions.

The precise mechanism of general anesthesia remains unclear. In the last two decades, there has been considerable focus on the hypothesis that anesthetics co-opt the neural mechanisms regulating sleep. This hypothesis is supported by ample correlative evidence at the level of sleep-promoting nuclei, but causal investigations of potent inhaled anesthetics have not been conducted. Here, we tested the hypothesis that chemogenetic activation of discrete neuronal subpopulations within the median preoptic nucleus (MnPO) and ventrolateral preoptic nucleus (VLPO) of the hypothalamus would modulate sleep/wake states and alter the time to loss and resumption of consciousness associated with isoflurane, a potent halogenated ether in common clinical use. We show that activating MnPO/VLPO GABAergic or glutamatergic neurons does not alter anesthetic induction or recovery time. However, activation of these neuronal subpopulations did alter sleep-wake architecture. Notably, we report the novel finding that stimulation of VLPO glutamatergic neurons causes a strong increase in wakefulness. We conclude that activation of preoptic GABAergic or glutamatergic neurons that increase sleep or wakefulness does not substantively influence anesthetic state transitions. These data indicate that the correlative evidence for a mechanistic overlap of sleep and anesthesia at the level of an individual nucleus might not necessarily have strong causal significance.

Intracerebral hemorrhage in the mouse altered sleep-wake patterns and activated microglia

Sleep-wake disturbances are both a risk factor and reported morbidity for intracerebral hemorrhage (ICH). ICH begins with a ruptured blood vessel and blood leakage into the parenchyma. In response to initial damage, pathophysiological processes ensue that both exacerbate and repair damage. Inflammation is a hallmark process of ICH, which includes microglia activation and increased cytokine signaling. Due to the dual role of cytokines as inflammatory signaling proteins and sleep regulatory substances (SRSs), we hypothesized that ICH would activate microglia, increase SRSs, and alter sleep-wake patterns following an experimental model of ICH in the mouse. Male mice were randomized to receive an injection of collagenase (ICH; n = 8) or saline (sham; n = 11) in the striatum of the right hemisphere. Sleep-wake activity was recorded for 6 full days after ICH via noninvasive sleep cages. Blood and tissue were collected at 7 days after ICH to quantify pro-inflammatory cytokines/SRSs (IL-1β, TNF-α, IL-6) and microglia deramification by skeleton analysis. There was an overall injury effect on sleep in mice subjected to ICH at the transition from dark (wake) to light (sleep) at 2, 3, 4, 5, and 6 days after ICH compared with shams. Further analysis confirmed that ICH mice had significantly earlier wake offsets at the dark/light transition and more robust circadian patterns of wake behavior than saline control mice. Spatiotemporal skeleton analysis indicated an increase in microglial cell number with a decrease in endpoints per cell (decreased ramification) for the ipsilateral ICH perihematomal region compared with saline control. There were no changes to plasma cytokine levels at 7 days after ICH when comparing each condition. This is the first known study to show changes in sleep-wake patterns after experimental ICH. Elucidation of mechanisms that link sleep, inflammation, and ICH offers new pharmacological opportunities and rehabilitative strategies to improve recovery in stroke patients.

Digital Cognitive–Behavioural Therapy for Insomnia (dCBT-I) Is Associated with Improved Sleep and Less Self-Report Use of Sleep Medication: A Large-Scale Randomized Controlled Trial

Background: Although several large trials have demonstrated the efficacy of digital cognitive–behavioural therapy for insomnia (dCBT-I), there is a need to validate a far-reaching dissemination of dCBT-I on recommended key outcomes of insomnia. We aimed to investigate the effect of self-guided dCBT-I on insomnia severity, sleep-wake patterns, use of sleep medication, and daytime impairment. Methods: We did a parallel-group superiority randomised controlled trial (RCT) comparing digital CBT-I with online patient education about sleep (PE). Interventions were available from a free-to-access website with an online automated screening test. Primary outcome was ISI score at nine-week follow-up, and secondary outcomes included self-reported use of sleep medication, sleep diary measures, and measures of daytime impairment. Findings: A total of 1721 adults who scored ³12 on the Insomnia Severity Index (ISI) were randomized, 868 to dCBT-I and 853 to PE. At nine-week follow-up, 584 (67%) in the dCBT-I group and 534 (63%) in the PE group completed online self-report ratings. The dCBT-I group had a significantly greater reduction in the primary outcome of insomnia severity compared with the PE group (Cohen’s d = -1·21; 95% Confidence Interval [CI], -1·05 to -1·38; p < ·001). Compared with the PE intervention, the number needed to treat with dCBT-I was 2·7 (95% CI 2·4 to 3·2) for response and 3·2 (95% CI 2·8 to 3·8) for remission of insomnia. The dCBT-I group were significantly less likely to use sleep medication (secondary outcome) at follow-up, compared with the PE group (Odds ratio [OR] = 0·49; 95% CI, 0·23 to 0·74; p < ·001), and reported lower daytime impairment. Interpretation: A self-guided dCBT-I programme made widely accessible is effective in reducing both night-time and daytime impairments associated with the insomnia disorder, while also reducing the likelihood of using sleep medication. Trial Registration: This trial was registered with ClinicalTrials.gov, NCT02558647. Funding Statement: The Norwegian Research Council; grant number 239985 and the Liaison Committee for education, research and innovation in Central Norway; grant number 90061500. Declaration of Interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf. BS, HK, OV, ORFS, GM, SP, AGH, PG, KL, and TCS report no conflicts of interest. FPT and LMR report having a financial and/or business interest in BeHealth Solutions and Pear Therapeutics, two companies that develop and disseminate digital therapeutics, including by licensing the therapeutic developed, based in part, on early versions of the software utilized in research reported in the enclosed paper. These companies had no role in preparing this manuscript. LMR is also a consultant to Mahana Therapeutics, a separate digital therapeutic company not affiliated with this research. Some of the research in this paper was conducted while FPT was a faculty member at the University of Virginia. At that time for FPT, and ongoing for LMR, the terms of these arrangements have been reviewed and approved by the University of Virginia in accordance with its policies. Ethical Approval Statement: The trial protocol was approved by the Regional Committees for Medical and Health Research Ethics in South East Norway (2015/134).

Peri- and Post-operative Amplitude-integrated Electroencephalography in Infants with Congenital Heart Disease

To identify the factors influencing brain injury in infants with congenital heart disease (CHD) after cardiac surgery. This retrospective study investigated 103 infants with CHD undergoing cardiac surgery between January 2013 and February 2016. Pre- and postoperative amplitude-integrated electroencephalography (aEEG) recordings were assessed for background pattern, sleep-wake cycle pattern and seizure activity. Logistic regression model was used to determine the influencing factors of brain injury. Pre-operatively, most infants in our study exhibited a normal background pattern, with 16.5% showing discontinuous normal voltage, whereas this pattern was observed in only 7.8% of infants postoperatively. The improvement in background pattern after surgery was significant (P<0.05) in infants at no more than 39 weeks of gestational age. Infants with postoperative sepsis or severe postoperative infection were prone to show a worse sleep-wake cycle pattern after heart surgery. The improvement in brain function of infants with CHD after cardiac surgery was associated with the gestational age and postoperative infection.

Aging Affects the Capacity of Photoperiodic Adaptation Downstream from the Central Molecular Clock.

Aging impairs circadian clock function, leading to disrupted sleep-wake patterns and a reduced capability to adapt to changes in environmental light conditions. This makes shift work or the changing of time zones challenging for the elderly and, importantly, is associated with the development of age-related diseases. However, it is unclear what levels of the clock machinery are affected by aging, which is relevant for the development of targeted interventions. We found that naturally aged mice of >24 months had a reduced rhythm amplitude in behavior compared with young controls (3-6 months). Moreover, the old animals had a strongly reduced ability to adapt to short photoperiods. Recording PER2::LUC protein expression in the suprachiasmatic nucleus revealed no impairment of the rhythms in PER2 protein under the 3 different photoperiods tested (LD: 8:16, 12:12, and 16:8). Thus, we observed a discrepancy between the behavioral phenotype and the molecular clock, and we conclude that the aging-related deficits emerge downstream of the core molecular clock. Since it is known that aging affects several intracellular and membrane components of the central clock cells, it is likely that an impairment of the interaction between the molecular clock and these components is contributing to the deficits in photoperiod adaptation.

Sleep duration, sleep variability, and impairments of visual attention.

Attentional networks are sensitive to sleep deprivation. However, variation in attentional performance as a function of normal sleep parameters is understudied. We examined whether attentional performance is influenced by (a) individual differences in sleep duration, (b) sleep duration variability, and/or (c) their interaction. A total of 57 healthy participants (61.4% female, Mage = 32.37 years, SD = 8.68) completed questionnaires, wore wrist actigraphy for 1 week, and subsequently completed the attention network test. Sleep duration and sleep duration variability did not predict orienting score, executive control score, or error rates. Sleep duration variability appeared to moderate the association between sleep duration with overall reaction time (β = -.34, t = -2.13, p = .04) and alerting scores (β = .43, t = 2.94, p = .01), though further inspection of the data suggested that these were spurious findings. Time of testing was a significant predictor of alerting score (β = .35, t = 2.96, p = .01), chronotype of orienting (β = .31, t = 2.28, p = .03), and age of overall reaction time (β = .35, t = 2.70, p = .01). Our results highlight the importance of examining the associations between variations in sleep-wake patterns and attentional networks in samples with greater variation in sleep, as well as the importance of rigorously teasing apart mechanisms of the sleep homeostat from those related to the circadian rhythm in studies examining cognition.

Dysregulation of Circadian Rhythms in Autism Spectrum Disorders

The alterations in neurological and neuroendocrine functions observed in the autism spectrum disorder (ASD) involves environmentally dependent dysregulation of neurodevelopment, in interaction with multiple coding gene defects. Disturbed sleep-wake patterns, as well as abnormal melatonin and glucocorticoid secretion, show the relevance of an underlying impairment of the circadian timing system to the behavioral phenotype of ASD. Thus, understanding the mechanisms involved in the circadian dysregulation in ASD could help to identify early biomarkers to improve the diagnosis and therapeutics as well as providing a significant impact on the lifelong prognosis. In this review, we discuss the organization of the circadian timing system and explore the connection between neuroanatomic, molecular, and neuroendocrine responses of ASD and its clinical manifestations. Here we propose interconnections between circadian dysregulation, inflammatory baseline and behavioral changes in ASD. Taking into account, the high relevancy of melatonin in orchestrating both circadian timing and the maintenance of physiological immune quiescence, we raise the hypothesis that melatonin or analogs should be considered as a pharmacological approach to suppress inflammation and circadian misalignment in ASD patients. This review provides a comprehensive update on the state-of-art of studies related to inflammatory states and ASD with a special focus on the relationship with melatonin and clock genes. The hypothesis raised above was analyzed according to the published data. Current evidence supports the existence of associations between ASD to circadian dysregulation, behavior problems, increased inflammatory levels of cytokines, sleep disorders, as well as reduced circadian neuroendocrine responses. Indeed, major effects may be related to a low melatonin rhythm. We propose that maintaining the proper rhythm of the circadian timing system may be helpful to improve the health and to cope with several behavioral changes observed in ASD subjects.

Children and Adolescents’ Sleep Patterns and Their Associations with Mental Health During the COVID-19 Pandemic in Shanghai, China

Background: School closures and home confinement due to the ongoing COVID-19 pandemic may lead to disrupted sleep patterns. Consequently, it could increase the risk of children and adolescents’ mental health disorders. We examined sleep patterns before and during the COVID-19 pandemic, and their associations with mental health in children and adolescents during the pandemic in Shanghai, China.Methods: In this natural experiment study, a total of 7,544 children and adolescents aged 6-17 years were randomly selected from ten schools in Shanghai, China in the first wave of the survey between January 3 and 21, 2020. Approximately two months after the COVID-19 outbreak declared, a second wave of the survey was conducted among 4,391 children and adolescents from six schools. In total, 2,250 individuals were surveyed in both waves. Participants’ mental health status (depression, anxiety and stress), sleep patterns and other demographic information were measured in both waves. Multivariate regression analysis was used to examine the associations between sleep patterns and mental health status. Multiple imputation was used to reduce the risk of bias from missing data.Findings: During the COVID-19 pandemic, a total of 873 participants (19.9%), 1,100 participants (25.1%), and 670 participants (15.3%) reported depression, anxiety and stress symptoms, respectively. Significant changes of both sleep duration and sleep-wake cycle patterns were observed before and during the COVID-19 pandemic. Moreover, shorter sleep duration and late to rise patterns (including early to bed late to rise and late to bed late to rise) were found to be associated with higher odds of having mental illnesses during the pandemic.Interpretation: These results suggest there is pressing need to monitor children and adolescents’ health behaviour and mental health and develop timely evidence‐based strategies and interventions to mitigate adverse behavioural and psychological impacts caused by these unprecedented challenges.Funding Statement: This research was funded by the National Natural Science Foundation of China (grant number 71804110) for Mi Xiang and supported by Global Public Health strand of the Elizabeth Blackwell Institute for Health Research, funded under the University of Bristol’s QR GCRF strategy. Declaration of Interests: None.Ethics Approval Statement: Ethics approval was obtained from the Ethics Committee of Shanghai Jiaotong University School of Medicine (SJUPN-201813). Written, informed consent was obtained from caregivers of all participants.

When the girdle of social timing relaxes: Effects of the COVID-19 lockdown on human sleep

Increased regularity of sleep-wake patterns and more sleep: The ‘lockdown’-induced relaxation of social schedules had positive effects on people’s sleep. However, not everyone slept well in this unprecedented situation. - submission by Christine Blume, Marlene H. Schmidt

Evaluation of the Vibe Actigraph in Patients With Chronic Obstructive Pulmonary Disease: A Pilot Study.

Study objective: To validate the Vibe actigraph in assessing sleep-wake patterns compared to polysomnography (PSG) in patients with COPD. Methods: Nine stable COPD patients wore actigraphs while undergoing PSG. The correlation between total sleep time (TST), total sleep period (TSP), sleep onset latency (SOL), wake after sleep onset (WASO), and sleep efficiency was determined for corresponding measurements from the actigraph and PSG. Sensitivity, specificity, and positive and negative predictive values were calculated for the actigraph, considering PSG the gold standard. Levels of agreement between the variables of PSG and the actigraph were estimated using Bland-Altman plots. Results: A strong and statistically significant correlation was noted between PSG and the actigraph in detecting movement during sleep [mean activity score (counts)], TST and TSP (all rs = 0.83; p = 0.005). The median agreement of sleep and wake counts between PSG and the actigraph was 73% and the Cohen’s Kappa value was 0.66. The medians of sensitivity and specificity of the actigraph for detecting sleep versus PSG were 84 and 66%, respectively. The median positive and negative predictive values of the actigraph were 74 and 72%, respectively. Conclusions: This study demonstrated that, under controlled laboratory conditions, the Vibe actigraph in its default settings is a promising tool for the detection of sleep-wake parameters in a small number of ambulatory patients with COPD. Clinical Impact: The actigraph used in this pilot study suggests that these devices could provide clinically relevant information in COPD to better understand the relationship between sleep and health in this population.

The association between 25-hydroxyvitamin D levels and children's sleep-wake patterns: a prospective cohort study

ObjectiveTo explore the association between vitamin D in cord blood or in venous blood and children's sleep-wake patterns at two years of age. MethodsData were from 209 children in a birth cohort, Shanghai Sleep Birth Cohort Study (SSBC). 25-Hydroxyvitamin D (25(OH)D) was assessed in cord blood and venous blood samples at two years of age by electrochemiluminescence immunoassay. Children's sleep-wake patterns were measured with the Brief Infant Sleep Questionnaire (BISQ) and Acti-Watch at two years of age. ResultsThe prevalence of vitamin D deficiency (defined as <50 nmol/L) was 50.4% in cord blood and 28% at two years of age. The cord blood 25(OH)D level was not significantly associated with children's sleep at two years of age. Children with 25(OH)D deficiency at two years old had shorter reported and actigraphic night sleep duration (NSD) and total sleep duration (TSD) than those with normal 25(OH)D concentration. 25(OH)D level at two years old was positively associated with night and total sleep duration (βreported-NSD = 0.6, p = 0.011; βreported-TSD = 0.6, p = 0.029; βactigraphic-NSD = 0.82, p = 0.003; βactigraphic-TSD = 0.78, p = 0.006), but was not associated with daytime sleep duration. There was no significant association between 25(OH)D level with night waking duration and midpoint of sleep either measured subjectively or objectively. ConclusionWe found that not cord blood 25(OH)D level but two-year-old 25(OH)D level was associated with children's sleep-wake patterns at two years of age. These findings suggest more attention should be paid to the assessment of 25(OH)D levels in children with short sleep duration.

Photoacoustic treatment mitigates cognitive dysfunction in a model of sleep-wake rhythm disturbance.

Sleep-wake rhythm disturbances, which are characterized by abnormal sleep timing or duration, are associated with cognitive dysfunction. Photoacoustic treatments including light and sound stimulation have been found to be effective in modulating sleep patterns and improving cognitive behavior in abnormal sleep-wake pattern experiments. In this study, we examined whether light and sound interventions could reduce sleep-wake pattern disturbances and memory deficits in a sleep rhythm disturbance model. We established a model of sleep rhythm disturbance in C57BL/6J mice via a sleep deprivation method involving manual cage tapping, cage jostling, and nest disturbance. We used a Mini Mitter radio transmitter device to monitor motor activity in the mice and fear conditioning tests to assess cognitive function. Our results indicated that an intervention in which the mice were exposed to blue light (40-Hz flickering frequency) for 1 hour during their subjective daytime significantly improved the 24-hour-acrophase shift and reduced the degree of memory deficit induced by sleep deprivation. However, interventions in which the mice were exposed to a 40-Hz blue light at offset time or subjective night time points, as well as 2 Hz-blue light at 3 intervention time points (subjective day time, subjective night time, and offset time points), had no positive effects on circadian rhythm shift or memory deficits. Additionally, a 2000-Hz sound intervention during subjective day time attenuated the 24-hour-acrophase shift and memory decline, while 440-Hz and 4000-Hz sounds had no effect on circadian rhythms. Overall, these results demonstrate that photoacoustic treatment effectively corrected abnormal sleep-wake patterns and cognitive dysfunction associated with sleep-deprivation-induced disturbances in sleep-wake rhythm. All animal experiments were approved by the Experimental Animal Ethics Committee of Drum Tower Hospital Affiliated to the Medical College of Nanjing University, China (approval No. 20171102) on November 20, 2017.

Pupillometry evaluation of melanopsin retinal ganglion cell function and sleep-wake activity in pre-symptomatic Alzheimer's disease.

Melanopsin-expressing retinal ganglion cells (mRGCs), intrinsically photosensitive RGCs, mediate the light-based pupil response and the light entrainment of the body's circadian rhythms through their connection to the pretectal nucleus and hypothalamus, respectively. Increased awareness of circadian rhythm dysfunction in neurological conditions including Alzheimer's disease (AD), has led to a wave of research focusing on the role of mRGCs in these diseases. Postmortem retinal analyses in AD patients demonstrated a significant loss of mRGCs, and in vivo measurements of mRGC function with chromatic pupillometry may be a potential biomarker for early diagnosis and progression of AD. We performed a prospective case-control study in 20 cognitively healthy study participants: 10 individuals with pre-symptomatic AD pathology (pre-AD), identified by the presence of abnormal levels of amyloid β42 and total Tau proteins in the cerebrospinal fluid, and 10 age-matched controls with normal CSF amyloid β42 and Tau levels. To evaluate mRGC function, we used a standardized protocol of chromatic pupillometry on a Ganzfeld system using red (640 nm) and blue (450 nm) light stimuli and measured the pupillary light response (PLR). Non-invasive wrist actigraphy and standardized sleep questionnaires were also completed to evaluate rest-activity circadian rhythm. Our results did not demonstrate a significant difference of the PLR between pre-AD and controls but showed a variability of the PLR in the pre-AD group compared with controls on chromatic pupillometry. Wrist actigraphy showed variable sleep-wake patterns and irregular circadian rhythms in the pre-AD group compared with controls. The variability seen in measurements of mRGC function and sleep-wake cycle in the pre-AD group suggests that mRGC dysfunction occurs in the pre-symptomatic AD stages, preceding cognitive decline. Future longitudinal studies following progression of these participants can help in elucidating the relationship between mRGCs and circadian rhythm dysfunction in AD.

Sleep-wake patterns and white matter integrity influence cognitive control in young adults

Sleep-wake patterns and white matter integrity influence cognitive control in young adults

Trends in sleep-wake patterns of primary school-age children: a comparison between 1995 and 2016

Trends in sleep-wake patterns of primary school-age children: a comparison between 1995 and 2016

Hammock and nesting in preterm infants: randomized controlled trial.

To compare the physiological variables and the sleep-wake pattern presented by preterm in nesting and hammock positions after diaper change. This is a crossover randomized controlled trial. It was conducted with 20 preterm infants who, after diaper change, were placed in nests or hammocks. These preterm infants were evaluated for physiological variables (heart rate and oxygen saturation) and behavioral variables (sleep and wakefulness). There was no statistically significant difference in the studied variables between nesting and hammock positions. However, regarding the categorical variable sleep, the comparison between the research phases for the hammock position showed differences between the baseline phase and the immediate recovery (p=0.00), baseline and late recovery (p=0.00), response and immediate recovery (p=0.00), response and late recovery (p=0.00). No differences were identified between the nest and the hammock; however, the use of the hammock favored the sleep of preterm infants compared to its non-use.

Serotonergic system may be involved in alterations of sleep homeostasis in spontaneously hypertensive rats.

Hypertension is associated with sleep disorders. Spontaneously hypertensive rats are derived from Wistar-Kyoto rats and widely used in research on hypertension. The present study investigated the propensity to sleep and electroencephalographic spectrum changes over 24hr in spontaneously hypertensive rats, and proposed the involvement of the serotonergic system in these alterations. Time-course analysis showed that spontaneously hypertensive rats exhibit hyperarousal during the light phase but hypersomnia during the dark phase. Spontaneously hypertensive rats also exhibited less slight fluctuation in electroencephalographic delta power density over 24hr as compared with Wistar-Kyoto rats, suggesting that the accumulation or elimination of sleep pressure was disrupted. Sleep deprivation disrupted the regulation of sleep homeostasis in spontaneously hypertensive rats, reflected by less sleep time and poor sleep quality during the recovery period. The density and activity of serotonergic neurons in the dorsal raphe nucleus were higher in spontaneously hypertensive rats compared with Wistar-Kyoto rats. Interestingly, we observed the absence of fluctuations in 5-hydroxytryptamine and 5-hydroxyindoleacetic acid across the sleep, wake, sleep deprivation and sleep recovery stages in spontaneously hypertensive rats, which were dramatically different from Wistar-Kyoto rats. These results indicate that the disruption of sleep-wake pattern and sleep homeostasis in spontaneously hypertensive rats might be related to abnormalities of the serotonergic system.