Duration Of Sleep Stages Research Articles

The Sleeping Infant Brain Anticipates Development

From the age of 3months, infants learn relations between objects and co-occurring words [1]. These very first representations of object-word pairings in infant memory are considered as non-symbolic proto-words comprising specific visual-auditory associations that can already be formed in the first months of life [2-5]. Genuine words that refer to semantic long-term memory have not been evidenced prior to 9months of age [6-9]. Sleep is known to facilitate the reorganization of memories [9-14], but its impact on the perceptual-to-semantic trend in early development is unknown. Here we explored the formation of word meanings in 6- to 8-month-old infants and its reorganization during the course of sleep. Infants were exposed to new words as labels for new object categories. In the memory test about an hour later, generalization to novel category exemplars was tested. In infants who took a short nap during the retention period, a brain response of 3-month-olds [1] was observed, indicating generalizations based on early developing perceptual-associative memory. In those infants who napped longer, a semantic priming effect [15, 16] usually found later in development [17-19] revealed the formation of genuine words. The perceptual-to-semantic shift in memory was related to the duration of sleep stage 2 and to locally increased sleep spindle activity. The finding that, after the massed presentation of several labeled category exemplars, sleep enabled even 6-month-olds to create semantic long-term memory clearly challenges the notion that immature brain structures are responsible for the typically slower lexical development.

Efficacy and safety of almorexant in adult chronic insomnia: a randomized placebo-controlled trial with an active reference

Background and objectivesThe orally active dual OX1R and OX2R antagonist, almorexant, targets the orexin system for the treatment of primary insomnia. This clinical trial assessed the effect of almorexant on sleep maintenance and other sleep endpoints, and its safety and tolerability in adults. Patients and methodsProspective, randomized, double-blind, placebo-controlled, active referenced trial in male and female adults aged 18–64 years with chronic, primary insomnia. Patients were randomized 1:1:1:1 to receive placebo, almorexant 100 mg, almorexant 200 mg, or zolpidem 10 mg (active reference) for 16 days. Primary efficacy assessments were objective (polysomnography-measured) and subjective (patient-recorded) wake time after sleep onset (WASO). Further sleep variables were also evaluated. ResultsFrom 709 randomized patients, 707 (mean age 45.4 years; 61.7% female) received treatment and 663 (93.8%) completed the study. A significant decrease versus placebo in median objective WASO was observed with almorexant 200 mg at the start and end of randomized treatment (−26.8 min and −19.5 min, respectively; both p < 0.0001); subjective WASO also decreased over the two-week treatment period (p = 0.0006). Objective and subjective total sleep time (TST) were increased with almorexant 200 mg (p < 0.0001). Almorexant 200 mg significantly reduced objective and subjective latency to persistent sleep and latency to sleep onset at initiation of therapy, and provided longer duration of sleep stages with no suppression of slow-wave sleep. No impaired next-day performance, rebound insomnia, or withdrawal effects were observed. Adverse events were similar with almorexant and placebo. ConclusionAlmorexant reduced time to sleep onset and maintained sleep without residual effects on next-day performance or safety concerns. This study provides further support for the role of the endogenous orexin system in insomnia disorder. ClinicalTrials.gov registrationNCT00608985.

0768 BAYESIAN NETWORK MODELING OF DAYTIME AND NIGHTTIME SLEEP ARCHITECTURE

The complex pattern of sleep stages over a night (sleep architecture) exhibits abnormal patterns in disorders such as apnea and depression. Quantifying variability in sleep architecture caused by benign versus harmful factors may provide a powerful diagnostic tool. Current measures of sleep architecture, such as stage proportions, fail to capture the dynamics of human sleep stage transitions. Here, we investigate the effect of individual (age, sex, BMI) and previous sleep factors (time of day, time spent in a stage) on alternate measures of sleep architecture: transition probabilities (the likelihood of transition from one state to another) and stage duration distributions. We fit various discrete Bayesian networks to large amounts of sleep data (>9000 nights/naps) to determine the relational structure between variables. We find, in accordance with the literature, that sex, age, but not BMI significantly influence sleep stage durations. Specifically, older men have shorter bouts (more fragmentation) of REM sleep (11% more bouts < 6 minutes) and Slow Wave Sleep (2% more bouts < 6 mins) compared to older women. Older males and females had more fragmented sleep across all stages, although this pattern was stronger for males (older vs younger females = 3%, older vs younger males = 5% more < 6 minutes). Interestingly, transition probabilities are unaffected by sex, age, and BMI. Additionally, we find that the identity of the next stage is dependent on only the last two states. These findings demonstrate low complexity in sleep stage transitions, which can be useful for future work on a higher resolution continuous Bayesian network capable of predicting sleep stage sequences. Future work will also use Bayesian network modeling to characterize differences between healthy and unhealthy sleep architecture patterns.

Sleep stage distribution in persons with mild traumatic brain injury: a polysomnographic study according to American Academy of Sleep Medicine standards

Objective and backgroundSleep stage disruption in persons with mild traumatic brain injury (mTBI) has received little research attention. We examined deviations in sleep stage distribution in persons with mTBI relative to population age- and sex-specific normative data and the relationships between such deviations and brain injury-related, medical/psychiatric, and extrinsic factors. Patients and methodsWe conducted a cross-sectional polysomnographic investigation in 40 participants diagnosed with mTBI (mean age 47.54 ± 11.30 years; 56% males). MeasurementsAt the time of investigation, participants underwent comprehensive clinical and neuroimaging examinations and one full-night polysomnographic study. We used the 2012 American Academy of Sleep Medicine recommendations for recording, scoring, and summarizing sleep stages. We compared participants' sleep stage data with normative data stratified by age and sex to yield z-scores for deviations from available population norms and then employed stepwise multiple regression analyses to determine the factors associated with the identified significant deviations. ResultsIn patients with mTBI, the mean duration of nocturnal wakefulness was higher and consolidated sleep stage N2 and REM were lower than normal (p < 0.0001, p = 0.018, and p = 0.010, respectively). In multivariate regression analysis, several covariates accounted for the variance in the relative changes in sleep stage duration. No sex differences were observed in the mean proportion of non-REM or REM sleep. ConclusionsWe observed longer relative nocturnal wakefulness and shorter relative N2 and REM sleep in patients with mTBI, and these outcomes were associated with potentially modifiable variables. Addressing disruptions in sleep architecture in patients with mTBI could improve their health status.

Fragmentation of Rapid Eye Movement and Nonrapid Eye Movement Sleep without Total Sleep Loss Impairs Hippocampus-Dependent Fear Memory Consolidation.

Sleep is important for consolidation of hippocampus-dependent memories. It is hypothesized that the temporal sequence of nonrapid eye movement (NREM) sleep and rapid eye movement (REM) sleep is critical for the weakening of nonadaptive memories and the subsequent transfer of memories temporarily stored in the hippocampus to more permanent memories in the neocortex. A great body of evidence supporting this hypothesis relies on behavioral, pharmacological, neural, and/or genetic manipulations that induce sleep deprivation or stage-specific sleep deprivation. We exploit an experimental model of circadian desynchrony in which intact animals are not deprived of any sleep stage but show fragmentation of REM and NREM sleep within nonfragmented sleep bouts. We test the hypothesis that the shortening of NREM and REM sleep durations post-training will impair memory consolidation irrespective of total sleep duration. When circadian-desynchronized animals are trained in a hippocampus-dependent contextual fear-conditioning task they show normal short-term memory but impaired long-term memory consolidation. This impairment in memory consolidation is positively associated with the post-training fragmentation of REM and NREM sleep but is not significantly associated with the fragmentation of total sleep or the total amount of delta activity. We also show that the sleep stage fragmentation resulting from circadian desynchrony has no effect on hippocampus-dependent spatial memory and no effect on hippocampus-independent cued fear-conditioning memory. Our findings in an intact animal model, in which sleep deprivation is not a confounding factor, support the hypothesis that the stereotypic sequence and duration of sleep stages play a specific role in long-term hippocampus-dependent fear memory consolidation.

Restricting Time in Bed in Early Adolescence Reduces Both NREM and REM Sleep but Does Not Increase Slow Wave EEG.

School night total sleep time decreases across adolescence (9-18 years) by 10 min/year. This decline is comprised entirely of a selective decrease in NREM sleep; REM sleep actually increases slightly. Decreasing sleep duration across adolescence is often attributed to insufficient time in bed. Here we tested whether sleep restriction in early adolescence produces the same sleep stage changes observed on school nights across adolescence. All-night sleep EEG was recorded in 76 children ranging in age from 9.9 to 14.0 years. Each participant kept 3 different sleep schedules that consisted of 3 nights of 8.5 h in bed followed by 4 nights of either 7, 8.5, or 10 h in bed. Sleep stage durations and NREM delta EEG activity were compared across the 3 time in bed conditions. Shortening time in bed from 10 to 7 hours reduced sleep duration by approximately 2 hours, roughly equal to the decrease in sleep duration we recorded longitudinally across adolescence. However, sleep restriction significantly reduced both NREM (by 83 min) and REM (by 47 min) sleep. Sleep restriction did not affect NREM delta EEG activity. Our findings suggest that the selective NREM reduction and the small increase in REM we observed longitudinally across 9-18 years are not produced by sleep restriction. We hypothesize that the selective NREM decline reflects adolescent brain maturation (synaptic elimination) that reduces the need for the restorative processes of NREM sleep.

Polysomnographic Measurement of Sleep Duration and Bodily Pain Perception in the Sleep Heart Health Study.

To determine whether total sleep time (TST) and specific sleep stage duration are associated with bodily pain perception and whether sex, age, or subjective sleepiness modifies this relationship. Data from adults ages 39-90 y (n = 5,199) who took part in the Sleep Heart Health Study Exam 1 were analyzed. TST, rapid eye movement (REM) sleep time, and slow wave sleep (SWS) time were measured by unattended, in-home nocturnal polysomnography. Bodily pain perception was measured via the Short Form-36 questionnaire bodily pain component. We used logistic regression to examine associations between total and individual sleep stage durations and bodily pain perception controlling for age, sex, race, body mass index, apnea-hypopnea index, antidepressant use, and important cardiovascular conditions (smoking [pack-years], history of diabetes, and history of percutaneous coronary intervention and/or coronary artery bypass graft). In the fully adjusted model, REM sleep time and SWS time were not associated with "moderate to severe pain," whereas TST was: Each 1-h decrement in TST was associated with a 7% increased odds of "moderate to severe pain" (odds ratio 1.07, 95% confidence interval 1.002, 1.14). Due to modification of the association between SWS time and "moderate to severe pain" by sex (P for interaction = 0.01), we performed analyses stratified by sex: Each 1-h decrement in SWS time was associated with a 20% higher odds of "moderate to severe pain" among men (odds ratio 1.20, 95% confidence interval 1.03-1.42) whereas an association was not observed among women. Shorter TST among all subjects and shorter SWS time in men was associated with "moderate to severe pain." REM sleep time was not associated with bodily pain perception in this cohort.

Effects of positive end expiratory pressure administration during non-invasive ventilation in patients affected by amyotrophic lateral sclerosis: A randomized crossover study.

No studies have evaluated the impact of different settings of non-invasive ventilation (NIV) in patients affected by amyotrophic lateral sclerosis (ALS). We explored consequences of positive end-expiratory pressure (PEEP) application on effectiveness of ventilation, sleep architecture and heart rate variability (HRV) in patients with ALS naïve to ventilatory treatment. In two consecutive nights, 25 patients received in random order 0 or 4 cm H2 0 of PEEP during nocturnal NIV administration (Idea Ultra ResMed) with the same level of total positive inspiratory pressure. Polysomnographies were performed to evaluate sleep and NIV quality, as well as HRV. HRV was analyzed on 4-h periods and on 5-min segments of stable NREM sleep. We did not observe differences in gas exchanges during NIV with and without PEEP. Conversely, during PEEP application increases in leaks (41.4 ± 29.3% vs 31.0 ± 25.7%, P = 0.0007) and in autotriggerings (4.2 (IQR 1.3-10.0) vs 0.9 (IQR 0.0-3.0) events/h, P < 0.001, PEEP vs no PEEP, respectively) occurred. Besides, N3 sleep stage duration decreased (2.5% (IQR 0.0-18.0) vs 0.0% (IQR0.0-12.1), P = 0.001) and arousal/awakening index increased (16.9 ± 7.4 vs 13.4 ± 5.0 events/h, P = 0.01). Data on HRV were available in 15 patients. A higher low/high frequency ratio, either in the 4-h (3.8 ± 2.6 vs 2.9 ± 1.7, P = 0.04, PEEP vs no PEEP, respectively) or in the 5-min segments (2.6 ± 1.8 vs 1.45 ± 0.9 P = 0.01) was found during PEEP administration. In ALS patients, PEEP application during NIV was associated with worse NIV and sleep quality and with higher sympathetic activity.

Impact of Ramadan intermittent fasting on cognitive function in trained cyclists: a pilot study.

This study assessed selected measures of cognitive function in trained cyclists who observed daylight fasting during Ramadan. Eleven cyclists volunteered to participate (age: 21.6±4.8 years, VO2max: 57.7±5.6 ml kg−1·min−1) and were followed for 2 months. Cognitive function (Cambridge Neuropsychological Test Automated Battery (CANTAB), Reaction Time index (RTI) and Rapid Visual Information Processing (RVP) tests) and sleep architecture (ambulatory EEG) were assessed: before Ramadan (BR), in the 1st week (RA1) and 4th week of Ramadan (RA4), and 2 weeks post-Ramadan (PR). Both cognitive tests were performed twice per day: before and after Ramadan at 8-10 a.m. and 4-6 p.m., and during Ramadan at 4-6 p.m. and 0-2 a.m., respectively. Training load (TL) by the rating of perceived exertion (RPE) method and wellness (Hooper index) were measured daily. If the TL increased over the study period, this variable was stable during Ramadan. The perceived fatigue and delayed onset muscle soreness (DOMS) increased at RA4. Sleep patterns and architecture showed clear disturbances, with significant increases in the number of awakenings and light sleep durations during Ramadan (RA1 and RA4), together with decreased durations of deep and REM sleep stages at PR. RTI (simple and multiple reaction index) reaction and movement times did not vary over the study period. The RVP test showed reduced false alarms during Ramadan, suggesting reduced impulsivity. Overall accuracy significantly increased at RA1, RA4 and PR compared to baseline. At RA4, the accuracy was higher at 0-2 a.m. compared to 4-6 p.m. Despite the observed disturbances in sleep architecture, Ramadan fasting did not negatively impact the cognitive performance of trained cyclists from the Middle East.

P94. Effects of non-invasive ventilation on sleep and nocturnal ventilation in patients with amyotrophic lateral sclerosis

The majority of patients with amyotrophic lateral sclerosis (ALS) develop chronic ventilatory failure which substantially adds to disease burden and massively affects prognosis. Both quality of life and life expectancy can be influenced by non-invasive ventilation (NIV). Initiation of NIV is indicated in case of sleep-disordered breathing (SDB), daytime hypercapnia, or significant diaphragmatic weakness. Since nocturnal hypercapnia and sleep apnea substantially reduce sleep quality we investigated the effects of NIV on objective measures of both sleep quality and ventilation in patients with ALS. We retrospectively analysed polysomnography (PSG) and oxycapnometry (OC) data obtained from patients with ALS in whom NIV was initiated based on the presence of SDB. PSG and OC were used in all patients for establishing the diagnosis of SDB (t0), for treatment initiation (t1) and for follow-up examination at 3, 9, and 15 months (t2, t3, and t4, respectively). As outcome parameters we chose sleep efficiency (SE), slow wave sleep percentage (N3), REM sleep percentage (REM), apnea hypopnea index (AHI), oxygen desaturation index (ODI), desaturation time (T < 90), respiratory rate (RR) and maximal nocturnal transcutaneous carbon dioxide tension (tc-CO2). Records from 62 patients were analysed. Mean age was 63.2 years, and mean disease duration was 23.1 months. 28 patients were female, and 22 patients reported bulbar onset of ALS symptoms. All patients were started on pressure and volume-controlled bilevel ventilation via a nasal or oronasal interface. Comparison of the above parameters at t0 and t1 showed significant improvement of AHI and ODI, oxygenation, CO2 elimination, and sleep stage duration (N3, REM) in the first night on NIV. Sleep efficiency was neither improved nor reduced by NIV. At t2, t3 and t4 the number of PSG records available became smaller because in many patients, follow-up studies included rather polygraphy than PSG (t2, 33 patients, t3, 15 patients, t4, 11 patients with PSG data). ANOVA for repeated measures revealed stable normoxia and eucapnia under bilevel ventilatory support. Objective measures of sleep quality did not show any significant change over time. Increasing duration of NIV per day was found in all patients in the course of the disease, reflecting disease progression. In patients with ALS, NIV initiation significantly improves objective sleep quality, oxygenation and CO2 elimination in the first night of treatment. Over time, NIV is able to warrant nocturnal normoventilation with only minor changes to ventilator settings. Objective sleep quality does not significantly change in the first 15 months after onset of NIV.

No Associations between Interindividual Differences in Sleep Parameters and Episodic Memory Consolidation.

Sleep and memory are stable and heritable traits that strongly differ between individuals. Sleep benefits memory consolidation, and the amount of slow wave sleep, sleep spindles, and rapid eye movement sleep have been repeatedly identified as reliable predictors for the amount of declarative and/or emotional memories retrieved after a consolidation period filled with sleep. These studies typically encompass small sample sizes, increasing the probability of overestimating the real association strength. In a large sample we tested whether individual differences in sleep are predictive for individual differences in memory for emotional and neutral pictures. Between-subject design. Cognitive testing took place at the University of Basel, Switzerland. Sleep was recorded at participants' homes, using portable electroencephalograph-recording devices. Nine hundred-twenty-nine healthy young participants (mean age 22.48 ± 3.60 y standard deviation). None. In striking contrast to our expectations as well as numerous previous findings, we did not find any significant correlations between sleep and memory consolidation for pictorial stimuli. Our results indicate that individual differences in sleep are much less predictive for pictorial memory processes than previously assumed and suggest that previous studies using small sample sizes might have overestimated the association strength between sleep stage duration and pictorial memory performance. Future studies need to determine whether intraindividual differences rather than interindividual differences in sleep stage duration might be more predictive for the consolidation of emotional and neutral pictures during sleep.

Diminished Nap Effects on Memory Consolidation Are Seen Under Oral Contraceptive Use

Many young females take exogenous hormones as oral contraceptive (OC), a condition rarely controlled for in studies on sleep and memory consolidation even though sex hormones influence consolidation. This study investigated the effects of OCs on sleep-related consolidation of a motor and declarative task, utilizing a daytime nap protocol. Fifteen healthy, young females taking OCs came to the sleep lab for three different conditions: nap with previous learning, wake with previous learning and nap without learning. They underwent each condition twice, once during the ‘pill-active' weeks and once during the ‘pill-free' week, resulting in 6 visits. In all conditions, participants showed a significant off-line consolidation effect, independent of pill week or nap/wake condition. There were no significant differences in sleep stage duration, spindle activity or spectral EEG frequency bands between naps with or without the learning condition. The present data showed a significant off-line enhancement in memory irrespective of potential beneficial effects of a nap. In comparison to previous studies, this may suggest that the use of OCs may enhance off-line memory consolidation in motor and verbal tasks per se. These results stress the importance to control for the use of OCs in studies focusing on memory performance.

High Intensity Non-Invasive Positive Pressure Ventilation (HINPPV) for Stable Hypercapnic Chronic Obstructive Pulmonary Disease (COPD) Patients.

Introduction: High intensity non-invasive positive pressure ventilation (HI-NPPV) is an algorithm of non-invasive ventilation that has been shown to improve partial pressure of carbon dioxide (PaCO2), health-related quality of life and mortality in hypercapnic chronic obstructive pulmonary disease (COPD) patients. Objective: Assess 3 months of HI-NPPV in stable hypercapnic COPD patients. Methods: A single arm, non-randomized pilot study of HI-NPPV. Patients were eligible if they had clinically stable COPD and daytime arterial PaCO2 >50 mmHg. Results: Nine patients completed therapy. Patient characteristics: 2 male: 7 female, mean age of 64.4 years (SD ±6.6), mean forced expiratory volume in 1 second (FEV1) of 26% (SD±6.73), 8 patients on long term oxygen therapy (LTOT) and a median body mass index (BMI) of 26.6 (interquartile range [IQR] 25.5 - 32.5). Outcomes: There was a mean reduction in daytime PaCO2 by 4.66 mmHg (p=0.01) and bicarbonate by 2.16 mmHg (p=0.005). There was no statistically significant difference in lung function, maximal inspiratory pressures or 6 minute walk distance. There was no statistically significant difference in sleep duration, efficiency or percentage of sleep stage 3 ( N3) or rapid eye movement (REM). The Chronic Respiratory Questionnaire (CRQ) showed a trend towards improvement with an increase of 2.69 points (p=0.054), the dyspnea domain showed a statistically significant improvement (p=0.03). The Calgary Sleep Apnea Quality of Life Index (SAQLI) detected an improvement in daily functioning (p=0.007). The Severe Respiratory Insufficiency (SRI) Questionnaire showed a trend to improvement overall (p=0.05). Four patients had COPD exacerbations during the follow up period. Conclusions: HI-NPPV is able to substantially reduce PaCO2 in hypercapnic COPD patients; we detected a positive effect on quality of life measures with no significant change in sleep quality.

Hourly Awakening vs Continuous Contact Lens Sensor Measurements of 24-Hour Intraocular Pressure

All studies of 24-hour intraocular pressure (IOP) rhythm conducted to date have used repeated IOP measurements requiring nocturnal awakenings, potentially disturbing sleep macrostructure. To evaluate the effects on sleep architecture and IOP rhythm of hourly awakening vs a contact lens sensor (CLS) to continuously monitor IOP without awakening. Cross-sectional study at a referral center of chronobiology among 12 young healthy volunteers, with a mean (SD) age of 22.3 (2.3) years. Volunteers underwent two 24-hour IOP measurement sessions during a 2-month period. The eye order and session order were randomized. During one session, the IOP of the first eye was continuously monitored using a CLS, and the IOP of the fellow eye was measured hourly using a portable noncontact tonometer (session with nocturnal hourly awakening). During the other session, the IOP of the first eye was continuously monitored using a CLS, and the IOP of the fellow eye was not measured (session without nocturnal awakening). Overnight polysomnography was performed during the 2 sessions. A nonlinear least squares, dual-harmonic regression analysis was used to model the 24-hour IOP rhythm from the CLS data. Comparisons of acrophase, bathyphase, amplitude, and the midline estimating statistic of rhythm were used to evaluate the effect of hourly awakening on IOP rhythm. To evaluate the effects of hourly awakening on sleep architecture, comparisons of sleep structure were used, including total sleep period, rapid eye movement, wake after sleep onset, absolute and relative total sleep time, and non-rapid eye movement sleep (N1, N2, and N3). A 24-hour IOP rhythm was found in all individuals for the sessions with and without awakening (P < .05). Hourly awakening for nocturnal IOP measurements increased wake after sleep onset (P = .04) but did not seem to change total sleep time, total sleep period, sleep efficiency, or slow-wave and rapid eye movement sleep stage duration (P > .30). Hourly awakening during noncontact tonometer IOP measurements did not seem to alter the mean variables of the 24-hour IOP pattern evaluated using CLS, including signal, maximum signal, minimum signal, acrophase, and bathyphase (P > .15). The 24-hour IOP rhythms seem to be unaffected by hourly nocturnal awakening for IOP measurements in young healthy individuals.

Sleep Quality after Endoscopic Sinus Surgery in Patients with Sinonasal Polyposis

Objectives: Evaluate the effect of functional endoscopic sinus surgery (FESS) for nasal polyposis on sleep efficiency and polysomnographic parameters. Methods: This clinical trial was conducted on 15 patients with bilateral massive sinonasal polyposis who underwent FESS between August 2012 and September 2013. All participants were evaluated subjectively by employing the Pittsburgh Sleep Quality Index (PSQI) questionnaire and objectively (provided by polysomnographic parameters) before and 2 months after surgery. Results: The evaluation of subjective criteria of sleep quality assessed by PSQI showed significant improvement, particularly in nocturnal awakening ( P = .002). However, Apnea Hypopnea Index (AHI) was not reduced significantly after surgery ( P = .233). Among patients who had suffered from obstructive sleep apnea, AHI was improved in 7 patients, deteriorated in 3 patients, and did not change in 1 patient. Although the mean duration of REM sleep stage increased from 15.2 ± 10.7 to 18.9 ± 7.9, this change was not statistically significant. Furthermore,arousal index decreased dramatically from 31.6 to 17.1 ( P = .02) and sleep efficiency index was improved after the surgery ( P = .008). Conclusions: This study documented the effect of resuming nasal cavity patency on improvement of sleep efficiency after FESS. In spite of insignificant effect of FESS on apnea index, alteration of other sleep parameters like arousal index following surgery may have a positive effect on sleep quality.

ALCOHOL CONSUMPTION HABITS AND SLEEP QUALITY

Alcohol is the most widely used psychoactive substance, due to its easy production, availability of alcoholic beverages and fast action. Drinking alcohol can cause sleep disorders because it disrupts the sequence and duration of sleep stage. The aim of this study was to examine the influence of alcohol consumption on the quality and length of sleep of the first year students of doctoral studies at the Faculty of Medicine. Our study group included 42 patients who were in the first year of doctoral studies at the Faculty of Medicine in Nis. The research was conducted from November 2011 until April 2012 at the Faculty of Medicine. Out of the 42 subjects who were included in the research, 25 of them or 59.5% consumed alcohol, while 17 of them or 45% did not. Comparing the length of sleep of those who consumed alcohol with those who did not, the difference was not statistically significant. Alcohol consumption leads to poor quality of sleep, but it does not affect the length of sleep. Acta Medica Medianae 2014;53(2):10-15.

The CaV2.3 R-Type Voltage-Gated Ca2+ Channel in Mouse Sleep Architecture

Voltage-gated Ca(2+) channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca(2+) channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca(2+) channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca(2+) channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3(-/-) mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca(2+) influx into RTN neurons can trigger small-conductance Ca(2+)-activated K(+)-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca(2+) channels in rodent sleep. The role of CaV2.3 Ca(2+) channels was analyzed in CaV2.3(-/-) mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3(-/-) mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca(2+) channel expression. The detailed mechanisms of SWS increase in CaV2.3(-/-) mice remain to be determined. Low-voltage activated CaV2.3 R-type Ca(2+) channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future.

A Polysomnographic and Clinical Study of Sleep Disorders in Patients with Behçet and Neuro-Behçet Syndrome

Brainstem is the most common site of involvement in neuro-Behçet syndrome (NBS). On the other hand, the critical importance of this anatomical region in the regulation of sleep has been disregarded in the literature. We aimed to investigate the microstructure of sleep in patients with Behçet syndrome (BS) and NBS. Patients were allocated to 2 groups: (1) BS without any neurological involvement and (2) NBS with brainstem lesions only. A control group was also enrolled in this study. The comparison of polysomnographic parameters between all patients (BS and NBS) with the control group showed that sleep onset was longer (p = 0.006), the duration of superficial NREM sleep stage (N2) was significantly longer (p = 0.018), and the respiratory disturbance index was significantly higher (p = 0.034) in patients. Sleep apnea and restless legs syndrome are more commonly observed in BS and NBS. Our findings emphasize the importance of questioning the quality of sleep and its disorders in patients with BS in order to better handle the common somatic complaints in these patients, such as fatigue or daytime sleepiness.

Changes in sleep architecture after Type 2 Diabetes Mellitus (T2DM)

Introduction Type 2 Diabetes Mellitus (T2DM) is a syndrome in which multiple physiological changes are observed. The pathophysiology of diabetes such as polyphagia, polyuria, polydipsia, weight loss and/or changes in mood, such as depression or less physical activity and stress, contribute to physical and mental deterioration. Epidemiological studies report that the leading cause of death in diabetic patients is due to cardiovascular problems. It has been shown that the decrease in sleep duration combined with T2DM, increases the risk of cardiovascular events in hypertensive patients. Also, chronic sleep deprivation is linked to metabolic and cardiac disorders, and it has been suggested that respiratory conditions, such as obstructive sleep apnea, correlate with cardiovascular disease, diabetes and cancer. In order to explore if there is an association between T2DM and sleep quality, we analyzed through polysomnographic recordings (PSGR), the changes in the macro and micro sleep architecture using a streptozotocin model of T2DM. Materials and methods Six adult male Wistar rats (300–350 g) were implanted with chronic electrodes for PSGR. Rats were adapted to a 12/12 h light/dark cycle (light from 8:00 to 20:00). For T2DM induction, each rat was administered with 45 mg/kg of streptozotocin (SI) i.p. Measures of glucose level were taken on the third or fourth day after SI administration. Rats were selected with a 200 mg/dL minimum blood glucose level. Each rat underwent at least four PSGR which lasted six continuous hours (10:00–16:00). Sleep latency and duration, number of sleep stages, total percentage of Non REM sleep stages I, II and REM sleep, were quantified. Sleep spindles and theta activity were analyzed as well. All PSGR were compared to previous control recordings. Results Our preliminary results show that there is a significant increase in the density and voltage of sleep’s phasic phenomena (e.g. sleep spindles, theta activity, etc.) associated to T2DM induction, as well as a significant decrease in the number and duration of sleep stages. Conclusion Sleep micro architecture in both REM and NREM sleep is particularly enhanced by T2DM induction, whereas sleep stages are diminished. These preliminary results show a possible association between metabolic mechanisms (glucose) and sleep homeostatic processes. Acknowledgements Eva Gonzalez Trujano Carlos Jimenez Rodriguez Carlos Camacho Garcia Raul Cardoso Jose Luis Calderon.

Temporal association between sleep apnea-hypopnea and sleep bruxism events.

There is some evidence suggesting that obstructive sleep apnea-hypopnea syndrome is concomitant with sleep bruxism. The aim of this study was to investigate the temporal association between sleep apnea-hypopnea events and sleep bruxism events. In an open observational study, data were gathered from 10 male subjects with confirmed obstructive sleep apnea-hypopnea syndrome and concomitant sleep bruxism. Polysomnography and audio-video recordings were performed for 1night in a sleep laboratory. Breathing, brain, heart and masticatory muscle activity signals were analysed to quantify sleep and sleep stage duration, and number and temporal distribution of apnea-hypopnea events and sleep bruxism events. Apnea-hypopnea events were collected within a 5-min time window before and after sleep bruxism events, with the sleep bruxism events as the pivotal reference point. Two temporal patterns were analysed: (i) the interval between apnea-hypopnea events termination and sleep bruxism events onset, called T1; and (ii) the interval between sleep bruxism events termination and apnea-hypopnea events onset, called T2. Of the intervals between sleep bruxism events and the nearest apnea-hypopnea event, 80.5% were scored within 5min. Most intervals were distributed within a period of <30s, with peak at 0-10s. The T1 interval had a mean length of 33.4s and was significantly shorter than the T2 interval (64.0s; P<0.05). Significantly more sleep bruxism events were scored in association with the T1 than the T2 pattern (P<0.05). Thus, in patients with concomitant obstructive sleep apnea-hypopnea syndrome and sleep bruxism, most sleep bruxism events occurred after sleep apnea-hypopnea events, suggesting that sleep bruxism events occurring close to sleep apnea-hypopnea events is a secondary form of sleep bruxism.