Overnight Sleep Research Articles

Variability of Sleep Apnea Severity and Risk of Atrial Fibrillation: The VARIOSA-AF Study.

This study sought to determine night-to-night variability in the severity of sleep-disordered breathing (SDB) and the dynamic intraindividual relationship to daily risk of incident atrial fibrillation (AF) by using simultaneous long-term day-by-day SDB and AF monitoring. Night-to-night variability in SDB severity may result in a dynamic exposure to SDB related conditions impacting the timing and extent of cardiovascular responses. This study was an observational cohort study. Daily data for AF burden and average respiratory disturbance index (RDI) were extracted from pacemakers capable of monitoring nightly SDB and daily AF burden in 72 patients. Nightly RDI values were grouped into quartiles of severity within each patient. AF burdens of >5 min, >1 h, and >12 h were the outcome variables. A total of 32% of patients had a mean RDI of≥20/h, indicative of overall severe SDB. There was significant night-to-night variation in RDI reflected by an absolute SD of ±6.3 events/h (range 2 to 14 events/h) within any givenpatient. Within each patient, the nights with the highest RDI (in their highest quartile) conferred a 1.7-fold (1.2to2.2; p<0.001), 2.3-fold (1.6 to 3.5; p< 0.001), and 10.2-fold (3.5 to 29.9; p< 0.001) increase risk of having atleast 5 min, 1h, and 12 h, respectively, of AF during the same day compared with the best sleep nights (in their lowestquartiles). There is considerable night-to-night variability in SDB severity which cannot be detected by 1 single overnight sleep study. SDB burden may be a better metric with which to assess the extent of dynamic SDB related cardiovascular responses such as daily AF risk than the categorical diagnosis of SDB. (Night-to-Night Variability in Severity of Sleep Apnea and Daily Dynamic Atrial Fibrillation Risk [VARIOSA-AF]; ACTRN 12618000757213).

CA3 place cells that represent a novel waking experience are preferentially reactivated during sharp wave-ripples in subsequent sleep.

A popular model of memory consolidation posits that recent memories stored in the hippocampus are reactivated during sleep and thereby transferred to neocortex for long-term storage. This process is thought to occur during sharp wave-ripples (SWRs) in nonrapid eye movement sleep (NREM). However, whether the hippocampus consolidates all recent memories in the same manner remains unclear. An efficient memory system may extract novel information from recent experiences for preferential consolidation. In the hippocampus, memories are thought to be stored initially in CA3. Therefore, CA3 place cells that encode novel experiences may be preferentially reactivated during SWRs in subsequent sleep. To test this hypothesis, we recorded CA3 place cells in rats during exposure to a familiar and a novel environment and during subsequent overnight sleep. We found that CA3 place cells that preferentially coded a novel environment showed larger firing rate increases during SWRs in NREM than place cells that preferentially coded a familiar environment. Moreover, CA3 place cell ensembles replayed trajectories from a novel environment during NREM with higher fidelity than trajectories from a familiar environment. Together, these results suggest that CA3 representations of novel experiences are preferentially processed during subsequent sleep.

Autistic Traits Are Associated With Decreased Activity of Fast Sleep Spindles During Adolescence.

Autistic traits present a continuum from mild symptoms to severe disorder and have been associated with a high prevalence of sleep problems. Sleep spindles have a key function in sleep maintenance and in brain plasticity. Previous studies have found decreased spindle activity in clinical autism. Here we examine the associations between the entire range of autistic traits and sleep spindle activity in a nonclinical community cohort of adolescents. Our cohort is based on 172 adolescents born in 1998 (58.7% girls, mean age = 16.9 years, standard deviation = 0.1), who filled in the adult autism-spectrum quotient (AQ), consisting of total score, and social interaction and attention to details subscales. Participants underwent an ambulatory overnight sleep electroencephalography. Sleep spindles (amplitude, duration, density, and intensity) were automatically detected from stage N2 sleep, and divided to slow and fast spindles. Higher AQ total sum and social interaction sum associated with lower fast spindle amplitude and intensity (P < .04). No associations were observed for attention to details. Our findings indicate that a higher level of autistic traits in the nonclinical range among generally healthy adolescents associate with similar alterations in sleep spindle activity as observed in many neuropsychiatric conditions, indicating lower sleep-related brain plasticity. This indicates that sleep microstructures form a continuum that follows self-reported symptoms of autism.

The Impact of Pre-sleep Protein Ingestion on the Skeletal Muscle Adaptive Response to Exercise in Humans: An Update.

This review provides an update on recent research assessing the effect of pre-sleep protein ingestion on muscle protein synthesis rates during overnight sleep and the skeletal muscle adaptive response to exercise training. Protein ingested prior to sleep is effectively digested and absorbed during overnight sleep, thereby increasing overnight muscle protein synthesis rates. Protein consumption prior to sleep does not appear to reduce appetite during breakfast the following day and does not change resting energy expenditure. When applied over a prolonged period of resistance-type exercise training, pre-sleep protein supplementation has a beneficial effect on the increase in muscle mass and strength. Protein ingestion before sleep is hypothesized to represent an effective nutritional strategy to preserve muscle mass in the elderly, especially when combined with physical activity or muscle contraction by means of neuromuscular electrical stimulation. In conclusion, protein ingestion prior to sleep is an effective interventional strategy to increase muscle protein synthesis rates during overnight sleep and can be applied to support the skeletal muscle adaptive response to resistance-type exercise training.

Cerebral Hemodynamics in Sleep Apnea and Actigraphy-Determined Sleep Duration in a Sample of the Hispanic Community Health Study/ Study of Latinos.

We sought to evaluate cerebral hemodynamics in obstructive sleep apnea (OSA) and actigraphy-defined short sleep duration using transcranial Doppler ultrasound (TCD) blood flow velocity in a subsample of Hispanics/Latinos without stroke and cardiovascular disease. The sample consisted of consecutive participants at the Miami site of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) with overnight home sleep testing and 7 days of wrist actigraphy in the Sueño sleep ancillary study. Ninety-five participants had sleep data and TCD determined cerebral hemodynamics. We evaluated the association between OSA (apnea-hypopnea index [AHI] ≥ 5 events/h) and short sleep duration (< 6.8 hours; sample median) with cerebral blood flow velocities (CBFV) and pulsatility index (PI) for the middle cerebral (MCA) and basilar arteries (BA). Median age was 48 years (range 20-64) with 71% females. Twenty-eight percent of the sample had OSA (AHI ≥ 5 events/h) with median AHI of 10.0 (range 5.0-51.7) events/h. In unadjusted analyses, participants with OSA had lower median CBFV in the BA (30.5 cm/s [interquartile range:10.2] versus 39.4 cm/s [13.3] P < .05), but not the MCA, whereas short sleepers had higher median vascular resistance in the MCA (PI = 0.92 [0.18] versus 0.86 [0.14] P < .05) and BA (PI = 1.0 [0.17] versus 0.93 [0.24] P < .05). After full adjustment, OSA was associated with decreased CBFV (β [SE] = -5.1 [2.5] P < .05) in the BA. Short sleep was associated with increased PI (β [SE] = 0.05 [0.02] P < .05) in the MCA. In this sample of Hispanic/Latinos, OSA was associated with decreased daytime blood flow velocity in the BA, whereas actigraphy-defined short sleep duration was associated with increased cerebrovascular pulsatility in the MCA.

Sleep deprivation differentially affects subcomponents of cognitive control.

Although sleep deprivation has long been known to negatively affect cognitive performance, the exact mechanisms through which it acts and what cognitive domains are affected most is still disputed. The current study provides a theory-driven approach to examine and explain the detrimental effects of sleep loss with a focus on attention and cognitive control. Twenty-four participants (12 females; age: 24 ± 3 years) completed the experiment that involved laboratory-controlled over-night sleep deprivation and two control conditions, namely, a normally rested night at home and a night of sleep in the laboratory. Using a stop signal task in combination with electroencephalographic recordings, we dissociated different processes contributing to task performance such as sustained attention, automatic or bottom-up processing, and strategic or top-down control. At the behavioral level, we extracted reaction times, response accuracy, and markers of behavioral adjustments (post-error and post-stop slowing), whereas at the neural level event-related potentials (ERP) found in context of response inhibition (N2/P3) and error monitoring (ERN/Pe) were obtained. It was found that 24 hr of sleep deprivation resulted in declined sustained attention and reduced P300 and Pe amplitudes, demonstrating a gradual breakdown of top-down control. In contrast, N200 and ERN as well as the stop-signal reaction time showed higher resilience to sleep loss signifying the role of automatic processing. These results support the notion that sleep deprivation is more detrimental to cognitive functions that are relatively more dependent on mental effort and/or cognitive capacity, as opposed to more automatic control processes.

Doppler Radar-Based Non-Contact Health Monitoring for Obstructive Sleep Apnea Diagnosis: A Comprehensive Review

Today’s rapid growth of elderly populations and aging problems coupled with the prevalence of obstructive sleep apnea (OSA) and other health related issues have affected many aspects of society. This has led to high demands for a more robust healthcare monitoring, diagnosing and treatments facilities. In particular to Sleep Medicine, sleep has a key role to play in both physical and mental health. The quality and duration of sleep have a direct and significant impact on people’s learning, memory, metabolism, weight, safety, mood, cardio-vascular health, diseases, and immune system function. The gold-standard for OSA diagnosis is the overnight sleep monitoring system using polysomnography (PSG). However, despite the quality and reliability of the PSG system, it is not well suited for long-term continuous usage due to limited mobility as well as causing possible irritation, distress, and discomfort to patients during the monitoring process. These limitations have led to stronger demands for non-contact sleep monitoring systems. The aim of this paper is to provide a comprehensive review of the current state of non-contact Doppler radar sleep monitoring technology and provide an outline of current challenges and make recommendations on future research directions to practically realize and commercialize the technology for everyday usage.

The relationship between obstructive sleep apnea and diabetic retinopathy in type 2 diabetes patients, Zagazig University Hospitals, Egypt

Background and objective Obstructive sleep apnea (OSA) and type 2 diabetes mellitus (T2DM) commonly coexist. Both could be associated with a number of pathophysiological derangements involved in the development of diabetic retinopathy (DR). So, the aim of this study was to assess the possible association between OSA and DR. Patients and methods This is a cross-sectional observational study that was conducted on patients with T2DM. Two-field 45°-digital retinal images for each eye were used to evaluate DR and graded according to the English National Screening Program guidelines. OSA was evaluated on the basis of an inpatient overnight sleep study (polysomnography) using a computerized polysomnogram device. Results This work recruited 110 patients. OSA was observed in 60% (66 patients). OSA was found to be independently associated with both advanced DR [preprolifrative (R2) or proliferative (R3)] (odds ratio=6.29; 95% confidence interval: 1.08–6.65; P=0.04) and maculopathy (odds ratio=12.92; 95% confidence interval: 3.97–4.79; P Conclusion OSA was independently associated with advanced DR and maculopathy in T2DM patients. Moreover, severity of OSA was directly related to DR grade.

692: Obstructive sleep apnea is an unrecognized contributor to fatigue in pregnancy

Pregnant women often complain of fatigue but this is generally thought to be part of pregnancy due to hormonal changes. In the non-pregnant population obstructive sleep apnea (OSA) is a known contributor to fatigue but this has not been investigated in pregnant women. We therefore examined whether underlying OSA plays a role in fatigue during pregnancy. A secondary analysis of home sleep tests conducted among pregnant women for research purposes. All women were queried about symptoms of fatigue and daytime sleepiness using a fatigue scale and the Epworth Sleepiness Scale respectively. Women who reported that they experienced fatigue “often” were classified as cases. Excessive daytime sleepiness was considered present with a sleepiness score of ≥10. The presence of OSA was determined by an overnight home sleep test with an apnea-hypopnea index of ≥5 events/hour. Demographics and medical information was obtained by chart abstraction. Regression analyses were constructed to determine key contributors to fatigue. The sample size included 84 pregnant women (mean age 31.3±5.9 years, and mean gestational age 29.0±7.6 weeks). Thirty-six percent of women reported that they were “often” fatigued, 46% screened positive for daytime sleepiness, and 42% had OSA. Demographics are shown in Table 1. There was no association between fatigue and daytime sleepiness. In a logistic regression model, a complaint of fatigue was strongly associated with the presence of OSA (OR 5.1, 95%CI 1.4-19.3) after controlling for maternal age, gestational age, parity, BMI, race, and daytime sleepiness. Unrecognized OSA is a significant contributor to fatigue in pregnancy. Clinicians caring for pregnant women should consider OSA in women who are often fatigued.

Altered overnight levels of pro-inflammatory cytokines in men and women with posttraumatic stress disorder

BackgroundPosttraumatic stress disorder (PTSD) is associated with disturbed sleep and elevated levels of pro-inflammatory cytokines, including interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Studies in animals and healthy humans have also shown that disrupted sleep elevates pro-inflammatory cytokines, including IL-6 and TNF-α. A better understanding of overnight cytokine levels and sleep might shed light on possible mechanisms for elevated inflammation in PTSD. Thus, we investigated overnight levels of IL-6 and TNF-α in individuals with and without PTSD while recording sleep polysomnography (PSG). MethodSerum samples were collected from otherwise healthy, medication-free participants with chronic PTSD (n = 44; 50% female; M age = 30.34 ± 8.11) and matched controls (n = 49; 53% female; M age = 30.53 ± 6.57) during laboratory PSG. Levels of IL-6 and TNF-α were measured at hours 0, 2, 4, 6, and 8 after typical sleep onset time using serial serum samples. Plasma IL-6 and TNF-α levels were quantified using enzyme-linked immunosorbent assays. ResultsGrowth model analysis indicated a significantgroup by time interaction for IL-6 (t[247] = -2.92, p = .005) and a significant group by sex by time interaction for TNF-α (t[275] = 2.02, p = .04). PTSD positive men and women initially had higher IL-6 and TNF-α at sleep onset, but not at the end of their sleep cycle. Men with PTSD showed a peak of TNF-α at the end of the sleep cycle, whereas male control subjects demonstrated an inverted U-shaped profile. There were no significant differences in TNF-α levels overnight between women with and without PTSD. ConclusionTo our knowledge, this is the largest study to examine IL-6 overnight in a PTSD sample and the first study to examine overnight TNF-α in PTSD. Overnight IL-6 and TNF-α levels may be altered in individuals with PTSD compared to those without PTSD, and TNF-α trajectories also differed by sex. The current findings highlight the need to consider sex, sleep, time of day, and circadian variation when examining inflammation in PTSD. Additional research in broader study samples will be necessary to clarify associations between disrupted sleep, cytokines, and increased risk for disease in PTSD.

A novel adhesive biosensor system for detecting respiration, cardiac, and limb movement signals during sleep: validation with polysomnography.

BackgroundAlthough in-lab polysomnography (PSG) remains the gold standard for objective sleep monitoring, the use of at-home sensor systems has gained popularity in recent years. Two categories of monitoring, autonomic and limb movement physiology, are increasingly recognized as critical for sleep disorder phenotyping, yet at-home options remain limited outside of research protocols. The purpose of this study was to validate the BiostampRC® sensor system for respiration, electrocardiography (ECG), and leg electromyography (EMG) against gold standard PSG recordings.MethodsWe report analysis of cardiac and respiratory data from 15 patients and anterior tibialis (AT) data from 19 patients undergoing clinical PSG for any indication who simultaneously wore BiostampRC® sensors on the chest and the bilateral AT muscles. BiostampRC® is a flexible, adhesive, wireless sensor capable of capturing accelerometry, ECG, and EMG. We compared BiostampRC® data and feature extractions with those obtained from PSG.ResultsThe heart rate extracted from BiostampRC® ECG showed strong agreement with the PSG (cohort root mean square error of 5 beats per minute). We found the thoracic BiostampRC® respiratory waveform, derived from its accelerometer, accurately calculated the respiratory rate (mean average error of 0.26 and root mean square error of 1.84 breaths per minute). The AT EMG signal supported periodic limb movement detection, with area under the curve of the receiver operating characteristic curve equaling 0.88. Upon completion, 88% of subjects indicated willingness to wear BiostampRC® at home on an exit survey.ConclusionThe results demonstrate that BiostampRC® is a tolerable and accurate method for capturing respiration, ECG, and AT EMG time series signals during overnight sleep when compared with simultaneous PSG recordings. The signal quality sufficiently supports analytics of clinical relevance. Larger longitudinal in-home studies are required to support the role of BiostampRC® in clinical management of sleep disorders involving the autonomic nervous system and limb movements.

Cataplexy

Remarkably and almost invariably, the clinical phenomenon of cataplexy results from the loss of around 40 000 hypocretin-containing neurones in the lateral hypothalamus in the context of narcolepsy type 1....

Overnight retention of emotional memories is influenced by BDNF Val66Met but not 5-HTTLPR

Emotional memory may be modulated by BDNF Val66Met and 5-HTTLPR polymorphisms. However, the influence of these genetic variants on the overnight retention of emotional memories has not been investigated in humans. Thirty-six healthy female students were selected to participate in this study based on 5-HTTLPR genotype status (L’/L’, L’/S’, S’/S’). Participants were also genotyped for BDNF Val66Met (Val/Val, Met carriers). We measured recognition performance for positive, neutral and negative images before and after overnight sleep. We found a significant interaction between BDNF Val66Met genotype group and image valence on post-sleep recognition performance. This interaction was driven by greater memory for negative and positive images, relative to neutral images, in Met carriers. We also found that longer Rapid Eye Movement (REM) sleep duration predicted greater post-sleep recognition performance for negative images in Met carriers, but not in Val homozygotes. We observed no influence of 5-HTTLPR polymorphisms on post- sleep recognition performance for positive, neutral or negative images. Our findings support a modulatory role for BDNF Val66Met in overnight emotional memory retention in females. We discuss the implications of this finding for understanding the influence of BDNF Val66Met on depression vulnerability.

Deep Brain Stimulation of the Hypothalamus Leads to Increased Metabolic Rate in Refractory Obesity

Obesity has become a worldwide epidemic, with very few long-term successful treatment options for refractory disease. Deep brain stimulation (DBS) of the bilateral lateral hypothalamus (LH) in refractory obesity has been performed safely. However, questions remain regarding the optimal settings and its effects on metabolic rate. The goals of our experiment were to determine the optimal DBS settings and the actual effect of optimal stimulation on energy expenditure. After bilateral LH DBS implantation, 2 subjects with treatment refractory obesity underwent 4 days of metabolic testing. The subjects slept overnight in a respiratory chamber to measure their baseline sleep energy expenditure, followed by 4 consecutive days of resting metabolic rate (RMR) testing at different stimulation settings. On day 4, the optimized DBS settings were used, and sleep energy expenditure was measured again overnight in the room calorimeter. During daily testing, the RMR fluctuated acutely with changes in stimulation settings and returned to baseline immediately after turning off the stimulation. Optimal stimulation settings selected for participants showed a 20% and 16% increase in RMR for the 2 participants. Overnight sleep energy expenditure measurements at these optimized settings on day 4 yielded a 10.4% and 4.8% increase over the baseline measurements for the 2 participants. These findings have demonstrated the efficacy of optimized DBS of the LH on increasing the RMR acutely and maintaining this increase during overnight sleep. These promising preliminary findings have laid the groundwork for the possible treatment of refractory obesity with DBS.

Individual Differences in Slow-Wave-Sleep Predict Acquisition of Full Cognitive Maps.

Accumulating evidence suggests that sleep, and particularly Slow-Wave-Sleep (SWS), helps the implicit and explicit extraction of regularities within memories that were encoded in a previous wake period. Sleep following training on virtual navigation was also shown to improve performance in subsequent navigation tests. Some studies propose that this sleep-effect on navigation is based on explicit recognition of landmarks; however, it is possible that SWS-dependent extraction of implicit spatiotemporal regularities contributes as well. To examine this possibility, we administered a novel virtual navigation task in which participants were required to walk through a winding corridor and then choose one of five marked doors to exit. Unknown to participants, the markings on the correct door reflected the corridor’s shape (from a bird’s eye view). Detecting this regularity negates the need to find the exit by trial and error. Participants performed the task twice a day for a week, while their overnight sleep was monitored. We found that the more time participants spent in SWS across the week, the better they were able to implicitly extract the hidden regularity. In contrast, the few participants that explicitly realized the regularity did not rely on SWS to do so. Moreover, the SWS effect was strictly at the trait-level: Baseline levels of SWS prior to the experimental week could predict success just as well, but day-to-day variations in SWS did not predict day-to-day improvements. We propose that our findings indicate SWS facilitates implicit integration of new information into cognitive maps, possibly through compressed memory replay.

Trends In Infant Sleep: What Do The Data Show? What Are Caregivers’ Behaviors?

Parents of infants expect their baby will sleep safely in any of a number of products that are intended for overnight sleep (e.g., crib, bassinet, cradle, play yard) as well as products in which infants routinely nap (e.g., infant seat, swing). Yet each year, infants die while napping or sleeping. The Consumer Product Safety Commission (CPSC) is an independent federal agency charged with protecting the public from unreasonable risk of injury associated with consumer products, including infant sleep products. In this panel, technical experts from the CPSC address issues relating to infant sleep safety including physiological factors associated with infant death and findings from incident data. Case studies for two infant products (handheld infant carriers and infant bouncer seats) and focus group research findings with parents of infants shed light on consumer behavior as it relates to perceptions of infant comfort and product use.

Lying position classification based on ECG waveform and random forest during sleep in healthy people

BackgroundSeveral different lying positions, such as lying on the left side, supine, lying on the right side and prone position, existed when healthy people fell asleep. This article explored the influence of lying positions on the shape of ECG (electrocardiograph) waveform during sleep, and then lying position classification based on ECG waveform features and random forest was achieved.MethodsBy means of de-noising the overnight sleep ECG data from ISRUC website dataset, as well as extracting the waveform features, we calculated a total of 30 ECG waveform features, including 2 newly proposed features, S/R and ∠QSR. The means and significant difference level of these features within different lying positions were calculated, respectively. Then 12 features were selected for three kinds of classification schemes.ResultsThe lying positions had comparatively less effect on time-limit features. QT interval and RR interval were significantly lower than that in supine ({text{P}}, le ,0.01). Significant differences appeared in most of the amplitude and double-direction features. When lying on the left side, the height of P wave and T wave, QRS area and T area, the QR potential difference and ∠QSR were significantly lower than those in supine ({text{P}}, le ,0.01). However, S/R was significantly greater on left than those in supine ({text{P}}, le ,0.01) and on right ({text{P}}, le ,0.05). The height of T wave and area under T wave were significantly higher in supine than those on right ({text{P}}, le ,0.01). For the subject specific classifier, a mean accuracy of 97.17% with Cohen’s kappa statistic κ of 0.91, and AUC > 0.97 were achieved. While the accuracy and κ dropped to 63.87% and 0.32, AUC > 0.66, respectively when the subject independent classifier was considered.ConclusionsWhen subjects were lying on the left side during sleep, due to the effect of gravity on heart, the position of heart changed, for example, turned and rotated, causing changes in the vectorcardiogram of frontal plane and horizontal plane, which lead to a change in ECG. When lying on the right side, the heart was upheld by the mediastinum, so that the degree of freedom was poor, and the ECG waveform was almost unchanged. The proposed method could be used as a technique for convenient lying position classification.

Sleep-dependent enhancement of emotional memory in early childhood

Naps in early childhood support declarative memory consolidation. However, emotional memories are unique in the neural basis of encoding as well as the sleep physiology underlying consolidation. Specifically, while consolidation of declarative memories has been associated with slow wave sleep, a prevailing theory suggests that REM sleep is necessary for consolidation of memories with emotional valence. Thus, we presented children (34–64 months) with faces paired with mean or nice descriptions. There were no significant main effects of emotional valence on recognition memory. Change in memory accuracy also did not differ when probed after a nap compared to the change in memory accuracy after an interval awake. However, when memory was probed again following overnight sleep, the change in memory accuracy was greater if the child napped the previous day. Greater nap slow wave activity was associated with greater memory decay during the nap. Yet nap slow wave activity also predicted greater overnight improvement in memory. These results suggest that sleep bouts can interact to benefit memory in early childhood.

REM sleep and safety signal learning in posttraumatic stress disorder: A preliminary study in military veterans

BackgroundPosttraumatic Stress Disorder (PTSD) is associated with a number of negative physical and mental health consequences. Fear conditioning plays an important mechanistic role in PTSD, and PTSD patients also show deficits in safety signal learning. Sleep, particularly REM sleep, is linked to improved safety learning and extinction processes in animal models and healthy humans. No studies have examined the link between REM sleep and safety signal learning or extinction memory in clinical populations. MethodsThis study examined the relationship between REM sleep, safety signal learning, and extinction processes in veterans with PTSD (n = 13). Patients' overnight sleep was characterized in the laboratory via polysomnography (PSG). The next day, participants underwent a fear conditioning paradigm during which they acquired fear toward a visual cue. This testing session also included a visual cue that became a safety signal (CS-). Following conditioning, the veterans' sleep was monitored overnight again, after which they underwent extinction training. Following a third night of sleep, extinction recall and safety recall were tested. Bivariate correlations examined the relationship between the slope of safety signal learning and subsequent REM sleep, as well as the relationship between REM sleep and subsequent extinction recall and safety recall on the last day of testing. ResultsVeterans learned to differentiate the CS+ and the CS- on the first day of testing. Veterans who underwent safety learning more quickly on the first day of testing showed more efficient REM sleep that night (r = .607, p = .028). On the second day of testing, the patients successfully underwent extinction learning. Patients with a higher percentage of REM sleep on the last night of the study showed more safety recall early on the last day of testing (r = .688, p = .009). ConclusionTo our knowledge, this was the first study to examine the relationship between objective sleep and fear-potentiated startle performance in veterans with PTSD. Study methods were well tolerated by participants, supporting feasibility of the experimental design. Results indicated REM sleep was associated with both initial safety learning and subsequent safety recall. Taken together with previous studies in healthy controls, these preliminary results provide additional evidence suggesting REM sleep could play a mechanistic role in the maintenance of PTSD and thus identify a modifiable biological process to target in treatment of PTSD. These findings should be replicated in larger samples.

A Pilot Study of Impulse Radio Ultra Wideband Radar Technology as a New Tool for Sleep Assessment.

To validate Impulse radio ultra wideband pulse-doppler radar technology against polysomnography (PSG) for sleep assessment. In all, 12 participants were recruited and their overnight sleep was assessed both by a Novelda XeThru radar and PSG. Two subjects had two nightly recordings, whereas 10 had one recording. Epoch by epoch (30 seconds) comparisons from bedtime to rise time were conducted. Concordance was estimated in terms of the mean difference between the radar and the PSG estimates regarding sleep onset latency, wake time after sleep onset and total sleep time. In addition, accuracy, sensitivity, specificity and Cohen kappa were calculated. The mean difference (minutes) between the radar and the PSG registrations was -5.7 minutes (standard deviation [SD] = 22.1 minutes) for sleep onset latency, 6.4 minutes (SD = 32.5 minutes) for wake after sleep onset, and 1.5 minutes (SD = 24.6 minutes) for total sleep time. The mean values obtained for accuracy, sensitivity, specificity and Cohen kappa were 0.931, 0.961, 0.695 and 0.670, respectively. Impulse radio ultra wideband radar technology is a promising tool in terms of affordable and practical objective sleep assessment. Further technical development and more validation studies are needed in order to conclude about the utility potential of this device.