Deep brain stimulation of the anterior nucleus of the thalamus increases slow wave activity in non-rapid eye movement sleep.

OBJECTIVE: Previous studies suggest that intermittent deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) affects physiological sleep architecture. Here, we investigated the impact of continuous ANT DBS on sleep in epilepsy patients in a multicenter crossover study in 10 patients. METHODS: We assessed sleep stage distribution, delta power, delta energy, and total sleep time in standardized 10/20 polysomnographic investigations before and 12 months after DBS lead implantation. RESULTS: In contrast to previous studies, we found no disruption of sleep architecture or alterations of sleep stage distribution under active ANT DBS (p = .76). On the contrary, we observed more consolidated and deeper slow wave sleep (SWS) under continuous high-frequency DBS as compared to baseline sleep prior to DBS lead implantation. In particular, biomarkers of deep sleep (delta power and delta energy) showed a significant increase post-DBS as compared to baseline (36.67 ± 13.68 µV2 /Hz and 799.86 ± 407.56 µV2 *s, p < .001). Furthermore, the observed increase in delta power was related to the location of the active stimulation contact within the ANT; we found higher delta power and higher delta energy in patients with active stimulation in more superior contacts as compared to inferior ANT stimulation. We also observed significantly fewer nocturnal electroencephalographic discharges in DBS ON condition. In conclusion, our findings suggest that continuous ANT DBS in the most cranial part of the target region leads to more consolidated SWS. SIGNIFICANCE: From a clinical perspective, these findings suggest that patients with sleep disruption under cyclic ANT DBS could benefit from an adaptation of stimulation parameters to more superior contacts and continuous mode stimulation.

Extending sleep to confirm insufficient sleep syndrome is challenging.

Insufficient sleep syndrome (ISS) is prevalent, but poorly studied. This descriptive study was performed to determine its diagnostic challenges and clinical characteristics in a large (n = 3,461) retrospective sample from a single sleep laboratory. Based on actigraphy, polysomnography and multiple sleep latency tests, we diagnosed "suspected insufficient sleep syndrome" in patients with chronic sleepiness, short time in bed, longer sleep duration during weekends or vacation, and without evidence of other causes of sleepiness. For the diagnosis of "definite insufficient sleep syndrome", we additionally required objectively confirmed resolution of sleepiness with actigraphy-documented extension of time in bed. We diagnosed "suspected insufficient sleep syndrome" in 300 subjects. In 94 subjects, extension of sleep time with consecutive relief of sleepiness was attempted, but only 37 subjects succeeded, often despite being offered several attempts. "Definite insufficient sleep syndrome" was confirmed in 36 patients. In these subjects, mean time in bed after sleep extension was above 8 hr per night and 84 min longer than at baseline. Narcolepsy-like findings were frequently observed before sleep extension, but no sleep onset rapid eye movement sleep on polysomnography. This study indicates that fulfilling the diagnostic criteria of ISS is challenging in clinical practice. It further corroborates the importance of actigraphy and polysomnography for correct diagnosis.

Narcolepsy type 2: A rare, yet existing entity.

Because of unspecific diagnostic criteria, there is much controversy around narcolepsy type 2, its existence and its frequency. With this retrospective and purely descriptive study, we aimed to compare the frequency of narcolepsy type 2 compared to the well-described narcolepsy type 1, in a large (n = 3,782) retrospective sample from a single tertiary sleep centre. After 2 weeks washout of sleep-wake active medication, all patients with excessive daytime sleepiness (n = 1,392) underwent 2 weeks actigraphy, polysomnography and multiple sleep latency test, and all diagnoses were made along current diagnostic criteria. Narcolepsy type 1 was diagnosed in 91 patients, and 191 patients without cataplexy had multiple sleep latency test (MSLT) results indicating narcolepsy. After exclusion of shift work syndrome (n = 19), suspected insufficient sleep syndrome (n = 128), delayed sleep phase syndrome (n = 4) and obstructive sleep apnea (n = 34), six patients were diagnosed with narcolepsy type 2, of whom two patients later developed narcolepsy type 1. Altogether, our observations suggest that narcolepsy type 2 exists, but its frequency may be much lower compared to narcolepsy type 1. In addition, they emphasize the importance of scrupulously excluding other potential causes of sleepiness, if possible, with 2-week actigraphy and polysomnography.

Slow-wave sleep and motor progression in Parkinson disease.

Growing evidence from Alzheimer disease supports a potentially beneficial role of slow-wave sleep in neurodegeneration. However, the importance of slow-wave sleep in Parkinson disease is unknown. In 129 patients with Parkinson disease, we retrospectively tested whether sleep slow waves, objectively quantified with polysomnography, relate to longitudinal changes in Unified Parkinson's Disease Rating Scale motor scores. We found that higher accumulated power of sleep slow waves was associated with slower motor progression, particularly of axial motor symptoms, over a mean time of 4.6 ± 2.3 years. This preliminary finding suggests that deeper sleep relates to slower motor progression in Parkinson disease. Ann Neurol 2019;85:765-770.

Exploring the impact of experimental sleep restriction and sleep deprivation on subjectively perceived sleep parameters.

We aimed to investigate the effect of increased sleep pressure and shortened sleep duration on subjective sleep perception in relation to electroencephalographic sleep measures. We analyzed the data from a study in which 14 healthy male volunteers had completed a baseline assessment with 8 hr time in bed, a sleep deprivation (40 hr of wakefulness) and a sleep restriction protocol with 5 hr time in bed during 7 nights. In this work, we assessed perception index, derived through dividing the subjectively perceived total sleep time, wake after sleep onset and sleep latency duration by the objectively measured one at each condition. We found that total sleep time was subjectively underestimated at baseline and shifted towards overestimation during sleep restriction and after deprivation. This change in accuracy of subjective estimates was not associated with any changes in sleep architecture or sleep depth. Wake after sleep onset was significantly underestimated only during sleep restriction. Sleep latency was always overestimated subjectively without any significant change in this misperception across conditions. When comparing accuracy of subjective and actimetry estimates, subjective estimates regarding total sleep time and wake after sleep onset deviated less from electroencephalography derived measures during sleep restriction and after deprivation. We conclude that self-assessments and actimetry data of patients with chronic sleep restriction should be interpreted cautiously. The subjectively decreased perception of wake after sleep onset could lead to overestimated sleep efficiency in such individuals, whereas the underestimation of sleep time and overestimation of wake after sleep onset by actimetry could lead to further underestimated sleep duration.

Insufficient sleep: Enhanced risk-seeking relates to low local sleep intensity.

OBJECTIVES: Chronic sleep restriction is highly prevalent in modern society and is, in its clinical form, insufficient sleep syndrome, one of the most prevalent diagnoses in clinical sleep laboratories, with substantial negative impact on health and community burden. It reflects every-day sleep loss better than acute sleep deprivation, but its effects and particularly the underlying mechanisms remain largely unknown for a variety of critical cognitive domains, as, for example, risky decision making. METHODS: We assessed financial risk-taking behavior after 7 consecutive nights of sleep restriction and after 1 night of acute sleep deprivation compared to a regular sleep condition in a within-subject design. We further investigated potential underlying mechanisms of sleep-loss-induced changes in behavior by high-density electroencephalography recordings during restricted sleep. RESULTS: We show that chronic sleep restriction increases risk-seeking, whereas this was not observed after acute sleep deprivation. This increase was subjectively not noticed and was related to locally lower values of slow-wave energy during preceding sleep, an electrophysiological marker of sleep intensity and restoration, in electrodes over the right prefrontal cortex. INTERPRETATION: This study provides, for the first time, evidence that insufficient sleep restoration over circumscribed cortical areas leads to aberrant behavior. In chronically sleep restricted subjects, low slow-wave sleep intensity over the right prefrontal cortex-which has been shown to be linked to risk behavior-may lead to increased and subjectively unnoticed risk-seeking. Ann Neurol 2017;82:409-418.

Electrophysiological Evidence for Alternative Motor Networks in REM Sleep Behavior Disorder.

Patients with Parkinson's disease (PD) and REM sleep behavior disorder (RBD) show mostly unimpaired motor behavior during REM sleep, which contrasts strongly to coexistent nocturnal bradykinesia. The reason for this sudden amelioration of motor control in REM sleep is unknown, however. We set out to determine whether movements during REM sleep are processed by different motor networks than movements in the waking state. We recorded local field potentials in the subthalamic nucleus (STN) and scalp EEG (modified 10/20 montage) during sleep in humans with PD and RBD. Time-locked event-related ß band oscillations were calculated during movements in REM sleep compared with movements in the waking state and during NREM sleep. Spectral analysis of STN local field potentials revealed elevated ß power during REM sleep compared with NREM sleep and ß power in REM sleep reached levels similar as in the waking state. Event-related analysis showed time-locked ß desynchronization during WAKE movements. In contrast, we found significantly elevated ß activity before and during movements in REM sleep and NREM sleep. Corticosubthalamic coherence was reduced during REM and NREM movements. We conclude that sleep-related movements are not processed by the same corticobasal ganglia network as movements in the waking state. Therefore, the well-known seemingly normal motor performance during RBD in PD patients might be generated by activating alternative motor networks for movement initiation. These findings support the hypothesis that pathological movement-inhibiting basal ganglia networks in PD patients are bypassed during sleep. SIGNIFICANCE STATEMENT: This study provides evidence that nocturnal movements during REM sleep in Parkinson's disease (PD) patients are not processed by the same corticobasal ganglia network as movements in the waking state. This implicates the existence of an alternative motor network that does not depend directly on the availability of l-Dopa in the basal ganglia. These findings further indicate that some PD patients are able to perform movements in the dopamine depleted state, possibly by bypassing the pathological basal ganglia network. The existence and direct activation of such alternative motor networks might finally have potential therapeutic effects for PD patients.

Diagnostic delay in narcolepsy type 1: combining the patients' and the doctors' perspectives.

Narcolepsy type 1 is a neurological disorder characterized by a unique syndrome, including the pathognomonic symptom of cataplexy. The diagnosis can be confirmed by objective measures, such as typical findings in the multiple sleep latency test, reduced or undetectable levels of orexin (hypocretin) in the cerebrospinal fluid, and linkage to a specific HLA haplotype. Nevertheless, the mean time that elapses from symptom onset to the correct diagnosis ranges between 10 and 20 years, and the causes and correlates of this delay are poorly understood. Diagnostic delay was assessed on 52 well-defined patients with narcolepsy type 1, evaluating clinical, electrophysiological and neurochemical parameters and the results of a 41-item questionnaire developed to obtain the patients' perspective on various aspects of the diagnostic process. The mean time gap between disease onset and first medical consultation was 3.2 ± 5.1 years; the mean diagnostic delay was 8.9 ± 11.0 years. Prior to correct diagnosis, patients received a wide variety of misdiagnoses. The self-ratings of the patients revealed that the undiagnosed symptoms caused high levels of anxiety and unjustified criticism by family, friends and employers. Multiple regression analysis identified higher cerebrospinal fluid orexin levels (ß = 0.311, P = 0.01), and a longer interval between the onset of excessive daytime sleepiness and cataplexy (ß = 0.368, P = 0.002) as independent associates of longer diagnostic delay. The diagnostic delay decreased over the last decades (ß = -0.672, P < 0.001). In conclusion, delayed diagnosis of narcolepsy type 1 is very common, associated with many adverse consequences, and requires educational efforts to improve awareness on narcolepsy among healthcare providers and the general population.

Which diagnostic findings in disorders with excessive daytime sleepiness are really helpful? A retrospective study.

Due to extensive clinical and electrophysiological overlaps, the correct diagnosis of disorders with excessive daytime sleepiness is often challenging. The aim of this study was to provide diagnostic measures that help discriminating such disorders, and to identify parameters, which don't. In this single-center study, we retrospectively identified consecutive treatment-naïve patients who suffered from excessive daytime sleepiness, and analyzed clinical and electrophysiological measures in those patients in whom a doubtless final diagnosis could be made. Of 588 patients, 287 reported subjective excessive daytime sleepiness. Obstructive sleep apnea is the only disorder that could be identified by polysomnography alone. The diagnosis of insufficient sleep syndrome relies on actigraphy as patients underestimate their sleep need and the disorder shares several clinical and electrophysiological properties with both narcolepsy type 1 and idiopathic hypersomnia. Sleep stage sequencing on MSLT appears helpful to discriminate between insufficient sleep syndrome and narcolepsy. Sleep inertia is a strong indicator for idiopathic hypersomnia. There are no distinctive electrophysiological findings for the diagnosis of restless legs syndrome. Altogether, EDS disorders are common in neurological sleep laboratories, but usually cannot be diagnosed based on PSG and MSLT findings alone. The diagnostic value of actigraphy recordings can hardly be overestimated.

Improved vigilance after sodium oxybate treatment in narcolepsy: a comparison between in-field and in-laboratory measurements.

This two-centre observational study of vigilance measurements assessed the feasibility of vigilance measurements on multiple days using the Sustained Attention to Response Task and the Psychomotor Vigilance Test with portable task equipment, and subsequently assessed the effect of sodium oxybate treatment on vigilance in patients with narcolepsy. Twenty-six patients with narcolepsy and 15 healthy controls were included. The study comprised two in-laboratory days for the Maintenance of Wakefulness Test and the Oxford Sleep Resistance test, followed by 7-day portable vigilance battery measurements. This procedure was repeated for patients with narcolepsy after at least 3 months of stable treatment with sodium oxybate. Patients with narcolepsy had a higher Sustained Attention to Response Task error count, lower Psychomotor Vigilance Test reciprocal reaction time, higher Oxford Sleep Resistance test omission error count adjusted for test duration (Oxford Sleep Resistance testOMIS / MIN ), and lower Oxford Sleep Resistance test and Maintenance of Wakefulness Test sleep latency compared with controls (all P < 0.01). Treatment with sodium oxybate was associated with a longer Maintenance of Wakefulness Test sleep latency (P < 0.01), lower Oxford Sleep Resistance testOMIS / MIN (P = 0.01) and a lower Sustained Attention to Response Task error count (P = 0.01) in patients with narcolepsy, but not with absolute changes in Oxford Sleep Resistance test sleep latency or Psychomotor Vigilance Test reciprocal reaction time. It was concluded that portable measurements of sustained attention as well as in-laboratory Oxford Sleep Resistance test and Maintenance of Wakefulness Test measurements revealed worse performance for narcoleptic patients compared with controls, and that sodium oxybate was associated with an improvement of sustained attention and a better resistance to sleep.

Psychiatric Comorbidities in Restless Legs Syndrome.

Restless legs syndrome (RLS) is a neurological sleep disorder with frequent (39%) coexisting psychiatric comorbidities. Patients with any psychiatric comorbidity had fewer periodic leg movements in sleep. Psychiatric disorders should be taken into account in patients with RLS.

Increased sleep need and daytime sleepiness 6 months after traumatic brain injury: a prospective controlled clinical trial.

Post-traumatic sleep-wake disturbances are common after acute traumatic brain injury. Increased sleep need per 24 h and excessive daytime sleepiness are among the most prevalent post-traumatic sleep disorders and impair quality of life of trauma patients. Nevertheless, the relation between traumatic brain injury and sleep outcome, but also the link between post-traumatic sleep problems and clinical measures in the acute phase after traumatic brain injury has so far not been addressed in a controlled and prospective approach. We therefore performed a prospective controlled clinical study to examine (i) sleep-wake outcome after traumatic brain injury; and (ii) to screen for clinical and laboratory predictors of poor sleep-wake outcome after acute traumatic brain injury. Forty-two of 60 included patients with first-ever traumatic brain injury were available for follow-up examinations. Six months after trauma, the average sleep need per 24 h as assessed by actigraphy was markedly increased in patients as compared to controls (8.3 ± 1.1 h versus 7.1 ± 0.8 h, P < 0.0001). Objective daytime sleepiness was found in 57% of trauma patients and 19% of healthy subjects, and the average sleep latency in patients was reduced to 8.7 ± 4.6 min (12.1 ± 4.7 min in controls, P = 0.0009). Patients, but not controls, markedly underestimated both excessive sleep need and excessive daytime sleepiness when assessed only by subjective means, emphasizing the unreliability of self-assessment of increased sleep propensity in traumatic brain injury patients. At polysomnography, slow wave sleep after traumatic brain injury was more consolidated. The most important risk factor for developing increased sleep need after traumatic brain injury was the presence of an intracranial haemorrhage. In conclusion, we provide controlled and objective evidence for a direct relation between sleep-wake disturbances and traumatic brain injury, and for clinically significant underestimation of post-traumatic sleep-wake disturbances by trauma patients.

Topographic sleep EEG changes in the acute and chronic stage of hemispheric stroke.

After stroke, the injured brain undergoes extensive reorganization and reconnection. Sleep may play a role in synaptic plasticity underlying stroke recovery. To test this hypothesis, we investigated topographic sleep electroencephalographic characteristics, as a measure of brain reorganization, in the acute and chronic stages after hemispheric stroke. We studied eight patients with unilateral stroke in the supply territory of the middle cerebral artery and eight matched controls. All subjects underwent a detailed clinical examination including assessment of stroke severity, sleep habits and disturbances, anxiety and depression, and high-density electroencephalogram examination with 128 electrodes during sleep. The recordings were performed within 10 days after stroke in all patients, and in six patients also 3 months later. During sleep, we found higher slow-wave and theta activity over the affected hemisphere in the infarct area in the acute and chronic stage of stroke. Slow-wave, theta activity and spindle frequency range power over the affected hemisphere were lower in comparison to the non-affected side in a peri-infarct area in the patients' group, which persisted over time. Conversely, in wakefulness, only an increase of delta, theta activity and a slowing of alpha activity over the infarct area were found. Sleep slow-wave activity correlated with stroke severity and outcome. Stroke might have differential effects on the generation of delta activity in wakefulness and sleep slow waves (1-8 Hz). Sleep electroencephalogram changes over both the affected and non-affected hemispheres reflect the acute dysfunction caused by stroke and the plastic changes underlying its recovery. Moreover, these changes correlate with stroke severity and outcome.

Assessment of Fitbit Charge 4 for sleep stage and heart rate monitoring against polysomnography and during home monitoring in Huntington's disease.

STUDY OBJECTIVES: Wearable devices that monitor sleep stages and heart rate offer the potential for longitudinal sleep monitoring in patients with neurodegenerative diseases. Sleep quality reduces with disease progression in Huntington's disease (HD). However, the involuntary movements characteristic of HD may affect the accuracy of wrist-worn devices. This study compares sleep stage and heart rate data from the Fitbit Charge 4 (FB) against polysomnography (PSG) in participants with HD. METHODS: Ten participants with manifest HD wore an FB during overnight hospital-based PSG, and 9 of these participants continued to wear the FB for 7 nights at home. Sleep stages (30-second epochs) and minute-by-minute heart rate were extracted and compared against PSG data. RESULTS: FB-estimated total sleep and wake times and sleep stage times were in good agreement with PSG, with intraclass correlations of 0.79-0.96. However, poor agreement was observed for wake after sleep onset and the number of awakenings. FB detected waking with 68.6 ± 15.5% sensitivity and 93.7 ± 2.5% specificity, rapid eye movement sleep with high sensitivity and specificity (78.7 ± 31.9%, 95.6 ± 2.3%), and deep sleep with lower sensitivity but high specificity (56.4 ± 28.8%, 95.0 ± 4.8%). FB heart rate was strongly correlated with PSG, and the mean absolute error between FB and PSG heart rate data was 1.16 ± 0.42 beats/min. At home, longer sleep and shorter wake times were observed compared with hospital data, whereas percentage sleep stage times were consistent with hospital data. CONCLUSIONS: Results suggest the potential for long-term monitoring of sleep patterns using wrist-worn wearable devices as part of symptom management in HD. CITATION: Doheny EP, Renerts K, Braun A, et al. Assessment of Fitbit Charge 4 for sleep stage and heart rate monitoring against polysomnography and during home monitoring in Huntington's disease. J Clin Sleep Med. 2024;20(7):1163-1171.

Rapid Eye Movements during REM Sleep Differentiate PSP from Parkinson's Disease.

BACKGROUND: Little is known about the characteristics and occurrence frequencies of rapid eye movements (REMs) during REM sleep in movement disorders. OBJECTIVES: The aim of this study was to detect and characterize REMs during polysomnographically defined REM sleep as recorded by electro-oculography (EOG) in 12 patients with progressive supranuclear palsy (PSP), 13 patients with Parkinson's disease (PD) and 12 healthy controls. METHODS: Using a modified EOG montage, we developed an algorithm that automatically detects and characterizes REMs during REM sleep based on their presumptive saccadic kinematics. RESULTS: Compared to PD and healthy controls, REM densities and REM peak velocities were significantly reduced in PSP. These effects were most pronounced in vertical REMs. CONCLUSION: Ocular motor dysfunction, one of the cardinal features of PSP, seems to be equally at play during REM sleep and wakefulness. For future studies, we provide a novel tool for the unbiased analysis of REMs during REM sleep in movement disorders.

Excessive sleep need following traumatic brain injury: a case-control study of 36 patients.

Increased sleep need following traumatic brain injury, referred to in this study as post-traumatic pleiosomnia, is common, but so far its clinical impact and therapeutic implications have not been characterized. We present a case-control study of 36 patients with post-traumatic pleiosomnia, defined by an increased sleep need of at least 2 h per 24 h after traumatic brain injury, compared to 36 controls. We assessed detailed history, sleep-activity patterns with sleep logs and actigraphy, nocturnal sleep with polysomnography and daytime sleep propensity with multiple sleep latency tests. Actigraphy recordings revealed that traumatic brain injury (TBI) patients had longer estimated sleep durations than controls (10.8 h per 24 h, compared to 7.3 h). When using sleep logs, TBI patients underestimated their sleep need. During nocturnal sleep, patients had higher amounts of slow-wave sleep than controls (20 versus 13.8%). Multiple sleep latency tests revealed excessive daytime sleepiness in 15 patients (42%), and 10 of them had signs of chronic sleep deprivation. We conclude that post-traumatic pleiosomnia may be even more frequent than reported previously, because affected patients often underestimate their actual sleep need. Furthermore, these patients exhibit an increase in slow-wave sleep which may reflect recovery mechanisms, intrinsic consequences of diffuse brain damage or relative sleep deprivation.

Actigraphic assessment of periodic leg movements in patients with restless legs syndrome.

The diagnosis of restless legs syndrome (RLS) relies upon diagnostic criteria which are based on history only, and dopaminergic treatment is not normally the first choice of treatment for all patients. It would be worthwhile to identify patients non-responsive to dopaminergic treatment beforehand, because they may suffer from a restless legs-like syndrome and may require alternative treatment. We included retrospectively 24 adult patients fulfilling the four essential criteria for restless legs and 12 age-matched healthy controls. They were investigated by ambulatory actigraphy from both legs over three nights, and patients started treatment with dopamine agonists after this diagnostic work-up. We examined 12 responders to dopaminergic treatment and 12 non-responders and studied the association between response to dopaminergic treatment and the periodic limb movement index (PLMI) as assessed with actigraphy. Demographic characteristics, excessive daytime sleepiness and fatigue at baseline were similar in all three groups. Baseline RLS severity was similar between responders and non-responders [International Restless Legs Severity Scale (IRLS): 25 ± 9 and 24 ± 8]. Group comparisons of PLMI before treatment initiation showed significant differences between the three groups. Post-hoc pairwise comparisons revealed that healthy controls had significantly lower PLMI (4.9 ± 4.5) than responders (29.3 ± 22.7) and non-responders (13.3 ± 11.2). Similarly, the PLMI in responders was lower than in non-responders. PLMI day-to-day variability did not differ between responders and non-responders and there was no correlation between treatment effect, as assessed by the decrease of the IRLS and baseline PLMI. Our retrospective study indicates that actigraphy to assess periodic limb movements may contribute to a better diagnosis of dopamine-responsive restless legs syndrome.

A novel method to increase specificity of sleep-wake classifiers based on wrist-worn actigraphy.

The knowledge of the distribution of sleep and wake over a 24-h day is essential for a comprehensive image of sleep-wake rhythms. Current sleep-wake scoring algorithms for wrist-worn actigraphy suffer from low specificities, which leads to an underestimation of the time staying awake. The goal of this study (ClinicalTrials.gov Identifier: NCT03356938) was to develop a sleep-wake classifier with increased specificity. By artificially balancing the training dataset to contain as much wake as sleep epochs from day- and nighttime measurements from 12 subjects, we optimized the classification parameters to an optimal trade-off between sensitivity and specificity. The resulting sleep-wake classifier achieved high specificity of 80.4% and sensitivity of 88.6% on the balanced dataset containing 3079.9 h of actimeter data. In the validation on night sleep of separate adaptation recordings from 19 healthy subjects, the sleep-wake classifier achieved 89.4% sensitivity and 64.6% specificity and estimated accurately total sleep time and sleep efficiency with a mean difference of 12.16 min and 2.83%, respectively. This new, device-independent method allows to rid sleep-wake classifiers from their bias towards sleep detection and lay a foundation for more accurate assessments in everyday life, which could be applied to monitor patients with fragmented sleep-wake rhythms.

How reliable is a simplified MSLT nap termination protocol?

OBJECTIVE: According to current practical guidelines, naps of the Mean Sleep Latency Test (MSLT) must be terminated 15 min after sleep onset, which requires ad hoc scoring. For clinical convenience, some sleep clinics use a simplified protocol with fixed nap lengths of 20min. Its diagnostic accuracy remains unknown. METHODS: A subset of MSLT naps of 56 narcolepsy type 1 (NT1), 98 Parkinson's disease (PD), 117 sleep disordered breathing (SDB), 22 insufficient sleep syndrome (ISS) patients, and 24 patients with idiopathic hypersomnia (IH), originally performed according to the simplified protocol, were retrospectively adjusted to standard protocol (nap termination 15min after sleep onset or after 20min when no sleep occurs). This was feasible in 60% of MSLT naps; in this subset, we compared sensitivity and specificity of both MSLT protocols for identification of patients with and without NT1. RESULTS: Sensitivity of classical MSLT criteria for NT1, i.e. mean sleep latency ≤8.0min and ≥2 sleep onset rapid eye movement periods (SOREMPs), did not differ between protocols (95%). Specificity, however, was slightly lower (88.1% vs. 89.7%) in the simplified nap termination protocol, with 3 SDB patients and 1 ISS patient having false-positive MSLT findings in the simplified but not in the standard protocol. CONCLUSIONS: The use of a simplified MSLT protocol with fixed nap duration had no impact on MSLT sensitivity for NT1, but the longer sleep periods in the simplified protocol increased the likelihood of REM sleep occurrence particularly in non-NT1 conditions, resulting in a slightly lower MSLT specificity compared to the standard protocol.

Sleep spindle and slow wave activity in Parkinson disease with excessive daytime sleepiness.

STUDY OBJECTIVES: Excessive daytime sleepiness (EDS) is a common and devastating symptom in Parkinson disease (PD), but surprisingly most studies showed that EDS is independent from nocturnal sleep disturbance measured with polysomnography. Quantitative electroencephalography (EEG) may reveal additional insights by measuring the EEG hallmarks of non-rapid eye movement (NREM) sleep, namely slow waves and spindles. Here, we tested the hypothesis that EDS in PD is associated with nocturnal sleep disturbance revealed by quantitative NREM sleep EEG markers. METHODS: Patients with PD (n = 130) underwent polysomnography followed by spectral analysis to calculate spindle frequency activity, slow-wave activity (SWA), and overnight SWA decline, which reflects the dissipation of homeostatic sleep pressure. We used the Epworth Sleepiness Scale (ESS) to assess subjective daytime sleepiness and define EDS (ESS > 10). All examinations were part of an evaluation for deep brain stimulation. RESULTS: Patients with EDS (n = 46) showed reduced overnight decline of SWA (p = 0.036) and reduced spindle frequency activity (p = 0.032) compared with patients without EDS. Likewise, more severe daytime sleepiness was associated with reduced SWA decline (ß= -0.24 p = 0.008) and reduced spindle frequency activity (ß= -0.42, p < 0.001) across all patients. Reduced SWA decline, but not daytime sleepiness, was associated with poor sleep quality and continuity at polysomnography. CONCLUSIONS: Our data suggest that daytime sleepiness in PD patients is associated with sleep disturbance revealed by quantitative EEG, namely reduced overnight SWA decline and reduced spindle frequency activity. These findings could indicate that poor sleep quality, with incomplete dissipation of homeostatic sleep pressure, may contribute to EDS in PD.