Roland Popp

Reduced intra-cortical inhibition after sleep deprivation: A transcranial magnetic stimulation study

Sleep deprivation has multiple effects on brain function. It increases the risk for epileptic seizures both in healthy individuals and in patients with epilepsy. Furthermore it represents an effective antidepressive intervention with rapid onset. However, the mechanisms underlying these effects are still largely unknown. Transcranial magnetic stimulation (TMS) can be used as a non-invasive method for the measurement of motor cortex excitability. Here we used TMS for assessing sleep deprivation effects on cortical excitability in healthy individuals. Before and after 24 h of sleep deprivation, parameters of cortical excitability (resting motor threshold, short intracortical inhibition, intracortical facilitation, cortical silent period) were measured in a sample of 15 healthy volunteers (11 women, 4 men, aged between 21 and 30 years with a mean of 24.3±2.7 years). We detected a significant (p=0.042) reduction of short intracortical inhibition (SICI) after sleep deprivation. Motor threshold, intracortical facilitation and contralateral silent period remained unchanged. Our results confirm previous studies which have demonstrated changes of SICI after sleep deprivation. Our findings further suggest that the increased risk for epileptic seizures after sleep deprivation is mediated by a reduction of intracortical inhibition. Whether this mechanism is also involved in mediating the antidepressant effect of sleep deprivation has to be addressed by further studies in depressive patients.

Shortened night sleep impairs facial responsiveness to emotional stimuli

Sleep deprivation deteriorates mood, impairs the recognition of facial expressions, and affects the ability to regulate emotions. The present study investigated the effect of partial sleep deprivation on facial responses to emotional stimuli. Thirty-three healthy undergraduates were tested twice: after a night with (i) 8h and (ii) 4h sleep. Self-reported sleepiness and sustained attention (Psychomotor Vigilance Task) were assessed. Emotional reactivity was measured with facial Electromyogram (EMG) while participants were asked to respond with either compatible or incompatible facial muscles to emotional stimuli in order to study whether partial sleep deprivation caused slower reactions mainly in response to incompatible stimuli (due to an additional effort to suppress the compatible reaction caused by decreased inhibitory control) or in response to both compatible and incompatible stimuli. Self-reported sleepiness and reaction times in a sustained attention task significantly increased after one night of partial sleep deprivation. Facial reactions to emotional stimuli were decelerated. No significant interaction between sleep restriction and compatibility of the muscle to the picture valence could be observed. Hence, volitional facial reactions in response to emotional stimuli were slower after one night of reduced sleep, but affective inhibitory control was not significantly impaired. However, slowed facial responding to emotional stimuli may affect social interaction after sleep restriction.

Determinants of depressive symptoms in narcoleptic patients with and without cataplexy.

The present prospective study assesses depressive symptoms in narcoleptic patients with (NC+) and without (NC−) cataplexy (46 women, 40 men) and age- and sex- matched healthy controls. Seventy patients were under treatment with stimulants and/or anticataplectics. All subjects completed the Beck Depression Inventory (BDI), the Zung Self-Rating Depression Scale (SDS), the Global Impression of Severity of Depression (GSD), the Profile of Mood States (POMS) and Epworth Sleepiness Scale. Patients with narcolepsy were more depressed than controls (higher scores in BDI, GSD, SDS, and POMS [in the total score and in all subscale scores]); however, between the NC+ and NC− patient groups, no differences were found. Our study shows that the women and the patients using antidepressants and stimulants (combination) have a higher probability for depressive symptoms independent of the presence of cataplexy. The lack of difference between NC+ and NC− in the level of depression supports the assumption that the major psychosocial burden in narcolepsy is not necessarily associated with the presence of cataplexy.

The pupillographic sleepiness test in adults: Effect of age, gender, and time of day on pupillometric variables

The Pupillographic Sleepiness Test (PST) measures the level of alertness based on spontaneous oscillations in pupillary size. Reference data are available for male and female adults within the age range 20–60 years. The aim of the present multicenter study was to extend the age range for reference data from 20 to 79 years.

Impaired Vigilance Is Associated with Erectile Dysfunction in Patients with Sleep Apnea

INTRODUCTION Erectile dysfunction (ED) is frequent in patients with obstructive sleep apnea (OSA) and may act as a surrogate of endothelial dysfunction. Furthermore, impairments of vigilance and sustained attention are also commonly associated with OSA. AIM The purpose of this study was to evaluate whether there is an association between ED and sustained attention deficits. METHODS A prospective cross-sectional cohort of 401 male in-patients undergoing diagnostic polysomnography for suspected OSA and a 25-minute sustained attention test was analyzed. ED was assessed using the 15-item International Index of Erectile Function (IIEF-15) questionnaire. The Epworth Sleepiness Scale (ESS) served as a measure of daytime sleepiness. MAIN OUTCOME MEASURE Severity of impaired erectile function (EF) assessed by the IIEF-15, core task parameters of the sustained attention test (i.e., CR: correct reactions; V-CR: variation of correct reactions, CE: commission errors, RT: reaction time; V-RT: variation of reaction times). RESULTS Three hundred eighty-one consecutive patients presenting for in-lab polysomnography were included in the analysis. Impaired EF was diagnosed in 246 patients (65%). With increasing impairment of EF, patients scored significantly worse in all vigilance test parameters and demonstrated more severely diminished vigilance (normal EF: 11.9%, moderately impaired EF: 24.1%, and severely impaired EF: 34.9%). Multivariate regression analyses including established risk factors for ED, OSA, or sleepiness revealed a significant independent association between lower scores for EF and impairments on the following vigilance test variables: odds ratio (95% confidence interval) for V-CR: 0.52 (0.34-0.81), CE: 0.87 (0.80-0.95), and V-RT: 0.91 (0.87-0.96). The ESS was independently associated with both measures of performance instability: odds ratio for V-CR: 6.94 (2.97-16.23) and V-RT: 1.28 (1.14-1.44). CONCLUSIONS In OSA patients, the severity of impaired EF was associated with impaired vigilance performance, independent of other known risk factors for ED or OSA and not mediated by sleepiness. Potentially, the findings suggest a direct relationship between vascular or endothelial dysfunction and impairments in both EF and neurobehavioral cognitive function.

Impact of overnight traffic noise on sleep quality, sleepiness, and vigilant attention in long-haul truck drivers: Results of a pilot study

This study aimed to evaluate the impact of traffic noise along the motorway on sleep quality, sleepiness, and vigilant attention in long-haul truck drivers. This was a randomized, crossover, within-subject controlled study. Healthy long-haul truck drivers spent 6 consecutive nights in a real truck berth with full sleep laboratory equipment. During 3 nights, subjects were exposed to replayed traffic noise alongside motorways, whereas the other 3 nights were without traffic noise. Polysomnography was recorded during the nights and numerous sleepiness tests and vigilance examinations were performed during the following standardized working day. Outcome measures were compared between noisy and silent nights using the paired Wilcoxon test. Ten healthy long-haul truck drivers with a mean age of 36.3 ± 7.3 years completed the study as planned. On noisy nights, subjects had greater latencies to the rapid eye movement (REM) phase (90 ± 32 min vs 69 ± 16 min, P = 0.074) and higher percentages of sleep stage 1 (13.7 ± 5.5% vs 11.2 ± 4.4%; P = 0.059). Subjects also rated their sleep quality as having been better during nights without noise (28.1 ± 3.7 vs 30.3 ± 6.2, P = 0.092). The impact of these differences on daytime sleepiness and vigilance was rather low; however, mean Karolinska Sleepiness Scale (KSS) scores measured during the course of the following day were higher on six out of eight occasions after noisy nights. The effects of overnight traffic noise on sleep quality are detectable but unlikely to have any major impact on the vigilant attention and driving performance of long haul-truck drivers with low nocturnal noise sensitivity. This might not be true for subgroups prone to sleeping disorders.

The assessment of vigilance: normative data on the Siesta sustained attention test ☆

OBJECTIVE In several modern society duties individuals have to maintain their attention or vigilance over prolonged periods of time, even if the monitoring task is monotonous. The aim of our study was to obtain reference data on the 60-minute monotonous Siesta sustained attention test. METHODS Normative data were gathered in an age-stratified sample of 234 healthy participants (118 men; 116 women) between the ages of 20 and 79 years. The impact of age, gender, time of day, and time on task during performance was analyzed. RESULTS At least 20 participants from each age group and gender group were tested either in the morning or in the afternoon. The sample sizes were only smaller in the age group of 70 to 79 years. There was a notable age effect on all performance measures, with an increase in reaction times and false response rates from the youngest to the oldest group as well as a decrease in correct reactions with increasing age. Statistical analysis revealed no differences in speed and accuracy measures between men and women participants. There was no notable time-of-day effect but a clear impact of time-on-task speed and of correct reactions during the course of the test. The vigilance decrement had already occurred during the first half of the test. CONCLUSIONS Our results provide a normative database of performance parameters for different age groups in healthy adult participants. As sustained attention is sensitive to sleep loss and nonrestorative sleep, our data can be used as a reference for performance-based assessment of daytime sleepiness in participants with hypersomnia.

Erhebung zur Praxis der Durchführung von Multiplen Schlaflatenztests (MSLT) in akkreditierten Schlaflaboren@@@Assessment of the implementation of the multiple sleep latency test (MSLT) in accredited sleep labs

ZusammenfassungFragestellungVor dem Hintergrund der Ergebnisse einer von der Arbeitsgruppe Methodik der Deutschen Gesellschaft für Schlafforschung und Schlafmedizin (DGSM) durchgeführten Untersuchung zur Reliabilität der visuellen Auswertung von Schlafstadien in akkreditierten Schlaflaboren [18] hat die Arbeitsgruppe Vigilanz der DGSM eine Studie zur Reliabilität von Ergebnissen aus Multiplen Schlaflatenztests (MSLT) in akkreditierten Schlaflaboren initiiert. Die Studie wird in 2 Schritten durchgeführt. In diesem Beitrag werden zunächst die Ergebnisse einer Fragebogenaktion zur Erfassung der Praxis der Durchführung des MSLT dargestellt.MethodikEs wurde ein Fragebogen entwickelt, mit dem Informationen zur Durchführung von MSLT erhoben wurden. Dieser Fragebogen wurde im Januar 2004 an alle zu dieser Zeit akkreditierten Schlaflabore (N=268) verschickt. Die Responserate betrug bis Anfang April 2004 73,1%.ErgebnisseDie Ergebnisse belegen eine große Variabilität hinsichtlich der durchschnittlichen Anzahl der pro Jahr durchgeführten MSLT, der Anzahl der Tests pro Untersuchungstag, des Spektrums von Verdachtsdiagnosen, bei denen ein MSLT durchgeführt wird sowie der Kriterien zur Definition des Schlafbeginns, der REM-Schlaf-Latenz, der Beendigung eines MSLT-Durchgangs und der Bewertung von Ergebnissen als pathologisch.SchlussfolgerungDie beschriebene Heterogenität in der Durchführung und Bewertung von MSLT in akkreditierten Schlaflaboren hat Konsequenzen für die Reliabilität der Ergebnisse im Hinblick auf einen Vergleich der Ergebnisparameter mit Referenzdaten, die sich auf eine standardisierte Datenerhebung [1, 2, 7, 17, 22] beziehen. Eine Durchführung und Bewertung von MSLT nach den publizierten Richtlinien ist deshalb dringend zu empfehlen.SummaryQuestion of the studyOn the basis of the results of a study on the reliability of visual sleep stage scoring in accredited sleep laboratories performed by the “Methodological Aspects” working group of the German Society for Sleep Research and Sleep Medicine (DGSM) [18], the “Vigilance” working group of the DGSM initiated a study on the reliability of multiple sleep latency test (MSLT) results in accredited sleep laboratories. The study will be performed in two steps. Here the results of the first part—a questionnaire survey on practical aspects of the implementation of the MSLT and its interpretation—are presented.MethodsA questionnaire was developed to gather information on the implementation of the MSLT and the Maintenance of Wakefulness Test (MWT). In January 2004, this questionnaire was sent to all laboratories with accreditation at that time (N=268). The response rate was 73.1% in April 2004.ResultsThe results reflect great variability with regard to the number of MSLTs performed per year, the number of trials performed per day and patient, the range of tentative diagnoses, and the criteria used to define sleep onset, REM sleep latency, the end of a trial, and the assessment of results as pathological findings.ConclusionThe described heterogeneity in the implementation and assessment of multiple sleep latency tests in accredited sleep laboratories has implications for the reliability of results with regard to how the results compare with reference data derived from tests performed in a standardized way [1, 2, 7, 17, 22]. The implementation and assessment of multiple sleep latency tests according to published guidelines is therefore strongly recommended.