Hans Dorn

Interrater reliability for sleep scoring according to the Rechtschaffen & Kales and the new AASM standard

Interrater variability of sleep stage scorings has an essential impact not only on the reading of polysomnographic sleep studies (PSGs) for clinical trials but also on the evaluation of patients’ sleep. With the introduction of a new standard for sleep stage scorings (AASM standard) there is a need for studies on interrater reliability (IRR). The SIESTA database resulting from an EU‐funded project provides a large number of studies (n = 72; 56 healthy controls and 16 subjects with different sleep disorders, mean age ± SD: 57.7 ± 18.7, 34 females) for which scorings according to both standards (AASM and R&K) were done. Differences in IRR were analysed at two levels: (1) based on quantitative sleep parameter by means of intraclass correlations; and (2) based on an epoch‐by‐epoch comparison by means of Cohen’s kappa and Fleiss’ kappa. The overall agreement was for the AASM standard 82.0% (Cohen’s kappa = 0.76) and for the R&K standard 80.6% (Cohen’s kappa = 0.68). Agreements increased from R&K to AASM for all sleep stages, except N2. The results of this study underline that the modification of the scoring rules improve IRR as a result of the integration of occipital, central and frontal leads on the one hand, but decline IRR on the other hand specifically for N2, due to the new rule that cortical arousals with or without concurrent increase in submental electromyogram are critical events for the end of N2.

Interrater reliability between scorers from eight European sleep laboratories in subjects with different sleep disorders.

Interrater variability of sleep stage scorings is a well‐known phenomenon. The SIESTA project offered the opportunity to analyse interrater reliability (IRR) between experienced scorers from eight European sleep laboratories within a large sample of patients with different (sleep) disorders: depression, general anxiety disorder with and without non‐organic insomnia, Parkinsons disease, period limb movements in sleep and sleep apnoea. The results were based on 196 recordings from 98 patients (73 males: 52.3 ± 12.1 years and 25 females: 49.5 ± 11.9 years) for which two independent expert scorings from two different laboratories were available. Cohens κ was used to evaluate the IRR on the basis of epochs and intraclass correlation was used to analyse the agreement on quantitative sleep parameters. The overall level of agreement when five different stages were distinguished was κ = 0.6816 (76.8%), which in terms of κ reflects a ‘substantial’ agreement ( Landis and Koch, 1977 ). For different groups of patients κ values varied from 0.6138 (Parkinsons disease) to 0.8176 (generalized anxiety disorder). With regard to (sleep) stages, the IRR was highest for rapid eye movement (REM), followed by Wake, slow‐wave sleep (SWS), non‐rapid eye movement 2 (NREM2) and NREM1. The results of regression analysis showed that age and sex only had a statistically significant effect on κ when the (sleep) stages are considered separately. For NREM2 and SWS a statistically significant decrease of IRR with age has been observed and the IRR for SWS was lower for males than for females. These variations of IRR most probably reflect changes of the sleep electroencephalography (EEG) with age and gender.

Do mobile phone base stations affect sleep of residents? Results from an experimental double‐blind sham‐controlled field study

The aim of the present double‐blind, sham‐controlled, balanced randomized cross‐over study was to disentangle effects of electromagnetic fields (EMF) and non‐EMF effects of mobile phone base stations on objective and subjective sleep quality.

Effects of electromagnetic fields emitted by mobile phones (GSM 900 and WCDMA/UMTS) on the macrostructure of sleep

In the present double‐blind, randomized, sham‐controlled cross‐over study, possible effects of electromagnetic fields emitted by Global System for Mobile Communications (GSM) 900 and Wideband Code‐Division Multiple Access (WCDMA)/Universal Mobile Telecommunications System (UMTS) cell‐phones on the macrostructure of sleep were investigated in a laboratory environment. An adaptation night, which served as screening night for sleep disorders and as an adjustment night to the laboratory environment, was followed by 9 study nights (separated by a 2‐week interval) in which subjects were exposed to three exposure conditions (sham, GSM 900 and WCDMA/UMTS). The sample comprised 30 healthy male subjects within the age range 18–30 years (mean ± standard deviation: 25.3 ± 2.6 years). A cell‐phone usage at maximum radio frequency (RF) output power was simulated and the transmitted power was adjusted in order to approach, but not to exceed, the specific absorption rate (SAR) limits of the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) guidelines for general public exposure (SAR10g = 2.0 W kg−1). In this study, possible effects of long‐term (8 h) continuous RF exposure on the central nervous system were analysed during sleep, because sleep is a state in which many confounding intrinsic and extrinsic factors (e.g. motivation, personality, attitude) are eliminated or controlled. Thirteen of 177 variables characterizing the initiation and maintenance of sleep in the GSM 900 and three in the WCDMA exposure condition differed from the sham condition. The few significant results are not indicative of a negative impact on sleep architecture. From the present results there is no evidence for a sleep‐disturbing effect of GSM 900 and WCDMA exposure.

Effects of exposure to electromagnetic fields emitted by GSM 900 and WCDMA mobile phones on cognitive function in young male subjects

Results of studies on the possible effects of electromagnetic fields emitted by mobile phones on cognitive functions are contradictory, therefore, possible effects of long-term (7 h 15 min) electromagnetic field (EMF) exposure to handset-like signals of Global System for Mobile Communications (GSM) 900 and Wideband Code-Division Multiple Access (WCDMA) on attention and working memory were studied. The sample comprised 30 healthy male subjects (mean ± SD: 25.3 ± 2.6 years), who were tested on nine study days in which they were exposed to three exposure conditions (sham, GSM 900 and WCDMA) in a randomly assigned and balanced order. All tests were presented twice (morning and afternoon) on each study day within a fixed timeframe. Univariate comparisons revealed significant changes when subjects were exposed to GSM 900 compared to sham, only in the vigilance test. In the WCDMA exposure condition, one parameter in the vigilance and one in the test on divided attention were altered compared to sham. Performance in the selective attention test and the n-back task was not affected by GSM 900 or WCDMA exposure. Time-of-day effects were evident for the tests on divided and selective attention, as well as for working memory. After correction for multiple testing, only time-of-day effects remained significant in two tests, resulting in faster reactions in the afternoon trials. The results of the present study do not provide any evidence of an EMF effect on human cognition, but they underline the necessity to control for time of day.

Association between pupillary unrest index and waking electroencephalogram activity in sleep-deprived healthy adults

OBJECTIVE In recent years there has been growing interest in the use of pupillography as an objective and time-saving method to assess the level of sleepiness. The aim of our study was to further elucidate the validity of pupillography by investigating the association of pupillometric variables with subjective sleepiness and waking electroencephalogram (EEG) activity. METHODS The level of sleepiness of 24 young healthy adults was evaluated during 40h of sustained wakefulness using pupillography and subjective ratings with the Stanford sleepiness scale and a visual analog scale (VAS). During the assessment of sleepiness by pupillography, waking EEG was simultaneously recorded and subjected to spectral analyses. As a pupillographic measure of sleepiness the pupillary unrest index (PUI) was calculated. RESULTS PUI, subjective sleepiness, and power in the δ, θ, α1, β1, and β3 frequency band exhibited significant variations over time. PUI showed a prominent circadian modulation under high homeostatic sleep pressure. At time points of maximum PUI indicating a high level of sleepiness, significant increases were found in subjective sleepiness as well as in δ, θ, α1, and β1 power. Moreover, PUI showed a significant, high intraindividual correlation with subjective sleepiness and with power in the δ, θ, and α1 frequency band. CONCLUSION The novel finding of a close association between pupillometric variables and distinct changes in waking EEG activity underscores the validity of pupillography as a time- and cost-efficient objective measure of sleepiness that could ease the diagnostic and therapeutic workup of patients who report excessive daytime sleepiness.

The Effects of Donepezil on Postlearning Sleep EEG of Healthy Older Adults

INTRODUCTION Aging is associated with cholinergic hypofunction and memory decline. Cholinergic activity also plays a crucial role in sleep-dependent memory consolidation. The acetylcholinesterase inhibitor (AChE-I) donepezil has been found to increase sleep-related procedural memory consolidation in healthy older adults in a previous study. METHODS Data of the former study were reanalyzed with regard to the effects of donepezil on the sleep EEG of healthy older adults. This analysis was conducted with a special focus on spectral parameters of sleep, which have previously been linked to plasticity-related processes during sleep, i.e., sigma and delta activity. Forty-two participants (aged: 60-77 years) received 5 mg of the AChE-I donepezil orally 30 min before bedtime in a placebo-controlled, double-blind design. Power values for EEG delta, theta, alpha1, alpha 2, sigma, beta and gamma frequency bands were calculated for stage 2 NREM sleep, SWS and REM sleep. RESULTS In line with our hypotheses, the AChE-I donepezil led to an increase in sigma activity during stage 2 NREM sleep and delta activity during slow wave sleep. CONCLUSION These results suggest that an AChE-I facilitates processes of sleep-dependent memory consolidation in older adults.

Effects of mobile phone exposure (GSM 900 and WCDMA/UMTS) on polysomnography based sleep quality: An intra- and inter-individual perspective

BACKGROUND Studies on effects of radio frequency-electromagnetic fields (RF-EMF) on the macrostructure of sleep so far yielded inconsistent results. This study investigated whether possible effects of RF-EMF exposure differ between individuals. OBJECTIVE In a double-blind, randomized, sham-controlled cross-over study possible effects of electromagnetic fields emitted by pulsed Global System for Mobile Communications (GSM) 900 and Wideband Code-Division Multiple Access (WCDMA)/Universal Mobile Telecommunications System (WCDMA/UMTS) devices on sleep were analysed. METHODS Thirty healthy young men (range 18-30 years) were exposed three times per exposure condition while their sleep was recorded. Sleep was evaluated according to the American Academy of Sleep Medicine standard and eight basic sleep variables were considered. RESULTS Data analyses at the individual level indicate that RF-EMF effects are observed in 90% of the individuals and that all sleep variables are affected in at least four subjects. While sleep of participants was affected in various numbers, combinations of sleep variables and in different directions, showing improvements but also deteriorations, the only consistent finding was an increase of stage R sleep under GSM 900MHz exposure (9 of 30 subjects) as well as under WCDMA/UMTS exposure (10 of 30 subjects). CONCLUSIONS The results underline that sleep of individuals can be affected differently. The observations found here may indicate an underlying thermal mechanism of RF-EMF on human REM sleep. Nevertheless, the effect of an increase in stage R sleep in one third of the individuals does not necessarily indicate a disturbance of sleep.

Design and dosimetric analysis of a 385 MHz TETRA head exposure system for use in human provocation studies

A new head exposure system for double-blind provocation studies investigating possible effects of terrestrial trunked radio (TETRA)-like exposure (385 MHz) on central nervous processes was developed and dosimetrically analyzed. The exposure system allows localized exposure in the temporal brain, similar to the case of operating a TETRA handset at the ear. The system and antenna concept enables exposure during wake and sleep states while an electroencephalogram (EEG) is recorded. The dosimetric assessment and uncertainty analysis yield high efficiency of 14 W/kg per Watt of accepted antenna input power due to an optimized antenna directly worn on the subjects head. Beside sham exposure, high and low exposure at 6 and 1.5 W/kg (in terms of maxSAR10g in the head) were implemented. Double-blind control and monitoring of exposure is enabled by easy-to-use control software. Exposure uncertainty was rigorously evaluated using finite-difference time-domain (FDTD)-based computations, taking into account anatomical differences of the head, the physiological range of the dielectric tissue properties including effects of sweating on the antenna, possible influences of the EEG electrodes and cables, variations in antenna input reflection coefficients, and effects on the specific absorption rate (SAR) distribution due to unavoidable small variations in the antenna position. This analysis yielded a reasonable uncertainty of <±45% (max to min ratio of 4.2 dB) in terms of maxSAR10g in the head and a variability of <±60% (max to min ratio of 6 dB) in terms of mass-averaged SAR in different brain regions, as demonstrated by a brain region-specific absorption analysis.

Terrestrial Trunked Radio (TETRA) exposure and its impact on slow cortical potentials

BACKGROUND Studies have shown that exposure to radiofrequency electromagnetic fields (RF-EMF) in the mobile communication frequency range may induce physiological modifications of both spontaneous as well as event-related human electroencephalogram. So far, there are very few peer-reviewed studies on effects of Terrestrial Trunked Radio (TETRA), which is a digital radio communication standard used by security authorities and organizations in several European countries, on the central nervous system. OBJECTIVES To analyze the impact of simulated TETRA handset signals at 385 MHz on slow cortical potentials (SCPs). METHODS 30 young healthy males (25.2±2.7 years) were exposed in a double-blind, counterbalanced, cross-over design to one of three exposure levels (TETRA with 10 g averaged peak spatial SAR: 1.5 W/kg, 6.0 W/kg and sham). Exposure was conducted with a body worn antenna (especially designed for this study), positioned at the left side of the head. Subjects had 9 test sessions (three per exposure condition) in which three SCPs were assessed: SCP related to a clock monitoring task (CMT), Contingent negative variation (CNV) and Bereitschaftspotential (BP). RESULTS Neither behavioral measures nor the electrophysiological activity was significantly affected by exposure in the three investigated SCP paradigms. Independent of exposure, significant amplitude differences between scalp regions could be observed for the CMT-related SCP and for the CNV. CONCLUSIONS The present results reveal no evidence of RF-EMF exposure-dependent brain activity modifications investigated at the behavioral and the physiological level.