Eva-Maria Elmenhorst

Examining nocturnal railway noise and aircraft noise in the field: sleep, psychomotor performance, and annoyance.

BACKGROUND Traffic noise is interfering during day- and nighttime causing distress and adverse physiological reactions in large parts of the population. Railway noise proved less annoying than aircraft noise in surveys which were the bases for a so called 5 dB railway bonus regarding noise protection in many European countries. OBJECTIVES The present field study investigated railway noise-induced awakenings during sleep, nighttime annoyance and the impact on performance the following day. Comparing these results with those from a field study on aircraft noise allowed for a ranking of traffic modes concerning physiological and psychological reactions. METHODS 33 participants (mean age 36.2 years ± 10.3 (SD); 22 females) living alongside railway tracks around Cologne/Bonn (Germany) were polysomnographically investigated. These data were pooled with data from a field study on aircraft noise (61 subjects) directly comparing the effects of railway and aircraft noise in one random subject effects logistic regression model. Annoyance was rated in the morning evaluating the previous night. RESULTS Probability of sleep stage changes to wake/S1 from railway noise increased significantly from 6.5% at 35 dB(A) to 20.5% at 80 dB(A) LAFmax. Rise time of noise events had a significant impact on awakening probability. Nocturnal railway noise led to significantly higher awakening probabilities than aircraft noise, partly explained by the different rise times, whereas the order was inversed for annoyance. Freight train noise compared to passenger train noise proved to have the most impact on awakening probability. Nocturnal railway noise had no effect on psychomotor vigilance. CONCLUSIONS Nocturnal freight train noise exposure in Germany was associated with increased awakening probabilities exceeding those for aircraft noise and contrasting the findings of many annoyance surveys and annoyance ratings of our study. During nighttime a bonus for railway noise seems not appropriate.

Performance impairment during four days partial sleep deprivation compared with the acute effects of alcohol and hypoxia

OBJECTIVE Subjects were exposed to cumulated partial sleep deprivation (psd), alcohol intake and hypoxia in a sequential design to examine the impact on neurobehavioral performance. METHODS Sixteen healthy male volunteers were enrolled in this study and were exposed in turn, after adaptation and baseline measurements, to one day of periods of hypoxia, one day of alcohol intake and one day for recovering (with 8h time in bed TIB). Subsequently the exposition of those conditions is that the subjects spent 5h night restriction daily for four consecutive days, followed by two recovery days. Performance was tested five (or six) times per day with reaction time task (SRT) and unstable tracking task (UTT). RESULTS The performance impairment showed to be cumulative in both tests over the four sleep deprivation days and differed significantly from baseline. Corresponding performance deficits under the influence of the stressors were for SRT: four days psd, 13% O(2) concentration and a blood alcohol concentration (BAC) of around 0.4-0.6 per thousand for UTT: four days psd, 13% O(2) concentration and a BAC of around 0.6 per thousand. One night of 8h sleep restored performance nearly to baseline level. CONCLUSIONS A sleeping time of 5h per night for four consecutive days impairs performance in such a way that traffic safety may be compromised.

Aircraft noise effects on sleep: a systematic comparison of EEG awakenings and automatically detected cardiac activations

Polysomnography is the gold standard for investigating noise effects on sleep, but data collection and analysis are sumptuous and expensive. We recently developed an algorithm for the automatic identification of cardiac activations associated with cortical arousals, which uses heart rate information derived from a single electrocardiogram (ECG) channel. We hypothesized that cardiac activations can be used as estimates for EEG awakenings. Polysomnographic EEG awakenings and automatically detected cardiac activations were systematically compared using laboratory data of 112 subjects (47 male, mean+/-SD age 37.9+/-13 years), 985 nights and 23,855 aircraft noise events (ANEs). The probability of automatically detected cardiac activations increased monotonically with increasing maximum sound pressure levels of ANEs, exceeding the probability of EEG awakenings by up to 18.1%. If spontaneous reactions were taken into account, exposure-response curves were practically identical for EEG awakenings and cardiac activations. Automatically detected cardiac activations may be used as estimates for EEG awakenings. More investigations are needed to further validate the ECG algorithm in the field and to investigate inter-individual differences in its ability to predict EEG awakenings. This inexpensive, objective and non-invasive method facilitates large-scale field studies on the effects of traffic noise on sleep.

Annoyance and self-reported sleep disturbance due to night-time railway noise examined in the field

Railway noise interferes with daytime activities and disturbs sleep leading to annoyance of exposed residents. The main objective of this paper was to establish exposure-response relationships between nocturnal railway noise exposure and annoyance and to examine self-reported sleep disturbances as short-term reactions to noise. In a field study 33 residents living close to railway tracks in the Cologne/Bonn area (Germany) were investigated. Railway noise was measured indoors during nine consecutive nights at each site. Questionnaires referring to annoyance and non-acoustical factors were performed. Annoyance ratings increased significantly with the total number of trains and freight trains per night, and non-significantly with rising number of passenger trains and energy equivalent sound pressure level (L(Aeq)), when adjusting the model for non-acoustical variables. The total number of trains and the number of freight trains also significantly affected self-reported awakening frequency, but no other aspects of subjective sleep disturbances. The responses of this subject sample referring to railway noise in the previous night point to rather low impairments of exposed residents.

Circadian variation of metabotropic glutamate receptor 5 availability in the rat brain

The metabotrophic subtype 5 glutamate receptor (mGluR5) plays a critical role in synaptic plasticity besides its involvement in numerous neurological disorders, such as depression. As mGluR5 availability in humans is altered in sleep deprivation, we hypothesized that mGluR5 availability underlies a circadian variation. To investigate whether mGluR5 underlies potential circadian changes we measured its density in a randomized fashion at six different daytimes in 11 adult Sprague–Dawley rats. mGluR5 density was quantified by positron emission tomography (PET) using the radioactive ligand [11C]ABP688. [11C]ABP688 uptake was quantified in nine regions of interest with a reference tissue model. Significant differences in the binding potential (BPND) and therefore mGluR5 availability between the different circadian times were found in cortex, cingulate cortex, amygdala, caudate putamen and nucleus accumbens. Further post‐hoc statistical analysis (Tukey–Kramer test) of the different time‐points revealed significant changes in BPND between 07:00 hours (start of light‐on phase) and 15:00 hours (last time‐point of the light‐on phase) in the caudate putamen. This study shows that mGluR5 availability is increased during the light‐on, or sleep phase, of rodents by approximately 10%. Given that altered mGluR5 densities play a role in psychiatric disorders, further investigation is warranted to evaluate their circadian involvement in mood changes in humans.

Critical Appraisal of Methods for the Assessment of Noise Effects on Sleep

Various sleep measurement techniques have been applied in past studies on the effects of environmental noise on sleep, complicating comparisons between studies and the derivation of pooled exposure-response relationships that could inform policy and legislation. To date, a consensus on a standard measurement technique for the assessment of environmental noise effects on sleep is missing. This would be desirable to increase comparability of future studies. This manuscript provides a detailed description of the sleep process, typical indicators of disturbed sleep, and how noise interferes with sleep. It also describes and discusses merits and drawbacks of five established methods commonly used for the assessment of noise effects on sleep (i.e., polysomnography, actigraphy, electrocardiography, behaviorally confirmed awakenings, and questionnaires). Arguments supporting the joint use of actigraphy and a single channel electrocardiogram as meaningful, robust, and inexpensive methods that would allow for the investigation of large representative subject samples are presented. These could be used as a starting point for the generation of an expert consensus.

Recovery sleep after extended wakefulness restores elevated A1 adenosine receptor availability in the human brain.

Significance Our study reveals that prolonged sleep deprivation is accompanied by an A1 adenosine receptor (A1AR) upregulation in the human brain. Recovery sleep quickly restores A1AR availability to control levels. High individual A1AR availability is related to a low sleep pressure and good cognitive performance. Sleep deprivation is an efficient but short-lasting therapeutic strategy in depression. A causal sleep–wake dysregulation has been proposed, possibly mediated by cerebral adenosine and its A1AR. The restoration of the A1AR availability after recovery from sleep deprivation mimics the rapid relapse following the end of therapeutic sleep deprivation. Understanding the adenosine regulation under sleep restriction, especially regarding individual characteristics, might improve the rationale for the individual indication and design of therapeutic sleep modulation in depression. Adenosine and functional A1 adenosine receptor (A1AR) availability are supposed to mediate sleep–wake regulation and cognitive performance. We hypothesized that cerebral A1AR availability after an extended wake period decreases to a well-rested state after recovery sleep. [18F]CPFPX positron emission tomography was used to quantify A1AR availability in 15 healthy male adults after 52 h of sleep deprivation and following 14 h of recovery sleep. Data were additionally compared with A1AR values after 8 h of baseline sleep from an earlier dataset. Polysomnography, cognitive performance, and sleepiness were monitored. Recovery from sleep deprivation was associated with a decrease in A1AR availability in several brain regions, ranging from 11% (insula) to 14% (striatum). A1AR availabilities after recovery did not differ from baseline sleep in the control group. The degree of performance impairment, sleepiness, and homeostatic sleep-pressure response to sleep deprivation correlated negatively with the decrease in A1AR availability. Sleep deprivation resulted in a higher A1AR availability in the human brain. The increase that was observed after 52 h of wakefulness was restored to control levels during a 14-h recovery sleep episode. Individuals with a large increase in A1AR availability were more resilient to sleep-loss effects than those with a subtle increase. This pattern implies that differences in endogenous adenosine and A1AR availability might be causal for individual responses to sleep loss.

Inter-individual Differences in the Effects of Aircraft Noise on Sleep Fragmentation

STUDY OBJECTIVES Environmental noise exposure disturbs sleep and impairs recuperation, and may contribute to the increased risk for (cardiovascular) disease. Noise policy and regulation are usually based on average responses despite potentially large inter-individual differences in the effects of traffic noise on sleep. In this analysis, we investigated what percentage of the total variance in noise-induced awakening reactions can be explained by stable inter-individual differences. METHODS We investigated 69 healthy subjects polysomnographically (mean ± standard deviation 40 ± 13 years, range 18-68 years, 32 male) in this randomized, balanced, double-blind, repeated measures laboratory study. This study included one adaptation night, 9 nights with exposure to 40, 80, or 120 road, rail, and/or air traffic noise events (including one noise-free control night), and one recovery night. RESULTS Mixed-effects models of variance controlling for reaction probability in noise-free control nights, age, sex, number of noise events, and study night showed that 40.5% of the total variance in awakening probability and 52.0% of the total variance in EEG arousal probability were explained by inter-individual differences. If the data set was restricted to nights (4 exposure nights with 80 noise events per night), 46.7% of the total variance in awakening probability and 57.9% of the total variance in EEG arousal probability were explained by inter-individual differences. The results thus demonstrate that, even in this relatively homogeneous, healthy, adult study population, a considerable amount of the variance observed in noise-induced sleep disturbance can be explained by inter-individual differences that cannot be explained by age, gender, or specific study design aspects. CONCLUSIONS It will be important to identify those at higher risk for noise induced sleep disturbance. Furthermore, the custom to base noise policy and legislation on average responses should be re-assessed based on these findings.

Pilot workload during approaches: comparison of simulated standard and noise-abatement profiles.

INTRODUCTION A new noise-reduced landing approach was tested--a Segmented Continuous Descent Approach (SCDA)-with regard to the resulting workload on pilots. METHODS Workload of 40 pilots was measured using physiological (heart rate, blood pressure, blink frequency, saliva cortisol concentration) and psychological (fatigue, sleepiness, tension, and task load) parameters. Approaches were conducted in A320 and A330 full-flight simulators during night shift. SCDA was compared to the standard Low Drag Low Power (LDLP) procedure as reference. RESULTS Mean heart rate and blood pressure during the SCDA were not elevated, but were partly, even significantly, reduced (on average by 5 bpm and 4 mmHg from the flying captain). Cortisol levels did not change significantly with mean values of 0.9 to 1.2 ng ml(-1). Landing was the most demanding segment of both approaches as indicated by significant increases in heart rate and decreases in blink frequency. Subjective task load was low. DISCUSSION Both approach procedures caused a similar workload level. Interpreting the results, methodological limitations have to be considered, e.g., the artificial and controlled airspace situation in the flight simulator. Nevertheless, it can be concluded that under these ideal conditions, the SCDA is operable without a higher workload for pilots compared to the common LDLP.

Significance of time awake for predicting pilots' fatigue on short‐haul flights: implications for flight duty time regulations

European regulations restrict the duration of the maximum daily flight duty period for pilots as a function of the duty start time and the number of scheduled flights. However, late duty end times that may include long times awake are not specifically regulated. In this study, fatigue levels in pilots finishing their duty late at night (00:00–01:59 hour) were analysed and compared with pilots starting their duty early (05:00–06:59 hour). Fatigue levels of 40 commercial short‐haul pilots were studied during a total of 188 flight duty periods, of which 87 started early and 22 finished late. Pilots used a small handheld computer to maintain a duty and sleep log, and to indicate fatigue levels immediately after each flight. Sleep logs were checked with actigraphy. Pilots on late‐finishing flight duty periods were more fatigued at the end of their duty than pilots on early‐starting flight duty periods, despite the fact that preceding sleep duration was longer by 1.1 h. Linear mixed‐model regression identified time awake as a preeminent factor predicting fatigue. Workload had a minor effect. Pilots on late‐finishing flight duty periods were awake longer by an average of 5.5 h (6.6 versus 1.1 h) before commencing their duty than pilots who started early in the morning. Late‐finishing flights were associated with long times awake at a time when the circadian system stops promoting alertness, and an increased, previously underestimated fatigue risk. Based on these findings, flight duty limitations should consider not only duty start time, but also the time of the final landing.