Subjective sleepiness, simulated driving performance and blink duration: examining individual differences

The present study aimed to provide subject-specific estimates of the relation between subjective sleepiness measured with the Karolinska Sleepiness Scale (KSS) and blink duration (BLINKD) and lane drifting calculated as the standard deviation of the lateral position (SDLAT) in a high-fidelity moving base driving simulator. Five male and five female shift workers were recruited to participate in a 2-h drive (08:00-10:00 hours) after a normal night sleep and after working a night shift. Subjective sleepiness was rated on the KSS in 5-min intervals during the drive, electro-occulogram (EOG) was measured continuously to calculate BLINKD, and SDLAT was collected from the simulator. A mixed model anova showed a significant (P < 0.001) effect of the KSS for both dependent variables. A test for a quadratic trend suggests a curvilinear effect with a steeper increase at high KSS levels for both SDLAT (P < 0.001) and BLINKD (P = 0.003). Large individual differences were observed for the intercept (P < 0.001), suggesting that subjects differed in their overall driving performance and blink duration independent of sleepiness levels. The results have implications for any application that needs prediction at the subject level (e.g. driver fatigue warning systems) as well as for research design and the interpretation of group average data.     

Short sleep duration and long spells of driving are associated with the occurrence of Japanese drivers’ rear‐end collisions and single‐car accidents

Sleepiness and fatigue are important risk factors for traffic accidents. However, the relation between the accident type and lack of sleep as well as spells of driving has not been examined sufficiently. This study aimed to clarify that short sleep duration and long spells of driving are more associated with rear‐end collisions and single‐car accidents as compared with accidents of other types in cases of people who cause accidents. After removing drunken driving as a cause of accidents, 1772 parties involved in accidents were questioned. The quantities of rear‐end collisions and single‐car accidents were, respectively, 240 and 293. Logistic regression analysis showed that short nocturnal sleep (<6 h) and 10‐min increments of spells of driving were significantly associated not only with rear‐end collisions but also with single‐car accidents as compared with accidents of other types. Furthermore, younger age (≤25 years old) and nighttime (21:00–06:00 h) driving were significantly associated with single‐car accidents as compared with accidents of other types. To prevent such accidents, countermeasures must be considered in light of the characteristics of drivers involved in each type of accident described above.     

Sleep spindle dynamics during NREM and REM sleep following distinct general anaesthesia in control rats and in a rat model of Parkinson’s disease cholinopathy

On the basis of our previous studies and the important role of the thalamo‐cortical network in states of unconsciousness, such as anaesthesia and sleep, and in sleep spindles generation, we investigated sleep spindles (SS) and high‐voltage sleep spindle (HVS) dynamics during non‐rapid eye movement (NREM) and rapid eye movement (REM) sleep following different types of general anaesthesia in both physiological controls and in a rat model of Parkinson's disease (PD) cholinopathy, to follow the impact of anaesthesia on post‐anaesthesia sleep at the thalamo‐cortical level through an altered sleep spindle dynamics. We recorded 6 hr of spontaneous sleep in all rats, both before and 48 hr after ketamine/diazepam or pentobarbital anaesthesia, and we used 1 hr of NREM or REM sleep from each to validate visually the automatically detected SS or HVS for their extraction and analysis. In the controls, SS occurred mainly during NREM, whereas HVS occurred only during REM sleep. Ketamine/diazepam anaesthesia promoted HVS, prolonged SS during NREM, induced HVS of increased frequency during REM, and increased SS/HVS densities during REM versus NREM sleep. Pentobarbital anaesthesia decreased the frequency of SS during NREM and the HVS density during REM sleep. Although the pedunculopontine tegmental nucleus lesion prolonged SS only during NREM sleep, in these rats, ketamine/diazepam anaesthesia suppressed HVS during both sleep states, whereas pentobarbital anaesthesia promoted HVS during REM sleep. The different impacts of two anaesthetic regimens on the thalamo‐cortical regulatory network are expressed through their distinct sleep spindle generation and dynamics that are dependent on the NREM and REM state regulatory neuronal substrate.     

Reaction of sleepiness indicators to partial sleep deprivation,time of day and time on task in a driving simulator – the DROWSI project

Studies of driving and sleepiness indicators have mainly focused on prior sleep reduction. The present study sought to identify sleepiness indicators responsive to several potential regulators of sleepiness: sleep loss, time of day (TOD) and time on task (TOT) during simulator driving. Thirteen subjects drove a high‐fidelity moving base simulator in six 1‐h sessions across a 24‐h period, after normal sleep duration (8 h) and after partial sleep deprivation (PSD; 4 h). The results showed clear main effects of TOD (night) and TOT but not for PSD, although the latter strongly interacted with TOD. The most sensitive variable was subjective sleepiness, the standard deviation of lateral position (SDLAT) and measures of eye closure [duration, speed (slow), amplitude (low)]. Measures of electroencephalography and line crossings (LCs) showed only modest responses. For most variables individual differences vastly exceeded those of the fixed effects, except for subjective sleepiness and SDLAT. In a multiple regression analysis, SDLAT, amplitude/peak eye‐lid closing velocity and blink duration predicted subjective sleepiness bouts with a sensitivity and specificity of about 70%, but were mutually redundant. The prediction of LCs gave considerably weaker, but similar results. In summary, SDLAT and eye closure variables could be candidates for use in sleepiness‐monitoring devices. However, individual differences are considerable and there is need for research on how to identify and predict individual differences in susceptibility to sleepiness.     

Maternal perceptions of sleep problems among children and mothers during the coronavirus disease 2019 (COVID‐19) pandemic in Israel

Despite the marked impact of the coronavirus disease 2019 (COVID‐19) pandemic on the life of families and its possible negative implications for sleep, little is known about how sleep among parents and children has been impacted by this current crisis. In the present study, we addressed, for the first time, possible consequences of the COVID‐19 crisis and home confinement on maternal anxiety, maternal insomnia, and maternal reports of sleep problems among children aged 6–72 months in Israel (N = 264). Our results revealed a high frequency of maternal clinical insomnia during the COVID‐19 pandemic: 23% during the pandemic, compared to only 11% before the pandemic (retrospective reports about 1–2 months before the pandemic). About 80% of mothers reported mild‐to‐high levels of current COVID‐19 anxiety. The majority of mothers reported no change in their child’s sleep quality, duration, and sleeping arrangement. However, about 30% reported a negative change in child’s sleep quality and a decrease in sleep duration, and there were also mothers who reported a positive change. These findings suggest that the changes in sleep patterns during the COVID‐19 pandemic are varied and that no unified change for the worse should be expected. Further consideration of changes in sleep within the family context during this ongoing crisis is needed.