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Rats are known to use a 22-kHz ultrasonic vocalisation as a distress call to warn of danger to other members of their group. We monitored 22-kHz ultrasonic vocalisation emissions in rats (lean and obese) as part of a sleep deprivation study to detect the eventual presence of stress during the procedure. Unexpectedly, we detected ultrasonic vocalisation emission during rapid eye movement (REM) sleep, but not during non-REM (NREM) sleep, in all the rats. The event occurs during the expiratory phase and can take place singularly or as a train. No difference was detected in the number or duration of these events in lean versus obese rats, during the light versus the dark period, and after sleep deprivation. As far as we know, this is the first report showing that rats can vocalise during REM sleep., (© 2023 The Authors. Journal of Sleep Research published by John Wiley & Sons Ltd on behalf of European Sleep Research Society.)

The European Sleep Research Society aimed to estimate the prevalence, determinants and consequences of falling asleep at the wheel. In total, 12 434 questionnaires were obtained from 19 countries using an anonymous online questionnaire that collected demographic and sleep-related data, driving behaviour, history of drowsy driving and accidents. Associations were quantified using multivariate logistic regression. The average prevalence of falling asleep at the wheel in the previous 2 years was 17%. Among respondents who fell asleep, the median prevalence of sleep-related accidents was 7.0% (13.2% involved hospital care and 3.6% caused fatalities). The most frequently perceived reasons for falling asleep at the wheel were poor sleep in the previous night (42.5%) and poor sleeping habits in general (34.1%). Falling asleep was more frequent in the Netherlands [odds ratio = 3.55 (95% confidence interval: 1.97; 6.39)] and Austria [2.34 (1.75; 3.13)], followed by Belgium [1.52 (1.28; 1.81)], Portugal [1.34 (1.13, 1.58)], Poland [1.22 (1.06; 1.40)] and France [1.20 (1.05; 1.38)]. Lower odds were found in Croatia [0.36 (0.21; 0.61)], Slovenia [0.62 (0.43; 0.89)] and Italy [0.65 (0.53; 0.79)]. Individual determinants of falling asleep were younger age; male gender [1.79 (1.61; 2.00)]; driving ≥20 000 km year [2.02 (1.74; 2.35)]; higher daytime sleepiness [7.49 (6.26; 8.95)] and high risk of obstructive sleep apnea syndrome [3.48 (2.78; 4.36) in men]. This Pan European survey demonstrates that drowsy driving is a major safety hazard throughout Europe. It emphasizes the importance of joint research and policy efforts to reduce the burden of sleepiness at the wheel for European drivers.

In recent years, sleep medicine has evolved into a full-grown discipline, featuring a multidisciplinary approach to diagnosis and treatment of patients with sleep disorders. Sleep medicine cuts across the boundaries of different conventional disciplines and is therefore open to medical and non-medical professionals with different specialty backgrounds. The aim of the current paper is to introduce a qualification for those professionals whose main occupation is to practice sleep medicine in the setting of a sleep medicine centre. The drafting of guidelines dealing with requirements for such qualification was entrusted to a task force by the European Sleep Research Society. The guidelines are the result of a progressive consensus procedure in which standards were defined for education, training, and evaluation. The final step along this pathway is a theoretical and practical examination, providing proof of proficiency in the field of sleep medicine. This paper describes the object of specific competences, the scope of sleep medicine, and the qualification procedures that pertain to three professional categories: medical specialists, non-medical professionals with a university master degree (such as psychologists and biologists), and nurses and technologists. Indices of preceding practical experience and theoretical knowledge are presented in Appendices 1 and 2. These guidelines are a European standard. They may be adapted in the future according to new scientific insights. National certification programs that comply with these guidelines may be subject to homologation by the ESRS.

In the albino rat, a REM sleep (REMS) onset can be induced with a high probability and a short latency when the light is suddenly turned off (dark pulse, DP) during non-REM sleep (NREMS). The aim of this study was to investigate to what extent DP delivery could overcome the integrative thermoregulatory mechanisms that depress REMS occurrence during exposure to low ambient temperature (Ta). To this aim, the efficiency of a non-rhythmical repetitive DP (3 min each) delivery during the first 6-h light period of a 12 h:12 h light-dark cycle in inducing REMS was studied in the rat, through the analysis of electroencephalogram, electrocardiogram, hypothalamic temperature and motor activity at different Tas. The results showed that DP delivery triggers a transition from NREMS to REMS comparable to that which occurs spontaneously. However, the efficiency of DP delivery in inducing REMS was reduced during cold exposure to an extent comparable with that observed in spontaneous REMS occurrence. Such impairment was associated with low Delta activity and high sympathetic tone when DPs were delivered. Repetitive DP administration increased REMS amount during the delivery period and a subsequent negative REMS rebound was observed. In conclusion, DP delivery did not overcome the integrative thermoregulatory mechanisms that depress REMS in the cold. These results underline the crucial physiological meaning of the mutual exclusion of thermoregulatory activation and REMS occurrence, and support the hypothesis that the suspension of the central control of body temperature is a prerequisite for REMS occurrence.

The pattern of desynchronized sleep (DS) occurrence in the rat was studied during exposure to an ambient temperature (Ta) of 0 degrees C for 48 h and during a 12 h recovery period at laboratory Ta (23 degrees C) following the first and second 24 h of cold exposure. The exposure to low Ta induces a DS deprivation which is followed, during recovery, by a clear DS rebound. Both the decrease and the following increase in the amount of DS are due to changes in the frequency rather than in the duration of DS episodes. The frequency distribution of the intervals between the end of one DS episode and the beginning of the next (DS interval) has shown that two populations of DS intervals exist, i.e. short DS intervals (3 min). On the basis of this, two types of DS episodes have been identified: the 'single DS episode', which is both preceded and followed by a long DS interval, and the 'sequential DS episode', which is a DS episode occurring within a cluster or a sequence of DS episodes and is characteristically separated by short DS intervals. The occurrence of such sequential DS episodes in a 'DS cluster', allows a high amount of DS to occur without increasing the duration of the DS episode. DS clusters are repressed during cold exposure, when the DS drive is counteracted by the need to thermoregulate, and enhanced during recovery, when the DS drive is unrestrained. In contrast, the occurrence of single DS episodes is much less affected by such different experimental conditions.