Sleep and neurology, insomnia, sleep disordered breathing, nightmares and much more!

Dear members of the ESRS,

Dear readers of JSR,

welcome to the fifth edition of the Journal of Sleep Research in 2024, which will be published in October 2024.

This issue encompasses several reviews and meta-analyses on very different aspects of sleep research and sleep medicine, for example sensory gating and gaining in sleep or gastro-oesophageal reflux during sleep.

Furthermore, there is a broad range of articles covering sleep and neurology, insomnia, sleep-disordered breathing, nightmares, pain, memory consolidation, caffeine etc.

As always let me highlight a few of the articles for you:

Xie and Feeney (2024) touch on a largely neglected subject in sleep research: what is the impact of non-sexual touch on sleep quality? In their narrative review the authors want to shed light on associations between all kinds of non-sexual touch (affectionate touch, touch therapies, touch with animals and inanimate objects) and several aspects of sleep quality. It seems that so-called touch therapies (e.g. massage etc.) exert a positive influence on sleep quality. The same applies for affectionate touch (e.g. hugging). Touch deprivation and touch aversion, on the other hand, negatively impact sleep quality. Interestingly, positive associations between skin-to-skin contact and sleep quality has been shown clearly for newborns and infants.

The authors summarise that the existing database supports positive associations between touch and sleep quality, though further controlled studies are needed.

Sanli et al. (2024) investigated the effect of transcutaneous electrical nerve stimulation (TENS) for the management of Restless Legs Syndrome (RLS). 46 randomly selected patients with RLS were randomized to a) treatment with pramipexole plus 10 sessions of TENS or b) only pramipexole for four weeks. The IRLRS and the PSQI were used as outcome measures. In the combined treatment, stronger effects on both scales were observed for the combination treatment at posttreatment and at follow-up. Thus this study gives preliminary evidence that TENS as add on therapy might be beneficial for patients with RLS.

Moulder et al. (2024) studied whether the therapeutic effects of cognitive behavioural therapy for insomnia (CBT-I) depend on pre-existing sleep–wake discrepancy. This discrepancy was defined as an inconsistency between a persons's subjective and objective sleep (a common phenomenon in patients with insomnia). To this end, the authors studied a real-world sample of 386 patients who were treated in their outpatient insomnia clinic. All patients received a polysomnographic sleep study and a sleep diary which was used to calculate the sleep–wake discrepancy. CBT-I according to clinical standards was delivered in 6 weekly face to face sessions. Major outcome measures were the Insomnia Severity Index (ISI) and other questionnaires, which were administered pre- and post-treatment and at 3-months follow-up. According to the calculated sleep–wake discrepancy, the sample was split up in quintiles. With respect to specific sleep variables like sleep onset latency (SOL) or wake time after sleep onset (WASO) no difference could be found at post-treatment or follow-up between the five quintiles. In conclusion, the authors summarise that the extent of pre-existing sleep–wake discrepancy does not influence the outcome of CBT-I. These are important data, as they were gained from a real world clinical practice and as they stress that clinical CBT-I effects in patients with insomnia do not depend on sleep–wake state discrepancy.

Reichardt et al. (2024) were interested in the question whether naps containing REM sleep might facilitate the generalization of emotional memories. Mnemonic discrimination was measured with the emotional variant of the mnemonic separation task in a sample of 113 volunteers who spent a daytime nap between learning and testing, compared with another group who spent an equivalent time awake between both test sessions. Summarising, it was found that the discrimination of similar but previously unseen items to previously seen items, is enhanced in case of negative compared with neutral/ positive stimuli. Sleep and wake groups did not differ in memnoric performance. However, participants entering REM sleep when napping displayed increased generalisation of emotional memories, thus indicating that REM naps shape emotional memories in a way that enhances recognition at the expense of detailed memory representations.

Looking at a related issue, Lam et al. (2024) wanted to clarify whether a sleepless night might disrupt the resolution of emotional conflicts. 25 so-called healthy controls (young adults) underwent a protocol with a night of at home sleep control compared to a night of full sleep deprivation (SD) in the laboratory. Following both conditions, all participants completed an emotional conflict task with simultaneous EEG recordings to determine event related potentials (ERP). Emotional faces (happy or fearful) overlaid with words (fear or happy) were used as stimuli creating either congruent or incongruent trials – participants had to indicate whether the facial expression was happy or fearful. As outcomes accuracy and reaction times on the emotional conflict task and the P300 component of the ERPs were used. SD reduced alertness and led to longer reaction times and higher error rates. In the SD group, more errors occurred following congruent compared to incongruent trials. The authors conclude that these data support the assumption that SD may impair the regulation of emotional processing.