Dear Members of the ESRS,

Dear Readers of JSR,

Let me welcome you to the sixth edition of JSR in 2021.

I sincerely hope that 2021 was a good year for all of you!

JSR has seen an unrelenting wave of submissions, equaling the number of submissions we received in 2020. To me this seems a good sign of the health of the field of sleep research and sleep medicine. Again, in this issue several areas of sleep research and sleep medicine are covered. I like to highlight some of the papers in this issue for you:

ENIGMA-Sleep (Tahmasian et al., 2021): This acronym stands for “The Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA)” consortium. A group of over 50 authors submitted this paper outlining a master plan for combining neuroimaging and genetic data analyzing them with meta-analytic strategies, based on combining data sets across individual studies. The ENIGMA-Sleep group reflects the collaboration of several institutes from 15 countries and aims at performing large scale worldwide neuroimaging and genetic studies for better understanding the neurobiology of impaired sleep. It also looks at the neuronal consequences of sleep deprivation and the pathophysiology of sleep disorders. This article summarizes ongoing work and future strategies the ENIGMA-Sleep group is going to pursue. Please feel invited to participate and to get in contact.

Benedetti et al. (2021) investigated the heart rate detection by Fitbit ChargeHR (TM) by validating it with portable polysomnography. 25 healthy young adults participated in the study. They underwent multiple polysomnography and wore the Fitbit's photoplethysmographic device for a period of over 12 h. Compared were the heart rate data from polysomnography and from the Fitbit device and its algorithm. It turned out that correlations between polysomnography measured heart rate and Fitbit measured heart rate were very high. The authors conclude that high accuracy of pulse rate detection by Fitbit makes the device suitable for sleep related research applications in healthy participants under normal living conditions.

Maranci et al. (2021) publish an article with a very funny title: “Grumpy face during adult sleep. A clue to negative emotion during sleep?” What the authors did was to use video polysomnography including a face-focussed video to study nocturnal negative facial expressions in sleeping adults. The authors included normal health sleepers, patients with parasomnias, disorders of arousal and patients with rapid eye movement sleep disorder. It turned out that frowning was predominantly observed in REM sleep and at a lower frequency in Non-REM sleep. Interestingly, frowns were associated with clearer negative facial expressions in REM sleep and patients with RBD and a young patient with night terrors. Also observed were painful expressions, but rarely sadness and anger. The authors conclude from their data analysis that frowns persist during normal sleep, mostly in REM sleep, in adults, but overt negative facial expressions are confined to patients with parasomnias. The authors also speculate whether the frowns observed during REM sleep and negative emotional expressions could be used as a direct access to dream emotions.

Randler et al. (2021) also come up with a very innovative and novel design by investigating so-called “birders”. Birders are people who have birdwatching as a main leisure activity. Usually birders start their activities before or shortly after sunrise, thus they are early risers especially on weekends, thus experiencing a negative social jetlag on weekends. The study derived its data from an online survey with almost 2.500 birdwatchers (55% male) who answered questions about their sleep-wake times and about their birding activities. It turned out that birders show the same differences bet-ween weekdays and free days like most other people. Interestingly, days with birdwatching started earlier than weekdays and lasted longer. Thus birdwatching days are shifted towards an earlier sleep-wake rhythm in total. Birdwatchers also on birdwatching weekends lost 45 min of sleep compared to normal weekends. Interestingly, thus birders may suffer from short- and long-term consequences of negative social jetlag. The authors also suggest this type of results might be typical for other nature-related leisure activities.