Genetic-based signatures of the latitudinal differences in chronotype

The natural cycles of night and day, and their length, remain stable in near-equatorial African regions but they vary with latitude and season in Eurasia. This new environmental factor might shape the adaptation of circadian rhythms of Eurasians after the out-of-African dispersal of their African ancestors. To identify the genetic-based signatures of this adaptation, geographic variation in allele frequencies of more than 2300 genetic variants was analyzed using data from 5 African and 11 Eurasian populations of the 1000 Genomes Project. The genetic signatures of latitude-dependent polygenic selection were found more frequently within non-coding DNA regions associated with morningness–eveningness in genome-wide association studies (GWASs) than among polymorphisms hinted by GWASs of other traits/diseases and among polymorphisms sampled from pseudogenes and from protein-coding regions in either circadian clock genes or reference genes. Some of such variants were located within the introgressions of the Neanderthal’s genome into the genomes of Eurasians. © 2018 Informa UK Limited, trading as Taylor & Francis Grou

The Influence of a Reading Setup on Digital Reading Strategies in High School Students: Results of an Eye-Tracking Study

The paper aims to investigate the correlation between reading setup and digital reading strategies used by Russian schoolchildren. To study the influence of the reading setup factor, we conducted an eye-tracking study of high school students (N=66), which showed the dependence of digital reading strategies on the pre-reading task by experienced readers. The study showed that the pattern of skimming digital texts does not always appear explicitly, and revealed a significant influence on reading strategies of both reader's individual differences and the rhetorical organization of the text, as well as the reading task factor. The task of searching for specific information led to a more thorough primary reading of the entire text with fewer returns and transitions between the other semantic elements of the digital educational text. In the case of the text analysis task, the first reading was more cursory, but there was more jumping back and forth between paragraphs to establish the logical linkage of the text information. The influence of the reading setup on the digital reading strategy illustrates the importance of formulating the reading task correctly in order to ensure an effective digital reading experience.</p

Genetic-based signatures of the latitudinal differences in chronotype

The natural cycles of night and day, and their length, remain stable in near-equatorial African regions but they vary with latitude and season in Eurasia. This new environmental factor might shape the adaptation of circadian rhythms of Eurasians after the out-of-African dispersal of their African ancestors. To identify the genetic-based signatures of this adaptation, geographic variation in allele frequencies of more than 2300 genetic variants was analyzed using data from 5 African and 11 Eurasian populations of the 1000 Genomes Project. The genetic signatures of latitude-dependent polygenic selection were found more frequently within non-coding DNA regions associated with morningness–eveningness in genome-wide association studies (GWASs) than among polymorphisms hinted by GWASs of other traits/diseases and among polymorphisms sampled from pseudogenes and from protein-coding regions in either circadian clock genes or reference genes. Some of such variants were located within the introgressions of the Neanderthal’s genome into the genomes of Eurasians. © 2018 Informa UK Limited, trading as Taylor & Francis Grou

Association of obesity in shift workers with the minor allele of a single-nucleotide polymorphism (rs4851377) in the largest circadian clock gene (NPAS2)

A growing body of evidence has hinted at the involvement of the largest gene of the circadian clock family, NPAS2, in the regulatory mechanisms underlying the link between metabolic diseases and circadian rhythm disruption. We tested whether one of single-nucleotide polymorphisms in NPAS2 (rs4851377) is associated with obesity and alternations of sleep times in 126 male rotational shift workers (bus drivers). We confirmed positive association of Body Mass Index (BMI) with the difference between free and working days in sleep times, but this difference was smaller in the homozygotes for the minor allele. Moreover, BMI above 30 (obesity) was revealed in the majority of these homozygotes and in the minority of homozygotes for the major allele (11 of 21 or 52.4% and 3 of 40 or 7.5%, respectively). Further studies are required to replicate these results and to elucidate the mechanisms linking NPAS2ʹpolymorphism in with obesity in shift workers. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group

Effects of exposures to weak 2-Hz vs. 8-Hz electromagnetic fields on spectral characteristics of the electroencephalogram in afternoon nap

The human brain seems to be able to respond to low-level extremely low-frequency electromagnetic fields. Controlled laboratory studies of human sleep under exposure to such fields are scarce, especially on the effects of 1 Hz–16 Hz fields overlapping with the frequencies of the electroencephalographic (EEG) signal (e.g., delta, theta, alpha, and sigma activities). In a double-blind placebo-controlled study, we examined the effects of exposure to low-level electromagnetic fields of frequencies 2 Hz and 8 Hz on the EEG power density spectra in the range from 1 Hz to 16 Hz and sleep structure. Sleep of 14 young healthy volunteers was polysomnographically recorded during three 50-min afternoon naps (either without exposure or with 2 Hz/0.004 μT or 8 Hz/0.004 μT electromagnetic field). During the first 30 min of a nap the sham, 2 Hz or 8 Hz/0.004 μT exposures had the same effect. For the remaining 20 min, amount of stage 3 sleep and powers in 1 Hz-8 Hz range continued to build up under the 8 Hz/0.004μT and, especially, under the 2 Hz/0.004 μT exposure, whereas they did not change in the sham condition. Therefore, the low-level 2 Hz electromagnetic fields might stimulate deep sleep in the afternoon nap. © 2020 Informa UK Limited, trading as Taylor & Francis Group

When early and late risers were left to their own devices: six distinct chronotypes under “lockdown” remained dissimilar on their sleep and health problems

Under national “lockdown,” the habitual late risers need not wake up early, and, similarly to the early risers, they don’t lose much sleep on weekdays. We tested whether, despite a decrease in weekday sleep loss, the difference between distinct chronotypes in health and sleep problems persisted during “lockdown.” Two online surveys were conducted from 10th to 20th of May, 2020 and 2021, one of them after 6 non-working weeks and another after 14 working weeks (during and after “lockdown,” respectively). Participants were students of the same grade at the same university department (572 and 773, respectively). The self-assessments included the Single-Item Chronotyping (SIC) designed for self-choosing chronotype among several their short descriptions and several questions about general health, mood state, outdoors and physical activity, and sleep concerns. The results suggested that the responses to each of the questions were not randomly distributed over 6 distinct chronotypes. Such a nonrandomness was identified within each of three pairs of these chronotypes, evening vs. morning types (with a rising throughout the day vs. a falling level of alertness, respectively), afternoon vs. napping types (with a peak vs. a dip of alertness in the afternoon, respectively), and vigilant vs. lethargic types (with the levels of alertness being permanently high vs. low, respectively). Morning, afternoon, and vigilant types reported healthier sleep/mood/behavior/habits than three other types. The most and the least healthy sleep/mood/behavior/habits were reported by morning and evening types, respectively. These relationships with health and sleep problems and the frequencies of 6 chronotypes remained unchanged after “lockdown.” Such results, in particular, suggested that the association of evening types with poorer health and sleep might not be attributed to a big amount of weekday sleep loss. The accounting for this association might help in designing interventions purposed on reduction of sleep and health problems. © 2021 Taylor & Francis Group, LLC

Overlap between individual variation in personality traits and sleep-wake behavior

The efforts to link the individual differences in personality to the individual differences in sleep-wake behavior have a long history. One of the topics of such research might be to determine the strength of association between these two domains of individual variation. This requires the implementation of several inventories designed for integrative multidimensional assessments of a set of broad personality traits and a set of sleep-wake behavioral traits. Four independent samples were collected (in total, 759 individuals) for estimating general overlap between the domains of individual variation in personality psychology and chronobiology. Canonical correlation analyses provided the estimates of general overlap of six broad personality traits assessed with the 172-word RCIP (Rugby Cake Inventory of Personality) with six distinct sleep-wake adaptabilities assessed with the 72-item SWPAQ (Sleep-Wake Pattern Assessment Questionnaire) and the SWAT (Sleep-Wake Adaptability Test) in two, the 60- and 168-item, versions. It was demonstrated that general overlap between individual variation in two domains was significant and replicable albeit rather weak (6%–8%). Moreover, regression analyses of specific overlaps of each of six scales for assessing sleep-wake adaptability with a set of six scales for personality assessment suggested that a score on any of adaptability scales seemed to be a significant predictor of, at least, one of six scores on personality trait scales. Studies in other tongues are desired for the replication of the results indicating the statistically significant general and specific overlaps between personality traits and sleep-wake adaptabilities. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature

An hour in the morning is worth two in the evening: association of morning component of morningness–eveningness with single nucleotide polymorphisms in circadian clock genes

Sub-constructs of morning–evening preference might be differentially related to polymorphisms in circadian clock genes. We previously reported significant association between a single nucleotide polymorphism in PER3 (rs2640909) and Morning but not Evening Lateness scale of the Sleep–Wake Pattern Assessment Questionnaire. To further explore such a scale-specific relationship, seven single nucleotide polymorphisms in five circadian clock genes were studied using exploratory and confirmatory samples (in total, n = 698). The association of rs2640909 with Morning Lateness scale was not replicated in the confirmatory sample but remained significant in the merged sample. Moreover, we found and confirmed an association of this scale with rs1159814 in RORα. The results provided further evidence for differential relationship of polymorphisms in circadian clock genes with morning and evening components of morning–evening preference. We also suggested possibility to take into account the pattern of geographic variation in allele frequency for prioritization of circadian clock polymorphisms in candidate gene studies. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Differences between male and female university students in sleepiness, weekday sleep loss, and weekend sleep duration

Introduction: Women and men experience sleep differently and the difference in intrinsic desire for sleep might underlie some of the observed male-female differences. The objective of this cross-sectional questionnaire study of university students was to determine male-female differences in self-reported sleepiness and sleep-wake patterns. Methods: Five questionnaires were completed by 1650 students at four Russian universities. Results: Compared to male students, female students reported a lower subjective sleep quality score, had a higher morning sleepability score and lower nighttime and daytime wakeability scores. They more often reported excessive daytime sleepiness and expected to be sleepier at any time of the day with the largest male-female difference around the times of sleep onset and offset. On free days, they reported a longer sleep duration and an earlier sleep onset. Free-weekday difference was larger for sleep duration and smaller for sleep onset. Such male-female differences showed similarity to the differences observed in university and high school students from different countries around the globe. There was no significant male-female difference in weekly averaged sleep duration, weekday sleep duration, hours slept, midpoint of sleep on free days, free-weekday difference in sleep offset, social jetlag, and morningness-eveningness score. Therefore, when studies rely on these self-reports, the most salient male-female differences might not be immediately evident. Conclusions: It seems that the intrinsic desire for longer sleep duration might contribute to a higher susceptibility of female students to weekday sleep loss. Among these students, negative effects of reduced sleep duration might be more common and more detrimental. © 2021 The Foundation for Professionals in Services for Adolescent