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Although objectively measured characteristics of sleep efficiency and quality were found to be better in women than men, women more frequently than men suffer from poor or insufficient or non-restorative sleep. We explored this apparent paradox by testing the sex-associated differences in electroencephalographic (EEG) indicators of two opponent processes of sleep-wake regulation, the drives for sleep and wake. We tried to provide empirical support for the hypothesis that a stronger women's sleep drive can explain better objective characteristics of sleep quality in women than men, while a stronger women's wake drive can be an explanation of a higher frequency of sleep-related complaints in women than men. To our knowledge, this was the first attempt to examine the associations of sex with scores on the 1st and 2nd principal components of the EEG spectrum that can serve as objective spectral EEG markers of the opponent drives for sleep and wake, respectively. The particular prediction was that, in women compared to men, not only the 1st principal component score but also the 2nd principal component score could be higher (i.e. both drives could be stronger). In a sample of 80 university students (40 females), the EEG signals were recorded during 160 afternoon napping attempts (50 min or longer). The difference between male and female students in sleep latencies did not reach a statistically significant level. In accordance with our prediction, both principal component scores were found to be higher in female than in male students irrespective of sleep stage. It is likely that the influence of the wake drive is entirely overlooked in the polysomnographic studies due to the predominant contribution of the indicators of the sleep drive to the conventional objective characteristics of sleep quality. Therefore, a stronger women's sleep drive can be an explanation of women's better sleep quality in the results of polysomnographic studies. On the other hand, if a stronger women's wake drive can influence the perception of their sleep quality, this can explain their more frequent sleep-related complaints. [ABSTRACT FROM AUTHOR]

The aim of the study is investigation of nighttime sleep effect on the performance of a cognitive setting in terms of the coupling of EEG rhythms. The coupling of 5 rhythm: beta-1, beta-2, gamma, alpha and theta rhythms of EEG during the formation and testing of cognitive set was studied for 120 students (17 with short-term night sleep and 15 with a full night sleep). Multi-channel EEG was recorded. EEG evaluation was carried out by continuous wavelet transform based on the “mother” complex Morlet wavelet in the range of 1–35 Hz. Maps of the distribution of the values of the modulus of the wavelet transformation coefficient, which reflect amplitude changes of the potentials were analyzed. The Pearson correlation coefficient was a measure evaluating the coupling of EEG rhythms. The subjects with a short night’s sleep showed almost all of the relations of EEG rhythms (8 couples) during the formation stage of presentation. Students with a full night’s sleep showed statistically significant coupling of the following pairs of rhythms: alpha–beta-1, alpha–gamma and beta-2–gamma. Students with short-term night sleep demonstrated the 3 significant couples: alpha–beta-1, beta-1–gamma and beta-2–gamma during the testing stage. Well-slept students showed an increase in the number of connections (6 couples) in relation to the stage of formation of the set due to the addition of connections with the theta rhythm. The obtained data could indicate that the thalamo-cortical and cortico-hippocampal structural-functional associations work differently in the groups of subjects.

The association of insufficient sleep with reduced self-perceived health was previously well established. Moreover, it was sometimes shown that the indicators of poorer health were significantly related to chronotype and weekday-weekend gaps in sleep timing and duration. It remains to be elucidated, however, whether chronotype and these gaps can contribute to the reduced health self-ratings independently from shortened sleep duration or, alternatively, their relationship with health can be simply explained by their association with insufficient sleep on weekdays. In an online survey, we tested whether the self-rated health of university students can be predicted by several individual characteristics of the sleep-wake cycles, such as chronotype, weekday and weekend sleep times, weekday-weekend gap in sleep times, sleepability and wakeability at different times of the day, etc. Responses to a question about general health and to items of several questionnaires for chronobiological assessment were collected from smartphones of 1582 university students (mean age ± standard deviation was 19.5 ± 1.7 y). The results of regression analyses suggested that lower odds of having good self-rated health were significantly associated with an earlier weekday risetime, a later weekday bedtime, and, consequently, a shorter weekday time in bed. After accounting for weekday sleep, self-rated health showed significant association with neither chronotype nor weekday-weekend differences in sleep duration and timing. Besides, the adverse health effects of reduced weekday sleep were independent from the significant adverse effects of several other individual sleep-wake characteristics including poorer nighttime sleepability and lower daytime wakeability. We concluded that university students perceive the negative health impacts of losing sleep by waking up early on weekdays irrespective of their night sleep quality and daytime level of alertness. Their chronotype and weekday-weekend difference in sleep times might not be among significant contributors to this perception. It is of practical importance to consider the reduction of weekday sleep losses among the interventions aimed at preventing sleep and health problems. [ABSTRACT FROM AUTHOR]

It was hypothesized that human sleep might respond to the fields emitted by such natural sources as magnetic activity of the sun and the earth's magnetic fields. However, the experiments aimed on testing this hypothesis remain scarce. Previously, we found an increase in the amounts of stages N2 or N3 during napping of good sleepers under exposure to low-level (0.004 µT) electromagnetic fields of frequencies 1 Hz or 2 Hz. It remains unexplored whether these fields might additionally decrease latency to stage N1. In this study, we selected 13 people with falling asleep problems to examine the effects of low-level electromagnetic fields on sleep latency. Sleep of these study participants was polysomnographically recorded during three 50-min afternoon napping attempts, either with exposure to either 2 Hz/0.004 µT or 8 Hz/0.004 µT electromagnetic fields or without exposure. We did not find that the sham exposure differed from the 2 Hz and 8 Hz exposures in latency to N1, while latency to N2 after the sham exposure was even shorter than after either the 2 Hz or 8 Hz exposure. We concluded that, although the effects of tested fields might be beneficial for sleep intensity (e.g., due to prolongation of N3), they might not be additionally effective against the falling asleep problems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Afternoon nap is regarded as a potent behavioral strategy minimizing sleepiness and fatigue. The benefits of afternoon naps require the accumulation of, at least, 3 min of stage 2 sleep. However, there are practical disadvantages of nap longer than 10–15 min, such as greater length of time consumed by the nap, appearance of slow wave sleep causing greater sleep inertia right after the nap, and possible detrimental impact of such nap on subsequent nocturnal sleep. We previously found that a binaural beat treatment that is a dichotic presentation of two almost equivalent pure tones with slightly different frequencies led to a reduction of latency to stage 2 sleep. To replicate this result and to examine whether such reduction leads, in turn, to the earlier appearance of slow wave sleep, we asked 23 and 21 healthy volunteers to nap in the afternoon for 30 and 20 min, respectively. Almost half of volunteers showed latency to stage 2 longer than 17 min, but most of them responded to the treatment by its reduction. The following occurrence of slow wave sleep reduced level of alertness self-assessed right after the nap. We concluded that latency to stage 2 sleep might be experimentally challenged by binaural beating. [ABSTRACT FROM AUTHOR]

A model of sleep-wake regulatory process was applied to examine several common believes associated with the so-called "social jetlag", e.g. 1) sleep lost on weekdays due to the scheduled early wakeups might be partly recouped by getting extra sleep on weekends and 2) the weekday sleep loss is greater in evening- than in morning-oriented individuals. Weekday-weekend sleep times reported in 19 previously published papers for 20 samples of morning- and evening-oriented individuals were utilized as an input to the model. The results of statistical analyses and simulations of these times suggested that 1) sleep cannot be caught up on weekends and 2) evening- and morning-oriented individuals are not, in general, dissimilar on the amount of weekday sleep. We concluded that chronobiologial mechanisms underlying "social jetlag" require rethinking and that studying mathematical models of sleep-wake regulatory process allow the quantitative predictions about weekday sleep loss in different ages and diurnal types. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

People sleep less in response to setting social clocks earlier relative to the sun clocks. We proposed here a model-based approach for estimating sleep loss as the difference between weekend and weekday risetimes divided on the difference between weekend risetime and weekday bedtime. We compared this approach with a traditional approach to estimating sleep curtailment as the difference in weekly average sleep duration in two conditions. Weekday and weekend sleep times reported for 320 samples provided possibility of testing whether evening types with later weekend sleep times and larger social jetlag differ from morning types with earlier weekend sleep times and smaller social jetlag on amount of sleep lost (1) throughout the week and (2) in response to an advance of weekday wakeups, for instance, after the expected installation of perennial Daylight Saving Time (DST). We found that (1) an amount of sleep lost due to advancing shift of weekday wakeups depends upon neither chronotype nor weekend sleep times nor social jetlag, (2) a very large amount of sleep is usually lost by evening types with later weekend sleep times and larger social jetlag and (3) an essential sleep loss is caused by our usual work/school schedules, even in morning types with early weekend sleep times and small social jetlag. As compared to such permanent sleep losses experienced by any types, an additional loss due to switching from Standard Time (ST) to perennial DST are expected to be relatively small. We also found that the traditional way of calculation of sleep curtailment leads to paradoxical conclusions, such as (1) sleep loss is larger when social jetlag is smaller, not larger, (2) sleep loss is larger when weekend sleep times are earlier, not later, (3) despite 1-h difference between two student samples in weekday wakeups, their sleep losses can be identical. [ABSTRACT FROM AUTHOR]