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 crosssectional 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 signiicant male-female difference in weekly averaged sleep duration, weekday sleep duration, hours slept, midpoint of sleep on free days, freeweekday 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.

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Background: Our work/study culture is biased towards the circadian clocks of “morning types”, whereas “evening types” are forced to advance their weekday waking times relative to weekend waking times. Since the experimental research consistently reveals a >2 h difference between these two chronotypes in the positions of their endogenous circadian phases, we hypothesized the necessity to permit a >2 h difference between them in weekday waking times to equalize their irrecoverable loss in sleep on weekdays. Methods: A total of 659 and 1106 participants of online surveys identified themselves as morning and evening types, respectively. The hypothesis was tested by applying a model of sleep–wake regulation for simulating sleep times reported by 245 lecturers of these two types, and by comparison of sleep times of these types among these lecturers and 1520 students. Results: The hypothesis was supported by results showing that, if, on weekdays, an “average” morning type wakes at 6 a.m., the equalization of the weekday sleep loss of the two chronotypes would require the waking time of an “average” evening type to be no earlier than 8 a.m. Conclusions: These results may be implemented in a model-based methodology for the correction of weekday waking times to equalize weekday sleep loss.

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INTRODUCTION: Purposeful cognitive brain activity of an individual depends on blood supply to the cells of the cerebral cortex (CC), and on their autonomic innervation. AIM: To identify peculiarities of the brain hemodynamics and heart rhythm variability (HRV) in young men performing cognitive tasks with unequal effectiveness. MATERIALS AND METHODS: The study involved 42 practically healthy young men (mean age 19.40 1.20 years). The brain hemodynamics was studied using Reo-Spektr-2 rheograph (Neurosoft, Russia) in the initial condition of relative rest and in modeled purposeful cognitive activity. Synchronously with record of rheoencephalogram, rhythmocardiogram was recorded using Varicard 2.51 hardware-software complex (Ramena, Russia). Purposeful cognitive activity was modeled in Physiotest program for psychophysiological studies with use of behavioral model: Schulte Table Test in a two-color SchulteGorbov modification. In statistical data processing, cluster and correlation analyses were used. RESULTS: Based on the effectiveness of SchulteGorbov Table Test, the sample of subjects was divided to two clusters (n = 28 and n = 14). Comparison of clusters in the initial condition of relative physiological rest and during cognitive activity revealed differences in rheoencephalographic parameters, which reflects unequal hemodynamic supply of the brain in representatives of the given clusters. Differences in HRV parameter were found reflecting the different levels of tension of adaptation mechanisms in the initial condition and in cognitive activity. The results of the correlation analysis demonstrated different dependence between the parameters of rheoencephalogram, HRV and parameters of the effectiveness of Schulte-Gorbov Test in representatives of different clusters. CONCLUSIONS: (1) High-effective subjects are characterized by shorter time of propagation of the rheographic wave and longer time of slow blood filling of the right vertebral artery basin, and by higher rheographic index asymmetry coefficient in the basin of the left internal carotid artery and of vertebral arteries of both hemispheres during cognitive activity compared to low-effective subjects. (2) Physiological support of purposeful activity of an individual with unequal effectiveness of salvation of cognitive tasks is characterized not only by different levels of brain hemodynamics and activity of autonomic regulatory mechanisms, but also by certain type of correlation relationships of these parameters with parameters of purposeful behavior, in particular, with the total time of fulfilment of the task and efficiency coefficient.