Space agencies such as the National Aeronautics and Space Administration of the United States, the Russian Federal Space Agency, the European Space Agency, the China National Space Administration, the Japan Aerospace Exploration Agency, and Indian Space Research Organization, although differing in their local political agendas, have a common interest in promoting all applied sciences that may facilitate man's adaptation to life beyond the earth. One of man's most important adaptations has been the evolutionary development of sleep cycles in response to the 24 hour rotation of the earth. Less well understood has been man's biological response to gravity. Before humans ventured into space, many questioned whether sleep was possible at all in microgravity environments. It is now known that, in fact, space travelers can sleep once they leave the pull of the earth's gravity, but that the sleep they do get is not completely refreshing and that the associated sleep disturbances can be elaborate and variable. According to astronauts' subjective reports, the duration of sleep is shorter than that on earth and there is an increased incidence of disturbed sleep. Objective sleep recordings carried out during various missions including the Skylab missions, space shuttle missions, and Mir missions all support the conclusion that, compared to sleep on earth, the duration in human sleep in space is shorter, averaging about six hours. In the new frontier of space exploration, one of the great practical problems to be solved relates to how man can preserve "normal" sleep in a very abnormal environment. The challenge of managing fatigue and sleep loss during space mission has critical importance for the mental efficiency and safety of the crew and ultimately for the success of the mission itself. Numerous "earthly" examples now show that crew fatigue on ships, trucks, and long-haul jetliners can lead to inadequate performance and sometimes fatal consequences, a reality which has caused many space agencies to take the issue of sleep seriously.
Keywords: Astronauts, Fatigue management, Gravity, Human factors, Sleep, Space
OBJECTIVES: The aim is to evaluate the mutual influences between sleep duration/sleep deprivation (SD) and the sleep stealers/adolescent risk behaviours.
METHODS: The national survey is a component of the Health Behaviour in School-Aged Children (HBSC) study, it is based on a school-based self-completed questionnaire; 3476 students were randomly selected from 139 randomly chosen Portuguese schools using as an unit the class, 53.8% were girls; 45.9% attended the 8th grade and 54.1% the 10th grade; the mean age was 14.9 years. The measured variables were: 1) gender and age; 2) sociodemographics; 3) sleep duration during the week and during weekends and computed SD; 4) screen time (computer use during the week and during the week end (PC use); watching TV and mobile phone use; 5) earlier sexual behaviour; 6) violent behaviours: fights, use of weapons; 7) use of tobacco, alcohol and drugs. The statistical analysis included Pearson chi-square tests and logistic regression.
RESULTS: Excessive use of mobile phone, of computer use during weekdays, and internet facilities; substance use; violence and earlier sexual relations had significantly higher prevalence in sleep deprived adolescents. By logistic regression only using PC during weekdays, tobacco, drugs and weapons were associated to SD, while SD was associated to PC use during weekdays, tobacco use and drugs' use. Computer uses tend to be associated among themselves. Mobile phone is associated with computer practices and with alcohol and tobacco use. Tobacco is associated with most risk behaviours. Alcohol use is associated with other substance use, computer use and violent behaviours. Violence behaviours, earlier sex and drugs use tend to be associated among themselves.
CONCLUSIONS: Sleep stealers use and risk behaviours are more prevalent in sleep deprived adolescents, but, in spite of significant individual associations, models of risk behaviours are still lacking.
Keywords: Screen time, Substance use, Violence, Earlier sex, Sleep curtailment, Adolescence
Abnormal clot microstructure plays a pivotal role in the pathophysiology of thromboembolic diseases. Assessing the viscoelastic properties of clot microstructure using novel parameters, Time to Gel Point (TGP), Fractal Dimension (df) and clot elasticity (G'gp) could explain the increased cardiovascular and thromboembolic events in patients with Obstructive Sleep Apnoea Hypopnea Syndrome (OSAHS). We wanted to compare TGP, df, and G'gp and their diurnal variation in OSAHS and symptomatic comparators. thirty six patients attending a sleep disturbed breathing clinic with symptoms of OSAHS were recruited. TGP, df and G'gp were measured alongside standard coagulation screening, thrombin generation assays, and platelet aggregometry at 16:00 h and immediately after an in-patient sleep study at 07:30 h. OSAHS group had significantly lower afternoon df than comparators (1.705±0.033 vs. 1.731±0.031, p<0.05). df showed diurnal variation and only in the OSAHS group, being significantly lower in the afternoon than morning (p<0. 05). Diurnal changes in df correlated with 4% DR, even after controlling for BMI (r=0.37, p=0.02). The lower df in the afternoon in OSAHS suggests a partial compensatory change that may make up for other pro-clotting abnormalities/hypertension during the night. The change to the thrombotic tendency in the afternoon is biggest in severe OSAHS. df Shows promise as a new microstructural indicator for abnormal haemostasis in OSAHS.
Keywords: Sleep apnoea, Clot microstructure, Fractal dimension, Gel time, Clot elasticity - G', Coagulation
In humans, a person's chronotype depends on environmental cues and on individual characteristics, with late chronotypes prevailing in youth. Social jetlag (SJL), the misalignment between an individual's biological clock and social time, is higher in late chronotypes. Strong SJL is expected in Uruguayan university students with morning class schedules and very late entertainment activities. Sleep disorders have been reported in Antarctic inhabitants, that might be a response to the extreme environment or to the strictness of Antarctic life. We evaluated, for the first time in Uruguay, the chronotypes and SJL of 17 undergraduate students of the First Uruguayan Summer School on Antarctic Research, using Munich Chronotype Questionnaire (MCTQ) and sleep logs (SL) recorded during 3 phases: pre-Antarctic, Antarctic, and post-Antarctic. The midsleep point of free days corrected for sleep debt on work days (MSFsc,) was used as proxy of individuals' chronotype, whose values (around 6 a.m.) are the latest ever reported. We found a SJL of around 2 h in average, which correlated positively with MSFsc, confirming that late chronotypes generate a higher sleep debt during weekdays. Midsleep point and sleep duration significantly decreased between pre-Antarctic and Antarctic phases, and sleep duration rebounded to significant higher values in the post-Antarctic phase. Waking time, but not sleep onset time, significantly varied among phases. This evidence suggests that sleep schedules more likely depended on the social agenda than on the environmental light-dark shifts. High motivation of students towards Antarctic activities likely induced a subjective perception of welfare non-dependent on sleep duration.
Keywords: Circadian rhythms, Sleep habits, Munich Chronotype Questionnaire, Antarctica, Uruguayan Antarctic Scientific Base, Artigas
BACKGROUND AND AIMS: Aging in men is associated with various physical and mental symptoms, including sleep problems and sexual dysfunction. The aim of this study was to determine the status of sleep disorders and sexual dysfunction in men aged 45-75 years in Ilam, Iran.
MATERIALS AND METHODS: In this population-based cross-sectional study, 390 men aged 45-75 years were selected by cluster randomization in Ilam-Iran. Data were collected using 0-100 brief sexual function inventory and the sleep disorder questionnaires.
RESULTS: Totally, 34.6% of men complained about sleep disorders: 17.4% about falling asleep, 12.8% about frequent nocturnal awakenings, 12.8% about waking up in the early hours in the morning and problem in falling asleep again, and 24.9% about fatigue and tiredness despite getting enough sleep. There was a significant relationship between all aspects of sexual function and the common problems related to sleep (p<0.001). The older, unemployed, illiterate men, those with inadequate income, those affected by chronic diseases, and/or urinary incontinence had significantly inferior sexual function compared with the others.
CONCLUSION: According to the high prevalence of sleep disorders in men as well as its association with sexual dysfunction, adopting health measures in this regard is necessary.
Keywords: Middle-aged, Oldness, Sleep disturbances, Sexual dysfunction, Iran
More information is needed to better understand the effect of caffeine on sleep quality at the community level. In a population-based, cross-sectional study design, we aimed to assess the effect of caffeine intake on sleep quality by the use of a multivariate exposure-effect model, adjusted for relevant confounders. All Atahualpa residents aged ≥40 years were identified during a door-to-door survey and interviewed with the Pittsburgh Sleep Quality Index (PSQI) and a structured instrument designed to estimate the daily amount of caffeine intake. An exposure-effect model was built using augmented inverse probability weighting taking into account variables that were associated with exposure (using a probit model) and variables that were associated with outcome (in a linear model). Out of 779 eligible individuals, 716 (92%) were included. Consumption of<100 mg/day of caffeine was recorded in 320 (45%) participants, from 100 to 200 mg/day in 299 (42%), and >200 mg/day in 97 (13%). Mean score in the PSQI was 4.5±2.2 points, with 203 (28%) individuals classified as poor sleepers (≥6 points). The exposure-effect model, adjusted for variables associated with the exposure (symptoms of depression, total cholesterol blood levels and smoking) and the outcome (age, symptoms of depression, physical activity and fasting glucose levels), revealed no effect of caffeine intake in sleep quality (average exposure effect: 0.027, 95% C.I.: - 0.284 to 0.338, p=0.866). This population-based study shows that caffeine intake has no effect on sleep quality in community-dwelling adults living in a rural village of Ecuador.
Keywords: Caffeine intake, Coffee, Sleep disorders, Sleep quality, Population-based study, Atahualpa
Systemic Lupus Eritematosus (SLE) is a systemic inflammatory disease often treated with the agent cyclophosphamide (CY), known by provoking important adverse reactions to the organism. Ader and Cohen have demonstrated an alternative way of administrating this agent based on pavlovian conditioning, in order to reduce the aggression caused by CY. Considering the influence of the temporal organization on learning and memory processes, the purpose of this study was to understand the temporal aspects involved in the conditioned immunomo-dulation. In a search for circadian modulation, we selected NZB/W (F1) female mice, a strain that spontaneously develop SLE. Divided into two major groups, the animals were submitted, in different phases of day, to a classical conditioning immunomodulation protocol, consisting in weekly parings of saccharin solution and CY injections. The success of the paradigm was evaluated by comparing lifespan among the groups. Simultaneously, it was monitored the water intake behavior, in order to correlate the stability of two rhythmic parameters, amplitude and spectral power density of the 24-h rhythm, with the progression of SLE. Our results indicate that mice could benefit from the conditioning task performed either in the light phase or in the dark phase of the LD cycle, as expressed by an increased lifespan. Concerning the rhythmic parameters, there was evidence of association between the rhythmic stability and the evolution of SLE, demonstrated by the maintenance of healthy levels of amplitude and spectral potency of the 24-h rhythm in animals exposed to the conditioning paradigm.
Keywords: Classical conditioning, Circadian drinking behavior, Immunomodulation, Rhythmic stability, NZB/W, Learning
The aim of this study was to investigate the possible anxiolytic-like effects of striatal MT2 activation, and its counteraction induced by the selective blockade of this receptor. Furthermore, we analyzed this condition under the paradigm of rapid eye movement (REM) sleep deprivation (REMSD) and the animal model of Parkinson's disease (PD) induced by rotenone. Male Wistar rats were infused with intranigral rotenone (12 µg/µL), and 7 days later were subjected to 24 h of REMSD. Afterwards the rats underwent striatal microinfusions of selective melatonin MT2 receptor agonist, 8-M-PDOT (10 µg/µL) or selective melatonin MT2 receptor antagonist, 4-P-PDOT (5 µg/µL) or vehicle. Subsequently, the animals were tested in the open-field (OP) and elevated plus maze (EPM) tests. Results indicated that the activation of MT2 receptors produced anxiolytic-like effects. In opposite, the MT2 blockade did not show an anxiogenic-like effect. Besides, REMSD induced anxiolytic-like effects similar to 8-M-PDOT. MT2 activation generated a prevalent locomotor increase compared to MT2 blockade in the context of REMSD. Together, these results suggest a striatal MT2 modulation associated to the REMSD-induced dopaminergic supersensitivity causing a possible dopaminergic influence in the MT2 anxiolytic-like effects in the intranigral rotenone model of PD.
Keywords: Melatonin, MT2 receptor, Rotenone, Anxiety, Striatum, Parkinson's disease