1,121 research outputs found
Schlafregulation
Zusammenfassung: Die Zirkadianrhythmik und die Schlafhomöostase regulieren die zeitliche Abfolge und die Struktur des Schlafes bei Mensch und Tier. Beim Menschen fĂŒhrt das Zusammenspiel dieser 2Prozesse zu einer konsolidierten Wachepisode von etwa 16h und einer konsolidierten Schlafepisode von etwa 8h. Dabei wirkt ein zirkadian reguliertes Wachsignal dem sich aufbauenden Schlafdruck (Schlafhomöostat) wĂ€hrend der Wachzeit entgegen. Störungen in diesem Zusammenspiel können zu kognitiven LeistungseinbuĂen, TagesschlĂ€frigkeit und Schlafproblemen fĂŒhren, was oft bei Schichtarbeitern, Jetlag, Ă€lteren Leuten, und Patienten, die am verzögerten oder verfrĂŒhten Schlafphasen-Syndrom leiden, der Fall ist. Ergebnisse aus der Molekularbiologie und Zellphysiologie dieser beiden Prozesse fĂŒhrten zu folgenden Erkenntnissen: Die suprachiasmatischen Kerne (SCN) reprĂ€sentieren den zentralen zirkadianen Schrittmacher. Es gibt eine RĂŒckkopplung zu den SCN ĂŒber das Neurohormon Melatonin. Das ventrolaterale prĂ€optische Areal (VLPO) ist besonders wichtig fĂŒr die Initiation des Schlafes. Das Nukleosid Adenosin triggert das VLPO. Ein ultradianer Oszillator im mesopontinen Hirnstamm steuert den regelmĂ€Ăigen Wechsel zwischen NREM- und REM-Schlaf. Der Schlaf-Wach-Zyklus und der NREM-REM-Schlaf-Zyklus induzieren regelmĂ€Ăig auftretende neuromodulatorische VerĂ€nderungen in Vorderhirnstrukture
Schlaf und zirkadiane Rhythmik im Alter
Zusammenfassung: Mit steigendem Alter nimmt die nĂ€chtliche Schlafkonsolidierung ab, kurze Nickerchen ĂŒber den Tag nehmen zu, und die Schlafzeit verschiebt sich in frĂŒhere Stunden. Die Schlafregulation hĂ€ngt von der Interaktion zwischen einem zirkadianen Schrittmacher (biologische Uhr) und dem Schlafhomöostaten (je lĂ€nger die Wachphase, desto gröĂer der Schlafdruck) ab. Wir konnten an gesunden Ă€lteren Personen zeigen, dass sich die Amplitude zirkadianer Rhythmen (z. B. die Melatonin-Sekretion) und die Tiefschlafdauer verringert. Gleichzeitig nimmt die MĂŒdigkeit am Nachmittag zu, wie auch die Tendenzâim Gegensatz zu jĂŒngeren Personenâam frĂŒhen Abend einzuschlafen. Da Licht der Hauptzeitgeber ist, um die biologische Uhr zu stabilisieren, brauchen Ă€ltere Menschen tagsĂŒber und am Abend genĂŒgend Licht und sollten wĂ€hrend des Tages keine oder nur kurze Nickerchen machen, um in der Folge den Schlaf in der Nacht zu verbesser
In Athletes, the Diurnal Variations in Maximum Oxygen Uptake Are More Than Twice as Large as the Day-to-Day Variations
In competitive sports any substantial individual differences in diurnal variations in maximal performance are highly relevant. Previous studies have exclusively focused on how the time of day affects performance and disregarded the maximal individual diurnal variation of performance. Thus, the aims of this study were (1) to investigate the maximum diurnal variation in maximum oxygen uptake (VO2max), (2) to compare the diurnal variation of VO2max during the day to the day-to-day variation in VO2max, and (3) to investigate if there is a time-of-day effect on VO2max. Ten male and seven female athletes (mean VO2max: 58.2 ± 6.9 ml/kg/min) performed six maximal cardiopulmonary exercise tests including a verification-phase at six different times of the day (i.e., diurnal variation) and a seventh test at the same time the sixth test took place (i.e., day-to-day variation). The test times were 7:00, 10:00, 13:00, 16:00, 19:00, and 21:00. The order of exercise tests was the same for all participants to ensure sufficient recovery but the time of day of the first exercise test was randomized. We used paired t-tests to compare the nadir and peak of diurnal variations, day-to-day variations and the difference between diurnal and day-to-day variations. The mean difference in VO2max was 5.0 ± 1.9 ml/kg/min (95% CI: 4.1, 6.0) for the diurnal variation and 2.0 ± 1.0 ml/kg/min (95% CI: 1.5, 2.5) for the day-to-day variation. The diurnal variation was significantly higher than the day-to-day variation with a mean difference of 3.0 ± 2.1 ml/kg/min (95% CI: 1.9, 4.1). The linear mixed effects model revealed no significant differences in VO2max for any pairwise comparison between the different times of the day (all p > 0.11). This absence of a time-of-day effect is explained by the fact that peak VO2max was achieved at different times of the day by different athletes. The diurnal variations have meaningful implications for competitive sports and need to be considered by athletes. However, the results are also relevant to research. To increase signal-to-noise-ratio in intervention studies it is necessary to conduct cardiopulmonary exercise testing at the same time of the day for pre- and post-intervention exercise tests
Circadian rhythms in cognitive performance: Methodological constraints, protocols, theoretical underpinnings
Abstract The investigation of time-of-day effects on cognitive performance began in the early days of psychophysiological performance assessments. Since then, standardised, highly controlled protocols (constant routine and forced desynchrony) and a standard performance task (psychomotor vigilance task) have been developed to quantify sleep-wake homeostatic and internal circadian time-dependent effects on human cognitive performance. However, performance assessment in this field depends on a plethora of factors. The roles of task difficulty, task duration and complexity, the performance measure per se, practice effects, inter-individual differences, and ageing are all relevant aspects. Therefore, welldefined theoretical approaches and standard procedures are needed for tasks pinpointing higher cortical functions along with more information about time-dependent changes in the neural basis of task performance. This promises a fascinating challenge for future research on sleep-wake related and circadian aspects of different cognitive domains
Non-24-Hour Sleep-Wake Disorder Revisited â A Case Study
The human sleep-wake cycle is governed by two major factors: a homeostatic
hourglass process (process S), which rises linearly during the day, and a
circadian process C, which determines the timing of sleep in a ~24-h rhythm in
accordance to the external lightâdark (LD) cycle. While both individual
processes are fairly well characterized, the exact nature of their interaction
remains unclear. The circadian rhythm is generated by the suprachiasmatic
nucleus (âmaster clockâ) of the anterior hypothalamus, through cell-autonomous
feedback loops of DNA transcription and translation. While the phase length
(tau) of the cycle is relatively stable and genetically determined, the phase
of the clock is reset by external stimuli (âzeitgebersâ), the most important
being the LD cycle. Misalignments of the internal rhythm with the LD cycle can
lead to various somatic complaints and to the development of circadian rhythm
sleep disorders (CRSD). Non-24-hour sleep-wake disorders (N24HSWD) is a CRSD
affecting up to 50% of totally blind patients and characterized by the
inability to maintain a stable entrainment of the typically long circadian
rhythm (tau > 24.5 h) to the LD cycle. The disease is rare in sighted
individuals and the pathophysiology less well understood. Here, we present the
case of a 40-year-old sighted male, who developed a misalignment of the
internal clock with the external LD cycle following the treatment for
Hodgkinâs lymphoma (ABVD regimen, four cycles and AVD regimen, four cycles). A
thorough clinical assessment, including actigraphy, melatonin profiles and
polysomnography led to the diagnosis of non-24-hour sleep-wake disorders
(N24HSWD) with a free-running rhythm of tau = 25.27 h. A therapeutic
intervention with bright light therapy (30 min, 10,000 lux) in the morning and
melatonin administration (0.5â0.75 mg) in the evening failed to entrain the
free-running rhythm, although a longer treatment duration and more intense
therapy might have been successful. The sudden onset and close timely
connection led us to hypothesize that the chemotherapy might have caused a
mutation of the molecular clock components leading to the observed elongation
of the circadian period
Effects of scale, question location, order of response alternatives, and season on self-reported noise annoyance using ICBEN scales : a field experiment
The type of noise annoyance scale and aspects of its presentation such as response format or location within a questionnaire and other contextual factors may affect self-reported noise annoyance. By means of a balanced experimental design, the effect of type of annoyance question and corresponding scale (5-point verbal vs. 11-point numerical ICBEN (International Commission on Biological Effects of Noise) scale), presentation order of scale points (ascending vs. descending), question location (early vs. late within the questionnaire), and survey season (autumn vs. spring) on reported road traffic noise annoyance was investigated in a postal survey with a stratified random sample of 2386 Swiss residents. Our results showed that early appearance of annoyance questions was significantly associated with higher annoyance scores. Questionnaires filled out in autumn were associated with a significantly higher annoyance rating than in the springtime. No effect was found for the order of response alternatives. Standardized average annoyance scores were slightly higher using the 11-point numerical scale whereas the percentage of highly annoyed respondents was higher based on the 5-point scale, using common cutoff points. In conclusion, placement and presentation of annoyance questions within a questionnaire, as well as the time of the year a survey is carried out, have small but demonstrable effects on the degree of self-reported noise annoyance
Predicting melatonin suppression by light in humans:Unifying photoreceptor-based equivalent daylight illuminances, spectral composition, timing and duration of light exposure
Lightâinduced melatonin suppression data from 29 peerâreviewed publications was analysed by means of a machineâlearning approach to establish which light exposure characteristics (ie photopic illuminance, five αâopic equivalent daylight illuminances [EDIs], duration and timing of the light exposure, and the dichotomous variables pharmacological pupil dilation and narrowband light source) are the main determinants of melatonin suppression. Melatonin suppression in the data set was dominated by four light exposure characteristics: (1) melanopic EDI, (2) light exposure duration, (3) pupil dilation and (4) Sâconeâopic EDI. A logistic model was used to evaluate the influence of each of these parameters on the melatonin suppression response. The final logistic model was only based on the first three parameters, since melanopic EDI was the best single (photoreceptor) predictor that was only outperformed by Sâconeâopic EDI for (photopic) illuminances below 21 lux. This confirms and extends findings on the importance of the metric melanopic EDI for predicting biological effects of light in integrative (humanâcentric) lighting applications. The model provides initial and general guidance to lighting practitioners on how to combine spectrum, duration and amount of light exposure when controlling nonâvisual responses to light, especially melatonin suppression. The model is a starting tool for developing hypotheses on photoreceptorsâ contributions to light's nonâvisual responses and helps identifying areas where more data are needed, like on the Sâcone contribution at low illuminances
Blue blocker glasses as a countermeasure for alerting effects of evening LED - screen exposure in teenagers
peer reviewe
Preliminary evidence that both blue and red light can induce alertness at night
<p>Abstract</p> <p>Background</p> <p>A variety of studies have demonstrated that retinal light exposure can increase alertness at night. It is now well accepted that the circadian system is maximally sensitive to short-wavelength (blue) light and is quite insensitive to long-wavelength (red) light. Retinal exposures to blue light at night have been recently shown to impact alertness, implicating participation by the circadian system. The present experiment was conducted to look at the impact of both blue and red light at two different levels on nocturnal alertness. Visually effective but moderate levels of red light are ineffective for stimulating the circadian system. If it were shown that a moderate level of red light impacts alertness, it would have had to occur via a pathway other than through the circadian system.</p> <p>Methods</p> <p>Fourteen subjects participated in a within-subject two-night study, where each participant was exposed to four experimental lighting conditions. Each night each subject was presented a high (40 lx at the cornea) and a low (10 lx at the cornea) diffuse light exposure condition of the same spectrum (blue, λ<sub>max </sub>= 470 nm, or red, λ<sub>max </sub>= 630 nm). The presentation order of the light levels was counterbalanced across sessions for a given subject; light spectra were counterbalanced across subjects within sessions. Prior to each lighting condition, subjects remained in the dark (< 1 lx at the cornea) for 60 minutes. Electroencephalogram (EEG) measurements, electrocardiogram (ECG), psychomotor vigilance tests (PVT), self-reports of sleepiness, and saliva samples for melatonin assays were collected at the end of each dark and light periods.</p> <p>Results</p> <p>Exposures to red and to blue light resulted in increased beta and reduced alpha power relative to preceding dark conditions. Exposures to high, but not low, levels of red and of blue light significantly increased heart rate relative to the dark condition. Performance and sleepiness ratings were not strongly affected by the lighting conditions. Only the higher level of blue light resulted in a reduction in melatonin levels relative to the other lighting conditions.</p> <p>Conclusion</p> <p>These results support previous findings that alertness may be mediated by the circadian system, but it does not seem to be the only light-sensitive pathway that can affect alertness at night.</p
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