Schlafregulation

Zusammenfassung: Die Zirkadianrhythmik und die Schlafhomöostase regulieren die zeitliche Abfolge und die Struktur des Schlafes bei Mensch und Tier. Beim Menschen führt 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) während der Wachzeit entgegen. Störungen in diesem Zusammenspiel können zu kognitiven Leistungseinbußen, Tagesschläfrigkeit und Schlafproblemen führen, was oft bei Schichtarbeitern, Jetlag, älteren Leuten, und Patienten, die am verzögerten oder verfrühten Schlafphasen-Syndrom leiden, der Fall ist. Ergebnisse aus der Molekularbiologie und Zellphysiologie dieser beiden Prozesse führten zu folgenden Erkenntnissen: Die suprachiasmatischen Kerne (SCN) repräsentieren den zentralen zirkadianen Schrittmacher. Es gibt eine Rückkopplung zu den SCN über das Neurohormon Melatonin. Das ventrolaterale präoptische Areal (VLPO) ist besonders wichtig für die Initiation des Schlafes. Das Nukleosid Adenosin triggert das VLPO. Ein ultradianer Oszillator im mesopontinen Hirnstamm steuert den regelmäßigen Wechsel zwischen NREM- und REM-Schlaf. Der Schlaf-Wach-Zyklus und der NREM-REM-Schlaf-Zyklus induzieren regelmäßig auftretende neuromodulatorische Veränderungen in Vorderhirnstrukture

Schlaf und zirkadiane Rhythmik im Alter

Zusammenfassung: Mit steigendem Alter nimmt die nächtliche Schlafkonsolidierung ab, kurze Nickerchen über den Tag nehmen zu, und die Schlafzeit verschiebt sich in frühere Stunden. Die Schlafregulation hängt von der Interaktion zwischen einem zirkadianen Schrittmacher (biologische Uhr) und dem Schlafhomöostaten (je länger die Wachphase, desto größer der Schlafdruck) ab. Wir konnten an gesunden älteren Personen zeigen, dass sich die Amplitude zirkadianer Rhythmen (z. B. die Melatonin-Sekretion) und die Tiefschlafdauer verringert. Gleichzeitig nimmt die Müdigkeit am Nachmittag zu, wie auch die Tendenz—im Gegensatz zu jüngeren Personen—am frühen Abend einzuschlafen. Da Licht der Hauptzeitgeber ist, um die biologische Uhr zu stabilisieren, brauchen ältere Menschen tagsüber und am Abend genügend Licht und sollten während des Tages keine oder nur kurze Nickerchen machen, um in der Folge den Schlaf in der Nacht zu verbesser

Predicting melatonin suppression by light in humans:Unifying photoreceptor-based equivalent daylight illuminances, spectral composition, timing and duration of light exposure

Light‐induced melatonin suppression data from 29 peer‐reviewed publications was analysed by means of a machine‐learning approach to establish which light exposure characteristics (ie photopic illuminance, five α‐opic 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) S‐cone‐opic 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 S‐cone‐opic 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 (human‐centric) 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 non‐visual responses to light, especially melatonin suppression. The model is a starting tool for developing hypotheses on photoreceptors’ contributions to light's non‐visual responses and helps identifying areas where more data are needed, like on the S‐cone contribution at low illuminances

Lighting color temperature impacts effort-related cardiovascular response to an auditory short-term memory task

To better understand the impact of environmental light on processes that underlie cognitive activity, Lasauskaite and Cajochen (2018) recently proposed a theoretical model that predicts how light's correlated color temperature (CCT) affects effort. Here we tested whether the effects of CCT of light on effort-related cardiovascular response also extend to another sensory input—hearing. In two experimental blocks, participants were exposed to either low (2800 K) or high correlated color temperature (6500 K) light with an illumination level of 500 lux for 15 min before and while they performed an auditory n-back task varying in difficulty level (low difficulty/1-back vs. moderate difficulty/2-back). Mental effort was indexed as sympathetic beta-adrenergic impact on the heart, measured via cardiac pre-ejection period and systolic blood pressure. Based on the theoretical model, we hypothesized that light with a high CCT should lead to lower mental effort compared to light with a low CCT in both the low and moderate task difficulty conditions. Moreover, moderate task difficulty should lead to stronger effort compared to an easy task. The results did not show expected differences in invested effort levels between the task difficulty conditions (1-back vs. 2-back task) measured by cardiac pre-ejection period and systolic blood pressure. However, in line with our prediction, the results indicated that higher CCT of light decreased effort during an auditory memory task. Task performance was higher in easy than moderate task difficulty but was not altered by lighting conditions. Furthermore, we found no significant associations between cardiovascular reactivity and changes in mood, sleepiness, light, task, or effort ratings. Taken together, our results provide first evidence that higher CCT of light reduces the amount of effort invested during cognitive tasks for which hearing is needed. Given that this study was conducted under controlled laboratory conditions and with healthy young participants, additional research is needed to demonstrate that our results generalize to real-life applications. Nevertheless, we recommend that lower CCT of light should be avoided in learning and work contexts, as it might lead to higher effort and cardiovascular reactivity that may contribute to the development of cardiovascular health problems. Instead, we recommend higher CCT of light during daytime for wellbeing and health

Encoding difficulty promotes postlearning changes in sleep spindle activity during napping

Learning-dependent increases in sleep spindle density have been reported during nocturnal sleep immediately after the learning session. Here, we investigated experience-dependent changes in daytime sleep EEG activity after declarative learning of unrelated word pairs. At weekly intervals, 13 young male volunteers spent three 24 h sessions in the laboratory under carefully controlled homeostatic and circadian conditions. At approximately midday, subjects performed either one of two word-pair learning tasks or a matched nonlearning control task, in a counterbalanced order. The two learning lists differed in the level of concreteness of the words used, resulting in an easier and a more difficult associative encoding condition, as confirmed by performance at immediate cued recall. Subjects were then allowed to sleep for 4 h; afterward, delayed cued recall was tested. Compared with the control condition, sleep EEG spectral activity in the low spindle frequency range and the density of low-frequency sleep spindles (11.25-13.75 Hz) were both significantly increased in the left frontal cortex after the difficult but not after the easy encoding condition. Furthermore, we found positive correlations between these EEG changes during sleep and changes in memory performance between pre-nap and post-nap recall sessions. These results indicate that, like during nocturnal sleep, daytime sleep EEG oscillations including spindle activity are modified after declarative learning of word pairs. Furthermore, we demonstrate here that the nature of the learning material is a determinant factor for sleep-related alterations after declarative learning

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_max= 470 nm, or red, λ_max= 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

Non-Visual Effects of Light on Melatonin, Alertness and Cognitive Performance: Can Blue-Enriched Light Keep Us Alert?

Light exposure can cascade numerous effects on the human circadian process via the non-imaging forming system, whose spectral relevance is highest in the short-wavelength range. Here we investigated if commercially available compact fluorescent lamps with different colour temperatures can impact on alertness and cognitive performance

Incidence of depression in relation to transportation noise exposure and noise annoyance in the SAPALDIA study

Prospective evidence on the risk of depression in relation to transportation noise exposure and noise annoyance is limited and mixed. We aimed to investigate the associations of long-term exposure to source-specific transportation noise and noise annoyance with incidence of depression in the SAPALDIA (Swiss cohort study on air pollution and lung and heart diseases in adults) cohort. We investigated 4,581 SAPALDIA participants without depression in the year 2001/2002. Corresponding one-year mean road, railway and aircraft day-evening-night noise (Lden) was calculated at the most exposed façade of the participants' residential floors, and transportation noise annoyance was assessed on an 11-point scale. Incident cases of depression were identified in 2010/2011, and comprised participants reporting physician diagnosis, intake of antidepressant medication or having a short form-36 mental health score < 50. We used robust Poisson regressions to estimate the mutually adjusted relative risks (RR) and 95% confidence intervals (CI) of depression, independent of traffic-related air pollution and other potential confounders. Incidence of depression was 11 cases per 1,000 person-years. In single exposure models, we observed positive but in part, statistically non-significant associations (per 10 dB) of road traffic Lden [RR: 1.06 (0.93, 1.22)] and aircraft Lden [RR: 1.19 (0.93, 1.53)], and (per 1-point difference) of noise annoyance [RR: 1.05 (1.02, 1.08)] with depression risk. In multi-exposure model, noise annoyance effect remained unchanged, with weaker effects of road traffic Lden [(RR: 1.02 (0.89, 1.17)] and aircraft Lden [(RR: 1.17 (0.90, 1.50)]. However, there were statistically significant indirect effects of road traffic Lden [(β: 0.02 (0.01, 0.03)] and aircraft Lden [β: 0.01 (0.002, 0.02)] via noise annoyance. There were no associations with railway Lden in the single and multi-exposure models [(RR; both models; : 0.88 (0.75, 1.03)]. We made similar findings among 2,885 non-movers, where the effect modification and cumulative risks were more distinct. Noise annoyance effect in non-movers was stronger among the insufficiently active (RR: 1.09; 95%CI: 1.02, 1.17; p; interaction; = 0.07) and those with daytime sleepiness [RR: 1.07 (1.02, 1.12); p; interaction; = 0.008]. Cumulative risks of Lden in non-movers showed additive tendencies for the linear cumulative risk [(RR; per 10dB of combined sources; : 1.31 (0.90, 1.91)] and the categorical cumulative risk [(RR; triple- vs. zero-source ≥45 dB; : 2.29 (1.02, 5.14)], and remained stable to noise annoyance. Transportation noise level and noise annoyance may jointly and independently influence the risk of depression. Combined long-term exposures to noise level seems to be most detrimental, largely acting via annoyance. The moderation of noise annoyance effect by daytime sleepiness and physical activity further contribute to clarifying the involved mechanisms. More evidence is needed to confirm these findings for effective public health control of depression and noise exposure burden

The independent association of source-specific transportation noise exposure, noise annoyance and noise sensitivity with health-related quality of life

Noise exposure is affecting health-related quality of life (HRQoL). There are many modelling approaches linking specific noise sources with single health-related outcomes. However, an integrated approach is missing taking into account measured levels as well as noise annoyance and sensitivity and assessing their independent association with HRQoL domains. Therefore, we investigated the predictive association of most common transportation noise sources (aircraft, railway and road traffic) as well as transportation noise annoyance and noise sensitivity with HRQoL using data from SAPALDIA (Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults). We assessed 2035 subjects, who participated in the second and third wave of SAPALDIA (3&4) and had complete information on exposure, outcome and covariates. At SAPALDIA3, we calculated annual means (Lden) of source-specific transportation noise exposure at the most exposed facade of participant's dwelling floor height. Participants reported noise annoyance on the widely used 11-point ICBEN scale and answered to 10 questions assessing individual noise sensitivity. To assess the potentially predictive effect of these noise exposures, HRQoL was assessed about 8 years later (SAPALDIA4) using the SF-36. We performed predictive multiple quantile regression models to elucidate associations of noise parameters measured at SAPALDIA3 with median SF-36 scores at SAPALDIA4. Source-specific transportation noise exposures showed few yet not consistent associations with HRQoL scores. We observed statistically significant negative associations of transportation noise annoyance with HRQoL scores covering mental health components (adjusted difference in SF-36 mental health score between highest vs. lowest annoyance tertile: -2.54 (95%CI: -3.89; -1.20). Noise sensitivity showed strongest and most consistent associations with HRQoL scores covering both general and mental health components (adjusted difference in SF-36 scores between highest vs. lowest sensitivity tertile: Mental health -5.96 (-7.57; -4.36); general health -5.16 (-7.08; -3.24)). Within all noise parameters, we predominantly observed negative associations of noise sensitivity with HRQoL attaining a magnitude of potential clinical relevance. This implies that factors other than transportation noise exposure may be relevant for this exposure-outcome relation. Nonetheless, transportation noise annoyance showed relevant associations with mental health components, indicating a negative association of transportation noise with HRQoL